No-tillage mulch with green manure retention improves maize yield by increasing the net photosynthetic rate

Abstract

Green manure being return to fields has been widely used in arid areas, as an effective technical measure to improve soil fertility and increase crop yield. Although a large number of studies have shown that green manure return to field can promote crop yield increase, the physiological mechanism of different green manure return methods to promote crop yield increase has not been well explained. This study aims to further understand the relationship between soil water and nitrogen environment, crop roots and photosynthesis, and further clarify the physiological mechanism of green manure return methods to improve maize yield. A field experiment was carried out at an arid oasis region in northwestern China from 2020 to 2022. The five treatments were treated as follows: (i) conventional tillage and leisure (CT), (ii) no-tillage and green manure cover the surface (NTG), (iii) no-tillage and removal of above-ground green manure (NT), (iv) tillage in which green manure is mixed with soil (TG), and (v) tillage in which green manure is partially removed from the ground and roots are incorporated into the soil (T). Results showed that the NTG and TG treatments significantly increased maize grain yield (GY). The GY of NTG and TG significantly increased by 13.0–34.3 % and 11.6–32.1 % compared with CT. In addition, NTG and TG significantly increased soil water storage (SWS) and soil total nitrogen (STN), increased maize root biomass (RB), increased maize leaf area index (LAI), leaf chlorophyll content (SPAD), and net photosynthetic rate (Pn), and decreased leaf senescence index (FSLA) compared with CT. The structural equation model showed that increasing SWS and STN could increase LAI by promoting root growth of maize, thus increasing Pn and finally increasing GY. Therefore, NTG can be a suitable green manure return method to increase maize yield in arid oasis irrigated areas.