Effects of water and nitrogen coupling on winter wheat yield and water or nitrogen use efficiency under high-low seedbed cultivation pattern

Abstract: High and low seedbed cultivation has been widely used to combine ridge and flat planning patterns during wheat production in Shandong Province of the North China Plain (NCP). Land utilization rate and crop productivity can be better improved with the higher efficiency of water-nitrogen use for sustainable production, compared with flat cultivation. The winter wheat is planted on both alternate high and low beds on the flat land under cultivation. However, it is still lacking on the underlying mechanism of this cultivation pattern for better improvement and popularization. This study aims to clarify the effects of different water and nitrogen rate on grain yield, water consumption, aboveground biomass, water use efficiency, nitrogen partial fertilizer productivity, and net benefits. A field experiment was also carried out during the 2020-2021 and 2021-2022 growing seasons using a split zone design. The main area was divided into three levels of nitrogen rates (N1: 300, N2: 240, and N3: 180 kg/hm2). The subplot was set as the three levels of irrigation quotas (W1: 120, W2: 90, and W3: 60 mm). The flat cultivation with 120 mm irrigation amount and 300 kg/hm2 nitrogen amount was set as the control (CK) group. A systematic evaluation was implemented to determine the effects of water and nitrogen management on crop productivity, as well as water and nitrogen use efficiency under high and low seedbed cultivation. The results showed that the high and low seedbed cultivation significantly improved the crop grain yield by 14.8%-17.6%, water use efficiency by 15.9%-16.9%, nitrogen partial fertilizer productivity by 14.8%-17.6%, and net benefits by 23.9%-32.7%, compared with the flat cultivation. Consequently, high and low seedbed cultivation was a reliable agronomic practice for higher water or nitrogen use efficiencies and crop productivity, although there was no significant difference in the water consumption between high and low seedbed cultivation and flat cultivation. The coupling of water and nitrogen posed significant effects on water consumption, grain yield, aboveground biomass, water use efficiency, nitrogen partial fertilizer productivity, and net benefits (P<0.01). Specifically, the W2F2 decreased the crop yield by 2.8%-3.3% (P>0.05), whereas, the water use efficiency increased (P<0.05), compared with the W1F1. The optimal water and nitrogen rate was obtained in the higher water use efficiency, nitrogen partial fertilizer productivity, and net profits. The regression and spatial analysis demonstrated that the grain yield, water use efficiency, and net profits reached 95%-100% of the maximum simultaneously, when the water consumption was 536.3-594.3 mm, and the nitrogen application was 246.5-299.4 kg/hm2 in 2020-2021, while the water consumption was 527.2-559.4 mm, and the nitrogen application was 221.0-303.1 kg/hm2 in 2021-2022. An optimal combination was achieved in the water consumption of 536.3-559.4 mm (irrigation quota of 99.2-115.4 mm), and the nitrogen application of 246.5-299.4 kg/hm2, in order to maximize the grain yield, water use efficiency, and net profits. Therefore, a reasonable technical and theoretical reference can be offered for the multi-objective management of the water and nitrogen of winter wheat under high and low seedbed cultivation in areas with similar climate conditions to the NCP. Further study can be focused on the management of water and fertilizer (nitrogen, phosphorus, and potassium) rate of winter wheat under high and low seedbed cultivation with the various varieties and the soil type.