Soil Mulching Practices Increased Grain-Filling Capacity of Rainfed Maize (Zea mays L.) by Improving Soil Hydrothermal Condition and Leaf Photosynthetic Potential

Abstract

Grain-filling rate and duration largely affect the grain-filling capacity, which determines the grain yield of maize (Zea mays L.). Nevertheless, there is little about the mechanism of how various soil mulching practices affect the leaf photosynthetic potential and subsequent grain-filling capacity of maize. Field experiments were undertaken on rainfed summer maize in northwest China under flat cultivation without mulch (FNM), flat cultivation with straw mulch (FSM), flat cultivation with transparent film mulch (FTF), flat cultivation with black film mulch (FBF), ridge-furrow cultivation with transparent film mulch (RTF) and ridge-furrow cultivation with black film mulch (RBF) in 2021 and 2022. This study explored the impact of various soil mulching patterns on soil hydrothermal condition, leaf growth, photosynthetic potential, aboveground dry matter growth and grain-filling process of rainfed maize. The dynamics of leaf area index (LAI) and grain-filling were fitted with growth equations, and the relationships of grain-filling rate, leaf area duration and LAI withering rate were quantified. The results showed that, compared with FNM, other five soil mulching practices improved soil hydrothermal condition, the maximum LAI and leaf expansion rate but reduced leaf withering rate, thereby increasing radiation interception rate (RI) at the grain-filling stage. The soil mulching practices also increased leaf SPAD value, net photosynthetic rate, photosynthetic nitrogen use efficiency and the aboveground dry matter. Compared with FNM, other five practices extended the effective grain-filling period and the active period of grain-filling, increased the maximum and mean grain-filling rates, improved the 100-kernel weight and the average kernel per ear (KPE), thereby increasing grain yields by 9.2%, 33.7%, 38.0%, 46.3% and 58.6%, respectively. The functional relationships of grain-filling rate and accumulated leaf area duration (y = a/(1 + b*exp(−kx))), and the functional relationships of grain-filling rate and LAI withering rate (y = (a + cx + ex²)/(1 + bx + dx²)) were first proposed. In conclusion, various soil mulching practices improved the soil hydrothermal condition, green leaves growth process and RI, which improved the leaf photosynthetic potential and the grain-filling capacity, thereby increasing the 100-kernel weight, KPE and grain yield. This study can help us quantitatively describe and better understand the maize grain-filling process under various mulching practices.