Determining Threshold Values for a Crop Water Stress Index-Based Center Pivot Irrigation with Optimum Grain Yield

Anzhen Qin,Sen Li,Zhandong Liu,Ben Zhao,Dongfeng Ning,Aiwang Duan

doi:10.3390/agriculture11100958

Abstract

The temperature-based crop water stress index (CWSI) can accurately reflect the extent of crop water deficit. As an ideal carrier of onboard thermometers to monitor canopy temperature (Tc), center pivot irrigation systems (CPIS) have been widely used in precision irrigation. However, the determination of reliable CWSI thresholds for initiating the CPIS is still a challenge for a winter wheat–summer maize cropping system in the North China Plain (NCP). To address this problem, field experiments were carried out to investigate the effects of CWSI thresholds on grain yield (GY) and water use efficiency (WUE) of winter wheat and summer maize in the NCP. The results show that positive linear functions were fitted to the relationships between CWSI and canopy minus air temperature (Tc − Ta) (r2 > 0.695), and between crop evapotranspiration (ETc) and Tc (r2 > 0.548) for both crops. To make analysis comparable, GY and WUE data were normalized to a range of 0.0 to 1.0, corresponding the range of CWSI. With the increase in CWSI, a positive linear relationship was observed for WUE (r2 = 0.873), while a significant inverse relationship was found for the GY (r2 = 0.915) of winter wheat. Quadratic functions were fitted for both the GY (r2 = 0.856) and WUE (r2 = 0.629) of summer maize. By solving the cross values of the two GY and WUE functions for each crop, CWSI thresholds were proposed as being 0.322 for winter wheat, and 0.299 for summer maize, corresponding to a Tc − Ta threshold value of 0.925 and 0.498 °C, respectively. We conclude that farmers can achieve the dual goals of high GY and high WUE using the optimal thresholds proposed for a winter wheat–summer maize cropping system in the NCP.

Highlights

Irrigation plays a fundamental role in promoting agricultural production
The soil water content was depleted at maturity by winter wheat, causIn addition, through the linear equations between Tc − Ta (y) and crop water stress index (CWSI) (x) (r2 ≥ 0.719), ing a noticeably low soil water content during the vegetative period of summer maize
This explained why CWSI thresholds in wheat seasons exerted an influence on maize estimated to 0.925 ◦ C for winter wheat and 0.498 ◦ C for summer maize, respectively

Summary

Introduction

Irrigation plays a fundamental role in promoting agricultural production. With the development of irrigated farming, agriculture is the largest consumer of anthropic water on the planet, in which 70% of the global fresh water is consumed by the agricultural sector [1]. In the North China Plain (NCP), sprinkler and drip irrigation methods are commonly used in precision irrigation These techniques do not adapt well to a winter wheat (Triticum aestivum L.)–summer maize (Zea mays L.) cropping system due to the differences in row spacing, plant height, and planting densities between the crops [3]. Due to the over-depletion of aquifers, the NCP has become the severest groundwater depression zone in the world [5]. This especially expedites the development of water-saving techniques, making precision irrigation an inevitable trend for future agriculture in this area

Objectives

Results

Conclusion