氮肥运筹对夏玉米根系生长与氮素利用的影响

Effects of Nitrogen Application Rates on Root Growth and Nitrogen Use of Summer Maize

基于2季夏玉米田间试验,对比研究了尿素(纯氮0、80、160、240 kg/hm^2,基追比为2∶3;记为N0、N80、N160、N240)和控释氮肥(纯氮0、60、120、180、240 kg/hm^2,一次性基施;记为K0、K60、K120、K180、K_240)运筹对夏玉米根系生长、产量及土壤硝态氮分布和氮素吸收利用的影响。结果表明,施用尿素和施用控释氮肥的夏玉米整根各参数均表现为随施氮水平的提高呈先增加后减小的趋势。其中处理N160和处理K120的根系各项指标较高,且根长比根表面积和产量的拟合效果更优,更能反映不同氮肥运筹间产量的差异。与尿素相比,控释氮肥各处理土壤硝态氮累积量与作物需肥规律吻合较好,收获后0~200 cm土层硝态氮含量变幅较小,且硝态氮峰值所在土层深度较浅。2种氮肥中,处理N160与处理K120的籽粒产量、氮收获指数和氮素利用效率较高。其中处理K120的节肥增效潜力显著,其2季夏玉米平均氮收获指数和氮素利用效率分别较处理N160提高5.38%和4.96%,是适宜的氮肥运筹方式。

Field experiments（ 2013 and 2014） were carried out to improve nitrogen use efficiency and decrease nitrate nitrogen leaching for summer maize. Two nitrogen fertilizers,including urea（ with nitrogen application rates of 0,80,160 and 240 kg/hm^2,40% of nitrogen fertilizer was applied as basic and 60% of it was top dressed at bell stage; namely N0,N80,N160 and N240） and controlled-release fertilizer（ with nitrogen application rates of 0,60,120,180 and 240 kg/hm^2,all applied as basic fertilization; namely K0,K60,K120,K180 and K_240） were chosen to investigate the effects of different nitrogen application rates on root growth,yield,nitrogen absorption and nitrogen use efficiency of summer maize and nitrate nitrogen distribution in soil. The results showed that characteristic parameters of summer maize root at filling stage presented a trend of increase and then decreased along with the improvement of nitrogen application rate for both of the two nitrogen fertilizers. The characteristic parameters of summer maize root were higher in N160 of the urea treatments and higher in K120 of the controlled-release fertilizer treatments than those of the other treatments. In addition,compared with root surface area,total root length and yield had higher correlation. This meant that root length of summermaize played an important role in yield improvement under different nitrogen application rates.Furthermore,the nitrate nitrogen accumulation of the controlled-release fertilizer treatments agreed much better with the plant requirement for nitrogen than that of the urea treatments. In contrast to urea treatments,nitrate nitrogen content of the controlled-release fertilizer treatments had less variation and the maximum nitrate nitrogen content was shallower in 0 ~ 200 cm soil layer at harvest. Among the two nitrogen fertilizers treatments,N160 and K120 had greater yield,nitrogen harvest index and nitrogen use efficiency than other treatments. And K120 was potential in saving fertilizer and increasing efficiency,which could averagely increase nitrogen harvest index by 5. 38% and improve nitrogen use efficiency by4. 96% compared with N160 in two years. In conclusion,the nitrogen application rate of treatment K120 was appropriate for summer maize cultivation in Guanzhong Region,Shaanxi Province.