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Article

Organic Medium Enclosed Trough Growing Technique Improves Abelmoschus esculentus (Okra) Growth, Yield and Some Nutritional Components

by
Tyson T. Mokgalabone
,
Semakaleng Mpai
and
Ashwell R. Ndhlala
*
Green Biotechnologies Research Centre of Excellence, Department of Plant Production, Soil Science and Agricultural Engineering, University of Limpopo, Private Bag X1106, Sovenga 0727, South Africa
*
Author to whom correspondence should be addressed.
Appl. Sci. 2023, 13(9), 5645; https://doi.org/10.3390/app13095645
Submission received: 26 March 2023 / Revised: 21 April 2023 / Accepted: 28 April 2023 / Published: 4 May 2023
(This article belongs to the Special Issue The Pre- and Postharvest Physiology and Molecular Biology of Fruit and Vegetables)
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Abstract

:
Okra (Abelmoschus esculentus) is an important vegetable that has been indigenized in African countries where it is consumed as a relish. There is still, however, a lack of documented cultivation techniques for better yields. An organic medium-enclosed trough (OMET) system is a growing technique that has been developed to reduce water and nutrient seepage during plant production. The study objectives evaluated the effect of OMET on the growth, yield, and nutritional attributes of okra. A complete randomized block design was established to accommodate the two treatments: OMET and non-OMET, in a micro-plot under field conditions. The stem diameter and plant height were recorded weekly during plant growth, and a clear increasing trend in OMET over non-OMET was observed from week 4 of transplantation. The OMET growing technique significantly increased the stem diameter and plant height by 37 and 48%, respectively. When evaluating the yield attributes, a similar trend was observed, where the OMET system significantly increased the yield attributes of okra as follows: biomass by 50%, the number of branches by 50%, the number of pods per plant by 49%, fresh pod weight by 53%, and pod length by 51%, while there was no significant difference in pod diameter width. Non-essential amino acids compounds, including arginine, serine, glycine, aspartate acid, glutamic acid, alanine, and proline and essential amino acids, including histidine, threonine, methionine, lysine, tyrosine, leucine, phenylalanine, asparagine and glutamine, were highly maintained in OMET compared to non-OMET. OMET enhanced the upregulation of proteins, Ca, Mg, K, Mn, Na, P and Zn elemental nutrients in the disposal of less irrigation water than non-OMET. This growing technique could be recommended for small-scale and commercial farming to improve the okra production of nutrition.

1. Introduction

In response to changes in the climate which result in prolonged drought and extremely hot temperatures, there is immense pressure on researchers to develop strategies for crop production that are aimed at improving crop adaptation [1]. The organic medium-enclosed trough (OMET) is a growing technique that has been developed to reduce water and nutrient seepage during plant growth [2]. The OMET system uses polyethylene plastic to enclose a specific growth medium in a sandwich manner in such a way that no water or nutrients would escape the plant’s rooting zone (40 cm depth) [2]. Black polyethylene plastic mulch is the standard plastic mulch used in crop production. Worldwide, the increased usage of polyethylene mulch is due to its benefits when applied in the field; for example, it increases soil temperature, reduces weed problems, enhances moisture conservation, increases crop yields and leads to the more efficient use of soil nutrients [2].
Therefore, some of its advantages are similar to plastic mulching which reduces evaporation and creates a modified microclimate for the rooting area [2,3]. Research about such sustainable growing techniques contributes to the resolution of food and nutrition insecurity as the world’s population has been estimated to reach 9.7 billion in the year 2050 [4]. Food insecurity is associated with the consumption of an unbalanced diet consisting of primary macro and micronutrients [5]. Macro-nutrients contain nutrients that are required in large quantities (greater than 1 mL) for daily body functioning in comparison to their counterpart: micronutrients [6,7,8,9]. The consumption of any immoderate contents of these nutrients may lead to health undernourishment [5]. Therefore, food security can be improved by the consumption of diets that are rich in fruits and vegetables, which are known to be rich sources of nutrients. Furthermore, macro-nutrients such as carbohydrates, amino acids, fatty acids, and organic acids are involved in growth and development, respiration and photosynthesis, and hormone and protein synthesis in plants [10].
Research has demonstrated the impact of consuming indigenous fruits and vegetables as a potential weapon against malnutrition or diet-related diseases. Okra (Abelmoschus esculentus (L.) Moench), belonging to a Malvaceae botanical family, has been indigenized in African countries, where it is consumed as a relish in daily meals. The consumption of 1 cup of okra pods contains dietary fiber (3.2 g), carbohydrate (91.2 g), protein (2 g) and vitamin C (21.1 mg) [11]. In addition, okra contains noticeable amounts of amino-acid and mineral elements (iron, potassium, and calcium) [12]. Hypothetically, okra grown on the OMET growing technique can be a good source of nutrients to alleviate hidden hunger and malnutrition. Okra is a tropical to subtropical crop which is negatively affected by droughts [13]. In response to this challenge, extensive research has focused on cropping systems such as mulching with different materials to reduce the evaporation of irrigation water [14,15,16].
Yet, reports on the enhancement of the nutritional composition of okra using a sustainable cultivation practice in the disposal of lower irrigations are relatively few. In this study, okra was grown on the OMET technique to investigate the rate of improvement in the yield and possible nutrient enhancement. OMET growing techniques are a new cropping technique that should be evaluated for its efficacy in improving the nutritional composition before being recommended to the farming industry. In addition, there is also no comprehensive literature regarding the characteristics of the nutritional composition produced from the leaves and pods grown under the OMET system. Therefore, the objective of this study was based on the evaluation of the OMET growth technique on growth, yield and some nutritional compositions in okra pods and leaves.

2. Materials and Methods

2.1. Growing Conditions, Treatments and Experimental Design

The preliminary experiment was conducted on growth and yield attributes in the year 2020 under greenhouse and micro-plot conditions, and the micro-plot resulted in higher yields. The experiment was then repeated under an open field in a micro-plot condition at the Green Biotechnologies Research Centre of Excellence (GBRCE), University of Limpopo, South Africa (23°53″10′ S, 29°44″15′ E) from 1 September to 12 December 2021. The area was characterized by hot-dry weather with day/night temperatures ranging between 28 and 38 °C and a precipitation mean average of less than 500 mm. The OMET versus non-OMET trials were established following a randomized complete block design to accommodate 12 samples per treatment, which accounted for a population size of 36 (n = 36) and was replicated three times.

2.2. Plant Material, and Establishment of OMET Experimental Trial

The seeds of okra (Starke Ayres Pty Ltd., Cape Town, South Africa) and the spineless cultivar Clemson (a main season standard okra with very wide adaptability) of moderately ribbed and medium green straight spineless pods were sown in a disinfected 200 polystyrene seedling trays filled with a Hygromix® growing medium of up to four weeks post-emergence. The OMET system was prepared by demarcating an area of 200 m by 200 m space, whereby an underlying plastic was set underneath at a 40 cm height down the surface to cover a 30 cm growing plastic pot filled with the growth medium. Before transplanting, the plastic was carefully closed, and holes were created on top of the plastic with a diameter of 90 mm to allow a seedling intra-spacing of 40 cm × 40 cm.
The growth medium enclosed in this trough consisted of a Hygromix® growing medium, pasteurized (300 °C for 45 min) loam soil and fine sand at a 2:1:1 ratio as described by Mpai et al. [17]. The non-OMET system was prepared by planting the plants in 30 cm pots with the same spacing but without the use of any plastic.

2.3. Determination of Growth and Yield Components

After initiating the experiment, growth parameters, including stem diameter and plant height, were measured once per week during the vegetative maturity stage (week 1 to week 8), even though the experiment was carried out for 15 weeks. This is because plants focus on improving their growth parameters during the vegetative maturity stage. The plant height was measured with a meter stick ruler in centimeters, and the measurements were taken from 10 mm above the soil surface to the highest point of the stem apex. The stem diameter was measured at 30 mm above the soil surface using a digital Vernier caliper (KTV150-major Tech), and the results were expressed in mm. The experiment ran up to 15 weeks (110 days) when yield attributes, including the number of branches per plant, the number of pods per plant, fresh pods weight per plant in grams, and pod length and pod diameter in mm, were recorded.
The leaf and pod samples were oven-dried at 50 °C for 48 h and then ground into a fine powder before being subjected to the analysis of amino acids, protein and mineral nutrients.

2.4. Determination of Irrigation Water in Growth Medium

Irrigation water was calculated based on the sum of the total volume per treatment. Three marked pots were evaluated for moisture status using a moisture tester (Xlus, model: 10.43 × 1.18 × 2.17 inches, South Africa), and applications of 250 mL were irrigated when the moisture status was ‘dry’. Therefore, the frequency of irrigation needed and irrigation volume constituted the overall irrigation of water over time.

2.5. Determination of Amino Acids Contents

The dried leaf and pod samples were prepared for amino acid determination using an Amino Acid Analysis Application Solution (AccQ_Tag) derivatization kit following the methods described in Mpai et al. [18]. The analysis of individual amino acids, including Arginine (Arg), Serine (Ser), Glycine (Gly), Aspartate (Asp), Glutamate (Glu), Alanine (Ala), Proline (Pro), Histidine (His), Threonine (Thr), Methionine (Met), Lysine (Lys), Tyrosine (Tyr), Leucine (Leu), Phenylalanine (Phe), Asparagine (Asn) and Glutamine (Gln) was performed using the ultra-performance liquid chromatography analysis following the methods described by Mpai et al. [18].

2.6. Determination of Elemental Nutrients

A total of 10 g of dried leaf and pod material were digested in 40 mL of 4% nitric acid (HNO3), followed by placing the container on a vortex to allow for the complete wetting of the mixture. The materials were magnetically stirred, and thereafter incubated in a 95 °C water bath for 90 min, before being allowed to cool down at room temperature, filtered, and decanted into 50 mL tubes which were covered with foil, and then selected nutrient elements were analyzed using inductively coupled plasma optical emission spectrometry (ICPE-9000). The conditions of the analysis and the development of the mineral standard curve were similar to those reported by Mafokoane et al. [19].

2.7. Determination of Protein

The micro Kjeldahl method was used for the determination of proteins. Two grams (2 g) of each sample of the dried leaf and pod material was mixed with 10 mL of concentrated sulphuric acid (H2SO4) in a heating tube. One tablet of selenium catalyst was added to the tube, and the mixture was heated inside a fume cupboard. The digest was transferred into a 100 mL volumetric flask made up of distilled water. A total of 10 mL portions of the digest were mixed with an equal volume of 45% NaOH solution and poured into a Kjeldahl distillation apparatus. The mixture was distilled, and the distillate was collected into a 4% boric acid solution containing 3 drops of the indicator.
A total of 50 mL of distillate was collected and titrated as well. The sample was duplicated, and the average value was taken. The nitrogen content was calculated and converted to the percentage protein by using a protein conversion factor of 6.25 [19].

2.8. Statistical Analysis

Data were subjected to statistical analysis using GenStat 18th version statistical package (VSN International, Hempstead, UK). The mean separation for significant treatments was achieved using a t-test at a significance level of 5%.

3. Results and Discussion

3.1. Effect of OMET Growth Technique on Growth and Yield Components in Okra

The results for the growth parameters were recorded during the vegetative stage of the plant (from week 1 up to week 8), while yield components were recorded at week 15 (110 days after transplanting), as presented in Figure 1, Figure 2 and Figure 3 and Table 1. There was a significant (p ≤ 0.05) difference between the samples grown under the OMET and non-OMET growing techniques on the stem diameter and the plant height of the studied okra plant, as shown in Figure 1.
The OMET-grown okra resulted in a gradual increase in the stem diameter from week three, which further showed a two-fold thickness when compared to non-OMET-grown samples in week 8 (Figure 2). The stem diameter is an important agronomic trait for increasing okra’s yield potential [20,21,22]. According to Eshiet and Brisibe, [22] thin stems were not desirable because they were prone to lodging and a lower pod yield. The variation in stem diameter among the treatments might be related to the fact that stems contributed to a higher plant height for the capture of sunlight for the photosynthesis process [23]. The OMET growing technique significantly (p ≤ 0.05) improved the plant height compared to the non-OMET systems, as shown in Figure 3. There was a gradual increase in plant height which was two-fold taller than the non-OMET. Reddy et al. [24] validated how taller plants are crucial for accommodating a greater number of pods on the main stem, and this has a direct effect on the pod yield in okra. The ability of the OMET system to preserve water and nutrients, which resulted in the moderate availability of water and good nutrient solubility and absorption by the plants, was likely the cause of the growing technique’s effectiveness in increasing stem diameter and plant height [25].
The OMET growing technique significantly (p ≤ 0.05) improved the yield components of okra, as shown in Figure 4 and Table 1. At harvest, the OMET growing technique significantly increased the yield attributes as follows: the number of branches by 50%, the number of pods per plant by 49%, fresh pod weight by 53%, and pod length by 68% (Table 1). The pod diameter was unaffected by the OMET growing condition. The increase in the okra pod samples grown under the OMET growing condition may be attributed to the greater number of branches, stem diameter and plant height. These results support those of dos Santos-Fariasa et al. [26] and Shi et al. [27], which suggests that the fresh pod yield in okra is a complex character depending on component traits such as the number of branches, stem diameter, plant height, root length, fresh pod length and width, the number of seeds per plant and number of pods per plant. This study also supported the findings of Kumar and Reddy [28] and showed that branching capacity in okra had a direct effect on the pod yield and phenotypic traits associated with yield response, which are useful for improving the yield potential of okra in climate-smart agriculture. The results obtained in this study were also supported by those of Jha et al. [29], who reported that the use of plastic mulch significantly influenced the plant height, whereby okra yield was highest (8104 kg/ha) under silver plastic mulch. Plastic mulch enhanced the growth parameters such as the canopy length, plant height, leaf number, stem diameter, leaf length, and yield attributes of okra [14,15]. This may be attributed to the fact that plastic mulches can suppress annual weeds and offer other important benefits, such as organic matter, nutrients, moisture conservation, soil protection, and the moderation of soil temperature.

3.2. Effects of OMET Technique on Irrigation Water Quantity

The OMET growing technique significantly affected the amount of irrigation water as more water was used to irrigate the non-OMET-grown okra (p ≤ 0.05). The cumulative irrigation water increased throughout the weeks, as shown in Figure 5 demonstrating that the OMET system improved water retention. Hence, it enhanced growth and yield in the disposal of lower irrigation water. The results may be attributed to the fact that the OMET growing technique was practiced under an enclosed trough which eliminated water seepage, thus advocating for climate-smart agriculture. The results were similar to those reported by Ferreira [2], whereby the OMET growing technique improved the growth and yield of Swiss chard under the disposal of lower irrigation. The top plastic of the OMET system reduced the evaporation rate.

3.3. Effect of OMET Growing Technique on Amino Acid Composition of Okra Pods and Leaves

The effect of OMET growth technique significantly (p ≤ 0.05) affected the nutritional levels of okra. A total of 16 amino acid compounds were quantified in okra pods and leaves grown under the OMET and non-OMET growing techniques. The essential amino acid compounds included: Arg, Ser, Gly, Asp, Glu, Ala, and Pro and are illustrated in Figure 6A,B. On the other hand, non-essential amino acids such as His, Thr, Met, Lys, Tyr, Leu, Phe, Asn and Gln were quantified, as shown in Figure 7A,B.
Quantitatively, all essential amino acid compounds were 79% and 74%, higher than non-essential amino acids in okra pods and leaves when grown under OMET and non-OMET conditions, respectively. Glutamine (Glu) and aspartate (Asp) amino acids were the most predominant compounds in both pods and leaves of okra when grown under OMET and non-OMET growing conditions. The Glu contents ranged between 1.00 and 1.11 mg/kg in the pods and between 2.06 and 2.59 mg/kg in the leaves, respectively, in non-OMET to OMET, while Asp content ranged between 3.64 and 4.04 mg/kg and 2.38 and 2.73 mg/kg, respectively. Overall, the trend of the essential amino acids in okra pods grown under the OMET growing technique exhibited higher contents of Arg (1.06 mg/kg), Ser (0.51 mg/kg), Gly (0.52 mg/kg), Asp (1.11 mg/kg) and Glu (4.04 mg/kg), than those grown under a non-OMET growing technique in both okra pods and leaves (Figure 6A,B). However, a non-significant effect between OMET and the non-OMET growing technique was observed for Ala and Pro amino acid compounds in okra pods. All the quantified non-essential amino acids, which included Arg, Ser, Gly, Glu, Ala, Pro and Asp, were higher in OMET-grown leaves samples, as shown in Figure 7A,B. On the other hand, essential amino acids, including His, Lys, Met, Leu, Tyr and Phe, were higher in pods of okra grown under OMET (Figure 7A,B). Yet, Thr (0.38 mg/kg), Val (0.49 mg/kg), and ILe (0.36 mg/kg) were unaffected by the OMET growing technique. Okra leaves grown under the OMET growing technique exhibited higher contents of His, Tyr, Lys, Thr, Met, Val, ILe, Leu and Phe in comparison to non-OMET (Figure 7A,B).
In this study, the growth of okra under the OMET growth technique affected the nutritional composition on the basis of protein basic units: amino acids. It was interesting to observe that Glu and Asp were predominant amino acids in okra which were confirmed by a study reported by Sami et al. [30]. Glu and Asp were found to predominate soybean genotypes which had the highest preferred sensory score concerning good taste [20,31]. In addition, the OMET growth technique directly brought changes to primary factors such as soil temperature, light, water availability and evapotranspiration which affected amino acid nutritional composition. Amino acid accumulation was directly proportional to the growth of the environment temperature [32,33]. A study reported by Viana et al. [32] revealed that Asp increased linearly with temperature, which was a fact that can be proven by our results. Amino acids, including Ile, Met, Phe, Ala, Glu, and Pro, tended to increase with the temperature up to a certain threshold which, if it is surpassed, would lead to a drop in their contents [33]. For example, Pro showed a decrease at 22 °C, followed by Phe at 21 °C, Glu at 20 °C, Met at 19 °C and Ile at 16 °C [33].
Such evidence accounts for results obtained in this study which demonstrated the OMET growing technique to maintain higher amino acid contents than its counterparts. The OMET could have modified the root surface temperature to be more favorable than in non-OMET, whereby, the OMET condition could have reduced trans-evaporation, irrigation intervals, and water seepage and acted as a shade for the rooting zone. On the other hand, amino acids are known as defense mechanisms against abiotic conditions. The Pro is well known for its potential to regulate osmotic adjustment substances in response to cold resistance [10]. However, the content of Pro was moderately upregulated in the OMET growth technique and thus suggested the optimum growth temperature for okra production. This was further authenticated by the maintained higher contents of Glu: a precursor for Pro, which becomes depleted in cold environments. In limited water availability, reports by Khan et al. [10], demonstrated the translocation and exudation of amino acid compounds such as Pro, Ser, and Ala, from the shoot down to the roots which likely affected the soil’s water presence.

3.4. Effect of OMET Growing Technique on Elemental Nutrient Content in Okra Leaves and Pods

The protein content was significantly affected by the OMET growth technique in okra pods and leaves. Hence, samples grown under OMET contained higher protein levels in comparison to non-OMET. Furthermore, the levels of protein in the leaves were more than that detected in the pods, as shown in Table 2.
Evaluating the effect of the OMET growing technique showed a significant (p ≤ 0.05) impact on the mineral composition of okra. The results showed that elemental nutrients, including calcium (Ca), potassium (K), magnesium (Mg) and phosphorus (P), were predominant attributes for the nutritional status of okra leaves and pods. The highest content of Ca (237 mg/kg), Mg (163 mg/kg), K (110 mg/kg), and P (6.6 mg/kg) was recorded in OMET leaves, whilst the lowest contents for Ca (49 mg/kg), Mg (36.6 mg/kg) and P (4.8 mg/kg) were recorded in okra non-OMET pods, except for K (110 mg/kg) which recorded the lowest content in the leaves of non-OMET (Table 2). Thus, this suggested the great impact of OMET on enhancing the macronutrient contents. These macronutrients (calcium, potassium, and magnesium) were found in okra, and they contributed 8%, 9% and 14%, respectively, of the daily required nutritional value [34]. Calcium is well known for its function in maintaining bone and teeth health but is also critical to cell signaling, blood clotting, muscle contraction, and nerve functions. Dietary potassium intake has been demonstrated to significantly lower blood pressure in a dose-responsive manner in both hypertensive and normotensive individuals in observational studies [35]
Micro elemental nutrients, including (in descending order) selenium (Se), sodium (Na), zinc (Zn), iron (Fe), and molybdenum (Mn), were studied, and there were significant (p ≤ 0.05) differences among the studied samples. The results pointed out OMET-grown pods and leaves as exhibiting similar and the highest contents of Se (12.2 and 12.8 mg/kg) and Na (6.2 and 6.8 mg/kg), which were slightly higher than Se (11.8 mg/kg) and two-fold higher than the Na (3.7 mg/kg) content found in non-OMET leaves. OMET-grown leaves maintained the highest contents of Zn, Fe, and Mn, which were recorded to be up to three-fold, six-fold and two-fold higher than the mean values presented in non-OMET pods, as shown in Table 2. In this study, nutritional elements (in descending order): Ca, K, P, Mg, and NA were predominant in okra leaves and pods, irrespective of the growing technique (OMET). These results were similar to those reported by Maseko et al. [35], who stated that severe drought conditions of up to 30% water application increased Ca and Mg in Amaranthus cruentus species. The same study reported an increase in the contents of Zn, Na, P, and K with 60% of water availability. According to Kanda et al. [36], moderate deficit irrigation on cowpeas increased the carbohydrate and fiber content due to water availability around the root surface. These reports accounted for the impacts of water availability on okra nutrient availability. On the other hand, mulching using plant materials such as increased N, P, K, Ca and Mg nutrient contents in okra leaves [14]. Therefore, different cropping systems affected the nutritional composition. According to Fawibe et al. [15], plastic mulch under the Elaeis guineensis (Jacq.) canopy reduced to ash, crude protein, and carbohydrates compared to the canopy without mulching. In addition, different mulching materials, including Pueraria phaseoloides, Mucuna pruriens, Pennisetum pur-pureum, and Panicum maximum impacted the mineral element composition such that nitrogen, phosphorus, potassium, calcium and magnesium all increased in comparison to the no-mulch treatment [15]. In this study, the OMET growing technique maintained higher contents of the minerals than in non-OMET. In a non-OMET condition, samples were often under dry conditions caused by aeration, water seepage and trans-evaporation, which often led to moderate drought conditions. These drought conditions were reported to reduce element nutrients such as the proteins Zn, Fe, P and N [37]. Furthermore, it is possible to suggest that the consumption of approximately 50 g of okra pods and 25 g of leaves grown under OMET and cultivated in micro-plot conditions could ensure the 1000 mg for adults’ adequate intake of Ca, according to the National Academy of Medicine [38].

4. Conclusions

This study validates the use of the OMET growing technique to improve growth and yield attributes while improving the nutritional composition of okra vegetables. The essential amino acids compounds, including arginine, serine, glycine, aspartate acid, glutamic acid, alanine, and proline and non-essential amino acids, including histidine, threonine, methionine, lysine, tyrosine, leucine, phenylalanine, asparagine and glutamine were highly maintained in OMET compared to non-OMET. OMET enhanced the upregulation of proteins and macro and micro elemental nutrients in the disposal of less irrigation water than non-OMET.
It was observed that the OMET growing technique significantly enhanced the accumulation of all the tested essential amino acids in both the leaves and pods, with Phe and Lys (1.53 and 0.70 mg/kg) being the highest in the leaves and pods, respectively. The non-essential amino acid composition was improved by the OMET growing technique in both the leaves and pod, with Glu (2.73 and 4.05 mg/kg) being the highest. This growing technique is recommended for small-scale and commercial farming to improve the okra production of nutrition.

Author Contributions

T.T.M.: Experimentation, data gathering and first draft write-up, S.M.: Conceptualization and data analysis. A.R.N.: Funding acquisition, Conceptualization, and data analysis. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the National Research Foundation (NRF, Pretoria) (Grant number 12612) and the Department of Science and Innovations (DSI) of the South African Government (Grant number DSI/CON C2235/2021).

Informed Consent Statement

Animals and humans were not used in this study and therefore informed consent was not applicable.

Data Availability Statement

The research data are available upon request.

Acknowledgments

The authors would like to thank Ndivhuwo Mutshekwa for technical assistance.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. Freshly harvested okra plants (A) OMET and (B) non-OMET at day 110 after transplant.
Figure 1. Freshly harvested okra plants (A) OMET and (B) non-OMET at day 110 after transplant.
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Figure 2. Effect of OMET growth technique on the stem diameter of okra during vegetative stage (n = 12 per treatment).
Figure 2. Effect of OMET growth technique on the stem diameter of okra during vegetative stage (n = 12 per treatment).
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Figure 3. Effect of OMET growing technique on the plant height of okra during vegetative stage (n = 12 per treatment).
Figure 3. Effect of OMET growing technique on the plant height of okra during vegetative stage (n = 12 per treatment).
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Figure 4. Freshly harvested okra pods (A) OMET and (B) non-OMET grown at day 110 after transplant.
Figure 4. Freshly harvested okra pods (A) OMET and (B) non-OMET grown at day 110 after transplant.
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Figure 5. Effect of OMET growing condition on cumulative irrigation water during Okra vegetative growth.
Figure 5. Effect of OMET growing condition on cumulative irrigation water during Okra vegetative growth.
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Figure 6. Total contents of essential amino acids in okra leaves (A) and pods (B), respectively. Significantly different at * p ≤ 0.05 while ns = not significant. Mean separation was conducted using a t-test. Arg = Arginine, Ser = Serine, Gly = Glycine, Asp = Aspartate, Glu-glutamate, Ala = Alinine and Pro = Proline.
Figure 6. Total contents of essential amino acids in okra leaves (A) and pods (B), respectively. Significantly different at * p ≤ 0.05 while ns = not significant. Mean separation was conducted using a t-test. Arg = Arginine, Ser = Serine, Gly = Glycine, Asp = Aspartate, Glu-glutamate, Ala = Alinine and Pro = Proline.
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Figure 7. Total contents of non-essential amino acids in okra leaves (A) and pods (B), respectively. Significantly different at * p ≤ 0.05 while ns = not significant. Mean separation was conducted using a t-test. His = Histidine, Thr = Threonine, Lys = Lysine, Tyr = Tyrptophan, Met = Methionine, Val = Valine, Leu = Leucine, Phe = Phenylalanine.
Figure 7. Total contents of non-essential amino acids in okra leaves (A) and pods (B), respectively. Significantly different at * p ≤ 0.05 while ns = not significant. Mean separation was conducted using a t-test. His = Histidine, Thr = Threonine, Lys = Lysine, Tyr = Tyrptophan, Met = Methionine, Val = Valine, Leu = Leucine, Phe = Phenylalanine.
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Table
Table 1. Effect of OMET system growing technique on some yield components in okra.
Table 1. Effect of OMET system growing technique on some yield components in okra.
Number of BranchesNumber of Pods per PlantFresh Pod Weight (g)Pod Length (mm)Pod Diameter (mm)
OMET8.00 ± 0.24 ** 16.00 ± 0.40 ** 43.64 ± 2.02 * 172.43 ± 6.2 **27.26 ± 0.8 ns
Non-OMET4.00 ± 0.18 8.00 ± 0.29 20.30 ± 0.87 130.18 ± 2.8 28.65 ± 0.8 ns
F-Statistics1.231 **0.193 **2.078 *4.569 **1.886 ns
Values are expressed as the mean ± standard error (n = 12). For all the values within a column, different letter superscripts are significantly different at ns = not significant, * p ≤ 0.05, ** p ≤ 0.01.
Table
Table 2. Effect of OMET growing technique on elemental nutrient content in okra leaves and pods.
Table 2. Effect of OMET growing technique on elemental nutrient content in okra leaves and pods.
ParameterSamplesOMETNon-OMET
Proteins (%)Leaves3.1 ± 0.22 *2.70 ± 0.72
Pods2.4 ± 0.40 *2.01 ± 0.31
Elemental nutrients (mg/kg)
CaLeaves237.0 ± 9.91 *129.0 ± 5.63
Pods55.6 ± 3.44 ns49.0 ±3.11
MgLeaves163.0 ± 7.66 *110.0 ± 4.92
Pods40.3 ± 2.87 *36.6 ± 1.63
KLeaves110.0 ± 6.23 *53.1 ± 4.47
Pods170.0 ± 8.11 *156.0 ± 6.80
FeLeaves3.8 ± 0.80 *6.1 ± 1.31
Pods1.5 ± 0.34 ns1.6 ± 0.33
MnLeaves2.4 ± 0.41 ns1.9 ± 0.11
Pods1.0 ± 0.22 ns1.0 ± 0.22
NaLeaves6.8 ± 1.70 *3.7 ± 0.38
Pods6.2 ± 2.82 ns5.5 ± 1.19
PLeaves6.6 ± 1.21 *5.9 ± 0.92
Pods4.8 ± 1.63 ns4.8 ± 1.64
SeLeaves12.8 ± 2.73 ns11.8 ± 2.11
Pods12.3 ± 4.13 ns12.2 ± 3.93
ZnLeaves6.9 ± 1.32 ns6.7 ± 1.17
Pods2.9 ± 0.70 ns2.6 ± 0.52
Values are expressed as the mean ± standard error. For all the values within a row, * superscript represents significantly different while ns = not significant (p ≤ 0.05).
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Mokgalabone, T.T.; Mpai, S.; Ndhlala, A.R. Organic Medium Enclosed Trough Growing Technique Improves Abelmoschus esculentus (Okra) Growth, Yield and Some Nutritional Components. Appl. Sci. 2023, 13, 5645. https://doi.org/10.3390/app13095645

AMA Style

Mokgalabone TT, Mpai S, Ndhlala AR. Organic Medium Enclosed Trough Growing Technique Improves Abelmoschus esculentus (Okra) Growth, Yield and Some Nutritional Components. Applied Sciences. 2023; 13(9):5645. https://doi.org/10.3390/app13095645

Chicago/Turabian Style

Mokgalabone, Tyson T., Semakaleng Mpai, and Ashwell R. Ndhlala. 2023. "Organic Medium Enclosed Trough Growing Technique Improves Abelmoschus esculentus (Okra) Growth, Yield and Some Nutritional Components" Applied Sciences 13, no. 9: 5645. https://doi.org/10.3390/app13095645

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