秸秆还田下氮肥运筹对白土田水稻产量和氮吸收利用的影响

【目的】研究小麦秸秆直接还田条件下不同氮肥基追比例运筹方式对白土稻田水稻产量和氮素吸收利用的影响, 为华中低产白土稻田水稻合理施肥提供科学依据。【方法】设置2种小麦秸秆还田量(0和3000 kg/hm2)及3种氮肥基肥-分蘖肥-穗肥施用比例(80-0-20、 60-20-20 和40-30-30)和不施氮的对照, 共7个处理, 分别为N80-0-20、 N60-20-20、 N40-30-30、 N80-0-20+S、 N60-20-20+S、 N40-30-30+S和CK。水稻收获期采集代表性样品考察水稻产量结构性状, 同时测定水稻籽粒和秸秆产量, 分析籽粒和秸秆氮素含量, 计算水稻氮素吸收量和氮肥利用效率。【结果】基肥-分蘖肥-穗肥施用比例60-20-20的处理水稻籽粒产量最高, 两年试验较不施分蘖肥的对照分别增产9.4%~12.9%和7.4%~8.9%。实施小麦秸秆直接还田后, 水稻籽粒产量较不施秸秆的对照分别提高10.2%~23.4%和0.8%~5.5%。不施秸秆条件下, 基-蘖-穗肥施用比例60-20-20的处理水稻籽粒含氮量最高, 较不施氮的对照提高11.3%, 而秸秆含N量随中后期追肥比例的加大而提高。秸秆还田条件下, 氮肥后移能明显提高水稻籽粒和秸秆含氮量。水稻籽粒氮素吸收量, 基-蘖-穗肥比例60-20-20处理最多, 2011年较对照N80-0-20分别增加13.7%和24.8%, 2012年提高14.5%和9.2%; 秸秆氮素积累量则随中后期追肥用量的增加而增多, 基-蘖-穗肥比例40-30-30处理最多。不施秸秆条件下, 基-蘖-穗肥比例60-20-20的处理氮素干物质生产效率、 氮素稻谷生产效率、 氮收获指数均最高, 百公斤籽粒吸氮量最低。秸秆还田条件下, 氮素干物质生产效率和氮素稻谷生产效率均随中后期追肥量的增加而下降, 而百公斤籽粒吸氮量则最高。氮素农学效率、 氮肥回收利用率和偏生产力也是60-20-20比例的处理最高, 较对照N80-0-20农学效率分别提高4.90和2.44 kg籽粒/kg N, 氮肥利用率提高7.82和21.29个百分点, 偏生产力提高4.90和2.44个百分点。【结论】综合水稻产量、 氮素吸收量以及氮肥利用效率, 安徽省江淮丘陵低产白土地区, 小麦秸秆直接还田条件下, 单季中稻氮肥的基肥-分蘖肥-穗肥施用比例, 以60-20-20运筹方式较为适宜。

Effect of different nitrogen application on rice yield and N uptake of white soil under wheat straw turnover

Objectives] Effects of different nitrogen (N) ratios of basal and topdressing application on rice growth and N uptake in the condition of wheat straw direct turnover were studied to provide a scientific base for rice applying N rationally in low-yield white paddy soil of middle region of China. Methods]Two levels of wheat straw turnover (0 and 3000 kg / hm2 ) and three N application ratios of basal and topdressing (80 -0 -20, 60 -20 -20, and 40 -30 -30), and N omitted treatment were designed, which were reordered as N80-0-20 , N60-20-20 , N40-30-30 , N80-0-20 + S, N60-20-20 + S, N40-30-30 + S and CK, respectively. The representative samples were collected to investigate rice yield components at the harvest period, and the yields and N concentrations in grain and straw were also measured to determine N uptake and nitrogen use efficiency. Results] The treatment of N60-20-20 obtains the highest rice grain yields which are increased by 9. 4%-12. 9% in 2011 and 7. 4%-8. 9% in 2012, respectively, compared with the control N80-0-20 . In the condition of wheat straw direct turnover, rice grain yields are increased by 10. 2% - 23. 4% and 0. 8% - 5. 5% , respectively, compared with the no straw turnover treatments. The N content in rice grains of the N60-20-20 treatment reaches the highest, which is 11. 3% higher than that in the CK treatment, while the N contents in straw are increased with the increase of N topdressing application ratio at the mid-late period. Increasing N application rate of topdressing can promote the N contents in grains and straw in the condition of wheat straw turnover. The total N uptakes in rice grains reach the highest for the N60-20-20 treatment, and are significantly increased by 13. 7% and 24. 8% in 2011 and 14. 5% and 9. 2% in 2012, respectively, compared with the N80-0-20 treatment. The N uptakes in rice straw are increased with the increase of N topdressing application in mid-late period, and the uptake of the treatment N40-30-30 reaches the highest. The dry matter production efficiency, grain production efficiency and harvest index of nitrogen reach their peaks in the N60-20-20 treatment with no wheat straw turnover, in which the amount of N absorption per 100 kg grains drops to the lowest, while a contrary result shows when wheat straw turnover. The agronomy efficiency, apparent recovery efficiency and partial productivity of nitrogen are also significantly promoted in the N60-20-20 treatment by 4. 90 and 2. 44 kg grain per kg N, and 7. 82 and 21. 29, and 4. 90 and 2. 44 percentage points, respectively, compared with the N80-0-20 treatment. Conclusions] Considering rice grain yield, N uptake and nitrogen use efficiency, the 60 -20 -20 N application ratio of base-jointing-panicle development stages is suitable for single-reason rice in Jianghuai hilly land region with low-yield white soils, Anhui province under the condition of wheat straw direct turnover.