Absorption and Utilization of Nitrogen, Phosphorus, and Potassium in Rice Plants Under Site-Specific Nitrogen Management and Wheat-Residue Incorporation

To investigate the absorption and utilization of major nutrient elements of rice (Oryza sativa L.) plant when wheat (Triticum aestivum L.) residues returned to the field (residue incorporation, RI) or under site-specific nitrogen management (SSNM), the effects of RI and SSNM on harvest index, translocation, and transportation efficiency were evaluated in 2005–2006, using a midseason japonica rice cultivar of Yangjing 9538. The results showed that under same N level, compared with the no straw incorporation, RI reduced N content and the accumulations of N, phosphorus (P), and potassium (K) in rice plants at the early growth stage but maintained high levels of contents of P and K during the whole growth period. Moreover, RI improved the N use efficiency and the harvest index and biomass production efficiency of N, P, and K. Under RI with the same amount of wheat residues, rice plants in SSNM had less absorption of N and P than in the N fertilizer rate in farmer practice (FFP). However, the transportation percentages of N, P, and K from heading to maturity, as well as the harvest indices of N and P under SSNM, were higher than those under FFP. The results indicate that both RI and SSNM can increase the absorptions and use efficiencies of N, P, and K in rice plants, and their combination shows better effects.