Effect of straw-mulch-incorporation on nitrogen uptake and N fertilizer use efficiency of rice (Oryza sativa L.)

The objective of this study was to determine the effect of straw incorporation through mulching on nitrogen uptake and N-fertilizer use efficiency of rice. Two field experiments were conducted at the Baiyun Experimental Station, Guangdong Academy of Agricultural Sciences using “Tianyou998” hybrid rice in split plot design experiments with straw incorporation and N treatment as the main and split factors respectively. The results are as follows: (1) Straw incorporation enhances rice nitrogen uptake by 13.7%~20.3%. However, the percentage of N uptake at different growth stages to total N uptake remains unchanged. (2) Chlorophyll content (SPAD value) of rice leaves is significantly greater in straw incorporation than in non-straw incorporation treatments at mid-tillering (MT), panicle initiation (PI) and heading (HD) stages, except for the SSNM (site-specific nutrient management) treatment at MT stage. (3) Recovery efficiency (RE) of N-fertilizer is 8.23% (relatively 23.4%) higher in straw incorporation than in non-straw incorporation treatments (P<0.01). Agronomic efficiency (AE) and partial factor productivity (PFP) are also higher for straw incorporation treatments. (4) AE, RE and PFP are positively significantly correlated with N uptake from MT to PI. RE is positively significantly correlated with N uptake after heading. Application of N-fertilizer at MT to enhance N uptake from MT to PI is important for increasing AE, RE and PFP. Increasing N uptake at grain-filling stage is crucial for improving RE.