A three-year field study in Gansu, China found that returning green manure after wheat improves soil moisture and early-season soil temperature, strengthening maize roots and canopy cover. These gains raise chlorophyll (SPAD), net photosynthesis, and PSII efficiency while limiting NPQ, boosting biomass and grain yield. Green manure treatments outperformed conventional tillage across key growth and productivity indicators significantly overall consistently.
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Wheat–maize rotation is widely practiced in oasis-irrigated regions of Northwest China. While this system can partially alleviate the constraints of continuous cropping, it also has notable drawbacks: high evaporative losses and pronounced soil degradation during the fallow period, both of which can limit crop yields.
Sowing green manure after wheat and incorporating it into the soil can improve soil physicochemical properties, optimize the photosynthetic performance of subsequent crops, and ultimately increase yields. However, the photosynthetic and physiological mechanisms underlying yield gains under different green manure incorporation strategies remain poorly understood.
To address this gap, researchers in China conducted a three-year field experiment at a research station in the Shiyang River Basin (Gansu, China). They examined how different green manure return methods influence the soil moisture and temperature environment, maize root architecture, photosynthetic and chlorophyll fluorescence traits, and final grain yield, and they analyzed the relationships among these factors, according to a press release.
“We evaluated five treatments in this study: (i) conventional tillage without green manure (CT), (ii) no-tillage with total green manure mulching (NTG), (iii) no-tillage with removal of aboveground green manure (NT), (iv) tillage with total green manure incorporation (TG), and (v) tillage with only root incorporation (T).” shares corresponding author Aizhong Yu, a professor at Gansu Agricultural University.
Their findings, published in the Journal of Integrative Agriculture, showed that — relative to conventional tillage (CT) — both NTG and TG significantly increased soil water content in the 0–110 cm profile; raised soil temperature from the maize seedling (V3) to jointing stage (V6); and enhanced canopy cover, leaf stay-green, root length, net photosynthetic rate (Pn), transpiration rate (Tr), actual PSII photochemical efficiency (ΦPSII), maize biomass, and grain yield.
Overall, returning green manure to the field improved maize root architecture and canopy development primarily by increasing soil moisture. As soil water availability improved, root structure and canopy cover were optimized, which increased chlorophyll content (SPAD) and boosted Pn. Higher Pn, in turn, restrained increases in non-photochemical quenching (NPQ), helping maintain PSII activity and promote ΦPSII. The rise in ΦPSII ultimately increased biomass accumulation and, consequently, maize grain yield.
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