Effect of Water Irrigation Amounts and Nitrogen Fertilizer Levels on Teosinte Productivity and Optimal Economic N-Rates Under Salinity Stress

Effect of Water Irrigation Amounts and Nitrogen Fertilizer Levels on Teosinte Productivity and Optimal Economic N-Rates Under Salinity Stress Sherif A. Aboelgoud Forage Research Department Field Crops Research Institute Agricultural Research Center, Giza 12619 Ibrahim S. M. Mosaad (  ibrahim.mosad@arc.sci.eg ) Soil Fertility and Plant Nutrition Research Department Soil, Water and Environment Research Institute Agricultural Research Center, Giza 12619 Hesham A. Awad Water Requirements and Field Irrigation Research DepartmentSoil, Water and Environment Research Institute Agricultural Research Center, Giza 12619


Introduction
The most important abiotic stress for agriculture, and for teosinte speci cally, is drought. There is variability for drought tolerance in maize but, unlike teosinte, it has not been bred by drought tolerance. An example of the problem is provided by 1 ,who acknowledge that climate change is a major concern for humanity.
As climate projections for temperate regions indicate that temperature will increase, and precipitation will decrease over a few decades subsequently impacting water availability negatively. Hirich et al., 1 found that the growing season for maize would be shortened by 20 days due to increasing temperature decreasing water requirements by 13%. However, crop evapotranspiration is projected to increase by 15% resulting in an overall yield reduction of 2.5% by the century's end. Among the most important factors that affect drought in crops, in addition to climatic factors, are the lack of irrigation water or the irregularity of the irrigation process. Understanding crop water needs is essential for irrigation scheduling and water saving measures in an arid and semi-arid region because of its limited water supply.
Teosinte (Zea mexicana Schrad L.) is one of the most important summer forage crops which closely related to maize in most allometric trait. It has the advantage of tillering and regeneration as a fodder crop 2 . Teosinte and maize growth and yield, are most sensitive to nitrogen application under moisture stress conditions. Improper fertilizer and water management are the two major factors adversely affecting maize growth and productivity under dryland conditions. The main objective in agriculture production, so far, focused mostly on the increase of yield and production 3,4 .
In Egypt, the water resources are limited and restrict many crops production especially in newly reclaimed lands due to the establishment of intensive agricultural production in the Nile Delta and valley area. The agricultural area consumes more than 84% of the available water resources 5 . Three factors affect the agricultural water use such as the water needs (evapotranspiration) by the crop, water availability, and water holding capacity of the soil 6,7 . Also, climate changes, such as altered precipitation and temperature systems, have had negative effects on crop quantity and yields. Seasonal global temperatures have increased, with even larger changes observed in several regions Fertilizer application is one of the most effective and practical ways to control and improve yield and nutritional quality of crops for human consumption. In the current food production scenario across major cropping systems of the world, crop yield is limited more by availability of nitrogen (N) and water resources rather than by the crop genetics 8, 9 . Increased plant nitrogen adsorption was observed under irrigation only in drought years, and it was decreased in optimal or extremely wet years 10 . Nitrogen (N) is one of the critical nutrients for crop production and is generally applied in large quantities to soils 11 . The use of mineral nitrogen fertilization results in improved growth, higher biomass, and yield, and facilitates the metabolism to give a higher amount of protein in maize plant tissue 12,13 . Nitrogen directly in uences the amino acid composition of protein and thereby the nutritional quality of the economic production.
In the last several decades, the uses of irrigation and fertilization have led to increases in crop production and food security 14 . In regions that have waterscarce, high yield and improved water use e ciency (WUE) of crops can be obtained if water and nitrogen (N) are properly applied. While water and N have been the subject of research worldwide, studies are needed to advance our understanding of the complexity of their interaction 15 . Irrigation and fertilization are widely used for the production of food and forage crops, mostly because it alters the farm environment by changing the soil water contents and soil nutrients which result in the increase of soil fertility and growth environment. Therefore, it would be necessary to improve the water use e ciency and fertilizer production e ciency in arid and semiarid regions, especially for eld management purposes 16 . The interaction of nitrogen and irrigation has signi cant effects on maize biomass yield 16 . Also, Nilahyane et al showed that irrigation water, N, and application timing signi cantly affected the growth and DM yield of maize, especially at late vegetative and mid reproductive growth stages 15 .
The coupling effect of water and fertilizer is not distinct and more fertilizers can be used to compensate for the shortage of water under limited water resources. Meanwhile, through the coupling of water and fertilizer, N affects water consumption. But we still have limited information about the effects of different measures of controlling the supply of water and fertilizer on teosinte fresh and dry yield and optimal and economic optimal nitrogen rate. Thus, the present study's aim was to focus on the relationships between the irrigation amount and N fertilizer input levels on teosinte fresh and dry yield and optimal and economic optimal nitrogen rate.

Experimental setup
Two eld experiments were setup on clay soil at El-Serw Agric. Res. Station Farm, Damietta Governorate, Egypt. The farm is located at 31o 22' N latitude and 31o 64' E longitude during the two summer seasons 2020 and 2021 to study the effect of irrigation amount at three levels (100%, 80% and 120% from irrigation water requirements) and nitrogen fertilizer levels (60, 90 and 120 kg N fed −1 ) on the yield productivity and its quality of teosinte (Zea mexicana, L.) genotype Damietta.
The analysis of the surface soil layer (0 to 60 cm) at the start of the experiments was as follows: soil saturation extract for EC analysis (ECe) 6.55 dS m −1 with pH (H 2 O, 1 soil to 2.5 H 2 O) value of 8.2 and contained 5.21 g kg −1 Walkley-Black carbon, 0.30 g kg -1 total nitrogen by the Kjeldhal method 17 , 7.97 mg kg −1 0.5 M NaHCO3-extractable P 18 and 448 mg kg −1 1 N NH4OAc-extractable K 19 . The soil study experiment is classi ed as moderately saline soil (ECe 8-16 dS/m) based on the USDA classes 20 . The experimental farm was irrigated from the El-Serw drainage, which was irrigated from a point approximately 20 km from the beginning of the drainage (EC 1.2:1.4 dS m-1, SAR 10.5:11.3), so the irrigation water classi cation is considered to be water that increases salinity problems 13,21 . Some hydro physical properties of the soil at the experimental site are presented in Table 1. According to the Köppen climate classi cation, the area has an arid climate with dry hot summers and wet cool winters 22 . Meteorological conditions (mean precipitation (mm), surface pressure (kPa), percentage humidity (Table 2), and maximum, minimum, and main temperature, dew/forest point, and wet bulb temperature (°C) at the teosinte cultivation experimental site during the two winter seasons ( Figure 1).

Experimental design
The treatments were laid out in a strip-plot experimental design with three replicates, the plot size was 6x7 m 2 . The seeds were drilled in hills 20 cm apart with 20 kg/ fed seeding rate. Planting date was 23rd and 21st May in 1st and 2nd seasons, respectively. The preceding winter crop for both seasons was berseem in the two seasons. Irrigation treatments were allocated at the vertical plots, while the assessed nitrogen fertilizer in the form of ammonium nitrate (33.5%) levels were occupied the horizontal plots as follows: Vertical plots (Irrigation levels, I): 1 = 100% Irrigation requirements (Full Irrigation), 2 = 80% from irrigation requirements and 3 = 120% from irrigation requirements (the irrigation treatments were started after the life irrigation). Horizontal plots (Nitrogen fertilization rates, N): N1 = 60 kg N fed −1 , N2 = 90 kg N fed −1 and N3 = 120 kg N fed −1 . The nitrogen doses were divided into three equal doses. The rst dose was added after 21 days from sowing, the second and the third doses were added after the rst and the second cuts, respectively.
Agricultural practices were done as recommended by forage Research Department. Three cuts were taken during each summer season after 55, 95 and 120 days from sowing.
Agronomic characters: Fresh forage yield (ton/ fed); was weighed in kg/ plot then converted into ton/ fed.
Dry forage yield (ton/ fed); 100g plant samples from each plot were dried at 105°C till constant weight and dry matter percentage (DM %) was estimated then dry forage yield (ton/ fed) was calculated by multiplying fresh forage yield (ton/ fed) X DM%.
Water relations: 1. Actual evapotranspiration (Eta) "cm/fed). Gravimetric soil samples from 0.15 m to 0.60 m depth were collected after planting, before and after irrigation and after cutting to determine the actual water consumption. Total consumed water was calculated according to the equation suggested by Israelsen and Hansen 23 as follows: Where: ETa= actual evapotranspiration (cm). i= soil layer. n= total number of soil layer. 2= (%) soil moisture on mass basis after irrigation. 1= (%) soil moisture on mass basis before irrigation. b= soil bulk density. D= layer depth (cm).
2. Applied water application (Ea), according to ICID 24 as: Optimal and economic optimal N rate Optimum N rates Quadratic N response curves to fertilizer N rates were constructed for each irrigation amount using three N rates (Table 3 and  The ratio of the cost of fertilizer N to the price of teosinte fresh yield was referred to as cost: price ratio (CPr).
The Nop and Neop were calculated according to Thind et al. 27 and Mosaad et al. 13 using the following equations: where Y is fresh yield (kg fed −1 ), x is the fertilizer N rate (kg fed −1 ), and a, b, c is regression parameters.
Statistical analysis: Data

Agronomic traits
Fresh and dry yields: Data in Table 3 show that there were signi cant differences among the studied traits i.e., irrigation amount on fresh and dry yields. Fresh and dry yield increased with cut two in the two seasons. Full irrigation recorded the highest means value of fresh yield (7.66 and 7.36 t fed −1 , in the 1st and second seasons ( ) respectively) in the third cut, that is true for dry matter (1.230 and 1.295 t fed −1 in the two seasons). Decreasing irrigation with 20% decrease the highest mean value (30%) in the rst season in the second cut and (20%) in the second one. Also, increasing water irrigation amounts with the same percent decrease the highest fresh and dry yield (19 and 29% in the two seasons) for the second cut. Decrease or increase irrigation amounts with ±20% recorded lowest means for fresh and dry yields. Regarding to total forage of teosinte, full irrigation achieved the heaviest total yield (19.28 and 18.43 ton/fed in the two seasons, respectively) followed by +20% accesses water irrigation while, decreasing water irrigation e.g., -20% recorded the last value of total fresh weight of forage teosinte. Data of total dry matter yield of teosinte recorded the same trend.
Regarding to N-fertilizer rates, Nitrogen in various levels affected signi cantly fresh and dry yields in all cuts ( Table 3). The highest mean of adding nitrogen fertilizer recorded the highest means (7.48, 7.36 and 1.250, 1.235 ton/fed) for fresh and dry yields in the 1st and 2nd seasons respectively. Nitrogen (N) is an essential nutrient and key limiting factor in crop production of different agro-ecosystems. Moreover, In uencing of N-fertilizer levels on total fresh and dry yields recorded the highest value when the plots received 120 kg N/fed.
Interactions between the studied traits recorded the signi cance of difference on fresh and dry yields at 0.05 levels of con dence ( Table 3). The highest means (9.87, 8.62, 1.601 and 1.543 t fed −1 ) recorded for fresh and dry yields in the two seasons in the second cut, respectively. Table (3) showed the effect of water amounts and N-fertilizer rates on fresh and dry yields over cuts. The heaviest weight of fresh and dry yields (23.14, 21.68 and 3.82, 3.84 ton/fed in the rst and second seasons, respectively) came from the treatment of full irrigation and the highest N-rates followed by +20% water applications and -20% water irrigation at the same N-rates came the last treatment for the yield of fresh and dry.

Data in
The reduction of yield and yield component under waters stress could be due to numerous reasons including decrease of photosynthesis e ciency, leaf area, net assimilation production, and reduction of water and mineral absorption by the root which ultimately decline developmental and vegetative growth. The results indicate that increasing irrigation intervals to 120% reduced all the studied characteristics likely due to water stress de cit. Inadequate available soil water reduces the metabolic activity of maize, decreases its dry matter accumulation, and reduces its photosynthetic level by reducing the chlorophyll content in leaves 33 . our results show that in the third cut, full irrigation produced the highest mean value of fresh yield (7.66 and 7.36 t fed −1 in the rst and second seasons, respectively) and dry matter (1.230 and 1.295 t fed −1 in the two seasons). Reduced irrigation by 20% reduces the highest mean value (30%) in the rst season in the second cut and (20%) in the second cut. Increasing irrigation amounts by the same percentage also reduce the highest fresh and dry yield (19 and 29 percent in the two seasons) for the second cut. Reduce or increase irrigation amounts, with 20% being the lowest recorded mean for fresh and dry yields.
Further, water stress had a greater effect on the growth and development of maize through the seedling stage than the other three stages. Water stress reduced growth and biomass due to decreased intercepted photosynthetically active radiation and radiation-use e ciency. These effects extended into the reproductive stage and nally decreased total gain weight and yield 34 . Water de cit stress through the later vegetative and maturation stage directly decreased yield and its components. Yield was reduced after water-de cit stress occurred during the late vegetative stage and was exacerbated by additional stress during the maturation stage. In all treatments, yield decrease was proportional to the severity of the water stress. However, water stress used had a larger effect on maize yield during the maturation stage than during the late vegetative stage 35 .
In terms of nitrogen fertiliser rates, nitrogen at various levels had a signi cant impact on fresh and dry yields in all cuts. In the rst and second seasons, the highest mean of adding nitrogen fertiliser recorded the highest means (7.48, 7.36, and 1.250, 1.235 t fed −1 ) for fresh and dry yields. Nitrogen (N) is an essential nutrient and key limiting factor in crop production of different agro-ecosystems. Nitrogen is the major nutrient required by pearl millet under agri-horti system which positively increases the growth attributes and improve the yield 36 .
Stem diameter and plant height: Recording data in Table 4   Nitrogen fertilizer rates affected signi cantly stem diameter and plant height. The thickest stem and tallest plant obviously from cut2 under the highest level of nitrogen while, the thinnest stem diameter and plant height recorded from the plots received 60 kg N/fed. The increase in N application, the plant photosynthesizing area, and the assimilate production were increased, therefore caused more plant height, more number of shoots per plant, greater leaf area/plant and thus increased fresh forage weight per plant 29,30  Regarding with the interaction among water irrigation amounts and nitrogen fertilizer levels, there were signi cant differences in all cuts except the third cut for stem diameter character and second cut for plant height. The thickest stem diameter was (2.81 and 2.93 cm in the second cut in the 1st and 2nd seasons, respectively) under full irrigation and the highest nitrogen rates. Whereas, the tallest plant recorded in the two seasons in the third cut under full irrigations amounts and the highest rate of nitrogen fertilizer. These results indicated that using 100% irrigation amount resulted increasing in yield with the highest dose of N-fertilizer.

Optimal and economic optimal N rate
The proportion of variability (R 2 ) for relationships between nitrogen fertilization rates and teosinte total fresh yield was close to 1.00 (P < 0.01) showing that the quadratic model could adequately describe the teosinte fresh yield response to nitrogen fertilization rate.  A decrease in the amount of irrigation water from the recommended rate of 20% resulted in an increase in the optimum rate of nitrogen as well as the economic optimum rate at 175.12 and 162.23 kg N fed −1 , respectively. This is attributed to the effect of low irrigation water, which leads to a drought of the soil and plants, which leads to a high loss of nitrogen fertilization by volatilization due to drought. Soil water affects nutrient transformation from unavailable to available form or vice versa, and thereby the total uptake amount. It also in uences the availability of applied nutrients and e ciency through its effect on various nutrient loss mechanisms such as volatilization, nitri cation, and/or urease hydrolysis 37 . Also, the increase in the amount of irrigation water from the recommended rate of 20% led to a very high increase in the optimum rate of nitrogen as well as the economic optimum rate at 225.55 and 211.01 kg N fed −1 , respectively. However, this is due to the effect of increasing the irrigation water over the recommended amount, which also leads to a high loss of nitrogen fertilization by escaping with the excess water to the agricultural drainage channels. Rong and Xuefeng indicated that excess N fertilizer and irrigation application rates have been provide for crop, and cause more NO 3 leaching 38 .
While the optimum rate of nitrogen and the economic optimum rate of nitrogen at the recommended amount of irrigation water is at 155. 19  Applied irrigation water and actual evapotranspiration: Impact of irrigation treatments on amount of applied water and actual evapotranspiration values are presented in  Table 6 Means of interactions between irrigation amount and nitrogen fertilizer rates on applied irrigation water (m3/fed) and actual evapotranspiration "ET a " (m 3 /fed) of teosinte in 2020 and 2021 seasons Treatments Applied irrigation water m3/fed Actual evapotranspiration m3/fed treatment (I-100) was managed for high productivity, whereas de cit irrigation treatment (I-60) was maintained at 60% of eld capacity. Water stress was applied continuously during the growing cycle 42 .
Water utilization e ciency (WU t E), water use e ciency (WUE) and irrigation water application (Ea): Water utilization e ciency (WUtE) values for teosinte fresh weight yield as affected by the tested variables during 2020 and 2021 growing season are presented in Table 7. Results showed that average water utilization e ciency (WUtE) values were affected by irrigation treatments and nitrogen level treatments. The obtained results in Table 7 indicate that the average water utilization e ciency (WUtE) as affected by irrigation treatments and N-fertilizer rates in the two seasons were 6.68, 7.21&7.88 and 6.54, 7.15 & 7.66 kg m −3 in the rst and second seasons, respectively. Data showed higher application e ciency mean values, differed from 0.83 to and 0.83 to 81% at 60 to 120 N-rates than those in 100% to +20% water application.
E ciency water utilization is a limiting factor to crop production. The results of our study revealed that irrigation treatments and nitrogen level treatments had an effect on average water utilization e ciency (WUtE) values. Also, the results show that the average water utilization e ciency (WUtE) as affected by irrigation treatments and N-fertilizer rates in the rst and second seasons was 6.68, 7.21&7.88 and 6.54, 7.15&7.66 kg m-3, respectively. These results collaborate with Ewis et al. whose, reported that WUtE was positively responded to increasing nitrogen level up to 150 kg N fed −1 which mainly due to the effect of nitrogen on improving the growth of roots and shoots of maize in turn improved water absorption from soil 40 .
While the results of water use e ciency means were 8.0, 8.7, and 9.5 and 7.8, 8.9, and 9.2 kg fresh weight for 100 percent full irrigation in the two seasons when N-fertilizer doses were applied. The obtained results agree with Shi et al. whose, showed WUE was higher in the dry-cultivation treatment since yields decreased relatively less than the supply of irrigation water 43 . However, higher WUE can be achieved by relating de cit stress at the late vegetative stage somewhat than maturation stage 44 .
Data, on the other hand, revealed higher application e ciency mean values ranging from 0.83 to and 0.83 to 81% at 60 to 120 N-rates than at 100-120% water application. The high irrigation water application (Ea) values under the conditions of the experiment were due to precise land leveling na proper selection of plot size for irrigation teosinte under clay soil conditions 45 . These results declared that adding water at 100% (full irrigation) may improve application e ciency. This is logic and expected result and it is attributable to more irrigation events applied under full irrigation, similar results were obtained by Yousri and Ewis et al., whose, stated that applying full irrigation practice signi cantly increased grain yield of maize 39,40 .

Conclusions
Although, all water relationships gave the best mean values for actual evapotranspiration, water utilization and use e ciencies also, higher application e ciency values at full irrigation and 120 kg N-levels than the other treatments. Furthermore, the results revealed that the economical yield of teosinte fresh cuts was higher when using 211.01 kg N fed −1 with 120% of the recommended irrigation rate than when using 148.22 kg N fed −1 with the recommended irrigation rate. As a result, we recommend 211.01 kg N fed −1 to achieve an optimum economic yield of teosinte fresh cuts, particularly in saline soil, with 120% of the recommended irrigation rate.