Abstract
High N loss and low N use efficiency (NUE), caused by high N fertilizer inputs and inappropriate fertilization patterns, have become important issues in the rice (Oryza sativa L.) growing regions of southern China. Changing current farmer fertilizer practice (FFP, 225 kg ha–1 N as three applications, 40% as basal fertilizer, 30% as tillering fertilizer and 30% as jointing fertilizer) to one—time root—zone fertilization (RZF, 225 kg ha–1 N applied once into 10 cm deep holes positioned 5 cm from the rice root as basal fertilizer) will address this problem. A two—year field experiment covering two rice growing regions was conducted to investigate the effect of urea one—time RZF on rice growth, nutrient uptake, and NUE. The highest NH4+–N content for RZF at fertilizer point at 30 d and 60 d after fertilization were 861.8 and 369.9 mg kg–1 higher than FFP, respectively. Rice yield and total N accumulation of RZF increased by 4.3–44.9% and 12.7–111.2% compared to FFP, respectively. RZF reduced fertilizer—N loss by 56.3–81.9% compared to FFP. The NUEs following RZF (mean of 65.8% for the difference method and 43.7% for the labelled method) were significantly higher than FFP (mean of 35.7% for the difference method and 14.4% for the labelled method). In conclusion, RZF maintained substantial levels of fertilizer—N in the root—zone, which led to enhanced rice biomass and N uptake during the early growth stages, increased fertilizer—N residual levels and reduced fertilizer—N loss at harvest. RZF produced a higher yield increment and showed an increased capacity to resist environmental threats than FFP in sandy soils. Therefore, adopting suitable fertilizer patterns plays a key role in enhancing agricultural benefits.
Highlights
Rice is an important staple food crop for more than 3 billion people in the world and for about 60% of the Chinese population [1]
Rice yield increased as the N rate rose at each stage (Fig 3a)
There was a good quadratic relationship between yield and N applied as a basal fertilizer (R2 = 0.941ÃÃ), and the yield increment order as the N rate rose was basal fertilizer > jointing fertilizer > panicle fertilizer
Summary
Rice is an important staple food crop for more than 3 billion people in the world and for about 60% of the Chinese population [1]. The Chinese national average N application rate for rice increased from 145 kg N ha–1 in 1997 to 300 kg N ha–1 in 2006, which is significantly higher than the global average. It even reached 360 kg N ha–1 in the Taihu lake region [3]. Inappropriate fertilization patterns and excessive use of N fertilizer have resulted in considerable N losses through ammonia (NH3) volatilization and leaching [5, 6] This has meant that NUE has been as low as ~35% (15–20% lower than other major rice growing countries) [6]
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