Optimization of water and fertilizer management improves yield, water, nitrogen, phosphorus and potassium uptake and use efficiency of cotton under drip fertigation

Highlights

• Field experiments on cotton under drip fertigation were conducted in northern Xinjiang, China.

• Full irrigation 1.0 ETc with fertilizer rate 250–43.7–41.5 kg ha⁻¹ (N–P–K) obtained the highest yield.

• The average ratio of absorbed N, P and K was 1:0.25:1.22.

• The nutrient uptake to produce 100 kg of lint cotton was 8.8–15.0 kg N, 2.3–3.5 kg P and 11.3–17.2 kg K.

Abstract

As a fiber crop and oil crop, cotton plays an important role in the economic development of northwest China, but the lack of appropriate field water and fertilizer management strategies has restricted the harmonious development of cotton industry and environment. Field experiments were implemented to explore the coupling effects of various drip irrigation and fertilizer levels on the dry matter, yield, water and fertilizer use efficiency of cotton. The three drip irrigation levels included 1.0 ET_C (full irrigation), 0.8 ET_C (20% deficit) and 0.6 ET_C (40% deficit), where ET_C is the crop evapotranspiration. The five fertilizer (N-P-K) levels were F₁ (150–26.2–24.9 kg ha⁻¹), F₂ (200–34.9–33.2 kg ha⁻¹), F₃ (250–43.7–41.5 kg ha⁻¹), F₄ (300–52.4–49.8 kg ha⁻¹) and F₅ (350–61.1–58.1 kg ha⁻¹). The results revealed that the seed cotton yield and lint yield showed increasing trends as the irrigation water amount increased at the same fertilizer level during 2012–2014. When full irrigation (1.0 ET_C) was applied, the dry matter accumulation, seed cotton yield, N, P and K accumulation in plants and water productivity were the highest under F₄ (300–52.4–49.8 kg ha⁻¹) in 2012 and 2014. However, the lint yield was highest in 2012 and 2013 under F₃ (250–43.7–41.5 kg ha⁻¹). At the same irrigation level, N, P and K use efficiencies were higher at low fertilization rates than those at high fertilization rates in 2012 and 2013. Deficit irrigation and fertilization levels led to a severe decrease in cotton yield. N, P and K use efficiencies were low under F₄. Comprehensively considering cotton yield, N, P and K uptake and use efficiency, the application of irrigation amount of 1.0 ET_C and N-P-K rate of 250–43.7–41.5 kg ha⁻¹ was the best drip fertigation strategy for cotton production in arid regions of northwest China.

Introduction

Cotton is an important economic crop, which plays an important part in the agricultural and industrial economic structure of China (Qian et al., 2014; Li et al., 2019). China's cotton production ranks first around the world, and the annual production of cotton lint has increased from 4.34 to 6.18 million tons between 1994 and 2014 (FAO, 2018). The Xinjiang Autonomous Region, located in northwest China is the main producing area of cotton in China as a result of abundant light and heat resources (Zhang et al., 2016a). However, the limited water resources in this region largely restrict the local agricultural development. Although drip irrigation under plastic mulching has been widely used in arid regions of China (Li et al., 2015b; Yan et al., 2019; Qi et al., 2020, Shi et al., 2020), local farmers still lack proper field water and fertilizer management strategies. The conventional excessive irrigation and fertilization can lead to low water and fertilizer use efficiency, waste of water and contamination of water resources (Wang et al., 2018; Wang et al., 2019).

Water is one of the important factors limiting cotton growth. Drought stress can thus significantly reduce the biological yield of cotton and hinder the absorption and accumulation of nitrogen, phosphorus and potassium (Hu et al., 2002). Many researchers have revealed that both deficit and excessive irrigation reduced seed cotton yields (DeTar, 2008, Ünlü et al., 2011, Papastylianou and Argyrokastritis, 2014). In addition, Zhang et al. (2016b) found that irrigation can significantly increase the nitrogen accumulation and nitrogen use efficiency, and the deficit irrigation (60% ET_C, where ET_C is the crop evapotranspiration) inhibited the absorption of nitrogen (N). However, some researchers believe that reasonable deficit irrigation can not only save water and keep reasonable proportions of crop vegetative and reproductive growth, but also promote root growth and improve root absorption in cotton (Du et al., 2007, Hassanli et al., 2009). In addition, irrigation method also has a great impact on the growth and development of cotton. Tang et al. (2005) suggested that the alternate drip irrigation could be applied in arid areas to save irrigation water. Rajak et al. (2006) found that drip irrigation lead to a higher cotton yield and water use efficiency compared with furrow irrigation. Wang et al. (2012a) also showed that drip irrigation significantly increased seed cotton yield, plant N uptake, and N use efficiency and decreased NO₃-N in the leakage water. Overall, cotton yield and fertilizer use efficiency can be enhanced by appropriate irrigation amounts and methods.

Reasonable fertilization can also increase cotton growth, yield and fiber quality (Wu et al., 2014, Geng et al., 2016). High yield of cotton is directly affected by the amount of nitrogen absorbed and the duration of absorption (Gong et al., 2015). When the application amount of nitrogen was 375 kg ha⁻¹, the highest fiber yield and agronomic N use efficiency were obtained by Chen et al. (2016). Applying N at the beginning of an irrigation cycle was useful for enhancing cotton yield and fertilizer use efficiency (Hou et al., 2009). The lack of N, P and K can significantly affect cotton growth. The fiber length and strength of cotton will be reduced when lack of N. K deficiency had adverse effects on reproductive growth and increased the soluble sugar to free amino acid ratio and C/N ratio (Read et al., 2006, Hu et al., 2017). Higher biomass, yield, nitrogen, phosphorus and potassium nutrient use efficiency can be obtained when using combined N, P and K fertilizer (Xin et al., 2010). In addition, other researchers have studied the effects of fertilizer ratio or added regulators on enhancing the fertilizer use efficiency of cotton. Yang et al. (2014) observed that applying plant growth regulators could improve the partial factor productivity and agronomic K use efficiency. In short, the reasonable application of N, P and K is beneficial to the growth of cotton and improves the fertilizer use efficiency.

In recent years, many researchers have investigated the influences of various irrigation and N application rates on cotton growth, yield, water productivity and nitrogen use efficiency (NUE) under drip fertigation conditions. It was found that cotton yield increased with the increasing nitrogen and irrigation amounts, but the WUE and NUE decreased significantly in high-water and high-N treatments (Aujla et al., 2005, Thind et al., 2008, Jayakumar et al., 2015). Janat (2008) reported that, relative to the maximum N rates applied in furrow irrigation, 100–150 kg ha⁻¹ N was sufficient for lint yield, nitrogen uptake and recovery of cotton under drip irrigation. In addition, Wang et al. (2010) found that seed cotton yield first increased and then declined as the water and phosphorus (P) amount increased. Reasonable irrigation and N, P and K ratios can ensure crop yield, avoid both water and fertilizer waste, and reduce the environmental impact of excessive fertilizer application (Li et al., 2009). Improper drip fertigation was more likely to exacerbate salt loss or accumulation in the root zone compared with the conventional fertilization methods (Wu et al., 2014). Appropriate irrigation and fertilization can promote the coordinated growth of cotton root crowns and shape a reasonable canopy structure, which is conducive to the accumulation of above-ground biomass and lays a foundation for high yields (Deng et al., 2015).

It is clear from the above review that previous studies have focused largely on the effects of single irrigation and fertilization or the interacting effects of water and N on cotton growth and lint yield. Studies on the influences of various irrigation amounts as along with N, P and K rates and ratios on the dry matter accumulation, yield, nutrient absorption and fertilizer use efficiency of drip-fertigated cotton are still lacking. Therefore, the objectives of the present study were to (1) explore the coupling influences of various irrigation and fertilization levels on the dry matter accumulation and nutrient uptake of cotton, and (2) determine an appropriate irrigation and fertilization regime to maximize cotton yield and fertilizer use efficiency. This study is expected to provide scientific basis for optimal water and fertilization management of drip-fertigated cotton in arid regions.