Crithmum maritimum L. Biomass Production in Mediterranean Environment

Abstract

Crithmum maritimum L., similarly to other halophytes, could be an essential plant in marginal areas of the Mediterranean basin; it can grow with low inputs and thus tackle environmental risks of soil erosion and biodiversity caused by climate change. The leaves can be used as food because of their good chemical and nutritional parameters, as a cosmetic product and in medicine. The three treatments studied in the context of organic farming (control without input, irrigated with irrigation water only and fertigated with organic liquid fertilizer diluted in irrigation water) have provided encouraging results; in fact, regardless of the meteorological trend of the two years of experimentation, the production of aerial biomass remained at satisfactory levels and in particular, in the year following the transplantation, the production saw a significant increase in the treatments tested with low inputs (irrigated and fertigated). So, in the second year of production, a low nitrogen input with fertigation induced the plants to produce significantly more leaf biomass than the irrigated treatment, which in turn was significantly superior to the control. The production results for dry biomass are encouraging and may promote the spread of the local germplasm of this species around the Conero Park, where it is being studied to produce fermented vegetable conserves.

1. Introduction

Sea fennel (Crithmum maritimum Linnaeus 1753) is a perennial halophyte species typical of coastal ecosystems belonging to the Apiaceae family [1].

Halophytes represent approximately 1% of all worldwide land plants, including nearly 2500 species [2]. They are commonly found in coastlines worldwide where they are subjected to several abiotic stresses, including exposure to fluctuating soil salinity or temporal droughts [2]. In a global scenario where agricultural land is increasingly limited due to salinization and desertification processes, together with a shortage of freshwater, halophytes have been highlighted as an interesting crop with potential for exploitation in saline or salinized soils where other species are not able to grow [3]. Most conventional crops are glycophytes, whose growth is affected by salt excess, impairing their growth by affecting nutrient and water uptake [4].

In the Mediterranean basin, it is necessary to identify the most promising species in terms of adaptation capacity, required inputs, and yields [5,6] because this area has a higher risk of damage for agriculture due to climate change; in fact, there is environmental vulnerability due to the effects of climate change, including water scarcity, soil erosion, desertification and loss of biodiversity [7].

Agricultural abandonment can have both negative and positive consequences; for instance, while abandonment of certain areas has increased carbon sequestration and habitats for large mammals as a positive consequence, in other areas, this can cause a considerable loss in cultural heritage landscapes [8].

Trends in Europe such as land abandonment in rural areas, biodiversity loss and climate change have reinvigorated debates about the need to preserve land for rural development, nature conservation or carbon sequestration, all while avoiding competition with food production [9,10]. In response to the competition for land, making use of marginal land is often advocated as a solution to achieve these bioenergy, biodiversity or carbon sequestration goals without impacting food production [11,12]. Sustainable agricultural production from marginal lands can be attained by adopting an integrated natural resource management approach that includes all aspects of soil, water, plants and climate to find long-term sustainable solutions for the marginal lands and waters [13].

Halophytes have developed morphological, physiological and biochemical adaptations to tolerate excess salt and reproduce under high saline conditions of at least 200 mM NaCl [14,15]; they can be used for several commercial purposes, such as vegetables [16,17], in medicine [18,19], ornamental landscaping [17,20], environmental protection and wildlife support [21,22]. Among the halophytes, sea fennel has been proposed as a potential crop for biosaline agriculture [23,24,25]; it can be used for the development of sustainable agroecosystems that require fewer inputs than conventional ecosystems [26] and that provide multiple services that can address climate change problems and tackle problems related to certain poor agricultural practices, such as the preference for cultivation of annuals over multiannuals, use of weak drainage systems and inefficient water use management [27,28,29], beyond implementation of green infrastructures that can limit some negative impacts of urban environments on their inhabitants [30] and be used as a “cash crop” due to its high economic potential [23] or, more recently, as an “emergingvegetable crop” [31]. In parallel with the environmental benefits, C. maritimum L. has several usage areas, such as in food, medicine and cosmetics, because of its nutrients [32], phytochemicals [33,34] and essential oils [35].

Given the recent interest in the exploitation of this halophyte for human consumption and as a source of bioactive compounds in the nutraceutical industry in Central Italy [36] and the growing interest of the European Union with the funding of a project on innovative sustainable organic sea fennel-based cropping systems to boost agrobiodiversity, profitability, circularity and resilience to climate changes in Mediterranean small farms, the present study aimed to enhance the production of Crithmum maritimum L. in the area of Conero Regional Natural Park. In fact, our purpose was to implement the agronomic results in organic cropping systems previously obtained in Zenobi et al., 2021 [26] where preliminary results are present due to the total absence of information in the scientific literature on C. maritimum L. cultivated in hilly cropping systems; furthermore, the first year of data refers to the year of planting the crop, while in the present work, the data are for a species already established in a cropping system and under full production.

2. Materials and Methods

2.1. Experimental Site

The experimental site was located at an organic farm called “Paccasassi del Conero”, located in Camerano, Italy (43°53′ N, 13°55′ E), at an altitude of 100 m above sea level and a slope gradient of 10% on silty-clay soil classified as Calcaric Gleyic Cambisol [37]. The weather data were provided by ASSAM (Agenzia Servizi al Settore Agroalimentare delle Marche, Osimo Stazione, Ancona, Italy). The climate of the site is Mediterranean, corresponding to the type Csfa with no dry season and hot summer (Koppen–Geiger Map classification (1980–2016), https://people.eng.unimelb.edu.au/mpeel (accessed on 25 January 2022).

Soil characterization was performed immediately before transplanting (

Table 1. Soil properties in the 0–30 cm layer in the experimental plots in 2020–2021.

Soil Properties	Values
Sand (g kg−1)	129 ± 18
Silt (g kg−1)	449 ± 17
Clay (g kg−1)	422 ± 20
Soil organic matter (g kg−1)	11.0 ± 2.1
Total nitrogen (g kg−1)	0.8 ± 0.1
pH	8.1 ± 0.9
Bulk density (Mg m−3)	1.40 ± 0.4
Volumetric soil water content (%):
Field capacity	44.0 ± 1.2
Permanent wilting point	18.0 ± 2.4
Total available water	26.0 ± 1.8

) using a total of three soil samples that were taken from the depth of 0–30 cm.

2.2. Experimental Site

The experimental site covered about 400 m² and was laid out in a randomized block design with three replicates. Three treatments were compared: control rainfed treatment without fertilization (CT), irrigation with water (IR) and fertigation with liquid fertilizer and water (FR) (Figure 1).

Each replication had a size of 120 m², with each plot consisting of 40 m²; the planting pattern adopted was 0.45 m × 0.45 m, with a density of 9.8 plants m⁻², corresponding to 98,000 plants ha⁻¹.

This plant density ensures adequate inter- and intra-row spacing to maximize the leaf area exposed to the sun [23]; in fact, C. maritimum L. is a heliophilous plant, and because of its tendency to branch and its laterally and deeply expanded root system, the plant must have enough space to develop. So, each plot contained 200 plants spread in four rows, of which the two central rows were the ones sampled in three test areas.

The dates of all agronomic practices are reported in

Table 2. Agronomic management practices adopted during the two-year experimental period.

Agro-Technique	2020	2021
Ploughing (40 cm)	13 October 2019
Harrowing and seed bed preparation	25 October 2019
Mulching with sheeting	3 February 2020
Transplantation	17 February 2020
Manual weed control		16 March 2021
Transplantation failure plants		26 March 2021
Fertigation and irrigation	15 March 2020; 10 April 2020; 5 May 2020; 18 May 2020; 26 May 2020	29 March 2021; 5 May 2021; 19 May 2021
Harvesting	29–31 July 2020	29–30 June 2021

.

2.2.1. Seedling Collection and Transplantation

The techniques of the first year, with seed bed preparation and mulching, were described in detail in Zenobi et al., 2021 [26]. At the end of summer 2020, we counted the diseased or non-surviving plants in the post-harvest period, so as to plan sowing in plateau pots to restore them for the year 2021 with the same plant density as that used in 2020. In October 2020, the seeds, collected on the Adriatic coast, in the Marche region of Conero Regional Natural Park, were sown in plateau pots within a substratum consisting of a mix of topsoil and peat (50:50 ratio). The plateau pot was placed in a greenhouse with a convertible roof; this structure made it possible both to maintain an average temperature of 15 °C for the whole winter season and to easily provide plants with the radiation without them being shaded by surrounding structures or vegetation. After the third week of March, we transplanted the plants germinated in plateau pots when they had three or four leaves, and we put them in at the same spots of the failed plants. Plants of C. maritimum L. that had already been in the field for over one year of experimental site research did not receive any phytosanitary treatment.

2.2.2. Irrigation and Fertigation

Irrigation system consisted of control head, pumping and filtration unit and was installed with the tubes positioned on the ground, below the mulching sheet, so that the water was diffused by means of low-pressure sprays directly next to the plants and their root systems, so that it could be easily absorbed, thus avoiding irrigation with large volumes of water and maintaining low-pressure use. The system was connected to a central programming unit (Rain Bird © ESP-RZ/RZXe, Aix-en-Provence, France), from which watering operations could be automated. The controller was in turn connected to a sensor in the field that detected the humidity at a given depth. The primary line of the tubes reached the connection point, from which the secondary supply lines diverged via the valve unit. The system consisted of two lines of tubes, each with a total length of 250 m, distributed in two lines (irrigated and fertigated) in the three blocks. Irrigation planning was carried out considering the rainfall regime and the soil moisture level, which was continuously monitored by a probe (Rain Bird © SMRTY Soil Moisture Sensor, Tucson, AZ, USA); at 65% of total available water (TAW), the water supply started. Along these tubes, there were 5 nozzles m⁻¹ (a total of 1250 nozzles), with a flow rate of 2 L h⁻¹. During the growing season, the water amount provided for both fertigation and irrigation treatments was 25,000 L, corresponding to 210 mm. Fertigation was carried out with “Solabiol” liquid fertilizer, which is permitted for use in organic farming systems (N = 1.5%, C = 10%, pH = 6.4) as follows; a dose of 1.20 L was diluted in 20 L of water for each fertigation round, and this solution passed from a bucket to the fertigation lines via a “Venturi” pumped system (TEFEN © MixRite™ 2.5, Nahsholim, Israel). For the fertigation treatment, 25 kg ha⁻¹ units of N were added to the water.

2.3. Measurements

Biomass Production Evaluation

Biomass production was evaluated at different phenological stages and at the single-plant level in three test areas for each replication.

The phenological time location for identifying the exact time of harvesting was at 75% of the linear transect of 6 m to the right and left of the two central rows of each plot, i.e., with flower buds equal to 75% of the plants last surveyed, and this refers to the total count excluding orders.

The epigeal biomass was cut at 5 cm from the ground level and after plant sampling, the leaves and branches were separated and carefully cleaned of soil residues, limiting the loss of leaves as much as possible. Each fresh plant was separately weighed using a laboratory balance to assess the fresh weight. After that, the biomass was placed in an oven at 105 °C for two days, after which its dry weight was determined.

In each year, 2020 and 2021, a total of 270 plants were sampled: within the replication of each treatment, 3 test areas were identified from which 10 plants were taken; from the biomass values measured for the 30 plants from the replication of each treatment, we determined the average production of epigeal biomass of each plot and at the end of each treatment.

The values obtained for all replications within the same treatment were averaged, and the standard deviation was determined. Production per hectare for each treatment was calculated from the average fresh unit production, considering the actual plant density. Yield per hectare was then calculated using the following formula:

Total yield (t ha⁻¹) = (Biomass sampled plant weight (g) × plant density (n. plants ha⁻¹)) × 10⁻⁶

where biomass sampled plant weight is the average production per plant for each treatment type (g plant⁻¹), plant density is the number of plants per ha, and 10⁻⁶ is the conversion factor from g to t. The means and standard deviations of the total production in the plots within the same treatment were then calculated and compared with the results of other treatments.

In the second year, the plants sampled were individuals that survived the winter of 2020–2021.

2.4. Statistical Analysis

All statistical analyses were performed with R statistical software [38]. Good analysis is based on a model that is biologically relevant and uses realistic assumptions [39]. To select the model that could fit the biomass parameters better, several models were built by using the “stats” [40] and “nlme” [41] R (3.5.1.1, Rstudio Team, Boston, MA) packages based on statistics, which put a penalty on “complexity”, such as the Akaike Information Criterion (AIC) [42], the Bayesian Information Criterion (BIC) [43] and likelihood ratio tests (LRTs) [44]. Based on the previous model analyses, the full factorial model better fitted the biomass parameters. Before performing the analysis of variance (ANOVA), we checked that the full factorial model met the three assumptions of the ANOVA. The normality distribution of the model residuals was checked both graphically (QQ plot) and by performing the Shapiro–Wilk normality test. The homoscedasticity was checked using the Levene test. The final ANOVA assumption was satisfied by the experimental design and random sampling. When all three ANOVA assumptions were met, we applied the ANOVA to the model. When the ANOVA showed a significant difference between the factors (p-value < 0.05), we performed an estimated marginal means post hoc analysis by using the “emmeans” function with the Bonferroni adjustment of the “emmeans” R package [45].

3. Results

3.1. Thermo-Pluviometric Trend

The data collected in the weather station near the experimental site are shown in

Table 3. Thermo-pluviometric trend related to the sea fennel biological cycle during the 2020 and 2021 seasons compared to LTS (Long-Term Series) historical period (1998–2019).

Months	January	February	March	April	May	June	July
Rainfall (mm)								Total
LTS	54.0	46.3	67.3	72.0	60.0	55.0	52.0	406.6
2020	4.2	17.2	59.2	59.6	37.6	56.0	27.0	260.8
2021	78.8	20.4	24.8	33.0	23.8	7.8	38.2	226.0
Δ Rain 2020–2021	−74.6	−3.2	34.4	26.6	13.8	48.2	−11.2	34.8
Δ Rain LTS—2020	49.8	29.1	8.1	12.4	22.4	−1.0	25.0	145.8
Δ Rain LTS—2021	−24.8	25.9	42.5	39.0	36.2	47.2	13.8	180.6
Avg air T (°C)								Average
LTS	6.0	7.2	10.7	13.7	18.1	19.5	22.0	13.9
2020	7.2	11.0	10.2	14.0	18.7	21.8	24.4	15.3
2021	6.5	9.3	9.7	12.2	18.2	25.0	26.8	15.4
Δ Avg air T 2020–2021	0.7	1.7	0.5	1.8	0.5	−3.2	−2.4	−0.1
Δ Avg air T LTS—2020	−1.2	−3.8	0.5	−0.3	−0.6	−2.3	−2.4	−1.4
Δ Avg air T LTS—2021	−0.5	−2.1	1.0	1.5	−0.1	−5.5	−4.8	−1.5
Min air T (°C)								Average
LTS	2.9	3.5	6.6	9.4	13.3	14.0	16.0	9.4
2020	3.8	6.5	6.3	8.7	13.5	16.2	18.8	10.5
2021	3.2	5.2	4.6	7.1	12.7	19.1	21.5	10.5
Δ Min air T 2020–2021	0.6	1.3	1.7	1.6	0.8	−2.9	−2.7	0.0
Δ Min air T LTS—2020	−0.9	−3.0	2.3	0.7	−0.2	−2.2	−2.8	−1.1
Δ Min air T LTS—2021	−0.3	−1.7	2.0	2.3	0.6	−5.1	−5.5	−1.1
Max air T (°C)								Average
LTS	9.0	10.9	14.8	18.1	22.8	25.0	28.0	18.4
2020	12.3	16.7	15.0	19.7	23.6	26.3	28.9	20.4
2021	10.6	14.4	15.2	17.9	24.1	30.8	32.1	20.7
Δ Max air T 2020–2021	1.7	2.3	−0.2	1.8	−0.5	−4.5	−3.2	−0.3
Δ Max air T LTS—2020	−3.3	−5.8	−0.2	−1.6	−0.8	−1.3	−0.9	−2.0
Δ Max air T LTS—2021	−1.6	−3.5	−0.4	0.2	−1.3	−5.8	−4.1	−2.3

.

The 2020 and 2021 seasons were decidedly dry compared to the historical average of the previous twenty years; in fact, from January to July, the total cumulative rainfall was 40% lower. In particular, in the second quarter (April–June) of 2021, the period in which C. maritimum L. developed the leaf rosette, recorded only 64.6 mm of precipitation or 60% less than the same period in 2020 (153.2 mm) and even 70% less (187 mm) in the same quarter of the LTS (1998–2019). On average, the maximum and minimum air temperatures recorded from January to July both in 2020 and in 2021 were higher than those of the LTS (1998–2019) at about 1.5 °C; the second quarter of 2021 recorded a maximum temperature higher than the historical average in the months in May and June of over 1 °C and 5 °C, respectively.

3.2. Effect of Treatments and Year

The results of the ANOVA (

Table 4. Analysis of variance (ANOVA) applied to the mixed model.

		UFB (g Plant−1)			TFB (t ha−1)			UDB (g Plant−1)			TDB (t ha−1)
Factors	df	MS	F	p	MS	F	p	MS	F	p	MS	F	p
Y	1	109125	362.68	2.2 × 10−16 ***	1048.04	362.68	2.2 × 10−16 ***	707.72	125.78	5.2 × 10−15 ***	6.7970	125.78	5.2 × 10−15 ***
T	2	84651	281.34	2.2 × 10−16 ***	812.98	281.34	2.2 × 10−16 ***	1598.93	284.16	2.2 × 10−16 ***	15.3561	284.16	2.2 × 10−16 ***
Y × T	2	44854	149.07	2.2 × 10−16 ***	430.78	149.07	2.2 × 10−16 ***	589.56	104.78	2.2 × 10−16 ***	5.6621	104.78	2.2 × 10−16 ***
Residuals	48	301			2.89			5.63			0.0540

*** p < 0.001, Y = year, T = treatment, df = degrees of freedom, MS = arithmetic mean of the squares, F = Fisher test values, p = probability values of ANOVA levels, UFB = unit fresh biomass, TFB = total fresh biomass, UDB = unit dry biomass, TDB = total dry biomass.

) show significant differences associated with year (Y), treatments (T) and their interaction (Y × T) for almost all measured variables. Both “year” and “treatment” factors showed a significative difference at p < 0.001 for all analyzed variables. These differences were repeated in the same proportions even in the interaction of the two factors Y × T; the ANOVA shows that the statistical impact of this interaction maintained significant differences of p < 0.001 at the same level of the two factors for all biomass variables measured.

We observed similar values for the control treatment (CT) in the two years for both fresh biomass (UFB) and total fresh biomass (TFB) (

Table 5. Estimated biomass marginal mean differences calculated with the Bonferroni adjustment for two years with the same treatment. Means (±standard deviation) within each column followed by different lowercase and uppercase letters are significantly different (ANOVA, p < 0.05) between the two years in the same treatment and among the treatments (by averaging each of the values of the two years), respectively.

T	Y	UFB (g Plant−1)	TFB (t ha−1)	UDB (g Plant−1)	TDB (t ha−1)
CT	2020	82.9 (±26.5) a	8.0 (±2.6) a	12.7 (±1.6) a	1.2 (±0.1) a
CT	2021	75.1 (±7.0) a	7.4 (±0.7) a	9.0 (±1.5) b	0.9 (±0.1) b
Mean CT		79.0 (±19.2) C	7.7 (±1.9) C	10.9 (±2.4) C	1.1 (±0.2) C
IR	2020	112.1 (±18.6) b	11.1 (±1.8) b	18.2 (±2.9) b	1.8 (±0.3) b
IR	2021	198.0 (±14.3) a	19.4 (±1.4) a	24.5 (±2.4) a	2.4 (±0.2) a
Mean IR		155.0 (±47.0) B	15.2 (±4.6) B	21.4 (±4.1) B	2.1 (±0.4) B
FR	2020	120.0 (±17.5) b	11.8 (±1.7) b	20.1 (±3.1) b	2.0 (±0.3) b
FR	2021	311.7 (±14.0) a	30.5 (±1.4) a	39.2 (±2.4) a	3.8 (±0.2) a
Mean FR		215.8 (±99.8) A	21.2 (±9.8) A	29.7 (±10.2) A	2.9 (±1.0) A
Mean T		150.0 (±85.0)	14.7 (±8.3)	20.6 (±10.1)	2.0 (±1.0)

T = treatment, CT = control treatment (without irrigation and fertilization), IR = irrigation treatment with 210 mm ha⁻¹, FR = fertigation treatment with 25 kg N ha⁻¹ in 210 mm ha⁻¹ of water, Y = year, UFB = unit fresh biomass, TFB = total fresh biomass, UDB = unit dry biomass, TDB = total dry biomass.

), while for unit and total dry biomass (UDB and TDB), the values were significantly higher in the year 2020. In contrast, under both irrigated (IR) and fertigated (FR) treatments, the four biomass quantities measured (UFB, TFB, UDB and TDB) showed differences in the two years, with those measured in 2021 being significantly higher than those measured the previous year. Even averaging the two years, differences were noted between the three treatments tested.

Regarding treatments within the same year (

Table 6. Estimated biometric marginal mean differences calculated with the Bonferroni adjustment between the density treatments relative to weights of flower heads and tubules. Means (± standard deviation) within each column followed by different lowercase and uppercase letters are significantly different (ANOVA, p < 0.05) among the treatments in the same year and between the two years (by averaging each of the values of the three treatments), respectively.

T	Y	UFB (g Plant−1)	TFB (t ha−1)	UDB (g Plant−1)	TDB (t ha−1)
FR	2020	120.0 (±17.5) a	11.8 (±1.7) a	20.1 (±3.1) a	2.0 (±0.3) a
IR	2020	112.1 (±18.6) a	11.1 (±1.8) a	18.2 (±2.9) a	1.8 (±0.3) a
CT	2020	82.9 (±26.5) b	8.0 (±2.6) b	12.7 (±1.6) b	1.2 (±0.1) b
Mean 2020		105.0 (±26.1) B	10.3 (±2.6) B	17.0 (±4.1) B	1.7 (±0.4) B
FR	2021	311.7 (±14.0) a	30.5 (±1.4) a	39.2 (±2.4) a	3.8 (±0.2) a
IR	2021	198.0 (±14.3) b	19.4 (±1.4) b	24.5 (±2.4) b	2.4 (±0.2) b
CT	2021	75.1 (±7.0) c	7.4 (±0.7) c	9.0 (±1.5) c	0.9 (±0.1) c
Mean 2021		194.9 (±99.2) A	19.1 (±9.7) A	24.2 (±12.7) A	2.4 (±1.2) A
Mean Y		150.0 (±85.0)	14.7 (±8.3)	20.6 (±10.1)	2.0 (±1.0)

T = treatment, FR = fertigation treatment with 25 kg N ha⁻¹ in 210 mm ha⁻¹ of water, IR = irrigation treatment with 210 mm ha⁻¹, CT = control treatment (without irrigation and fertilization), Y = year, UFB = unit fresh biomass, TFB = total fresh biomass, UDB = unit dry biomass, TDB = total dry biomass.

), as already shown in previous studies [26], in the transplanting year (2020), the irrigated and fertigated treatments did not differ significantly from each other for the four measured variables (UFB, TFB, UDB and TDB) while both were significantly superior to the control treatment. In the second year of development planting (2021), on the other hand, the three treatments differed significantly for all four measured biomass variables (UFB, TFB, UDB and TDB). Even after averaging the treatments in each year, it can be seen that the second year, when the crop had been fully established, had higher productivity levels than the year of transplanting.

4. Discussion

After the preliminary productive results highlighted in Zenobi et al., 2021 [26], the present study aimed at further investigating the productive characteristics, in terms of the epigeal biomass yield of C. maritimum L., cultivated from germoplasma of local varieties well-adapted to Adriatic climates, when subjected to different levels of intensification.

In the described experimental context, we analyzed the possible effect of year and treatment factors on four biomass parameters. The 2020 and 2021 thermo-pluviometric trends influenced the development of the plants; in 2020, rainfall lower than the historical average affected the development of the transplanted individuals in the first year as already highlighted in previous studies [26], while in the year after transplanting, a higher amount of rainfall was seen in the first quarter than in 2020, which is more in line with the LTS (1998–2019), which facilitated establishment, while the vegetative development that takes place in the second quarter, in 2021, had higher temperatures than 2020 and the historical average and a lower accumulation of rainfall. Consequently, the irrigation and fertigation interventions in 2021 (three compared to five in 2020, which were necessary to favor the post-transplantation phases given the below-average rainfall) were decisive for biomass production; these inputs were exploited by plants that were well-adapted to the soil and developed fresh and dry biomass, both in unit and total, in significantly higher quantities than in the year of transplantation. For the rainfed unfertilized control, the particularly dry second quarter of 2021 caused a significant decrease in production, but only in the unit and total dry biomass compared to the transplant year, while the fresh biomass did not show a significant difference as observed in studies concerning hydroponic systems with a plant density three times higher than ours and harvested in two consecutive seasons but with lower values than our experiment [46].

Regarding the comparison of treatments in the same year, previous studies have already evaluated the four biomass variables (UFB, TFB, UDB and TDB) in the year of transplantation [26] with the irrigated (IR) and fertigated (FR) treatments not differing significantly from each other but both being significantly superior to the control treatment (CT). In the second year of production, the three treatments differed significantly in all four biomass variables analyzed (UFB, TFB, UDB and TDB); thus, the effect of fertilizer input with fertigation had a significant effect compared to the transplant year because the plants’ roots were already taking well to the soil, whereas in the transplant year, significant energy was spent by the plants in adapting to the soil and climatic conditions. The benefits of fertilization were found in experimental sites with other halophytes in pots [47], with targeted fertilization in dry lands [48] and in floating systems [49]; in both cases, fertilizer contributed to improved plant growth and biomass.

The productions in 2020 and 2021 of our irrigated treatments for C. maritimum L. showed similar values to those found for another perennial halophyte, Salicornia bigelovii Torr. Grown in a desert environment through biorefining [50], while the control that received no rainfall in the two years under study showed a superior production of fresh biomass per plant to crop systems of this species in pots conducted on sandy substrates [51].

This work, unique in the scientific literature and in the pedoclimatic context described, represents an important reference for the definition of the productivity of established Crithmum maritimum L. subjected to various agronomic treatments. The dynamics described confirm what was previously observed and described in Zenobi et al., 2021 [26] in the year of transplanting the crop. In the present work, on the other hand, production data relating to the fully established crop were analyzed, given that it is a perennial crop.

In fact, we observed the plant development in the second-year production; production results remain satisfactory in irrigated and fertigated treatments regardless of the weather season; the production values in this study show that this species develops more epigeal biomass under low levels of nitrogen inputs.

5. Conclusions

Crithmum maritimum L., as other halophytes, is an interesting possibility for marginal lands often subject to desertification and erosion of soil and plant biodiversity due to current climate change [49]. C. maritimum L. grows spontaneously in the coastal areas of the Conero Regional Park, located in the Marche region; in the nearby areas, attention to this species is increasing, as evidenced by PSR funding and European projects (SEAFENNEL4MED-PRIMA 2021). The development of agronomic production protocols that support studies on fermented preserves [36] may give a further impetus for the diffusion of Crithmum maritimum L. as a crop to be included in our low-input cropping systems. In fact, C. maritimum L., in the absence of inputs and being a facultative halophyte species [51,52], can give satisfactory production results regardless of the seasonal thermo-pluviometric trend in Mediterranean marginal land crop systems.