Sustainable and Traditional Irrigation and Fertigation Practices for Potato and Zucchini in Dry Mediterranean Regions

Abstract

Transforming irrigation practices is essential to address aquifer depletion and food security in Mediterranean regions facing climate change and water scarcity. Developing local and national resilience to climate change requires capacity building to boost soil health and adaptation to drought. Recent attempts undertaken by the SEALACOM Project reduced irrigation rates in protected agriculture. The purpose of this work is to enhance traditional farmer’s practices and promote the potential of advanced fertigation of field crops (i.e., potato and zucchini) cultivated under two different pedo-climatic conditions to improve water and nutrient use efficiency. Results showed the yield of zucchini and potato on SEALACOM plots with continuous fertigation was 22% and 17.8%, respectively, which was higher than the yield with traditional irrigation and fertilization practices. Elite potato tuber size was 40% higher in SEALACOM plots (p < 0.05). The farmer applied 359 L of water to produce 1 kg of fresh zucchini compared to 225 L by the SEALACOM Project, indicating a significant, 60% water saving in the SEALACOM practice. Compared to farmer’s practices of potato production, the SEALACOM Project achieved more than 50% higher water productivity. In zucchini production, farmers applied 19.5% more nitrogen and 19.6% more phosphorus fertilizers. Compared to 58 kg of N applied by the farmers, the SEALACOM Project applied 38 kg of N to produce 1 ton of Zucchini, showing a 34% saving in major nutrient application. To cultivate 1 kg of fresh potato tubers, SEALACOM utilized 4.06 g of nitrogen and 1.34 g of phosphorus, compared to the traditional practice, which required 13.2 g of nitrogen and 2.25 g of phosphorus. Water and nutrient saving and higher productivity and commerciality of the final product have a high positive impact on the farmer’s income and positive attitude towards the adoption of modern, sustainable practices.

1. Introduction

Climate change is expected to raise Lebanon’s mean annual temperature by 1.45 °C by mid-century and reduce precipitation by 2.7% by 2025 [1,2]. If current trends in water scarcity continue, the direct costs to the Lebanese economy caused by higher temperatures, fluctuating precipitation, and drought events are estimated to reach USD 138,900 million in 2080 [3], equivalent to 1.71% of current national gross domestic product. The resulting reduction in agricultural productivity will certainly threaten food security. Water scarcity causes yield reductions that can be offset by controlled irrigation to maintain sustainable crop production [4].

However, climate change has diminished the positive effect of soil organic carbon sequestration, reduced wheat yield up to 39%, and increased CO₂ and N₂O emissions from the soil [5]. Efforts to enhance on-farm irrigation management are crucial to addressing the growing challenges of a finite resource and maintaining food production [6]. To avoid excessive irrigation, which causes depleted water resources, controlled or deficit irrigation is recommended. This approach restricts excessive leaf growth and enhances fruit development, positively affecting water consumption and improving water use efficiency [7].

In Lebanon, emissions from energy, agriculture, and forestry-land use accounted for 58% of total emissions in 2019 [8]. The majority of these emissions were attributed to energy consumption, particularly from diesel engines powering pumps to extract water from individual wells, costing approximately USD 0.86 per liter. This issue is especially prevalent in the Bekaa Plain, where collective irrigation schemes are lacking [9]. Water scarcity has led to the chaotic drilling of unlicensed (i.e., illegal) wells and uncontrolled groundwater abstraction for irrigation to meet increasing demands for food and feed. This has resulted in aquifer depletion and the salinization of soil and water resources [10,11]. A study done 10 years ago in Lebanon reported more than 18,000 private, unlicensed wells in the Bekaa Plain, primarily used for irrigation with fossil energy [12].

Integrating climate-proof agriculture into a comprehensive management approach involves monitoring soil and climatic conditions and considering crop water and nutrient demands in relation to crop growth and development. This can support pro-active decision-making to anticipate economic and environmental losses. Improving water management in the country can reduce yield gaps and meet the challenges of food security and sustainable development goals (SDGs), specifically SDG 2. But this outcome is impossible to achieve without increased water productivity at the farm level.

A comprehensive multiscale analysis that couples plot scale tests with district-wide assessments can be useful to identify the technical and socio-economic driving forces behind low water productivity and yield gaps and to support the adoption of modern irrigation technology. The three-year national development priorities and strategy to revive the Lebanese national economy through targeted investments in various sectors [13], along with the Ministry of Agriculture’s five-year strategic plan [14], proposed investing in capacity building and upgrading the technical basis and productivity of irrigated agriculture. They also call for innovation campaigns in fertilization and irrigation practices, which can contribute significantly to national economic growth and recovery. Developing local and national resilience to climate change requires a thorough analysis of prevailing irrigation and fertilization practices at the farmer level to boost adaptation capacity to drought and ensure food security. Since agro-ecosystems largely depend on both natural and climatic processes, resilience must be combined with innovation, adaptation, and the development of sustainable agricultural practices [15].

A sustainable adaptation strategy can be achieved through information technology (IT) intervention and the adoption of permanent and simple field monitoring tools to control water application based on soil moisture and crop demands [16]. This practice maintains optimal soil health conditions and achieves higher yields with less water and nutrient input, thereby reducing the footprint of irrigated agriculture. In addition to other adaptation practices, the use of regulated irrigation can decrease the risks of nitrogen losses, nitrate leaching, and gas emissions from agricultural lands [17].

With net exploitable surface and groundwater estimated at around 2 billion m³ (Bm³), the 2012 National Water Sector Strategy assessed the available water resources at 2.7 Bm³, of which 2.2 Bm³ are surface water and 0.50 Bm³ are derived from groundwater recharge [18]. Since total groundwater abstraction by wells is estimated at 0.70 Bm³, under normal climatic conditions, the yearly deficit in groundwater is equivalent to 0.2 Bm³, causing a drop in the water table and decreased pumping. Recurring drought and depleted groundwater have caused local and regional drops in water table level [19]. However, in semi-arid regions, crop evapotranspiration (ET) is negatively correlated with groundwater depth, indicating a higher contribution of irrigation to crop water requirements in deeper aquifers. This is associated with better yields and more efficient water use in the root zone [20].

Over irrigation in field crop production has led to the intensive leaching of soluble pollutants, resulting in economic and environmental losses due to the deterioration of soil and groundwater quality [21]. Current irrigation practices in the Bekaa Plain threaten sustainable food production and challenge the implementation of SDGs. An optimized irrigation schedule and water accounting, combined with adequate nitrogen application, increased soil organic carbon, boosted soil fertility, and enhanced crop production and water use efficiency [22].

Despite governmental efforts to disseminate good practices among water users and farmers, adopt climatic information, and consider water balance [23], the increase in water use efficiency remains insufficient [24]. One of the main challenges hindering the expansion of such improvement is the lack of cost-effective and reliable data monitoring systems [6]. Field experiments based on climate-soil-crop-water smart agriculture practices have shown good potential to enhance the sustainability of local farming. These experiments indicate substantial water saving potential and improved agronomic productivity through a shift from traditional fertilization and irrigation practices to well managed modern fertigation systems [21].

Recent regional progress in determining crop water demands using data from a typical climatic year, correlated to crop growth cycles [25], did not significantly influence farmers’ attitudes towards effective irrigation management in the Mediterranean region. Conservation measures in the USA, such as better correlation between pumping and precipitation and adjusting the area of irrigated lands, did not close the gaps between groundwater recharge and pumping rates [26]. However, the application of deficit irrigation in major potato-growing regions in Lebanon [21] and Northern China [27] significantly increased potato water use efficiency (WUE) by 10% and irrigation water use efficiency (IWUE) by 31.6%, with a considerable reduction in ET by 26.3%.

Alternatively, greater success in reducing irrigation water use per irrigated area was achieved by using locally based climatic stations to estimate potential evapotranspiration (ET0) and link it to the crop phenological development [28]. However, previous research in the region did not consider the total amount of water applied, starting from land preparation, amelioration of pre-sowing soil moisture, and post-sowing water application to maintain optimal conditions for good sprouting. Published studies mainly count water application related to evapotranspiration and crop coefficient (Kc) after seedling establishment, i.e., they account for effectively applied water covering the crop production cycle from plant emergence to physiological maturity.

A weak extension service is an additional constraint to the dissemination of good agricultural practices and effective water management in the semi-arid areas. Therefore, it is crucial to create and sustain living labs and demonstration (and experimental) sites in the main agroclimatic zones of the East and South Mediterranean. These sites ensure continuous interaction and participatory learning with local farmers. To our knowledge, this is the first time effectively applied water is considered in conjunction with the total applied water, with both parameters integrally analyzed within the concept of water accounting and water productivity under field conditions.

Meeting the objectives of the SDGs and addressing challenges to boost national capacities in the food-water-energy nexus, a project named “SEALACOM” was launched in 2023. It aimed to sustainably manage sea and land resources by the community, support development, sustain the environment, and strengthen farmer resilience. Accordingly, the purpose of this paper is to compare locally prevailing unsustainable fertilization and irrigation practices with science-based techniques and climate-smart practices proposed by the project. It assesses the impact in terms of water and nutrient saving and efficient use for two open field crops (potato and zucchini) cultivated under two different pedoclimatic conditions, following the traditional and advanced fertigation methods.

2. Materials and Methods

To reach the objectives of the SEALACOM Project and address the sustainable use of water in agriculture with a low energy and environmental footprint, two experimental sites in two different soil zones of Lebanon were selected. The first Demo Sites (DS1) is located in Serein-Cental Bekaa (Casa of Zahle) at 33°52′38″ N and 36°02′59″ E, and the second Demo Sites (DS2) is located in Sultan Yacoub (Casa of West Bekaa) at 33°40′21″ N and 35°51′40″ E. The study was run in fall 2023 in the two DS representing two agroecological zones of the Bekaa Plain of Lebanon with a total area of 86251.8 ha, of which 45.8% represent cultivated agricultural lands (Figure 1).

The topography of the demo sites varies between level plains in Serein and undulating foot slopes in Sultan Yacoub. Both areas are surrounded from east and west by the sloping lands of Mount Lebanon and the Anti-Lebanon mountain chain. The average altitude of the first demo site (DS1), located at Serein, is 950 m, while that of the second demo site (DS2), located at Sultan Yacoub, is 850 m.

The annual climatic data were received from the climatic stations of Tal-Amara, Lebanese Agricultural Research Institute. DS1 is located within the semi-arid climatic zone with 566 mm of average annual precipitation falling in one season between November and March (Figure 2). The rest of the year is dry with mean high and low annual temperatures reaching 25.6 °C and 8.5 °C, respectively.

DS2 belongs to the dry-subhumid climatic zone with an average annual rainfall of 700 mm and mean high and low annual temperatures reaching 24.6 °C and 10.8 °C, respectively. According to the World Reference Base for Soil Classification [29], the area of the two DSs is represented by the dominance of Cambisols, Regosols, and Luvisols with the inclusion of Vertisols, Calcisols, Leptosols, Arenosols, and Andosols (Figure 3).

The soil cover of DS1 was classified as deep Eutric Regosols. The soil is of neutral pH and non-saline (

Table 1. Physio-chemical characteristics of soils of the two DSs before the experiment.

Soil Type	Depth, cm	Total Sand	Silt	Clay	CaCO3 Total	CaCO3 Active	Organic Matter	EC	pH H2O	Available Nutrients, ppm
		%						ds m−1		N	P2O5	K2O
Eutric Regosols DS1-Serein	0–20	36	18	46	5.6	1.9	2.74	0.49	7.6	23.8	354	280
	20–40	30	20	50	3.8	1.3	1.55	0.33	7.4	23.1	305	268
Eutric Cambisols DS2-Sultan Yacoub	0–20	26	12	62	5.8	1.9	1.25	0.34	7.7	32.2	206	578
	20–40	24	16	60	5.8	1.9	1.31	0.30	7.8	27.0	185	627

), clay texture with negligible content of CaCO₃. The soil has an average low organic matter content and is poor in total nitrogen, enriched with phosphorous, and moderately high in available potassium.

The soil cover of DS2 was classified as Eutric Cambisols. Soil texture is clay with low organic matter content and weakly basic pH (Table 1). The soil is non-saline, poor in nitrogen, enriched with available phosphorous, and highly enriched with potassium.

Farmers traditionally apply nutrients and water by fertigation using closed tanks, managing the types, amounts, and timing of applications themselves. This approach relied on traditional irrigation management tools with intermittent nutrient application. The SEALACOM Project adopted an advanced smart climate system, estimating irrigation water needs based on ET0 calculations from a nearby climatic station. The daily crop evapotranspiration (ETc) was defined by multiplying ETc by the crop coefficient (Kc). Crop coefficient (Kc) was proposed by Jensen [30] and used together with the FAO guidelines to estimate crop water requirements [31] to relate the evapotranspiration of a specific crop (ETc) to the calculated potential evapotranspiration (ET0) according to the equation:

ETc= ET0 × Kc

(1)

• where ETc is the Daily Crop Evapotranspiration [mm/day]
• ET0 is the Daily Reference Evapotranspiration [mm/day];
• Kc is crop coefficient.

Since Kc is crop dependent and unaffected by climate, it follows the crop’s growth and development dynamics, regardless of location. Kc values increased throughout the cropping season from 0.2 to 0.4, 0.6, 0.8, and 1.0 at full growth, then decreased to 0.7 by the end of the irrigation season, corresponding to the physiological maturity in potatoes and the onset of low night temperature (<10 °C) for zucchini.

Fertigation schedules usually divide the portion of the total recommended rate of nutrient to be injected into varying amounts or percentages for each application over the growing season. Small amounts (low concentration) are usually injected in the early plant growth stage, larger amounts at mid-season, and then it is diminished toward the end of the season. The overall picture is similar to the dynamic of the crop fraction (Kc). Therefore, nutrient concentrations (i.e., N, P, K, and Mg) were adjusted according to the crop’s age, starting from 50 mg/L and increasing to a maximum of 100 mg/L, with proportional increases in major and minor nutrients to meet the crop’s growing demands.

The basic factors in fertigation procedures to be taken into account are:

a.

Injection rate (injection pump capacity)

b.

Amount of material to be injected

c.

Time available for injection

The injection rate (a = b/c) must be calibrated using a graduated cylinder of 1000 mL as a container and a watch to control how much of the nutritive solution is injected in one minute. To calculate the mass of dry fertilizer (m) to be dissolved for the preparation of stock solution, we used the following equation.

$$\mathrm{M}={\displaystyle \frac{\mathrm{b} \times \mathrm{df}\times \mathrm{v}\times 100}{\mathrm{c}}}$$

(2)

• where M is the mass of soluble fertilizer (kg).
• b is the concentration of the final nutritive solution (mg L⁻¹ or kg m⁻³)
• df is the dilution factor (unitless)
• v is the volume of the barrel to prepare the stock solution (m³)
• c is the concentration of the given fertilizer

Therefore, to prepare 100 L or 0.1 m³ of stock solution, with a desired concentration (b) of the final solution equivalent to 100 mg L⁻¹ (100 g m⁻³ or 0.1 kg m⁻³) of nitrogen (N), at a dilution factor (df) = 100, i.e., one liter of stock solution is injected against 99 L of irrigation water, we proceeded as follows: The used fertilizer is Ammonium Sulfate (c = 21.5% NH₄-N). To calculate the needed amount of this fertilizer to be dissolved in a 100 L barrel, the calculation was done as follows:

$$\mathrm{M}={\displaystyle \frac{0.1{ \mathrm{kg} \mathrm{m}}^{-3}\times 100\times 0.1 {\mathrm{m}}^3\times 100\%}{21.5\%}}=4.651 \mathrm{kg}$$

Instead of using the relatively expensive, high-precision dosatron injectors (DOSATRON, USA), the project used the feasible venturi system (Venturi Pump, 1 inch Elysee – Cyprus) to modify the concentration of the final solution and control the ratio between nutrients. Venturi is recommended for the fertigation of large areas. This system allows for the homogeneous and regulated distribution of water and nutrients in a continuous feeding mode compared to the farmer’s intermittent fertigation using the traditional closed tank (Figure 4a,b).

Water-meters (2 inch - Flange Type- Solid- China) were installed in both the SEALACOM plot and the farmer’s plot to control the amount of applied water (Figure 5).

Zucchini (Cucurbita pepo) was cultivated in Serein (DS1) in an open field on a total area of 6000 m² starting also from August 2023. The field was subdivided into two equal parts, 3000 m² each. The SEALACOM project managed 3000 m² and the farmer managed the other 3000 m². The soil and irrigation water were similar in both treatments. Land preparation and time and density of sowing of the same Zucchini variety were also identical. SEALACOM used full fertigation with drip lines following the approach of continuous application of fertilizers and water. The farmer also used the drip system, but he used the traditionally followed intermittent application of nutrients.

Potato (Solanum Tuberosum), variety Spunta, was grown in Sultan Yacoub (DS2) on a total area of 2000 m². The farmer managed the control plot of 1000 m², followed intermittent application of nutrients using the closed tank for fertilizer injection through macro-sprinklers. The SEALACOM Project managed the neighboring plot of 1000 m². The project applied continuous feeding with the same type of fertilizers using a venturi system, complemented by improved water management and application using mini-sprinklers.

A comparison of crop production, fertilizer, and water use efficiency between the project plot and traditional farmer practices was conducted to identify gaps and improve efficiency in drylands. Farmers’ water application was monitored through water-meter readings and coordination meetings held face to face two to three times a week. These meetings included field visits to monitor and compare crop health conditions.

Additionally, a comparison of crop production, total yield performance, and fertilizer recovery (i.e., productivity in kg product per 1 g of applied nutrient) and water productivity (kg product per 1 m³ of applied water) was conducted. This aimed to explore the potential for sustainable agriculture and disseminate good practices to meet the requirements of SDGs, particularly access to water and food security.

3. Statistical Analysis

Statistical analysis for potato crops was done using the descriptive statistics on Excel 2016, Window 10 (USA). The means of yields, tuber calibration, and dry matter content, randomly harvested at physiological maturity from 1 m² in four replicates, were calculated, followed by the confidence intervals, considering a 95% significance level. The comparison of the means could be done through the confidence ranges obtained as [mean ± confidence interval]. If two confidence ranges are overlapped, then the means were not considered different (p < 0.05).

4. Results

4.1. Zucchini Yield

Seedlings were planted on the same day (16 August 2023) on nested plots with similar soil conditions and the same history of land use and management. It is noteworthy that the periodically harvested and cumulative yield of zucchini on SEALACOM plots with continuous fertigation was consistently higher compared to that achieved by farmers using traditional irrigation and fertilization practices (Figure 6).

At the beginning of the experiment, the gap between yields in the two systems was minimal, but it increased linearly throughout the vegetation season. The total cumulative yield from 3000 m² in each treatment was 1729 kg for the SEALACOM approach and 1417 kg for the farmer’s approach (

Table 2. Commercial yield of zucchini harvested in traditional and advanced irrigation and fertilization practices.

Total Zucchini Yield (kg from 3000 m2)	Farmer	SEALACOM
Sum for the 2023 season	1417	1729
Difference (kg)		+312
%		22.02

), corresponding to a 22% difference in harvested and realized product. Since the demonstration trial was conducted directly on the farmer’s land, with separate harvest on SEALACOM and the Farmer’s plots undertaken by the farmer’s workers the following day, the produce was weighed and sent to the local wholesale market. The farmer counted the cumulative yield in each treatment and periodically reported to us in writing. Following the principle that seeing is better than hearing, the project staff did not interfere with the harvest and realization processes. Therefore, as there were no yield replicates in the zucchini trial, statistical analysis could not be performed, and we only compared the total cumulative yield and related parameters.

4.2. Water Application to Zucchini

The basic amount of water applied under zucchini during the preparation phase was 100 mm. Subsequently, the effectively applied water by the farmer and the SEALACOM Project amounted to 1697.8 m³ ha⁻¹ and 1294.4 m³ ha⁻¹; respectively (

Table 3. Water application and water use efficiency in zucchini by traditional and advanced practices.

Indicator	Farmer	SEALACOM	Difference
Basic application m3 ha−1	1000.3	1000.3	No
Effectively applied m3 ha−1	1697.8	1294.4	−403.40
Total applied water m3 ha−1	2698.1	2294.7	−403.40
Tuber fresh yield, kg ha−1	4723.3	5763.3	+1040.00
Applied water productivity, kg m−3	1.75	2.51	+0.76
Effective water productivity, kg m−3	2.78	4.45	+1.67

). The difference in total and effective water application resulted in higher water use efficiency, which was equivalent to 1.75–2.51 kg m⁻³ for traditional farmer’s practice and 2.78–4.45 kg m⁻³ for the SEALACOM practice.

4.3. Fertilization Policy in Traditional and Advanced Practices

The farmer applied 19.5% more nitrogen and 19.6% more phosphorus than the SEALACOM project did on its plot. However, the farmer applied 286.8% less potassium and 142% less magnesium compared to the project approach. The project’s emphasis on sufficient application of K and Mg is justified by the significant contribution of K to plant resilience against climate-induced stresses [32] and crop yield [33]. Additionally, due to the local high soil pH and soil saturation with exchangeable Ca, researchers from the region highlighted the depletion of Mg from the soils and stressed the importance of Mg and the necessity of adding magnesium fertilizers [34] to maintain nutrient balance and boost soil fertility (

Table 4. Amount of total applied nutrients under zucchini (kg Deca⁻¹) in Serein (DS1).

Input	Farmer				SEALACOM
	N	P2O5	K2O	MgO	N	P2O5	K2O	MgO
Nutrients	27.52	11.39	6.05	2.01	22.15	9.16	23.40	4.87
Fertilizers	131.02	18.66	12.11	13.39	103.02	15.02	46.80	32.43

).

Difference in K and Mg application might have reflected on crop photosynthetic activity. Based on low nocturne temperature prevailing in highlands during the fall season, the color of plant leaves in the farmer’s plot turned into yellow-brown, compared to the green color in SEALACOM treatment reflecting better plant health and fruit shape. This treatment was less affected by decreasing temperature in late October and early November. These physiological changes were reflected in the measurements of normalized differential vegetation index (NDVI) values for zucchini (Figure 7), detected from Sentinel-2 Satellite Images throughout the season from 1 September 2023 to 11 December 2023. At the SEALACOM plot, the canopy of zucchini showed higher vegetation index values throughout the season, reflecting better plant health conditions and higher harvest potential. Monitoring crop NDVI can provide valuable, real time, information on crop water and nutrient status and allow for timely intervention to apply corrective measures.

Improved crop resilience to low temperature was also observed in the color of the longitudinal scratches along zucchini fruits, with the SEALACOM plot showing completely green fruits compared to the whitish green color in the farmer’s practice. This outcome has an important impact on the commercial value of the product.

4.4. Nutrient Use Efficiency in Zucchini Production

The SEALACOM Project achieved higher nutrient use efficiency, applying 38.43 kg of N to produce 1 ton of zucchini, compared to 58.25 kg N applied by the farmer (

Table 5. Ratio of applied nutrients in the traditional and advanced fertilization practice of zucchini in the two demo sites.

Ratio of Nutrients
SEALACOM				Farmer
N	P2O5	K2O	MgO	N	P2O5	K2O	MgO
1.00	0.41	1.06	0.22	1.00	0.41	0.22	0.07

). This represents a 34% saving in nitrogen and phosphorus application, which can prevent salt buildup and reduce the hazards of nitrate accumulation in the soil and groundwater.

The SEALACOM approach required 27.8 kg more potassium (K₂O) and 4.19 kg more magnesium (MgO) to produce 1 ton of zucchini, corresponding to 216.8% and 98.5% higher nutrient use efficiency compared to the farmer’s practice (Figure 8). However, the improved commercial quality of the product justifies the higher input of potassium and magnesium. Adequate potassium provision has been shown to boost crop resistance to water stress, particularly in drought- and temperature-sensitive crops [32].

The alternative fertilization policy for the late summer–fall season, which favors the application of potassium and magnesium due to their contributions to the metabolism and turgor pressure in the leave’s guard cells, has resulted in a different nutrient ratio compared to the standard practice. This discrepancy requires further investigation to verify the corresponding fertilization recommendations of late-season zucchini (Table 5).

Figure 8 clearly illustrates the different outputs of both practices, specifically the amount of nutrients (in grams) to produce 1 kg of fresh, healthy, zucchini. While the farmer applied 58.25 g of nitrogen to produce 1 kg of fresh zucchini, SEALACOM achieved a nitrogen saving of 9.82 g by applying only 38.48 g.

4.5. Water Application to Zucchini in the Farmer’s and SEALACOM Practices

Water savings in zucchini cultivation were achieved by using data from a climatic station to estimate water demand. This approach proved to be more efficient compared to traditional irrigation practices, which relied on farmers’ skills and subjective interaction with weather and soil conditions. The SEALACOM plot used 224.59 L of water to produce 1 kg of fresh zucchini, against the application of 359.46 L by the farmer. This indicates a significant water saving of 60% in the SEALACOM practice.

4.6. Potato Performance Under Traditional and Improved Practices

4.6.1. Tuber Yield

Monitoring the NDVI showed higher values for the SEALACOM potato plot from seedling until the period of maximum canopy development (Figure 7). After this stage, the potato plant starts senescing and transferring dry matter and nutrients towards the tubers. At the farmer plot, NDVI values continued to show a higher range during the tuber development stage, witnessing continued potato canopy growth triggered by excess irrigation and N application in the traditional practice. The difference in NDVI was proved by the higher potato dry matter accumulation and yield in the SEALACOM plot.

In the late potato fall season, the reduced length of daylight might have affected the low tuber production of 19,000 kg ha⁻¹ using the farmer’s practice compared to 22,000 kg ha⁻¹ with the SEALCOM fertilization and irrigation practice (

Table 6. Potato tuber yield * following different fertilization and irrigation policies.

Indicator	Farmer	SEALACOM
Tuber fresh yield production, kg ha−1	1900.00 b	2200.00 a

* Differences (a, b) between average values, within the same rows, are statistically significant at <0.05.

), indicating a 17.8% increase in favor of the SEALCOM practice. Despite the late sowing period (10 August), the obtained results are comparable with previous studies on summer potato crops sown in Bekaa during the first half of July, providing an average yield of 2.5 tons deca⁻¹.

Tubers were sampled at physiological maturity from a representative area of 2.8 m², and the fresh tuber yield and dry matter content were measured, and results were transferred to 1 Deca (1000 m²). Results showed no overlapping between confidence ranges, which means a significant difference exists between harvested potato yields from the SEALACOM plot and Farmer’s plot (

Table 7. Statistical analysis of tuber fresh yield collected a physiological maturity from plots fertigated continuously (SEALACOM) and plots fertigated with the traditional farmer’s approach in DS1 and DS2.

Treatment	Yield kg Deca−1				Mean *	SD	Confidence Interval	Confidence Range
	R1	R2	R3	R4				Min	Max
SEALACOM	2415.10	2376.30	2293.40	2379.80	2366.10 a	±51.58	35.74	2330.39	2401.88
Farmers	2157.50	2065.40	1982.90	2017.10	2055.70 b	±75.82	56.17	1999.50	2111.90

* Differences (a, b) between average values, within the same rows, are statistically significant at <0.05.

).

4.6.2. Tuber Calibration

The calibration of tuber size, harvested in four replicates, at full maturity, from 2 m length (equivalent to 2.8 m²), corresponding to an average of 5748.5 g and 6625.2 g from the farmer’s and SEALACOM plots, respectively, is presented in

Table 8. Statistical analysis of tuber calibration collected at full maturity stage from advanced fertigation (i.e., SEALACOM) and framer’s practice.

Tuber Size *, cm	SEALACOM					Farmer
	Average	SD ±	Confidence Interval	Confidence Range		Average	SD ±	Confidence Interval	Confidence Range
				Min	Max				Min	Max
<1.5	63.70 b	1.28	1.25	62.45	64.95	284.00 a	15.10	14.80	269.20	298.80
1.5–3.5	1403.30 a	15.29	14.98	1388.32	1418.28	1148.60 b	57.28	56.15	1092.40	1204.70
3.5–5.5	2169.00 a	66.35	65.02	2103.98	2234.02	2182.90 a	100.98	98.98	2083.90	2281.90
5.5–7.5	2989.20 a	139.50	136.71	2852.49	3125.91	2133.00 b	118.49	116.13	2016.90	2249.10

* Differences (a, b) between average values of tuber size, within the same rows, are statistically significant at <0.05.

. The statistical analysis of calibrated tubers into small diameter size (<1.5 cm), medium size (1.5–3.5 cm), large size (3.5–5.0 cm) and elite size (5.5–7.5 cm), showed a significant difference with the advantage of the SEALACOM approach to produce a larger quantity of elite size potato tubers (Table 8). It can be concluded that the yield of elite-size tubers was 40% higher in the SEALACOM plot.

4.6.3. Tuber Dry Matter Content

Since dry matter (DM) content in potato tubers is one of the main criteria for the cooked product and culinary preference, we tested the tuber dry matter content and compared the two practices based on four replicates of subsamples dried in the oven at 72 °C over three days. The statistical analyses of DM content showed an advantage in the SEALACOM approach, providing significantly higher DM content (

Table 9. Comparative dry matter content of potato tubers produced by continuous fertigation and traditional practices.

SEALACOM					Farmer
Average *	SD ±	Confidence Interval	Confidence Range		Average	SD ±	Confidence Interval	Confidence Range
			Min	Max				Min	Max
20.350 a	0.551	0.540	19.810	20.890	18.400 b	0.540	0.524	17.880	18.920

* Differences (a, b) between average values within the same rows are statistically significant at <0.05.

).

4.6.4. Water Application Under Potato in Farmer’s and SEALACOM Practices

The initial water application for land preparation in both treatments was substantial (357 mm). This considerable amount was necessary due to the extreme soil dryness resulting from a long, dry summer following the early June wheat harvest, which typically depletes soil moisture to a depth of over 2 m. Therefore, the amount of effectively applied water in the SEALACOM approach irrigated by mini-sprinklers was 111.2 m³ versus 521.33 m³ in the farmer’s practice with irrigation using macro sprinklers (

Table 10. Water application and water use efficiency in potato by traditional and advanced practices.

Indicator	Farmer	SEALACOM
Basic water application, m3 ha−1	3570.00	3570.00
Effectively applied water *, m3 ha−1	5210.33	1110.20
Total applied water, m3 ha−1	8780.33	4680.20
Applied water productivity fresh tubers, kg m−3	2.16	4.70
Effectively applied water productivity DM ** tubers, kg m−3	0.51	1.15
Increase in applied water productivity (kg DM per unit applied water)	1.15 − 0.51 = 0.64
% increase in applied water productivity	(0.642 × 100)/0.513 = 125.10
Effective water productivity Fresh Tubers, kg m−3	3.64	19.78
Effective water productivity DM Tubers, kg m−3	0.86 ***	4.86
Increase in effective water productivity (kg DM per unit applied water)	4.86−0.86 = 4.00
% increase in effective water productivity	(4.00 × 100)/0.86 = 465.12

* Since the start of fertigation and differential water application; ** DM content in potato tubers in SEALACOM = 24.55%, in Farmer’s plot = 23.76%; *** The base line for summer potato is 0.95 kg DM m⁻³. In this trial, the sowing of potato was late (15 August 2023). Autumn potato season is very short with low night T and provides 30–50% from the potential harvest of the normal summer season.

). Therefore, the total applied water was 468.2 m³ and 878.3 m³ in both practices, respectively.

Compared to the farmer’s practice, this outcome, in the SEALACOM approach, allowed for more than 50% better applied water productivity and more than doubled the productivity of effectively applied water. Our results show that to produce 1 kg of fresh potato, the farmer effectively applied 274.38 L of water against 50.61 L of water applied by the SEALACOM practice.

4.6.5. Nutrient Application Under Potato in the Farmer’s and SEALACOM Practices

Nutrient application under potatoes showed a similar trend like in zucchini, highlighting a pattern in traditional Lebanese farming practices. There is an overestimation of nitrogen and phosphorous inputs, while the importance of potassium and magnesium in the management of soil fertility and crop production is underestimated (

Table 11. Amount of applied nutrients under potato by advanced fertigation (i.e., SEALACOM) and framer’s practice (kg ha⁻¹).

Type of Nutrients	Farmer				SEALACOM
	N	P2O5	K2O	MgO	N	P2O5	K2O	MgO
Pure elements	250.8	42.7	93.0	3.0	89.4	29.5	118.8	6.4
Total Fertilizer equivalent	1166.5	70.0	186.0	18.7	415.6	48.3	237.6	40.1

).

Results of the experiment show the application of 250 kg ha⁻¹ and 42.7 kg ha⁻¹ versus 89.36 kg ha⁻¹ and 29.5 kg ha⁻¹ of nitrogen and phosphorous in the farmer’s practice and SEALACOM approach, respectively. Due to high potato demands in K and Mg, SEALACOM applied 30% and 50% more potassium and magnesium.

4.6.6. Nutrient Use Efficiency in Farmer’s and SEALACOM Practices of Late Season Potato Production

To produce 1 kg of fresh potato tubers, SEALACOM applied 4.06 g of nitrogen and 1.34 g of phosphorous, whereas the farmer applied 13.2 g and 2.25 g; respectively (Figure 9). Conversely, the SEALACOM practice applied 10.4% and 81.2% more potassium and magnesium, which resulted in the dominance of large tubers in the harvest using the project’s fertilization method.

The fertilization policy of late summer potato followed by the SEALACOM Project and the farmer shows different understandings of the role and importance of each element. This discrepancy indicates poor nutrient formulation in the traditional practice (

Table 12. Ratio of applied nutrients in the traditional and advanced fertilization practice under potato.

Ratio of Applied Nutrients
Farmer’s Practice				SEALACOM Practice
N	P2O5	K2O	MgO	N	P2O5	K2O	MgO
1.00	0.17	0.37	0.01	1.00	0.33	1.33	0.07

). While potassium should typically exceed nitrogen, as commonly recommended, the nitrogen level in the farmer’s potato production practice was three times higher than the applied potassium level.

5. Discussion

SEALACOM practice was more efficient in N and P utilization by the potato crop (Figure 9). Similarly, squash grown in Jordan demonstrated higher yields with lower N rates and better water and fertilizer utilization through full fertigation compared to the traditional practices. This approach can minimize production costs and reduce nitrate pollution in the soil-groundwater system [35]. Case studies from the region have reported nitrate accumulation and leaching, leading to significant groundwater contamination with nitrates [34,35,36].

Given the deficiency of organic and mineral nitrogen in the soils of the area [21,32], it is recommended to develop a farming practice with an adequate dose of nitrogen for successful crop production. This policy must take into account the soil and climate conditions, plant response to nutrients, and crop tolerance to drought to improve carbon and nitrogen metabolism and achieve production goals and water use efficiency [37,38,39].

The approach used to define crop water requirements has limitations, as the tested crop coefficients (Kc) for some field crops might not align with the FAO-56 Kc recommended values when determined for the same crops in different locations [40]. Therefore, to properly regulate nutrient ratios and amounts, it is advisable to determine the crop coefficient in situ using both climatic stations and lysimeters to coordinate the lower and higher ranges of Kc values. This method allows for more precise water and nutrient application by matching the Kc range with crop genotypes and specific water demands, as well as local soil and climatic conditions. Consequently, it enables the modification and control of nutrient concentrations through continuous fertigation.

Using the same genotypes of potato and zucchini, cultivated simultaneously in the same locations under similar soil and climate conditions, reduced variability due to the smoothing effect of systematic error. Therefore, it is crucial to upgrade environmental performance, sustainable agricultural production, and precision farming in Lebanon at both farm and national levels. Capacity building will enhance the requirement for mass, energy, and human labor inputs that support food security through sustainable production and environmental practices [41]. This aligns with the adoption of a multi-criteria approach to sustainable irrigated agriculture and crop endurance, addressing the challenges of food security and water scarcity in arid environments [42].

In China, moderate and precise water and nitrogen application within the targeted root zone of sweet potatoes, considering soil and water pools, improved tuber yield and quality and enhanced water and nitrogen use efficiency [43]. Three categories of farmers were identified in the Mediterranean: proactive, skeptical, and reluctant farmers, with a significant portion showing negative attitudes toward using digital technologies in agri-farming and environmental policies [44]. However, adopting feasible tools and simple techniques that demonstrate both economic and environmental resilience can lead to a breakthrough.

Given the significant average global increase in ET over the last three decades, at an annual rate of 1.33 (±0.84) mm per year, largely due to an average summer ET increase of 2.06%, the adoption of sustainable irrigation strategies is a prime concern [45]. Advanced soil and crop management, along with improved fertilization and irrigation practices in semi-arid zones, are among the key alternative farming options at all decision-making levels. These practices aim to improve carbon and nitrogen balance, enhance soil fertility, and boost crop yields [46].

Since 1970, a significant decrease in groundwater levels, with a drop between 20 and 25 m in the major aquifers of Lebanon, has been attributed to chaotic drilling of water wells and over exploitation [47]. Observations for Lebanon based on land subsidence and space information showed a total water storage decline in the Bekaa plain at a rate of 1.10 cm per year, caused by groundwater depletion [19].

Evidence of uncontrolled expansion of illegal wells and excess pumping calls for immediate interventions and the activation of water governance to improve water accounting and water productivity in Lebanon and the Eastern Mediterranean. A good example of groundwater governance comes from Jordan, where acts of violence and mismanaged irrigation practices from private wells, along with incorrect metering of pumped water and inefficient water conveyance, were detected and corrected to promote the wise use of limited water resources [10].

Adaptive responsive measures, such as the development and efficient use of water resources, were recommended in Jordan to reduce the impacts of drought and increased public demands on water resources and food security [48]. In the face of water scarcity and recurrent drought events in semi-arid Mediterranean conditions, implementing sustainable agricultural practices for more efficient use of limited water and soil resources becomes a national and regional priority. These practices aim to enhance nitrogen and water use efficiency and address the challenges of food security [49].

Quantifying evapotranspiration (ET) is crucial for a valid understanding of the global water cycle and precise resource management. However, accurately estimating ET, especially at local scales, has always been challenging [50]. Substantial progress has been made in estimating regional crop water demands using low-resolution platforms such as the FAO Water Productivity Portal-WAPOR [51], and AgSAT [52]. These platforms provide real-time and lagged information to support decision-making on regional water use. However, unless these remote sensing platforms are applicable at local scales and integrated into a land-based smart climate and agricultural management system, achieving sustainable irrigated agriculture remains challenging for medium and small farmers.

The results obtained in the SEALACOM approach using mini sprinklers showed trends similar to those of earlier studies on potato performance and water use efficiency conducted in the country using a drip system [21,53,54]. Our results indicated better performance of the Spunta variety tested in Lebanon compared to its performance in the Jordanian desert [55]. However, full fertigation of potatoes ensured better nutrient distribution within the root zone on the fine textured Mediterranean soils of Jordan and prevented rapid immobilization of applied nitrogen by soil microorganisms [55].

Similarly, with the drip-irrigated squash in Syria [56], our results consistently showed higher water productivity, i.e., better biomass production per unit of applied water. This was explained by the higher irrigation frequency and the reduced amount of water applied per each irrigation event.

Adopting a practical, field-validated, simple, low-cost, and efficient continuous fertigation system that considers crop water and nutrient requirements and soil conditions and integrates weather-based irrigation with crop performance under dry Mediterranean climate is crucial. This approach can significantly maintain high yields and crop water productivity, which are essential for food security in water-scarce regions [57]. Structural models that combine precision irrigation with slow-release nitrogen fertilizers and modern irrigation systems have significantly improved crop yield, N use efficiency, and water productivity [58].

Compared to traditional farmer irrigation practices, the use of good agricultural practices with strong deficit irrigation mitigated water stress through expanded root density and better water interception [59]. However, with the complex factors affecting water saving, crop performance, and water productivity in dry regions [60,61], local soil and climatic conditions as well as farmers’ attitudes and skills must always be considered.

6. Conclusions

The SEALACOM Project’s advanced methodology for assessing crop water demands and applying metered irrigation achieved increased yields and higher water use efficiency. This is crucial in an era of increasing drought incidences, which exacerbate water scarcity and put pressure on limited water resources. Compared to traditional practices, the improved SEALACOM fertigation method resulted in over a 22% increase in higher-quality zucchini yield, from 1417 kg ha⁻¹ to 1729 kg ha⁻¹, more than 23% water savings, and over 43% higher water productivity. Farmers expressed their intention to follow the SEALACOM approaches and adopt continuous feeding instead of intermittent fertilization, using a modern injector rather than a closed tank. Local farmers were trained in advanced fertilization and irrigation techniques.

In continuous feeding, higher yields and better quality zucchini and potatoes were obtained with doubled nitrogen and phosphorous use efficiency. For potato production, the improved practice using mini-sprinklers and continuous feeding resulted in a 17.8% yield increase, from 1900 kg ha⁻¹ to 2200 kg ha⁻¹, and a 40% increase in large tuber size (p < 0.05). The project methodology provided a better nutrient ratio formulation, aligning with soil conditions and crop demands to major nutrients. The efficient use of water and nutrients will reduce energy consumption for water pumping and application. Continuous feeding’s water and fertilizer savings have significant economic and environmental impacts, particularly in drylands.

Demonstrating water accounting and productivity based on totally and effectively applied water can help disseminate good, proactive practices, enhancing food production with a lower environmental footprint, higher sustainability, reduced production costs, and better commercial value of the final product. The findings from the SEALACOM Project are becoming part of local agricultural and water policies. Turning these results into an action plan requires strong commitment, decision-making, and capacity building to conserve and properly manage water resources, with special emphasis on groundwater, to enhance crop production. This is particularly important for the Bekaa Plain, where agriculture is the major source of income.