Chlorophyll meter-based nitrogen management for no-till direct seeded rice.

摘要

This study was aimed at determining whether chlorophyll meter (SPAD) can be used to increase N-use efficiency in no-till direct seeded rice. Field experiments were conducted in Yongzhou and Nanxian, Hunan Province, China in 2010. Two N management treatments were imposed in each site: SPAD-based N management (SBNM) and recommended fix-timing N management (FTNM). Partial factor productivity of applied N (PFP_N), grain yield, yield components, biomass production and related physiological traits were measured for each N management. Averaged across two sites, SBNM increased PFP_N by 26% compared with FTNM. The higher PFPN in SBNM was attributed to reduced N application rate. Moreover, PFP_N differed with site. Nanxian had higher PFP_N than Yongzhou, especially in SBNM (a more than 50% increase), because of both lower N application rate and higher grain yield. High soil fertility contributed to the increased grain yield in Nanxian. Nanxian had more panicle number per m2 and larger panicle size (spikelets per panicle) than Yongzhou, which resulted in greater sink size (spikelets per m2). Nanxian produced more aboveground biomass during pre-heading period but less aboveground biomass during post-heading period than Yongzhou, and the former led to higher total aboveground biomass accumulation. Low photosynthetic rate and accelerated leaf senescence were partly responsible for the low aboveground biomass accumulation during post-heading period in Nanxian. Our study suggests that increased PFP_N is possible using a SPAD to guide N application on no-till direct seeded rice, and it will be more effective to increase PFP_N by using SBNM combined with improving soil fertility and optimizing canopy development.