Effects of wheat straw mulch application and nitrogen management on rice root growth, dry matter accumulation and rice quality in soils of different fertility

The root is the most sensitive part of the plant. This study examined the effects of wheat straw mulch, nitrogen (N) management and soil fertility on rice root morphology, dry matter accumulation, grain yield and rice quality and explored the correlation between root morphology and rice quality indexes. Wheat straw mulch had an obvious inhibitory effect on rice root morphology, especially on the total root length and total root surface area at 20 days after transplanting in the high- and low-fertility soil. The low-fertility soil treatments had higher levels of inhibition. However, straw mulch significantly promoted root growth, increased dry matter accumulation in the subsequent growth periods and improved the grain yield and rice quality, which mainly reduced the percentage of chalky kernels and the chalkiness degree. Increasing the nitrogen fertilizer percentage applied as a basal or tillering fertilizer reduced the inhibition in the early growth period; for balanced rice root growth, dry matter accumulation, grain yield and rice quality, 30% as basal fertilizer, 30% as tillering fertilizer and 40% as panicle fertilizer were the best N management strategy. Correlation analysis showed that the rice quality was extremely significantly positively correlated (r = 0.30–0.59, P < 0.05) with the root morphology indexes of the brown rice and protein contents and was significantly or extremely negatively correlated (r = − 0.73 to − 0.28, P < 0.05) with the length–width ratio, percentage of chalky kernels, chalkiness degree and amylose content.