Research

19 pages, 2948 KiB

Open AccessArticle

Optimization of N Fertilizer Type and Ridge–Furrow Ratio to Improve Resource Use Efficiency and Grain Yield of Rain-Fed Winter Wheat in Loess Plateau, China

by Shengcai Qiang, Yan Zhang, Junliang Fan, Fucang Zhang, Wen Lin, Min Sun, Zhiqiang Gao and Xiwang Tang

Agronomy 2024, 14(1), 172; https://doi.org/10.3390/agronomy14010172 - 12 Jan 2024

Viewed by 895

Abstract

Ridge and furrow plastic mulch (RFPM) and nitrogen (N) application are effective strategies for improving crop productivity in China’s Loess Plain. However, it is not clear how the ridge–furrow ratio and nitrogen fertilizer type (NT) affect the use of water, nitrogen, heat, and [...] Read more.

Ridge and furrow plastic mulch (RFPM) and nitrogen (N) application are effective strategies for improving crop productivity in China’s Loess Plain. However, it is not clear how the ridge–furrow ratio and nitrogen fertilizer type (NT) affect the use of water, nitrogen, heat, and radiation resources for the enhancement of rain-fed wheat production. Two nitrogen fertilizer types (traditional urea (TU) and controlled-release urea (CRU)) and four planting patterns (conventional flat planting (F) and the RFPM system of 20 cm ridges with 40 cm furrows (R₂F₄), 40 cm ridges with 40 cm furrows (R₄F₄), and 60 cm ridges with 40 cm furrows (R₆F₄)) were tested from September 2018 to June 2021 during the winter wheat growing season. It was found that the RFPM system can increase soil thermal time (TT_soil) from 41.0 to 152.1 °C d compared to the F. RFPM system thermal effect, which reduced the vegetative growth period and prolonged the reproductive growth period for 2 to 7 days, which promoted an increase in the leaf area index (LAI) and final dry matter (DM) accumulation. These significantly increased the grain yield (GY) in the RFPM system by 51.6–115.2% and enhanced the thermal time use efficiency (TUE) by 48–99.5%, water productivity (WP) by 37.4–76.3%, radiation use efficiency (RUE) by 16.3–34.4%, and partial factor productivity of nitrogen (PFP_N) by 51.6–115.2% compared to F. Although a high ridge and furrow ratio in combination with CRU increased the GY and resource use efficiency, it also exacerbated the soil water depletion, especially in the soil layer between 40 and 140 cm. Overall, CRU combined with the 40 cm ridge and 40 cm furrow RFPM system maximized resource efficiency and increased wheat production on China’s Loess Plateau. Full article

(This article belongs to the Special Issue Agricultural Water Management in Arid, Semi-Arid and Drought Prone Areas)

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16 pages, 34654 KiB

Open AccessArticle

A Cotton Leaf Water Potential Prediction Model Based on Particle Swarm Optimisation of the LS-SVM Model

by Yonglin Gao, Tiebiao Zhao, Zhong Zheng and Dongdong Liu

Agronomy 2023, 13(12), 2929; https://doi.org/10.3390/agronomy13122929 - 28 Nov 2023

Cited by 1 | Viewed by 614

Abstract

Frequent monitoring of crop moisture levels can significantly improve crop production efficiency and optimise water resource utilisation. The aim of the present study was to generate moisture status maps using thermal infrared imagery, centring on the development of a predictive model for the [...] Read more.

Frequent monitoring of crop moisture levels can significantly improve crop production efficiency and optimise water resource utilisation. The aim of the present study was to generate moisture status maps using thermal infrared imagery, centring on the development of a predictive model for the cotton leaf water potential. The model was constructed using particle swarm optimisation (PSO) in conjunction with the least squares support vector machine (LS-SVM). Traditional SVM models suffer from high computational complexity, long training times, and inequality constraints in predicting leaf water potential. To address such issues, the PSO algorithm was introduced to improve the performance of the LS-SVM model. The PSO-optimised LS-SVM model exhibited notable improvements in performance when evaluated on two distinct test datasets (Alaer and Tumushuke). The research results indicate that the predictive accuracy of the PSO-LS-SVM model significantly improved, as evidenced by an increase of 0.05 and 0.04 in the

R^{2}

values, both of which reached 0.95. This improvement is reflected in the corresponding RMSE values, which were reduced to 0.100 and 0.103. Furthermore, a model was established based on data from three cotton growth stages, achieving high predictive accuracy even with fewer training samples. By using the PSO-LS-SVM model to predict leaf water potential information, the predicted data were mapped onto drone images, enabling the transformation of the leaf water potential from a point to an area. The present findings contribute to a more comprehensive understanding of the cotton leaf water potential by visually representing the spatial distribution of crop water status on a large scale. The results hold substantial significance for the improvement of crop irrigation management. Full article

(This article belongs to the Special Issue Agricultural Water Management in Arid, Semi-Arid and Drought Prone Areas)

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24 pages, 3619 KiB

Open AccessArticle

Impact of Mulching on Soil Moisture and Sap Flow Characteristics of Jujube Trees

by Yi He, Zhikai Qiu, Rui Liu, Min Tang and Pute Wu

Agronomy 2023, 13(11), 2799; https://doi.org/10.3390/agronomy13112799 - 12 Nov 2023

Viewed by 760

Abstract

The main purpose of this study was to assess the influence of grass planting and jujube branch mulching on soil moisture levels and jujube tree transpiration rates, with the ultimate goal of improving jujube tree production in rain-fed orchards. The study encompassed four [...] Read more.

The main purpose of this study was to assess the influence of grass planting and jujube branch mulching on soil moisture levels and jujube tree transpiration rates, with the ultimate goal of improving jujube tree production in rain-fed orchards. The study encompassed four treatments: jujube branch mulching (JBM), jujube branch mulching with white clover planting (JBM + WCP), white clover planting (WCP), and clean cultivation (CC). During a two-year experiment, it was observed that the JBM treatment exhibited the highest capacity for moisture conservation. Specifically, it resulted in an average increase of 2.69% (in 2013) and 2.23% (in 2014) in soil moisture content compared with the CC treatment. The application of statistical analysis revealed significant differences (p < 0.05) between JBM and JBM + WCP, as well as highly significant differences (p < 0.01) between JBM and WCP in the year 2013. In 2014, JBM exhibited significant differences (p < 0.01) from both JBM + WCP and WCP. Between April and August, JBM exhibited the highest soil moisture content, followed by CC, with WCP showing the lowest levels. From September to October, JBM retained its status as the treatment with the highest soil moisture content, JBM + WCP ranked second, and CC experienced a decline and recorded the lowest soil moisture content. Under sunny conditions, all treatments showed a broad peak curve in the daily variation of sap flow velocity. In cloudy weather, a multi-peak wave-like curve was observed with similar trends across treatments. Between April and August, the monthly average sap flow velocity of JBM ranked the highest, followed by CC, while WCP showed the lowest velocity. During the period of September to October, JBM maintained its lead in sap flow velocity, while JBM + WCP rose to the second position, and CC’s sap flow velocity dropped to the lowest level. JBM and WCP treatments showed significant differences (p < 0.01), and in 2014, JBM also had significant differences (p < 0.05) compared with JBM + WCP. The sap flow velocity was positively correlated with air temperature, vapor pressure deficit, wind velocity, photosynthetically active radiation, and soil temperature. Photosynthetically active radiation was identified as the main driving factor influencing jujube tree transpiration. In conclusion, the findings of this study demonstrate the effectiveness of using pruned jujube branches for coverage in rain-fed jujube orchards. This approach not only conserves mulching materials and diminishes the expenses associated with transporting pruned jujube tree branches away from the jujube orchard but also achieves multiple objectives, including increasing soil moisture, promoting jujube tree transpiration, and enhancing soil water utilization. These results have significant implications for the efficient utilization of rainwater resources in rain-fed jujube orchards and provide valuable insights for practical applications in orchard management. Full article

(This article belongs to the Special Issue Agricultural Water Management in Arid, Semi-Arid and Drought Prone Areas)

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16 pages, 4216 KiB

Open AccessArticle

RZWQM2 Simulated Irrigation Strategies to Mitigate Climate Change Impacts on Cotton Production in Hyper–Arid Areas

by Xiaoping Chen, Haibo Dong, Shaoyuan Feng, Dongwei Gui, Liwang Ma, Kelly R. Thorp, Hao Wu, Bo Liu and Zhiming Qi

Agronomy 2023, 13(10), 2529; https://doi.org/10.3390/agronomy13102529 - 29 Sep 2023

Viewed by 1147

Abstract

Improving cotton (Gossypium hirsutum L.) yield and water use efficiency (WUE) under future climate scenarios by optimizing irrigation regimes is crucial in hyper-arid areas. Assuming a current baseline atmospheric carbon dioxide concentration (

{[{C O}_{2}]}_{a t m}

) of 380 [...] Read more.

Improving cotton (Gossypium hirsutum L.) yield and water use efficiency (WUE) under future climate scenarios by optimizing irrigation regimes is crucial in hyper-arid areas. Assuming a current baseline atmospheric carbon dioxide concentration (

{[{C O}_{2}]}_{a t m}

) of 380 ppm (baseline, BL_0/380), the Root Zone Water Quality Model (RZWQM2) was used to evaluate the effects of four climate change scenarios—S_1.5/380 (

∆ T_{a i r}^{°} = 1.5 ° C, ∆ {[{C O}_{2}]}_{a t m} = 0

), S_2.0/380 (

∆ T_{a i r}^{°} = 2.0 ° C, ∆ {[{C O}_{2}]}_{a t m} = 0

), S_1.5/490 (

∆ T_{a i r}^{°} = 1.5 ° C, ∆ {[{C O}_{2}]}_{a t m} = + 110 p p m

) and S_2.0/650 (

∆ T_{a i r}^{°} = 2.0 ° C, ∆ {[{C O}_{2}]}_{a t m} = + 270 p p m

) on soil water content (θ), soil temperature (

T_{s o i l}^{°}

), aboveground biomass, cotton yield and WUE under full irrigation. Cotton yield and irrigation water use efficiency (IWUE) under 10 different irrigation management strategies were analysed for economic benefits. Under the S_1.5/380 and S_2.0/380 scenarios, the average simulated aboveground biomass of cotton (vs. BL_0/380) declined by 11% and 16%, whereas under S_1.5/490 and S_2.0/650 scenarios it increased by 12% and 30%, respectively. The simulated average seed cotton yield (vs. BL_0/380) increased by 9.0% and 20.3% under the S_1.5/490 and S_2.0/650 scenarios, but decreased by 10.5% and 15.3% under the S_1.5/380 and S_2.0/380 scenarios, respectively. Owing to greater cotton yield and lesser transpiration, a 9.0% and 24.2% increase (vs. BL_0/380) in cotton WUE occurred under the S_1.5/490 and S_2.0/650 scenarios, respectively. The highest net income ($3741 ha⁻¹) and net water yield ($1.14 m⁻³) of cotton under climate change occurred when irrigated at 650 mm and 500 mm per growing season, respectively. These results suggested that deficit irrigation can be adopted in irrigated cotton fields to address the agricultural water crisis expected under climate change. Full article

(This article belongs to the Special Issue Agricultural Water Management in Arid, Semi-Arid and Drought Prone Areas)

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22 pages, 12437 KiB

Open AccessArticle

Effects of Combined Application of Organic Fertilizer on the Growth and Yield of Pakchoi under Different Irrigation Water Types

by Shudong Lin, Chunhong Wang, Qingyuan Lei, Kai Wei, Quanjiu Wang, Mingjiang Deng, Lijun Su, Shiyao Liu and Xiaoxian Duan

Agronomy 2023, 13(10), 2468; https://doi.org/10.3390/agronomy13102468 - 25 Sep 2023

Cited by 1 | Viewed by 1938

Abstract

The long-term utilization of inorganic fertilizers in pakchoi cultivation can result in increased nitrate levels, potentially posing health risks to human consumers. For this study, we investigated the efficacy of organic fertilizers as a promising alternative for enhancing soil structure, improving fertility, and [...] Read more.

The long-term utilization of inorganic fertilizers in pakchoi cultivation can result in increased nitrate levels, potentially posing health risks to human consumers. For this study, we investigated the efficacy of organic fertilizers as a promising alternative for enhancing soil structure, improving fertility, and increasing the yield of pakchoi. A two-year field trial was conducted from 2022 to 2023 to examine the effects of the combined application of organic fertilizer on the growth and yield of pakchoi. Three types of irrigation water, namely fresh water (F), brackish water (B), and magnetized–ionized brackish water (MIB), were used in combination with five different organic fertilizer rates (0, 20, 40, 60, and 80 kg/ha, denoted as 0, 1, 2, 3, and 4). The results revealed that treatments F2, F3, B2, B3, and MIB3 significantly improved the growth indexes of pakchoi. Notably, treatments F3, B3, and MIB3 resulted in an earlier onset of the fast growth period for leaf area index and fresh weight. During this period, we observed the highest cumulative growing degree days (ΔCGDD) values, which were 628.36 °C for plant height (MIB4), 475.01 °C for leaf area index (B3), 259.73 °C for fresh weight (B3), and 416.82 °C for dry matter accumulation (B3). The logistic model indicated an increase in eigenvalue at an organic fertilizer application rate of 60 kg/ha, while excessive fertilization had inhibitory effects. Under brackish water irrigation, both plant height and leaf area index demonstrated significant positive effects on yield, with plant height having a particularly noteworthy direct effect at a coefficient of 0.935. MIB water irrigation demonstrated superior advantages for promoting pakchoi growth, leading to significantly higher rates of fresh weight and dry matter accumulation compared to traditional brackish water irrigation. The maximum value of each growth index exerted a significant direct influence on its respective growth parameter, whereas ΔCGDD demonstrated a relatively smaller or potentially negative effect. Applying organic fertilizer appropriately can assist in the production of pakchoi and provide a scientific basis for increasing yield. Full article

(This article belongs to the Special Issue Agricultural Water Management in Arid, Semi-Arid and Drought Prone Areas)

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23 pages, 4697 KiB

Open AccessArticle

Determination of the Most Efficient Forage Sorghum Irrigation Scheduling Strategies in the U.S. Central High Plains Using the AquaCrop Model and Field Experiments

by Forough Fazel, Hossein Ansari and Jonathan Aguilar

Agronomy 2023, 13(10), 2446; https://doi.org/10.3390/agronomy13102446 - 22 Sep 2023

Viewed by 896

Abstract

The current status of water resources in the U.S. Central High Plains necessitates adopting water conservation practices to move toward a sustainable agricultural economy. Identifying proper irrigation scheduling techniques is a conservative practice to maintain the sustainability of the agricultural systems. However, conducting [...] Read more.

The current status of water resources in the U.S. Central High Plains necessitates adopting water conservation practices to move toward a sustainable agricultural economy. Identifying proper irrigation scheduling techniques is a conservative practice to maintain the sustainability of the agricultural systems. However, conducting field experiments is time and money consuming. Thus, the utilization of crop models, such as AquaCrop, could be a convenient alternative to field experiments. The FAO AquaCrop model was calibrated and validated for simulating forage sorghum yield response to various deficit irrigation conditions in a semi-arid region. Afterwards, the model was used to investigate the efficiency of the pre-season and in-season irrigation scheduling scenarios. In this study, the soil water status at the planting time was considered as the indicator of the pre-season irrigation level. Therefore, the pre-season irrigation scenarios were arranged as the replenishment of soil water deficiency at the time of planting at up to 30, 50, and 100% of the soil’s total available water for the first 60 cm of soil depth and the same replenishment levels for the entire crop root zone (150 cm soil depth). Then, AquaCrop long-term (37 years) simulations of forage sorghum biomass and irrigation water use efficiency reactions to three levels of maximum allowable depletion (MAD) (40, 55, and 70%) were compared to three fixed irrigation interval (4, 6, and 10 days) scenarios by considering six pre-season irrigation conditions (36 scenarios). The scenarios analysis found the 10-day irrigation interval and the MAD levels of 55% and 70% to be the most efficient irrigation scheduling strategies if combined with pre-season irrigation that brought the crop root zone (0–150 cm soil depth) to field capacity. Moreover, the 40% MAD application was the least efficient strategy. This study’s outputs can be a baseline for establishing forage sorghum irrigation scheduling in the U.S. Central High Plains. However, exploring the interactions of irrigation scheduling strategies with other irrigation and agronomic practices, such as salinity management and fertilizer application, is highly recommended. Full article

(This article belongs to the Special Issue Agricultural Water Management in Arid, Semi-Arid and Drought Prone Areas)

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22 pages, 3954 KiB

Open AccessArticle

Optimizing Soil Moisture Conservation and Temperature Regulation in Rainfed Jujube Orchards of China’s Loess Hilly Areas Using Straw and Branch Mulching

by Min Tang, Rui Liu, Hongchen Li, Xiaodong Gao, Pute Wu and Chao Zhang

Agronomy 2023, 13(8), 2121; https://doi.org/10.3390/agronomy13082121 - 13 Aug 2023

Viewed by 907

Abstract

The implementation of the “Returning Farmland to Forest” project in the loess hilly region of China has led to the establishment of large-scale economic forests, which have become the dominant industry driving local economic development. However, the region faces challenges such as drought, [...] Read more.

The implementation of the “Returning Farmland to Forest” project in the loess hilly region of China has led to the establishment of large-scale economic forests, which have become the dominant industry driving local economic development. However, the region faces challenges such as drought, water shortages, and an uneven distribution of precipitation, which have a severe impact on the growth of economic forests, including jujube trees. Water stress significantly reduces yield and efficiency, posing a threat to the sustainable and healthy development of jujube ecological and economic forests. Therefore, this study aimed to address these issues by implementing straw mulching (SM) and jujube branch mulching (BM) measures in the mountainous jujube economic forests. Through long-term monitoring and statistical analysis, the study investigated the effects of different mulching treatments on soil moisture and soil temperature. The research findings reveal that both SM and BM significantly increased soil moisture in the 0–280 cm soil layer during the jujube growing season (p < 0.05). In both normal precipitation (2014) and drought (2015) years, SM increased average soil moisture content by 5.10% and 4.60%, respectively, compared to the uncovered treatment (CK). SM also had a positive impact on the soil moisture content in each layer of the soil profile. However, BM only increased soil moisture content in the 40–100 cm and 220–280 cm soil layers. Additionally, SM and BM reduced the variation of soil moisture, with SM showing a more significant effect in regulating soil moisture and achieving more stable moisture levels. During the jujube growing seasons in 2014 and 2015, SM and BM decreased soil temperature in the 0–10 cm soil layer. The temperature difference compared to CK decreased with increasing soil depth. SM had an overcooling effect, while BM reduced the temperature before the fruit expansion period and maintained warmth afterward. Both SM and BM also reduced the daily range and variation range of soil temperature, with SM having a more pronounced effect. The temperature of the 0–20 cm soil layer exhibited the strongest correlation with air temperature, and SM showed the weakest response. In conclusion, adopting straw mulching and jujube branch mulching in rain-fed jujube orchards in the loess hilly region not only saves materials and reduces costs but also contributes to water retention and temperature regulation. Straw mulching, in particular, plays a more significant role in moisture retention and temperature regulation and is advantageous for soil management in rain-fed jujube orchards. These research findings provide a scientific basis for optimizing water and heat management in orchards with limited water resources. Full article

(This article belongs to the Special Issue Agricultural Water Management in Arid, Semi-Arid and Drought Prone Areas)

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15 pages, 2728 KiB

Open AccessArticle

Distribution Characteristics of Rainfall Erosivity in Jiangsu Coastal Areas

by Feng Chen, Haibo Hu, Defeng Pan, Junyi Wang, Hua Zhang and Zheng Pan

Agronomy 2023, 13(7), 1829; https://doi.org/10.3390/agronomy13071829 - 10 Jul 2023

Viewed by 779

Abstract

The issue of regional soil and water loss caused by human activity is particularly severe in coastal regions. Since coastal reclamation areas are a valuable land reserve resource, it is of practical significance to understand the distribution characteristics of rainfall erosion and its [...] Read more.

The issue of regional soil and water loss caused by human activity is particularly severe in coastal regions. Since coastal reclamation areas are a valuable land reserve resource, it is of practical significance to understand the distribution characteristics of rainfall erosion and its impact on soil erosion for the prediction, evaluation, and management of regional soil and water resources. Rainfall erosivity should be updated and estimated from simplified indices. This paper analyzed the observed rainfall data of field runoff plots in Dongtai City, Jiangsu Province, between 2011 and 2017. According to the standard of erosive rainfall in coastal areas, reporting 10.8 mm of rainfall or 7.6 mm·h⁻¹ of I₃₀ (maximum 30 min rainfall intensity), the annual average erosive rainfall frequency in Dongtai City was 37.7 and the annual erosive rainfall was 1082.0 mm on average, which accounted for 51.6% and 90.6% of the total rainfall frequency and the total rainfall, respectively. Moreover, the annual average rainfall erosivity in the region from 2011 to 2017 was 7717.4 MJ·mm·hm⁻²·h⁻¹. The annual distribution of rainfall erosivity was irregular, with an average monthly erosivity value of 4501.8 MJ·mm·hm⁻²·h⁻¹. Since the accumulated rainfall erosivity of Dongtai City in the flood season (May to September) accounted for 88.1% of the total rainfall erosivity, it is essential to focus on preventing soil and water loss in the flood season. This paper established a rainfall-based model and a composite model and intensity appropriate for a single event and monthly rainfall erosivity in the region. Both models can be used to calculate the annual rainfall erosivity, but only the composite model based on rainfall amount and intensity is recommended for calculating single and monthly rainfall erosivity levels in Jiangsu coastal areas. The empirical formulas in Jiangsu coastal areas can be updated using more recent rainfall data and assess soil erosion risk accurately. Full article

(This article belongs to the Special Issue Agricultural Water Management in Arid, Semi-Arid and Drought Prone Areas)

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19 pages, 4988 KiB

Open AccessArticle

Effect of Irrigation Water Salinity on Soil Characteristics and Microbial Communities in Cotton Fields in Southern Xinjiang, China

by Bangxin Ding, Yungang Bai, Shuchen Guo, Zijian He, Bei Wang, Hongbo Liu, Jiangrui Zhai and Hongxia Cao

Agronomy 2023, 13(7), 1679; https://doi.org/10.3390/agronomy13071679 - 22 Jun 2023

Cited by 2 | Viewed by 1795

Abstract

Irrigation with saline water is a possible solution to alleviate freshwater shortages. The long-term use of saline water for irrigation requires consideration of the influence of salt on the environmental conditions of the soil. The objective of this field study was to determine [...] Read more.

Irrigation with saline water is a possible solution to alleviate freshwater shortages. The long-term use of saline water for irrigation requires consideration of the influence of salt on the environmental conditions of the soil. The objective of this field study was to determine the effects of three continuous years of saline water irrigation on physiochemical properties and microbial communities in drip-irrigated cotton fields. The three total dissolved solid (TDS) levels of irrigation water treatments were (i) 1 g L⁻¹ (fresh water, FWI), (ii) 3 g L⁻¹ (brackish water, BWI), and (iii) 7 g L⁻¹ (salt water, SWI). After three years, the electrical conductivity (EC), sodium adsorption ratio (SAR), and contents of K⁺, Na⁺, Mg²⁺, Cl⁻, and SO₄²⁻ in the SWI treatment were significantly higher than those in the FWI and BWI treatments, but there were no significant differences in EC and K⁺ between the FWI and BWI treatments. BWI treatment significantly increased microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), urease, and sucrase contents. The diversity and abundance of bacteria and fungi were not affected by saline water irrigation, but the microbial community structure was altered. Saline water irrigation resulted in an elevation in the bacterial abundance of the phylum Chloroflexi and a decline in Proteobacteria and Actinobacteria. For fungi, the abundance of the phylum Ascomycota in the BWI treatment was greater than that in the FWI and SWI treatments. Linear discriminant analysis effect size (NMDS) results indicated clear variation in the microbiota profiles between the FWI, BWI, and SWI treatments for bacteria. Regarding the fungal microbiota profiles, the BWI and SWI treatments had similar microbiota profiles but were different from the FWI treatment. The number of bacterial biomarkers gradually increased with increasing total dissolved solids of irrigation water, while the number of fungal biomarkers gradually decreased. Additionally, cotton yield was significantly and positively correlated with the observed species of fungi, while it was significantly and negatively correlated with EC. Redundancy analysis (RDA) showed that bacterial community structure was regulated by SAR and fungal community structure was regulated by soil salinity and bulk density (BD). Future research will need to look into how the structure of the microbial community and the associated functional microorganisms are gradually changing with increased irrigation frequency under saline irrigation, as well as explore and screen for advantageous functional microorganisms. Full article

(This article belongs to the Special Issue Agricultural Water Management in Arid, Semi-Arid and Drought Prone Areas)

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19 pages, 7050 KiB

Open AccessEditor’s ChoiceArticle

Spatiotemporal Variations of Reference Evapotranspiration and Its Climatic Driving Factors in Guangdong, a Humid Subtropical Province of South China

by Baoshan Zhao, Dongsheng An, Chengming Yan, Haofang Yan, Ran Kong and Junbo Su

Agronomy 2023, 13(6), 1446; https://doi.org/10.3390/agronomy13061446 - 24 May 2023

Cited by 4 | Viewed by 1196

Abstract

It is of great importance to study the changes in reference evapotranspiration (ET₀) and the factors that influence it to ensure sustainable and efficient water resource utilization. Daily ET₀ data calculated using the Penman–Monteith method from 37 meteorological stations [...] Read more.

It is of great importance to study the changes in reference evapotranspiration (ET₀) and the factors that influence it to ensure sustainable and efficient water resource utilization. Daily ET₀ data calculated using the Penman–Monteith method from 37 meteorological stations located within Guangdong Province in the humid zone of southern China from 1960 to 2020 were analyzed. The trend analysis and Mann–Kendall test were used to analyze the time series changes in ET₀ and major climatic factors (air temperature (T), relative humidity (RH), sunshine duration (SD), and wind speed (u₂)) for over 61 years. Sensitivity and contribution analyses were used to evaluate the driving factors of ET₀. The main findings of the study are as follows: (1) the trend in average annual ET₀ time series in Guangdong slightly increased at a trend rate of 1.61 mm/10a over the past 61 years, with most stations experiencing an increase in ET₀. During the same period, air temperature significantly increased, while RH and SD decreased; u₂ also decreased. (2) Sensitivity analysis showed that ET₀ was more sensitive to RH and T than SD and u₂, with ET₀ being most sensitive to RH in spring and winter and T in summer and autumn. (3) The contribution analysis showed that T was the dominant factor for ET₀ variation in Guangdong, followed by SD. SD was found to be the dominant factor in ET₀ changes in areas where the “evaporation paradox” occurred, as well as in spring and summer. The study concludes that the climate in Guangdong became warmer and drier over the past 61 years, and if the current global warming trend continues, it will lead to higher evapotranspiration and drought occurrence in the future. Full article

(This article belongs to the Special Issue Agricultural Water Management in Arid, Semi-Arid and Drought Prone Areas)

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20 pages, 1537 KiB

Open AccessArticle

Alternative Furrow Irrigation Combined with Topdressing Nitrogen at Jointing Help Yield Formation and Water Use of Winter Wheat under No-Till Ridge Furrow Planting System in Semi-Humid Drought-Prone Areas of China

by Jinzhi Wu, Haoyue Guan, Zhimin Wang, Youjun Li, Guozhan Fu, Ming Huang and Guoqiang Li

Agronomy 2023, 13(5), 1390; https://doi.org/10.3390/agronomy13051390 - 18 May 2023

Viewed by 1842

Abstract

Benefiting from the high–farmland construction program in China, one–off irrigation can be guaranteed in most fields in semi–humid drought–prone areas in China. However, little information is available on water and nitrogen (N) management in wheat production under this condition. This study aimed to [...] Read more.

Benefiting from the high–farmland construction program in China, one–off irrigation can be guaranteed in most fields in semi–humid drought–prone areas in China. However, little information is available on water and nitrogen (N) management in wheat production under this condition. This study aimed to explore the effects of alternative furrow irrigation (AFI) and topdressing N fertilizer (TN) on wheat productivity under a no–till ridge–furrow planting system in semi–humid drought–prone areas. The experimental design was as follows: two furrow irrigation (FI) methods, namely, EFI (every furrow irrigation) and AFI (alternative furrow irrigation) with 75 mm at the jointing stage were set as the main treatments. Two topdressing N (TN) patterns, namely, NTN (0 kg ha⁻¹ of N) and TN (60 kg ha⁻¹ of N) along with irrigation were set as the secondary treatments. Moreover, a traditional planting practice with no irrigation and no topdressing N (NINTN) was set as control. In 2018–2020, a field experiment was carried out to investigate the effects on soil water, leaf chlorophyll relative content (SPAD) and net photosynthetic rate (Pn), aboveground dry matter assimilates, grain yield, water use efficiency (WUE) and economic benefit. We found that both FI methods and TN patterns significantly influenced soil water content. Compared with NINTN, the soil water content in each combination of the FI method and TN pattern was effectively improved at the booting and anthesis stages, leading to the significant increase in SPAD and Pn in leaves, post–anthesis dry matter accumulation (POA), grain yield, WUE and economic benefit of winter wheat. Compared with the EFI, averaged across years and TN patterns, the AFI technique increased the soil water storage at booting and anthesis stages and significantly improved the Pn at early milk (4.9%) and early dough (7.5%) stages, POA (40.6%) and its contribution to grain (CRPOA, 27.6%), the grain yield (10.2%), WUE (9.1%) and economic benefit (9.1%). In addition, compared with the NTN, the TN pattern significantly increased the water computation by wheat from booting to maturity, enhanced leaf Pn after anthesis and POA, and finally resulted in the increase in grain yield (14.7–21.9%) and WUE (9.6–21.1%). Thus, the greatest improvement in the leaf photosynthetic characteristics, aboveground dry matter assimilates, grain yield, WUE and economic benefit was achieved under AFITN treatment. Above all, it can be concluded that the AFITN with AFI of 75 mm and TN of 60 kg ha⁻¹ at jointing was an alternative management strategy for optimizing yield formation and water use of winter wheat. This study provided new insights into improving wheat productivity in drought–prone areas where one–off irrigation can be guaranteed. Full article

(This article belongs to the Special Issue Agricultural Water Management in Arid, Semi-Arid and Drought Prone Areas)

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19 pages, 3232 KiB

Open AccessArticle

Fertilization Highly Increased the Water Use Efficiency of Spring Maize in Dryland of Northern China: A Meta-Analysis

by Jiao Shi, Huaiping Zhou, Minggang Xu, Qiang Zhang, Jianhua Li and Jinfeng Wang

Agronomy 2023, 13(5), 1331; https://doi.org/10.3390/agronomy13051331 - 10 May 2023

Cited by 1 | Viewed by 1486

Abstract

Water and fertilizer play an important role in crop growth in dryland areas. It is a necessity to improve the water use efficiency (WUE) of the crop once the water resource is limited. In northern China, where there is a wide shortage of [...] Read more.

Water and fertilizer play an important role in crop growth in dryland areas. It is a necessity to improve the water use efficiency (WUE) of the crop once the water resource is limited. In northern China, where there is a wide shortage of water resources, it is therefore necessary to investigate how fertilization affects the WUE of spring maize and to quantify the effects. A total of 33 published peer-reviewed papers were collected, and a meta-analysis and random forest model analysis were performed with 364 WUE comparisons, aiming to explore the effects of fertilization on the WUE of spring maize and to clarify the optimal conditions for WUE under fertilizer management. The results showed that fertilization significantly increased the WUE of spring maize by 56.72% (P < 0.01) when compared with non-fertilization. The WUE effect under the organic–inorganic fertilizer combination (MNPK) was approximately twice as high as that under inorganic fertilizer (NPK) or organic fertilizer (M). The greatest increase in WUE occurred at 0–100 kg ha⁻¹ of nitrogen application (NA). Under environmental conditions including 7 ≤ mean annual temperature in the test year (T) ≤ 10 °C, 400 ≤ mean annual precipitation in the test year (P) ≤ 600 mm, and mean altitude (A) > 1500 m, and soil conditions including 10 ≤ soil organic matter content (SOM) ≤ 14 g kg⁻¹ and available phosphorus (AP) < 5 mg kg⁻¹, the fertilization optimally enhanced the WUE of spring maize when the agronomic measures of ridge–furrow planting (RFP) and mulching film (MF) were used. The random forest model analysis indicated that the influence factors (i.e., fertilizer regimes, environmental factors, soil factors, and agronomic measures) caused 65.62% of the variation in spring maize WUE effects, while in all influence factors, fertilizer types related to fertilizer regimes caused the most variation. The initial available potassium (AK) and available nitrogen (AN) of the soil were negatively correlated to the WUE effect, indicating that fertilization imposed a better effect on the WUE of spring maize when the soil was infertile. Fertilization significantly increased the WUE of spring maize, and organic and inorganic fertilizer application provided an effective measure for the sustainable development of spring maize in northern China. After clarifying the required conditions for fertilization increasing WUE, high-efficiency water use may be achieved. Full article

(This article belongs to the Special Issue Agricultural Water Management in Arid, Semi-Arid and Drought Prone Areas)

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13 pages, 3381 KiB

Open AccessArticle

Evaluation of Two Surface Renewal Methods for Calculating the Sensible Heat Flux over a Tea Field Ecosystem in Hilly Terrain

by Huijie Hu, Yongzong Lu, Yongguang Hu and Risheng Ding

Agronomy 2023, 13(5), 1302; https://doi.org/10.3390/agronomy13051302 - 05 May 2023

Cited by 2 | Viewed by 1221

Abstract

Seasonal drought happens frequently in the lower slope hilly areas of China, which leads to a huge economic loss to China’s famous tea production. An accurate determination of the evapotranspiration (ET) value of different seasons can provide a crucial decision parameter [...] Read more.

Seasonal drought happens frequently in the lower slope hilly areas of China, which leads to a huge economic loss to China’s famous tea production. An accurate determination of the evapotranspiration (ET) value of different seasons can provide a crucial decision parameter for irrigation management. The surface renewal (SR) method is an accurate and inexpensive method compared with the eddy covariance (EC) method, which is widely used to calculate the sensible heat flux (H). The latent heat flux (LE) evapotranspiration can be estimated indirectly when combined with the energy–balance equation. This research investigated the traditional and improved calculation methods of H (SR_snyder and SR_chen), based on the surface renewal theory, over a tea field for one year. The calculation accuracy was obtained from the statistical analysis between the SR and EC methods. Different months’ applicability was evaluated to determine the best calculation method for the tea field. The traditional calculation method (SR_snyder) is based on the van slope model using the second, third, and fifth structure function. The improved SR model (SR_chen) introduces a third order temperature function and friction velocity for calculation. The results indicate that SR_chen shows a good calculation accuracy of H in the spring seasons (February to April), summer (May to July), and autumn (August to October). The determination coefficients of regression analysis (R²) ranges were [0.66, 0.88] with most values greater than 0.8. The root mean square error (RMSE) ranges were [34.15, 69.22] W/m². However, during this period, SR_snyder had a poor calculation accuracy of H, and the range of R² was [0.45, 0.74] with the RMSE ranges of [32.28, 63.25] W/m². In the winter (November to January), the calculation accuracy of both models was relatively low with R² almost 30% lower than that of other seasons. Therefore, this study suggests the use of the SR_chen method to estimate the H of a tea field ecosystem in the low slope hilly area of the Yangtze River region in the spring, summer, and autumn. While in the winter, the SR_snyder method is recommended. Full article

(This article belongs to the Special Issue Agricultural Water Management in Arid, Semi-Arid and Drought Prone Areas)

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19 pages, 1796 KiB

Open AccessArticle

Impacts of Irrigation Technology, Irrigation Rate, and Drought-Tolerant Genetics on Silage Corn Production

by Tina Sullivan, Matt A. Yost, Dakota Boren, Earl Creech, Boyd Kitchen, Randall Violett and Burdette Barker

Agronomy 2023, 13(5), 1194; https://doi.org/10.3390/agronomy13051194 - 24 Apr 2023

Viewed by 1355

Abstract

Many studies have examined individual water-saving management practices for corn (Zea mays L.), but few studies have looked at how combinations of practices might further enhance water optimization. The research objectives of this paper were to evaluate the impact of irrigation technology, [...] Read more.

Many studies have examined individual water-saving management practices for corn (Zea mays L.), but few studies have looked at how combinations of practices might further enhance water optimization. The research objectives of this paper were to evaluate the impact of irrigation technology, irrigation rate, and crop genetics, as well as their interactions, on silage corn yield and forage quality. Trials were conducted in three Utah locations from 2019 through 2021. The results from five site-years indicated that the best water optimization practices varied by site-year. Low-elevation sprinklers commonly applied water more efficiently, with four of the five site-years having improved or equivalent yield compared to mid-elevation sprinklers. Irrigation rate reductions and yield losses were not proportional, as a 25% irrigation reduction resulted in better silage quality and a 7% average yield loss across site-years. Further, targeted deficit irrigation (less water during vegetation and more during maturation) was inferior to a uniform deficit during all growth stages. Drought-tolerant genetics often maintained but did not improve yield in extreme water stress environments compared to non-DT genetics. No cumulative benefits were observed when combining irrigation technology, rate, and DT genetics. Irrigation technology had the greatest potential of the three factors to optimize water use in silage corn production in the Western U.S. region. Full article

(This article belongs to the Special Issue Agricultural Water Management in Arid, Semi-Arid and Drought Prone Areas)

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19 pages, 4661 KiB

Open AccessArticle

Effect of Plastic Film Colours and Perforations on Energy Distribution, Soil Temperature, and Evaporation

by Zunqiu Xu, Rony Wallach, Jian Song and Xiaomin Mao

Agronomy 2023, 13(3), 926; https://doi.org/10.3390/agronomy13030926 - 21 Mar 2023

Cited by 1 | Viewed by 1396

Abstract

Plastic film mulching is a commonly used agricultural measure in arid/cold regions to improve crop growth. Despite previous studies on the impact of film mulching on soil water/heat status and crop growth, it is not clear how plastic film colours and perforations affect [...] Read more.

Plastic film mulching is a commonly used agricultural measure in arid/cold regions to improve crop growth. Despite previous studies on the impact of film mulching on soil water/heat status and crop growth, it is not clear how plastic film colours and perforations affect energy distribution, soil temperature, and evaporation. Six sets of column experiments were performed with three plastic film colours: transparent (T), black (B), and silver-grey (G), and two perforation ratios: 4.49% and 21.44%, to monitor soil evaporation and soil/film mulching temperature. Using these two main control factors, a soil–mulch–atmosphere system (SMAS) model was established to simulate soil evaporation and energy distribution. The simulations of soil evaporation compared well with the measurements. The available net energy was positively related to the perforation ratio and transmittance of the plastic film, which further influenced soil temperature and altered energy distribution. Both simulated and measured results gave the following order for transpiration with the plastic films: T > B > G. The SMAS model was more accurate when a mulch with weak light transmittance covered the field. Moreover, by comparing simulated evaporation mass loss with and without considering heat conduction between the plastic mulch and the soil surface,

C_{s m}

, we found that it is feasible to exclude

C_{s m}

. However,

C_{s m}

is indispensable in the SMAS model for understanding the mechanism of plastic film mulching in agroecosystems, particularly at night. Full article

(This article belongs to the Special Issue Agricultural Water Management in Arid, Semi-Arid and Drought Prone Areas)

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21 pages, 3921 KiB

Open AccessArticle

Evaluating the Combined Effects of Water and Fertilizer Coupling Schemes on Pear Vegetative Growth and Quality in North China

by Yanan Liu, Meijian Bai, Yinong Li, Baozhong Zhang, Xianbing Wu, Yuan Shi and Hairuo Liu

Agronomy 2023, 13(3), 867; https://doi.org/10.3390/agronomy13030867 - 16 Mar 2023

Cited by 1 | Viewed by 1468

Abstract

Unreasonable fertilizer and irrigation applications and dosages in orchards in northern China result in poor vegetative growth and fruit quality. To reveal the combined effect of water and fertilizer coupling on vegetative growth and fruit quality, this study used pear as a field [...] Read more.

Unreasonable fertilizer and irrigation applications and dosages in orchards in northern China result in poor vegetative growth and fruit quality. To reveal the combined effect of water and fertilizer coupling on vegetative growth and fruit quality, this study used pear as a field experiment material, considering: (1) irrigation lower limits (55%, 65%, 75%θ_f, θ_f is field capacity) and (2) nitrogen fertilizer application (162, 324, 486 kg·ha⁻¹). Nine coupling schemes and a control treatment (C) were set up in the orthogonal combination. The results showed that, under the higher irrigation rate and nitrogen dose, the spring shoot length, base diameter, and leaves relative chlorophyll content values were increased by 36.77%, 31.86% and 12.91%, respectively. The response of each coupling scheme was different. However, selected water and nitrogen coupling schemes improved the fruit quality. The evaluation results indicated that medium irrigation and high fertilizer scheme were optimal. In conclusion, integrating the vegetative growth and fruit quality, it is recommended that the water and fertilizer coupling scheme for pear in the northern China is as follows: a lower irrigation limit of 65%θ_f and a nitrogen fertilizer amount of 486.00 kg·ha⁻¹. Full article

(This article belongs to the Special Issue Agricultural Water Management in Arid, Semi-Arid and Drought Prone Areas)

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20 pages, 3910 KiB

Open AccessArticle

The Suitability Assessment of Agricultural Drought Monitoring Indices: A Case Study in Inland River Basin

by Weiqi Liu, Shaoxiu Ma, Kun Feng, Yulai Gong, Linhao Liang and Mitsuru Tsubo

Agronomy 2023, 13(2), 469; https://doi.org/10.3390/agronomy13020469 - 05 Feb 2023

Cited by 2 | Viewed by 2088

Abstract

Drought monitoring is an important scientific basis for drought impact evaluation and the selection of mitigation strategies. Since the drivers of drought vary among regions, there is no universal drought index applicable to different regions. The Shiyang River Basin, an inland river basin, [...] Read more.

Drought monitoring is an important scientific basis for drought impact evaluation and the selection of mitigation strategies. Since the drivers of drought vary among regions, there is no universal drought index applicable to different regions. The Shiyang River Basin, an inland river basin, located in Gansu Province, China, has a closed water cycle system. Drought is a dominant nature disaster for the sustainable development of the region. Thus, this is an ideal area to explore the suitability of drought-monitoring indices. Here, we took the Shiyang River Basin as an example, in order to explore suitable indicators for agricultural drought monitoring in inland river basins. This study assessed the twelve different widely used drought indices used for monitoring the impact of drought on crop growth, represented by net primary production (NPP). The results showed that the vegetation status-based drought indices (VCI and NVSWI) had the highest significant correlation (0.6 ≤ |R| ≤ 1, p < 0.05) on NPP, and the integrated drought indices (DSI and ISDI) had the strong significant correlation (0.4 ≤ |R| < 0.6, p < 0.1). These four indices are good indicators for agricultural drought monitoring. Studies based on these four indices showed that agricultural drought has a tendency to slow down from 1982 to 2020. This is inconsistent with the monitoring of drought indices based on the meteorological variables that show a trend of increasing drought. This is mainly due to the increased efficiency of water management and its use in inland river basins. This indicates that other water resource information, such as runoff, should be included to construct an integrated agricultural drought-monitoring indices in management intensive regions, such as in an inland river basin. Full article

(This article belongs to the Special Issue Agricultural Water Management in Arid, Semi-Arid and Drought Prone Areas)

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17 pages, 7425 KiB

Open AccessArticle

Modelling Winter Rapeseed (Brassica napus L.) Growth and Yield under Different Sowing Dates and Densities Using AquaCrop Model

by Ziang Xie, Jiying Kong, Min Tang, Zhenhai Luo, Duo Li, Rui Liu, Shaoyuan Feng and Chao Zhang

Agronomy 2023, 13(2), 367; https://doi.org/10.3390/agronomy13020367 - 27 Jan 2023

Cited by 1 | Viewed by 1420

Abstract

The sowing date and density are considered to be the main factors affecting crop yield. The determination of the sowing date and sowing density, however, is fraught with uncertainty due to the influence of climatic conditions, topography, variety and other factors. Therefore, it [...] Read more.

The sowing date and density are considered to be the main factors affecting crop yield. The determination of the sowing date and sowing density, however, is fraught with uncertainty due to the influence of climatic conditions, topography, variety and other factors. Therefore, it is necessary to find a comprehensive consideration of these factors to guide the production of winter rapeseed. A reliable crop model could be a crucial tool to investigate the response of rapeseed growth to changes in the sowing date and density. At present, few studies related to rapeseed model simulation have been reported, especially in the comprehensive evaluation of the effects of sowing date and density factors on rapeseed development and production. This study aimed to evaluate the performance of the AquaCrop model for winter rapeseed development and yield simulation under various sowing dates and densities, and to optimize the sowing date and density for agricultural high-efficient production in the Jianghuai Plain. Two years of experiments were carried out in the rapeseed growing season in 2020 and 2021. The model parameters were fully calibrated and the simulation performances in different treatments of sowing dates and densities were evaluated. The results indicated that the capability of the AquaCrop model to interpret crop development for different sowing dates was superior to that of sowing densities. For rapeseed canopy development, the RMSE for three sowing dates and densities scenarios were 7–22% and 16–23%, respectively. The simulated biomass and grain yield for different sowing dates treatments (RMSE: 0.8–2.1 t·ha⁻¹, Pe: 0–35.3%) were generally better than those of different densities treatments (RMSE: 0.7–3.9 t·ha⁻¹, Pe: 8.2–90%). Compared with other sowing densities, higher overestimation errors of the biomass and yield were observed for the low-density treatment. Adequate agreement for crop evapotranspiration simulation was achieved, with an R² of 0.79 and RMSE of 26 mm. Combining the simulation results and field data, the optimal sowing scheme for achieving a steadily high yield in the Jianghuai Plain of east China was determined to be sowing in October and a sowing density of 25.0–37.5 plant·m⁻². The study demonstrates the great potential of the AquaCrop model to optimize rapeseed sowing patterns and provides a technical means guidance for the formulation of local winter rapeseed production. Full article

(This article belongs to the Special Issue Agricultural Water Management in Arid, Semi-Arid and Drought Prone Areas)

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18 pages, 12448 KiB

Open AccessArticle

Optimal Sowing Windows under Rainfall Variability in Rainfed Agriculture in West Africa

by Sehouevi Mawuton David Agoungbome, Marie-Claire ten Veldhuis and Nick van de Giesen

Agronomy 2023, 13(1), 167; https://doi.org/10.3390/agronomy13010167 - 04 Jan 2023

Cited by 3 | Viewed by 1546

Abstract

Climate change is exacerbating adverse impacts of water stress in rainfed agriculture. This paper seeks to identify safe sowing windows for smallholder farmers in the Sudanian region of West Africa (WA). We hypothesize that the traditional focus on the onset of the season [...] Read more.

Climate change is exacerbating adverse impacts of water stress in rainfed agriculture. This paper seeks to identify safe sowing windows for smallholder farmers in the Sudanian region of West Africa (WA). We hypothesize that the traditional focus on the onset of the season to start sowing leads to crop losses in years of high rainfall intermittency. AquaCrop, an FAO crop model, is used to simulate the yield response of maize (Zea mays L.) to sowing dates ranging from the 1st of May to the 30th of November at 20 locations in WA. We find that sowing directly after the first rains carries a higher risk of water stress, hampering crop development due to insufficient buildup of soil water storage to overcome dry spells. Based on three years of data per station on average, we identify safe sowing windows across the Sudanian region that secure optimal yield in 97% of all cases. We find that delaying sowing to mid-June (savanna and western part of the region) and to July (semi-arid region) ensures optimal yields. Of the three commonly applied local onset approaches covered in our evaluation, only LO10mm (10 mm/day on four consecutive days) achieves a similar yield result. The advantage of the safe window approach is that it is accessible for smallholders, who in many cases do not have access to local rainfall information. Full article

(This article belongs to the Special Issue Agricultural Water Management in Arid, Semi-Arid and Drought Prone Areas)

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18 pages, 6655 KiB

Open AccessArticle

Calibration of Soil Moisture Sensors (ECH₂O-5TE) in Hot and Saline Soils with New Empirical Equation

by Ibrahim I. Louki and Abdulrasoul M. Al-Omran

Agronomy 2023, 13(1), 51; https://doi.org/10.3390/agronomy13010051 - 23 Dec 2022

Cited by 3 | Viewed by 2194

Abstract

The use of soil moisture sensors is a practice applied to improve irrigation water management. ECH2O-5TE sensors are increasingly being used to estimate the volumetric water content (VWC). In view of the importance of the efficient use of these devices, six main factors [...] Read more.

The use of soil moisture sensors is a practice applied to improve irrigation water management. ECH2O-5TE sensors are increasingly being used to estimate the volumetric water content (VWC). In view of the importance of the efficient use of these devices, six main factors affecting the accuracy of sensor measurements were studied: soil moisture levels, soil salinity, temperature, organic matter, soil texture, and bulk density. The study showed that the electrical conductivity of the soil and the temperature independently affect the measurements, while the influence of other factors interferes with that of salinity. This study found that the sensor measurements of the VWC were closest to the actual VWC at the soil ECe and temperatures of 2.42 dS m⁻¹ and 25 °C, with root-mean-square errors (RMSE) of 0.003 and 0.004 m³ m⁻³. Otherwise, the measured VWC values of these sensor readouts significantly overestimated the actual VWC, with an increasing soil ECe and/or producing temperatures higher than the stated values, and vice versa. Given the importance of these sensors for obtaining accurate measurements for water management, a simplified empirical equation was derived using the data collected from a wide range of measurements to correct the influences of electrical conductivity and temperature on the measurement accuracy of the sensors, while considering the influence of the soil’s texture. Thus, the following equation was proposed: ϴva =

θ vs {((a E C e^{2} + b E C e + c) + (d T^{2} + e T + f))}^{- 1}

. The results concerning the measurement of different VWC levels via these sensors and the proposed L&O correction equation were compared with the corresponding actual VWC values determined by gravimetric methods. It was found that this empirical equation reduced the differences in the RMSE between the sensor readings for the VWC and the actual VWC from 0.072 and 0.252 to 0.030 and 0.030 m³ m⁻³ for 1 and 5 dS m⁻¹, respectively, with respect to the EC’s influence at 25 °C and reduced the RMSE from 0.053 and 0.098 to 0.007 and 0.011 at 3 and 50 °C, respectively, regarding the effect of the temperature at EC 2.42 dS m⁻¹ at different levels of the actual VWC values. Full article

(This article belongs to the Special Issue Agricultural Water Management in Arid, Semi-Arid and Drought Prone Areas)

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14 pages, 2294 KiB

Open AccessArticle

Optimizing Water and Nitrogen Management for Green Pepper (Capsicum annuum L.) under Drip Irrigation in Sub-Tropical Monsoon Climate Regions

by Zhiguang Dai, Xinyu Zhao, Hui Yan, Long Qin, Xiaoli Niu, Long Zhao and Yaohui Cai

Agronomy 2023, 13(1), 34; https://doi.org/10.3390/agronomy13010034 - 22 Dec 2022

Cited by 1 | Viewed by 1588

Abstract

Green pepper (Capsicum annuum L.) is one of the major vegetables cultivated in sub-tropical monsoon climate regions. However, with the unreasonable use of water and nitrogen (N) fertilizer, efficient water and N fertilizer management systems need to be identified. The goal of [...] Read more.

Green pepper (Capsicum annuum L.) is one of the major vegetables cultivated in sub-tropical monsoon climate regions. However, with the unreasonable use of water and nitrogen (N) fertilizer, efficient water and N fertilizer management systems need to be identified. The goal of this project was to investigate the coupling effects of different amounts of water and N on green pepper yield, water use efficiency (WUE), as well as N use efficiency (NUE) in sub-tropical monsoon climate regions. The optimum combination of water and N inputs was determined for multi-objective optimization through the multiple regression analysis and the combinations of likelihood functions. The pot experiment was conducted during the green pepper growing seasons (May–September) of 2019 and 2020 in a greenhouse at Nanchang, Jiangxi of China that included three water deficit levels, i.e., mild deficit (W1: 95~80%θFC, %θ field capacity simplified as %θFC), moderate deficit (W2: 80~65%θFC), and severe deficit (W3: 65~50%θFC), and four levels of nitrogen application (N_app) rate, i.e., 6.0 (N1), 3.0 (N2), 1.5 (N3), and 0.0 g plant⁻¹ (N4), for a total of twelve treatments (i.e., 3 × 4) with six replications. Results show that water levels have an extremely significant effect (p < 0.01) on green pepper yield and WUE, but no effect on NUE (p > 0.05). N treatments have significant effects on green pepper yield, WUE, and NUE. Meanwhile, the effects of water levels and N treatment interaction on WUE and NUE were extremely significant (p < 0.01), but varied on yield between the two years. The maximum yields (576.26 and 619.00 g plant⁻¹) occurred when the water level and N_app rate were 80~65%θFC and 6.0 g plant⁻¹. While the water level and N_app rate were 80~65%θFC and 3.0 g plant⁻¹, the WUEs and NUEs reached the maximum, which were 20.14 and 17.71 g L⁻¹, 76.54, and 77.73 g⁻¹ in 2019 and 2020. The dualistic and quadric regression equations of irrigation amount and N_app rate indicated that the yield, WUE and NUE cannot reach the maximum at the same time. By establishing a multiobjective optimization model using combinations of likelihood functions, it was concluded that the water level shall be controlled in 80~65%θFC and the N_app rate is 3.78 g plant⁻¹, which can be used as the suitable strategy of water and N management for the maximum comprehensive benefits of yield, WUE, and NUE for green pepper. The obtained optimum combination of water and N inputs can provide a scientific basis for irrigation and fertilization optimization and management in sub-tropical monsoon climate regions. Full article

(This article belongs to the Special Issue Agricultural Water Management in Arid, Semi-Arid and Drought Prone Areas)

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20 pages, 1640 KiB

Open AccessArticle

Environmental and Socioeconomic Determinants of Virtual Water Trade of Grain Products: An Empirical Analysis of South Korea Using Decomposition and Decoupling Model

by Golden Odey, Bashir Adelodun, Seulgi Lee, Khalid Adeola Adeyemi, Gunho Cho and Kyung Sook Choi

Agronomy 2022, 12(12), 3105; https://doi.org/10.3390/agronomy12123105 - 07 Dec 2022

Cited by 2 | Viewed by 1445

Abstract

The world’s sustainable growth is being severely hampered by the inefficient use of water resources. Despite the widely acknowledged importance of trade in global and regional water and food security, societal reliance on local production, as well as international trade, remains inadequately assessed. [...] Read more.

The world’s sustainable growth is being severely hampered by the inefficient use of water resources. Despite the widely acknowledged importance of trade in global and regional water and food security, societal reliance on local production, as well as international trade, remains inadequately assessed. Therefore, using South Korea as a case study, this study fills in this research gap by applying the virtual water concept, the logarithmic mean divisia index (LMDI) method, and the Tapio decoupling model. The virtual water concept was used to estimate South Korea’s net virtual water trade for major grain crops from 1992 to 2017. Then, the LMDI method was utilized to assess the driving factors causing changes in net virtual water trade. Lastly, the Tapio decoupling model was used to investigate the decoupling relationships between economic growth and the driving factors of net virtual water trade. The results showed that South Korea remains a net importer of virtual water flows with respect to grain crops, with an average import of 16,559.24 million m³ over the study period. In addition, the change in net virtual water trade could be attributed to the water intensity effect, product structure effect, economic effect, and population effect. However, water intensity and economic effects were the major decisive factors for decreases and increases in net virtual water trade, respectively, while the population and product structure effects had minor positive influences on the net virtual water trade. Furthermore, water intensity and economic growth showed a strong decoupling in most periods, while the decoupling state between product structure and economic growth was observed as expansive negative decoupling. Likewise, population size and economic growth showed a weak decoupling in most periods. The results reveal South Korea’s status as it concerns the virtual water trade of grain crops, thus providing valuable insights into the sustainability of trade activities for the management of local water resources. Full article

(This article belongs to the Special Issue Agricultural Water Management in Arid, Semi-Arid and Drought Prone Areas)

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15 pages, 1261 KiB

Open AccessFeature PaperArticle

Stem Characteristic Associated with Lodging Resistance of Rice Changes with Varied Alternating Drought and Flooding Stress

by Jinjing Liu, Zhenchang Wang and Xiangping Guo

Agronomy 2022, 12(12), 3070; https://doi.org/10.3390/agronomy12123070 - 04 Dec 2022

Cited by 1 | Viewed by 1911

Abstract

A two-year field experiment was executed to investigate the impact of different controlled irrigation and drainage regimes on the morphological and mechanical traits related to the lodging resistance of rice in Jiangsu province, China. Three irrigation regimes were comprised of conventional flooding practices [...] Read more.

A two-year field experiment was executed to investigate the impact of different controlled irrigation and drainage regimes on the morphological and mechanical traits related to the lodging resistance of rice in Jiangsu province, China. Three irrigation regimes were comprised of conventional flooding practices (CK), controlled irrigation and drainage mode I (CID-1), and controlled irrigation and drainage mode II (CID-2). Results indicated that there was no significant difference in the heights of rice plants under the three irrigation regimes, but the average diameter of CK treatment was 21% higher than that of CID-2 in the 2013 season. Similarly, the value of the section modulus of CK was significantly higher than that of CID-2 (p < 0.05). On the contrary, the length of basal internodes of CK and CID-1 was significantly lower than that of CID-2 in 2013 (p < 0.05). For both seasons, the safety factor against stem breakage (SFs) of CID-2 always had the lowest value under different irrigation regimes, which might be related to the significantly lower values of bending strength of culm at breaking (S) and the bending stress (BS) as well as lower ash content and cellulose content in CID-2 compared with CK and CID-1. Collectively, properly increasing the depth of water levels after heavy rain under the current water-saving mode (CID-1) would not increase the risk of lodging for rice plants, whereas if the water depth after heavy rain was kept higher than 20 cm (CID-2), the SFs would be significantly lower than that of CK, and the rice plants would be much more likely to undergo lodging. Full article

(This article belongs to the Special Issue Agricultural Water Management in Arid, Semi-Arid and Drought Prone Areas)

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21 pages, 2991 KiB

Open AccessArticle

Optimal Effects of Combined Application of Nitrate and Ammonium Nitrogen Fertilizers with a Ratio of 3:1 on Grain Yield and Water Use Efficiency of Maize Sowed in Ridge–Furrow Plastic Film Mulching in Northwest China

by Zhengjun Cui, Yuhong Gao, Lizhuo Guo, Bing Wu, Bin Yan, Yifan Wang, Hongsheng Liu, Gang Li, Yingze Wang and Haidi Wang

Agronomy 2022, 12(12), 2943; https://doi.org/10.3390/agronomy12122943 - 24 Nov 2022

Cited by 3 | Viewed by 1440

Abstract

Improving water use efficiency is essential for the advancement of agricultural production, particularly in arid and semiarid regions. Two-year field experiments were conducted to study the effects of ridge–furrow (RF) and flat planting (FP) plastic film mulching combined with five different nitrogen (N) [...] Read more.

Improving water use efficiency is essential for the advancement of agricultural production, particularly in arid and semiarid regions. Two-year field experiments were conducted to study the effects of ridge–furrow (RF) and flat planting (FP) plastic film mulching combined with five different nitrogen (N) fertilizers, N1 (KNO₃), the nitrate (NO₃⁻)/ammonium (NH₄⁺) mixtures with different pure nitrogen ratios N2 (1:1), N3 (1:3), and N4 (3:1), and the control N5 (urea) on maize dry matter accumulation, soil water content, grain yield, water use efficiency (WUE), and N partial factor productivity. Our results showed that RF and N4 were more efficient than FP for increasing maize grain yield, WUE, and nitrogen partial factor productivity, and there was a significant interaction for cultivation practices × N formulation. RF and 3:1 NO₃⁻/NH₄⁺ significantly increased grain yield by 14.73% and 13.15%, and 20.07% and 24.14% in 2016 and 2017, respectively, compared to FP and nitrate only. RFN4 produced the highest grain yield in 2016 and 2017 due to the highest dry matter accumulation at filling and physiological maturity stage, ear rows per spike, and row grains per row. Over two growing seasons, the WUE and N partial factor productivity under RFN4 were 18.75% and 29.17% more on average than those of other treatments. Therefore, RFN4 is an effective planting system for increasing the simultaneity of grain yield and WUE for maize production in rain-fed agriculture. Full article

(This article belongs to the Special Issue Agricultural Water Management in Arid, Semi-Arid and Drought Prone Areas)

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15 pages, 21659 KiB

Open AccessArticle

Effect of the Release of Gravel Elements on Soil Nutrients and Jujube Fruit Yield under Wet-and-Dry Cycles

by Qiaoling Liu, Yangyang Li, Wangcheng Li, Qikun Su, Bo Ma, Min Mu, Zhenjiang Jia and Guangxing Zhao

Agronomy 2022, 12(11), 2881; https://doi.org/10.3390/agronomy12112881 - 17 Nov 2022

Cited by 3 | Viewed by 1669

Abstract

This study sought to evaluate the potential of mulched gravel to release nutrients in the field by conducting trials with three variations of wet-and-dry cycling of the soil beneath gravel mulch and bare soil. The results revealed that quartz, muscovite, clinochlore, and albite [...] Read more.

This study sought to evaluate the potential of mulched gravel to release nutrients in the field by conducting trials with three variations of wet-and-dry cycling of the soil beneath gravel mulch and bare soil. The results revealed that quartz, muscovite, clinochlore, and albite were the most abundant minerals in the gravels. Throughout the whole wet-and-dry cycle, the total content of 30 elements measured in the gravel-mulched soil was higher than in the bare soil treatment, and the content of the total element rose with increasing wet–dry cycle humidity. The enrichment ratio (B_r) of each element in soil under gravel mulch relative to bare soil was in the sequence Mg > Ca > K > Cr > Na > Mn > V > Zn > Fe > Ti > Si > C > N > B> Co > (B_r = 0) > Pb > Cu > Ga > P > Sn > Sr > Al > Be > Li > Mo > Ni > Se > As > S. Under gravel mulch, the elements impacted by the wet–dry cycle are primarily rock-forming, whereas the elements affected under bare soil are primarily trace elements. The wet-and-dry cycles of gravel affected soil nutrients mainly by increasing soil K, Ca, Na, and Mg contents. The differences in soil K and Ca contents significantly affected the growth of jujube trees and the jujube fruit yield. A dry/wet cycle level of 5 L/d per tree under gravel cover conditions can effectively improve soil nutrients and increase the jujube fruit yield without causing environmental problems. Full article

(This article belongs to the Special Issue Agricultural Water Management in Arid, Semi-Arid and Drought Prone Areas)

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