Assessing the effects of precipitation and irrigation on winter wheat yield and water productivity in North China Plain

Highlights

• Optimal irrigation schedules were determined at different precipitation site-years.

• Two irrigations at greening and jointing stages was optimal for most site-years.

• Two irrigations coordinated pre-anthesis water demand, which favored yield and WP.

• High water productivity was achieved by optimization of pre- and post-anthesis ET.

Abstract

Achieving high crop yield with less irrigation is important to improve water productivity (WP) and irrigation water productivity (IWP) in water-limited regions in the North China Plain (NCP). Coupling the impacts of precipitation and irrigation on the crop yield is, therefore, an essential tool for understanding crop response to different water sources and forecasting irrigation water requirements. In this study, the CERES-Wheat model was used to simulate winter wheat yield, WP, and IWP under different irrigation schedules (no, deficit, full, and automatic irrigation) and three precipitation category years (wet, normal, and dry years). Results showed that the amount of precipitation fluctuated significantly over site-years, leading to considerably varied irrigation water requirements. For the wet year, deficit two irrigations at greening and jointing stages (treatment 11) alleviated water stress during key winter wheat growth periods, contributing to increasing biomass, yield, WP, and IWP. However, when reducing the irrigation amount by 50%, a significant increase in WP and a nonsignificant difference in yield were found at Fengqiu and Shangqiu. Two irrigation applications 11 improved pre-anthesis biomass and wheat yield while achieving high WP and IWP in normal and dry years (except for extreme drought conditions). The finding also indicated that the distribution of growing season precipitation exerted a significant impact on irrigation time. If the early season precipitation was low, shifting the irrigation to an earlier time to ensure pre-anthesis water requirements, which can synchronously achieve the goals of increasing WP and maintaining a higher yield. In conclusion, optimizing irrigation strategies to various precipitation conditions will be a promising and effective practice for wheat production and water conservation.

Introduction

Winter wheat (Triticum aestivum L.) is one of the main food crops in the North China Plain (NCP) (Wang et al., 2016), production of which accounts for about 70% of entire wheat production in China (Lu and Fan, 2013, Lv et al., 2017). However, water shortage greatly constrains the wheat production over this region (Fang et al., 2010, Wang et al., 2001). The rainfall during the winter wheat growth period can meet only 25–40% of crop water demands, leaving a 200–300 mm water deficit in the NCP (Cao et al., 2013a, Liu et al., 2001). Thus, supplemental irrigation is essential to fulfilling the large crop water demand for maintaining high wheat production (Chen et al., 2015, Zhang et al., 2003, Zhou et al., 2007).

Groundwater is the major source of irrigation water in the NCP. Traditional irrigation strategies generally apply more than 300 mm of water during the growing season, which has led to low water productivity (WP) (Li et al., 2012). Over-exploitation of groundwater has reduced the groundwater table, caused severe environmental problems, and threatened sustainable agricultural development (Chen et al., 2003, Han et al., 2016, Wang et al., 2009). Substantial improvement should be made to reduce or even eliminate the current agricultural use of groundwater (Difallah et al., 2017, Wang et al., 2001). However, supplemental irrigation is essential to obtaining a higher winter wheat yield (Fang et al., 2010, Kijne et al., 2003). Consequently, efficient and sustainable water management is urgently needed to resolve the conflict between yield improvement and irrigation water consumption.

To ensure the long-term sustainability of irrigated agriculture, water-saving irrigation schedules with high yields will become more important. Deficit irrigation, typically defined as an irrigation strategy that the application of irrigation water below the full crop water requirement, is a promising approach to minimizing irrigation water use (Tari, 2016). Deficit irrigation only at critical growth stages has been broadly utilized to increase water productivity (Chai et al., 2016, Jensen et al., 2014, Kang and Zhang, 2004). This approach can close the gap of crop water requirements at sensitive growth stages and allows moderate water stress at nonsensitive growth stages. However, inconsistent irrigation strategies are recommended based on the evaluation of the effectiveness of irrigation schedules (Bian et al., 2016, Sun et al., 2019, Xu et al., 2016). These differences may be attributed to the large variability of seasonal precipitation. Seasonal precipitation is a key factor for wheat yield in NCP, as it directly affects the irrigation water demand and water balance of winter wheat (Chen et al., 2014, Dar et al., 2017). Thus, the development of appropriate and effective water-saving practices needs to consider the differences in seasonal precipitation.

Previous studies were mainly location-specific field experiments (Chen et al., 2010, Wu et al., 2006, Zhang et al., 2017). But field experiments are time- and labor–costly because of the critical input data requirement in soil types, cultivars, meteorological data, and management practices. Therefore, process-based modeling is a valuable and feasible tool used to assess the effect of different climate conditions and irrigation schedules on crop yield and productivity (Geerts and Raes, 2009, Heng et al., 2007). DSSAT model has high accuracy in simulating crop growth and development (Jones et al., 2003), including phenology dates, biomass, and grain yield. CERES-Wheat, which is embedded in the DSSAT software, is a wheat growth simulation model and has been widely evaluated by many researchers to assess the effect of irrigation water on wheat production (Arora et al., 2007, Attia et al., 2016, Benli et al., 2007). The optimized irrigation schedules have been thoroughly studied and widely applied to improve wheat yield and increase WP (Qin et al., 2018). Li et al. (2005) and Xu et al. (2018) reported that two irrigations could be adequate for winter wheat in the NCP. Lv et al. (2011) proposed that single irrigation at jointing could produce a higher yield and WP than traditional practices. In Shandong province, Bian et al. (2016) found that two irrigations of 60 mm at both jointing and heading stages resulted in a higher yield than applying 120 mm only at the jointing stage. However, these studies are scattered, based on the finite set of irrigation experiments in local-orientated climate conditions, and have less capability of extrapolation in making accurate schedules. Considering the large spatial variation in rainfall, the irrigation performance needs further comprehensive analysis. It is imperative to choose multiple stations based on the different growing season precipitation patterns to fully investigate suitable irrigation schedules and assess water use utilization.

Thus, in this study, six representative stations were selected from different rainfall types along the West-East and South-North, integrated with the CERES-Wheat model to simulate the effects of different irrigation schemes (rainfed, deficit, full, and automatic irrigation) on yield, and to explore irrigation treatments of high yield and high WP. The CERES-Wheat model was used in this study with the objectives to (1) evaluate winter wheat yield, evapotranspiration (ET), and WP response to different irrigation schedules, and (2) explore high WP and irrigation water productivity (IWP) to provide theoretical support for popularization and application of optimizing irrigation measures.