Assessing the performance of wheat (Triticum aestivum L.) crop by managing irrigation and nitrogen fertilizer under a semi-arid environment

Arid regions in India and the world are facing the problem of water scarcity. The leading causes of water scarcity are the changes in climatic conditions, rapid increase in population, and increase in agriculture (El-Hendawy et al. 2017; Pradhan et al. 2019; Sharma et al. 2022). Climate change has led to an increase in temperature, due to which most countries are becoming warmer and drier (Perry et al. 2009; Sharma et al. 2018a, 2018b; Mehta & Yadav 2021). Approximately 75% of fresh water is used by the agriculture sector, which further aggravates the scenario (Prathapar 2000). On average, the water requirement of a wheat crop is 45 cm, which can vary with factors such as the type of soil irrigation method and crop variety (St-Martin et al. 2017; Fellah et al. 2018). Wheat crop belongs to the category of crops having high water requirement per hectare (Mishra 2017; Gunawat et al. 2022). Well-drained loam, sandy loam, and clay loam soil are conducive to the growth of wheat (Behera & Panda 2009a; Li et al. 2010). According to the World Bank report, the state government demotivates the cultivation of water-intensive wheat crops and other water-guzzling crops, which is affecting water sustainability and narrowing fiscal space (World Bank Report on Rajasthan 2018; Mundetia et al. 2023). Wheat (Triticum aestivum L.) is one of the most dominant crops that covers approximately 32% of the total land under cereal cultivation globally and ranks first among all the other cereals (Tari 2016). Better matching of fertilizer and irrigation rates suitable to the local climate and soil type can increase the productivity of wheat (Boudjabi & Chenchouni 2021; English et al. 2002). Without compromising productivity and profitability, using the optimum quantity of nutrients is vital for agricultural sustainability (Salim & Raza 2020). Proper water management is extremely important for maintaining crop production in the arid and semi-arid regions where water is usually a limiting factor in crop growth.

Globally, India ranks fourth in wheat production (after Russia, USA, and China) and contributes approximately 8.7% of the total wheat production (Ramadas et al. 2019). Wheat is the second most important food crop in India, particularly in the north-western and northern parts of India. It is cultivated on an area of approximately 19–20 million hectares, which accounts for approximately 54% of the total irrigated area in India. Groundwater is predominantly used in irrigation in Indian agriculture, particularly in semi-arid regions, due to the limited supply of surface water (Zhai et al. 2018; Sreedevi et al. 2019). In 2016, wheat production in India was 2,750 kg/ha, whereas that in China was 5,393 kg/ha (Agricultural Statistics at a Glance 2017 Government of India). Nearly 86% of wheat production in India occurs in five states, namely Uttar Pradesh, Punjab, Haryana, Rajasthan, and Madhya Pradesh (Nagarajan 2005). The total average irrigated land area of the semi-arid zone of Rajasthan is 0.37 million hectares, and the cultivated wheat grain yield is approximately 3,315 kg/ha (Gunawat et al. 2016). The semi-arid region of Rajasthan is highly fertile. Because of limited irrigation water availability, there is a challenge to the cultivation of wheat crops. In this context, adaptation strategies can help increase wheat production under changing climate conditions (Hussain et al. 2018). Irrigation water availability is limited worldwide, which necessitates the development and exploration of new water-saving irrigation technologies and methods to reduce water losses through deep percolation and soil surface evaporation (Mandal et al. 2005; Ahmadi et al. 2011; Liu & Wang 2018; Bouaroudj et al. 2019; Kumar et al. 2020).

Farmers generally use a high quantity of fertilizer dose and a large amount of irrigation water at frequent intervals to increase agricultural yield (Musick et al. 1994; Hussain et al. 1995; Boudjabi et al. 2015, 2019). According to Ul-Allah et al. (2018), managing low irrigation water consumption at various plant growth stages, with minimal consequences on crop growth and quality, has remained a top priority of various studies worldwide. Intensive use of agrochemicals leads to water and soil quality degradation, which seems to be a serious global issue (Panda et al. 2003). Nitrogen is an effective plant nutrient that affects plant growth, water-use efficiency, and nitrogen-use efficiency in wheat crops (Mehrabi & Sepaskhah 2018; Bandyopadhyay et al. 2019). Temperature and its related seasonal changes are also deleterious for agricultural production (Mehta & Yadav 2022). The increase in temperature is directly linked to climate changes, which may cause harm to crop production, livestock, fishery, and associated sectors (Rojas-Downing et al. 2017; Mbow et al. 2019). On the other side, the plant–soil–water relation increases productive water utilization and improves agriculture management (Fan et al. 2018). Thus, understanding the linkage between harvest yield and water-use efficiency is essential to facilitate the growth of various semi-arid crops and develop water management practices (Halitligil et al. 2000; Wiedenfeld 2000; Fellah et al. 2018). Deficit irrigation is a useful method that helps in the complete development process of plants requiring a limited amount of water (Fereres & Soriano 2006; Ali & Talukder 2008; Behera & Panda 2009b; Geerts et al. 2009; Bezzalla et al. 2018). Considering the limitation of land allocation for wheat production, ensuring an increase in the water-use efficiency by using well-planned water-saving techniques in agriculture is essential. This study was conducted at the experimental level with only a single variety of wheat crop, i.e. Raj 3077. In water-deficient areas, a suitable irrigation method helps farmers save crops and water (Liu et al. 2013). These insights allow for assessing the impact of fertilizer doses and different irrigation periods on wheat crop development.

Improved nutrient use efficiency will not only help to lower the cost of crop production by reducing fertilizer use but also help to reduce fertilizer contamination. Even though using less fertilizer increases nutrient use efficiency, farmers are concerned about optimizing profit. So, it's essential to find a balance between nutrient efficiency and crop productivity. To address these gaps, this study aims to find the best combination of nitrogen fertilizers and irrigation in wheat crops for improved nutrient management strategy in the semi-arid region of Rajasthan. For optimal agricultural productivity, a proper irrigation schedule and N application modes are crucial. Even though significant work has been done on irrigation scheduling and N application modes during wheat production (Si et al. 2020; Zain et al. 2021). However, deep knowledge of split N application modes under various irrigation scheduling in winter wheat is still lacking. The response of wheat to the use of N fertilizers and irrigation is not well understood in the semi-arid region of Rajasthan. As a result, there has been uncertainty about the use of recommended fertilizer rates with proper irrigation. To answer the research questions, the main objective of the study is to study the effect of nitrogen fertilizer rates and irrigation frequency on the growth and yield of wheat crops using field experiments in the semi-arid region of Rajasthan, India. The outcomes of the present study will give insights into how proper irrigation of winter wheat's crop performance can be improved by adjusting integrated irrigation and N fertilizer management.

Before performing an experiment in the field, soil samples were collected to determine initial soil physico-chemical properties. Different physico-chemical parameters such as soil moisture, soil water holding capacity, pH, electric conductivity, micronutrients, and NPK content of the experimental field soil were analyzed in the laboratory. The experimental site has coarse-to-medium textured loamy soils.

The soil pH ranged from 7.2 to 7.5, electrical conductivity was 755–761 μS/cm, and bulk density was 1.43–1.47 g/cm³. The soil has medium water holding capacity of 28.8–29.6%. It has a low nitrogen (N) content (77.6–80.3 kg/ha), a moderate phosphorus (P) content (2.01–2.13 kg/ha), and a high potash (K) content (492.7–507.1 kg/ha). Table 1 presents the data regarding soil water holding capacity, porosity, moisture content, bulk density, particle density, micronutrients (Fe, Mn, Zn, and Cu), and carbonates.

A total of 12 experiments with 4 replicates were conducted by combining different doses of fertilizer (100% RD, 125% RD, 50% RD, and no fertilizer) with respect to the recommended dose (RD) of 150 kg/ha and three irrigation intervals (15, 21, and 25 days). Irrigation water was applied using the surface flood method. At the time of irrigation, 50 mm of irrigation water was applied at each sub-plot at various intervals. Detailed information on different treatments is presented in Table 2.

Agricultural land was prepared using standard tillage equipment, and seed plantation on the land was performed manually. The wheat cultivar ‘Raj 3077’ was used in the experiment because it is well-adapted to the region and grows well under light-to-moderate saline/alkaline conditions, which allowed flexible sowing dates. Seeds were sown in the last week of November (28th November) for three consecutive years from 2014 to 2016, with a seed rate of 125 kg/ha. At the time of land preparation, compost manure of cow dung was mixed in the topsoil. Afterward, nitrogen fertilizer (urea) was applied at the tillering stage of growth according to the doses mentioned in different treatments. The weeding process was performed using spud between 30 and 60 days after sowing. Thereafter, harvesting was performed using a parcel harvester on April 10 each year. The total grain biomass was determined for each treatment immediately after harvesting. Moisture correction was not performed on the yield values. Wheat plants were harvested at ground level from 2 m × 2 m of each sub-plot to determine biomass yields.

Crop yield data of 3 years were analyzed using the basic statistical method (average, standard deviation, maximum-minimum biomass, and yield from four replicas were calculated). Pairwise comparison is a widely used method for comparison in agricultural research (Carmer & Walker 1985). The commonly used test for pairwise comparison is the least significant differences (LSD) test, which is suitable for a planned pair comparison (Gomez & Gomez 1984). The procedure to use the LSD test was described by Fisher (1936). Generally, the F-test is used to test the hypothesis that all means are equal. The two treatments are considered different if the absolute difference between the two-sample means is more than the calculated LSD.

The given procedure was applied to analyze different treatments and the average value of crop yield to determine the significant difference among different pairs of means.

Different experiments were conducted for three consecutive years (2014–15, 2015–16, and 2016–17) at the field level. Treatment-wise growth was recorded for root and shoot length at 20, 40, and 60 days. Table 3 presents basic statistics of root and shoot length at the pre-determined time points (20, 40, and 60 days after treatment) for all 3 years. The growth pattern for both root length and shoot length was found to be similar in all 3 years of study. Root and shoot length was found to increase with time. The maximum root and shoot length was observed at 60 days in T-5 and T-3 in the first year (2014–15), in T-12 in the second year (2015–16), and T-11 and T-3 in the third year (2016–17) (Table 3). Table 4 presents the data for different morphological parameters related to plant spike, leaf, root, and stem for all 3 years. The values of all the parameters reflected a high crop yield. As shown in Table 4, the values of all parameters were highest in T-5 and lowest in T-2, indicating that plant growth is directly dependent on fertilizer quantity. LSD value is calculated at a fixed level of significance which can help in differentiating between significant and nonsignificant differences among any pair of treatment means. According to the LSD test, different letters in a column represent the significant difference in the morphological parameters at a 5% significance level. It means that means are not significantly different and are assigned a common letter.

The data for crop yield (kg), biomass (kg), root length (cm), and shoot length (cm) of the wheat crop for all three study years were categorized into four groups, according to the fertilizer quantity used (0, 50, 100, and 125%) and the three irrigation intervals (Table 5).

The results indicated that the effects of fertilizer quantity and irrigation interval on crop yield, biomass, root length, and shoot length were different among the four groups. In the first group (T-3, T-1, T-2), crop yield was highest in the treatment in which the maximum root length was observed, and biomass was highest in the treatment in which the maximum shoot length was observed. A similar pattern was observed in all 3 years. In the second group (T-7, T-4, T-6), crop yield was highest in the treatment in which the maximum root length was observed. In the third group (T-11, T-8, T-10), biomass was highest in the treatment in which the maximum shoot length was observed. In the last group (T-5, T-12, T-9), no specific pattern was observed. Overall, the increase in fertilizer quantity and irrigation interval was found to significantly increase the yield, and the yield was maximum in T-5 (2.20 kg or 4,525.46 kg/ha) in the year 2015–16 (with the irrigation interval of 15 days and fertilizer dose of 125%). The year-wise yield comparison indicated that most treatments resulted in a high yield in the first year (2014–15); however, the yield was found to decrease in the second year (2015–16) and the third year (2016–17).

One-way ANOVA was used to statistically analyze the effects of different fertilizer treatments on crop yield for all 3 years. Differences between the yields were evaluated using the LSD test; the results are presented in Table 6. In Table 7, the means within columns not followed by the same letter are significantly different at the p < 0.05 level, based on the Fisher (LSD) test. In Group I: (zero fertilizer with different irrigation periods), only one treatment of comparison was found significant (T-2 vs. T-1) for three consecutive years. Group II (50% fertilizer with different irrigation) and Group III (fertilizer with RDs with different irrigation periods) exhibited no significant difference among treatments. In Group IV (125% of RD fertilizer with different irrigation periods), only one comparison of treatment (T-5 vs. T-9) was found to be significant in 3 years (2014–15 and 2015–16).

The value for crop yield was statistically analyzed by one-way ANOVA using the LSD test. In the first year (2014–15), only four comparisons of treatments were found to be significant. In the second year (2015–16) and the third year (2016–17), six and nine comparisons of treatments were found significant. Means within columns not followed by the same letter are significantly different at the level of p < 0.05 based on the Fisher (LSD) test (Table 8).

Data for crop yield were further statistically analyzed using the LSD test. In the case of average data, only 11 comparisons of treatments were found to be significant. Means within columns not followed by the same letter are significantly different at the level of p < 0.05 based on the Fisher (LSD) test (Table 9).

In the semi-arid region of Rajasthan, water is an essential element due to its limited availability, and thus, it is a limiting factor for crop development and yields in this region. Water stress is responsible for a decline in crop yield, which suggests its role in crop growth and productivity (Abd El-Mageed et al. 2017; Mostafa et al. 2021). The results of this study validated that nitrogen fertilizer application and irrigation management extensively affect wheat crop growth and development. This result is consistent with those of Zain et al. (2021) for winter wheat crop in the North China Plain. The 12 combinations of fertilizer amount (0, 50, 100, and 125% of RD) and water irrigation intervals (15, 21, and 25 days) were applied in an RCBD field experiment. The morphological parameters, root length, shoot length, crop yield, and biomass were statistically analyzed to determine the crop response. Root and shoot length at 20-, 40-, and 60-day intervals showed a similar pattern of increased growth with time in all the years. Crop yield in many of the treatments was high in the first year (2014–15); however, it decreased in the second year (2015–16) and the third year (2016–17).

The year-wise comparison showed that the three treatment groups with 0, 100, and 50% fertilizer quantity and different irrigation intervals exhibited high crop yield, with maximum root and shoot length and high biomass; however, this pattern for overall average crop yield, root length, and shoot length was not observed in the fourth group of 125% fertilizer quantity. Increased fertilizer quantity and irrigation frequency have been shown to significantly increase the yield (Sandhu et al. 2019), which is highest observed in the treatment T-5 (15 days interval irrigation and 125% fertilizer) with 4,525.5 kg/ha in the year 2015–16 and 4,247 kg/ha for 3 years average. Abdou et al. (2021) reported the same observation and found that a small increase in the nitrogen amount could be responsible for increased crop yield. Differences between the yields of the treatments using the LSD test show that in a pairwise comparison, and some treatments are not worthy of use for crop cultivation in the semi-arid region of Rajasthan.

The present study analyzed the effects of different treatments and irrigation intervals on crop yield production through field experiments. This study provided field-level primary results that can be utilized to develop better practices for region-specific agriculture of wheat crops. The growth pattern for both root length and shoot length was found to be similar in all 3 years of study. The maximum root and shoot length was observed at 60 days in T-5 and T-3 in the first year (2014–15). The average maximum shoot length after 40 days of treatment was observed in T-3 (36.4 cm) in 2014–15, whereas the average minimum shoot length was found in T-7 (21.2 cm) in 2015–16. The crop yield was found to be maximum (4,525.46 kg/ha) in T-5 (1.25 times the RD of urea and 15-day irrigation interval) in the year 2015–16, which was the highest among all three experimental years. From the results of this study, it can be concluded that the wheat is a water-intensive crop and its yield is directly linked to water availability and recommended fertilizer dose. As highlighted in the World Bank Report (2018), in semi-arid regions (e.g. Rajasthan) with limited water resources, intensive agriculture of water-guzzling crops by using groundwater is unlawful as it disrupts water balance in such regions. The present study reports a shift in the cropping pattern toward less water-intensive highly productive crops or mixed cropping and sustainable agricultural practices in such regions. In the context of climate change, advanced agriculture practices, appropriate amounts of nitrogen fertilizer application, and water-saving irrigation methods are the key factors for sustainable wheat production in Rajasthan.

All relevant data are included in the paper or its Supplementary Information.

The authors declare there is no conflict.