**4. Irrigation lines and mulches**

Using suitable machinery, it will be necessary to make the bedding (furrows or edges). The main irrigation lines (pipes: hydraulic PVC) are the ones that will carry the greatest flow of water to the irrigation sections. In each irrigation section, the secondary irrigation lines (irrigation belt) are installed, these lines are the ones that will be on the edges [1]. Once the entire irrigation system is installed, it is time to start installing the plastic mulches on the furrows (personal communication). The emitters

#### **Figure 2.**

*Bedding system: Irrigation strap, plastic, and tomato plants grown in soil with high sodium concentration. (Courtesy Dr. Víctor García-Gaytán).*

in the strips are responsible for efficiently distributing the water in each irrigation section. The amount of water applied to each plant will be calculated based on the irrigation flow rate, soil type, demand, and growth stage of the tomato (personal communication). For industrial production dimensions, it will be necessary to install the best brand of irrigation belt that the market offers, which provides durability and resistance to the pressure exerted by the irrigation flow (personal communication) (**Figure 2**).

#### **5. Nutrient solution in fertigation**

The application of irrigation and nutrition will be monitored by qualified personnel (personal communication). The monitoring will be carried out from the irrigation room, where the semiautomated/automated irrigation head will be installed. The farm manager must have computer skills to program the nutrient application events/ times in the irrigation sections (personal communication). In nutrient injection systems, it is essential to have a container for the application of special solutions (biostimulants: seaweed extract, protein hydrolyzates, humic acids, phosphites, bacteria, and fungi). Special solutions are to correct nutritional deficiencies, stress, or control pests and diseases quickly and effectively. The dose, handling, mixing, and application must be supervised/monitored by experts in plant nutrition (personal communication).

High yield and product quality of crops are only possible if nutrition is optimized, this includes nutrient solution composition, water supply, nutrient solution temperature, dissolved oxygen concentration, electrical conductivity, and pH of the nutrient solution [10]. Oxygen content in nutrient solutions has an effect on the yield of sweet pepper and melon about 20% and 15% [11]. EC is related to the amount of ions available to plants in the root zone [12]. pH and EC monitoring helps to eliminate the problem associated with fertilization, showing the nutrient availability to the crops [13]. There must be a mutual relationship between the anions and cations of the nutrient solution [14]. The nutrient interactions are generally measured in terms of growth response and change in the concentration of nutrients [15]. Proper knowledge of possible synergistic and antagonistic interactions between nutrients [16] is required. Differences in nutrients concentrations between desired levels in the solutions and those found in the tap water represent the amounts of nutrients per volume nutrient solution (meq L−1), which should be added through fertilizers [17]. The efficient acquisition of water and mineral elements y plants roots is a prerequisite for sustainable intensification of crop production [18]. Root growth is important for effective exploration of soil and interception of nutrients [19]. Interaction with microorganisms is also significant [20]. When the roots absorb excessive cation compared with anions, the roots offset this by excreting protons (H+ ), which generally leads to rhizosphere acidification. When they absorb more anions than cations, the roots excrete hydroxyl (OH<sup>−</sup> ). Hydroxyl reacts with carbon dioxide to form bicarbonate (HCO3 − ), which leads to rhizosphere alkalization [21]. The calcium levels Ca(NO3)2 as a soluble fertilizer and nitrogen should be considered in the irrigation systems; in addition, it should be considered that the Ca2+ in the soil solution competes with K+ , Mg2+, and N [22]. To achieve high-quality yield, a balance of nutrients in the rhizosphere must be maintained for each stage of growth [23]. The manipulation of the climate of the greenhouse (RH, temperature, level of environmental CO2) can compensate the negative effects of high salinity on the yield and quality of the fruit [23].

#### **5.1 Monitoring of soil and fertigation frequency**

The monitoring of soil moisture, the frequency of fertigation, the proper functioning of the emitters should be checked continuously, to prevent the accumulation of salts on the surface of the soil and prevent nutritional imbalances. The surface layer of the soil tends to accumulate high concentrations of salts after evaporation or transpiration, when the irrigation water contains soluble salts [24]. Monitoring the saturated extract medium provides an assessment of both the applied salinity load and the concentration of fertilizer salts [24]. Transpiration during the day may cause significant differences between the water content in the rhizosphere and that in the bulk soil [25]. Selective electrode analysis of NO3-N concentration of soil solution sample obtained by suction lysimetry, it is a good monitoring method [26].

Soil testing to monitor nutrient availability in the root zone is a valuable alternative [27]. The distribution of NO3-N in the soil profile is very greatly influenced by fertigation frequency in sandy-loam soil [28]. Soil-moisture sensor-based irrigation system in bell pepper significantly reduced the applied irrigation resulting in 7–62% less irrigation water applied compared with fixed time irrigation treatment without compromising marketable yield [29]. Smart irrigation, where a well-scheduled and well-dosed irrigation regime is essential, as by applying the right amount of water at the right time, one avoids plant demand being either exceeded or not met [30]. Despite the potential of fertigation for effective water and N saving, in practice, there is a need for improvement in the management of this technology to make it effective [31]. Increasing the irrigation frequency significantly enhanced the transpiration flux so that the transpiration flux of plants under low irrigation-P level at 10 daily irrigation events was similar to that of plants of lettuce under high solution-P [32].

#### **5.2 Bioprotection of roots**

Optimization is needed in the nutrition of crops, which involves the use of biostimulants to counter oxidative stress and the management of strain bioformulations (bacteria and fungi) that protect and stimulate root for the acquisition of nutrients [1]. Biostimulant action is diverse, but it can include N metabolism activation, P release on soil, stimulation of soil microbial activity, and root stimulation [33]. These include seaweed extract [34, 35], protein hydrolyzates [36, 37], humic acids [38, 39], phosphites [40, 41]. Bacteria and fungi also stimulate and protect the roots [1], these include beneficial microorganisms, which can be free-living, rhizospheric, or endosymbiotic [42]. According to [43], specialized plant membrane transporters can be used to enhance yields of staple crops, increase nutrient content, and increase resistance to key stresses, including salinity, pathogens, and aluminum toxicity.
