Abstract:

In order to investigate the effects of nitrogen fertilizer reduction on rice yield, quality, and nitrogen fertilizer utilization efficiency under the concentrated coverage of wheat straw betweem rows for returning to the field, rice varieties of Nanjing 9108 and Nanjing 5055, which were widely planted in the middle and lower reaches of the Yangtze River, were used as test materials in the present study. Two nitrogen fertilizer treatments were set up under equal row spacing transplantation, namely, no nitrogen application (T1) and local customary nitrogen application rate (quick acting nitrogen fertilizer, T2). Four fertilization treatments were set up under the concentrated coverage of wheat straw between rows for returning to the field and the transplanting of wide and narrow rows, namely, local customary nitrogen application rate (quick acting nitrogen fertilizer, T3), nitrogen reduction rate of 10% (combination of controlled release nitrogen fertilizer and quick acting nitrogen fertilizer, T4), nitrogen reduction rate of 20% (combination of controlled release nitrogen fertilizer and quick acting nitrogen fertilizer, T5), and nitrogen reduction rate of 30% (combination of controlled release nitrogen fertilizer and quick acting nitrogen fertilizer, T6). The results showed that the transplanting of wide and narrow rows could increase rice yield compared to the transplanting with equal row spacing, with an average yield increase of 3.30% for both varieties. Under the same transplanting mode, reducing nitrogen by 10% significantly (P<0.05) reduced the effective panicles, yet maintained high yield. Reducing nitrogen by 20%-30% could stabilize the rice yield at the average level of Jiangsu Province. Reducing nitrogen by 10%-20% could improve the appearance quality of rice. Nanjing 9108 and Nanjing 5055 got the highest taste value with the nitrogen reduciton rate of 30% and 10%-20%, respectively. The reduction of nitrogen rate resulted in an increase in the recovery efficiency of nitrogen (RE_N) of both rice varieties. The highest RE_N for Nanjing 9108 and Nanjing 5055 was found with the nitrogen reduction rate of 20% and 10%, respectively. In summary, under the concentrated coverage of wheat straw between rows for returning to the field, combined application of controlled release nitrogen fertilizer and urea, with the nitrogen reduction rate of 10% to 20% as compared with the local customary rate could achieve higher nitrogen absorption and utilization efficiency and better rice quality, hence realize the goals of reducing nitrogen, stabilizing yield, and improving quality and efficiency.

Key words: concentrated coverage of wheat straw between rows for returning to the field, reduction of nitrogen fertilizer, rice, yield, quality, nitrogen fertilizer utilization rate