Characterization of Nitrogen Uptake and Utilization in Rice under Different Planting Methods

Abstract

A field experiment was conducted with three planting methods including precision artificial transplanting with dry nursery middle and strong seedlings (AT), mechanical transplanting with small seedlings (MT) and direct seeding (DS) using early-maturing late japonica rice (EMLJ), late-maturing medium japonica rice (LMMJ) and medium-maturing medium japonica rice (MMMJ) (including conventional rice and hybrid rice). The results showed that the N content and uptake in plants were DSMTAT at jointing and ATMTDS at heading and maturity. Total N uptake at maturity with AT was 11.68% and 39.03% higher than that with MT and DS and that with MT was 24.49% higher than that with DS. N uptake rate was DSMTAT before jointing and ATMTDS from jointing to heading and from heading to maturity. Maximum N uptake rate of AT and MT appeared in the period from jointing to heading, and that of DS with MMMJ appeared from jointing to heading while that with EMLJ and LMMJ appeared before jointing. N periodic accumulation from jointing to heading and from heading to maturity were ATMTDS and the difference among different planting methods all reached significant or very significant level. N recovery efficiency of AT, MT and DS were 44.49%, 39.00%, and 31.41%, respectively. N recovery efficiencies among different varieties with AT and MT were EMLJLMMJMMMJ, and that with DS was MMMJLMMJEMLJ, and in the case for the same type of variety, that of conventional japonica rice was higher than that of hybrid japonica rice. N requirement for 100 kg grain of AT, MT, and DS were 1.959 (1.900–2.009), 1.842 (1.681–1.914), and 1.638 (1.540–1.721) kg, respectively. It was no significant differencebetween AT and MT while both were significantly higher than that of DS for conventional japonica rice. For hybrid japonica rice, the differences among different planting methods were all significant. N requirement for 100 kg grain among different growth type of varieties with DS was MMMJLMMJEMLJ while that with AT and MT was not significantly different. It is important to select scientific planting method and suitable variety type for achieving effective nitrogen uptake and utilization.