吉林省中部黑土区秸秆全量深翻还田条件下春玉米氮肥适宜用量研究

  【目的】  基于多年玉米秸秆全量深翻还田试验，探究吉林省中部黑土区春玉米氮肥适宜用量及群体氮素累积与分配特征。  【方法】  本试验于2017—2019年在吉林省公主岭市进行，为双因素田间试验。主因素为施氮水平，分别为0 (N0)、60 (N60)、120 (N120)、180 (N180)、240 (N240)、300 (N300)、360 (N360) kg/hm2；副因素为品种，分别为富民985 (Fumin 985)和翔玉211 (Xiangyu 211)。测定不同生育时期玉米各器官干物质积累量、吸氮量及产量构成。  【结果】  增施氮肥对玉米产量影响显著，年份、处理、品种对产量的影响具有明显的交互作用。N0处理的产量随着年限的增加而逐年递减，2018年和2019年相比于2017年产量分别降低10.9%和26.2%；各处理间差异也逐渐增大，2017年N180处理比N0处理产量增加23.2%，到2019年N180处理比N0处理产量增加55.1%；品种间比较，2017—2019年翔玉211产量均高于富民985产量，并且翔玉211适宜施氮量略高于富民985适宜施氮量。春玉米干物质积累量随着施氮水平的提高呈现先上升后降低的趋势，不同氮肥处理的茎、叶干物质积累量和氮积累量均于吐丝期至乳熟期达到最大值，成熟期N180处理的茎、叶、籽粒干物质积累量最高；不同施氮水平下，花后氮积累量分配比例呈现先升后降的趋势。不同施氮水平下，秸秆理论带入全氮养分量差异明显，且不同施氮水平的氮还田量随着秸秆还田年限的增加而逐渐上升，2017年，N300处理下氮还田量最高，为68.9 kg/hm2，较N0、N360处理分别增加155.0%、15.2%；2019年，N240处理下氮还田量最高，为109.9 kg/hm2，较N0、N360处理分别增加156.7%、33.4%。本研究以2017和2019年数据拟合方程，计算得出秸秆全量深翻还田后玉米最佳经济产量为13028 kg/hm2，适宜氮肥用量为162 kg/hm2。  【结论】  在吉林中部黑土区，多年连续秸秆全量深翻还田条件下，虽然年际条件、品种对产量有显著影响，氮肥依然是玉米高产稳产的重要因素，适宜的氮肥用量有利于提高吐丝至乳熟期玉米的干物质积累。本试验条件下保持产量水平12～13 t/hm2的氮肥适宜用量为160～165 kg/hm2。

Suitable nitrogen application rate for spring maize under full straw mulching in black soil area of central Jilin Province

  【Objectives】  This study investigated the suitable N application rate, accumulation, and distribution characteristics of spring maize in the black soil area of central Jilin Province. Maize straw was returned to the field in full for many years.   【Methods】  This experiment was conducted in Gongzhuling City, Jilin Province, from 2017 to 2019. The main plot was nitrogen level at 0 (N0), 60 (N60), 120 (N120), 180 (N180), 240 (N240), 300 (N300), and 360 (N360) kg/hm2. The subplot was maize cultivar. The dry matter, nitrogen uptake and yield composition of maize organs at different growth stages were measured in Fumin 985 and Xiangyu 211.   【Results】  Increasing N fertilizer application (P<0.05) affected maize yield, with differences across the years, cultivars, and their interactions. N0 treatment yield decreased across the years, and the yield in 2018 and 2019 was 10.9% and 26.2% lower than in 2017, respectively. The yield of N180 in 2017 was increased by 23.2% and increased by 55.1% in 2019 compared with N0. Xiangyu 211 yield was higher than Fumin 985 from 2017 to 2019; the suitable N application rate for Xiangyu 211 was slightly higher than Fumin 985. The dry matter accumulation in spring maize increased at first and subsequently decreased with an increase in N level. The dry matter accumulation in stem and leaf and N accumulation in the treatments reached the maximum value from silking to milk stage. The dry matter accumulation in stem, leaf, and grain under N180 was the highest at the maturity stage. Under different N application levels, the distribution ratio of N accumulation after anthesis increased first and then decreased. There were (P<0.05) differences in the total N content based on the straw theory. The amount of N returned by straws increased gradually across the years. In 2017, the quantity of N re-entry under N300 treatment was the highest (68.9 kg/hm2), surpassing N0 and N360 treatments by 155.0% and 15.2%, respectively. In 2019, N re-entry under N240 treatment was the highest (109.9 kg/hm2), exceeding N0 and N360 treatments by 156.7% and 33.4%, respectively. The fitted models for 2017 and 2019 showed that maize's optimal economic yield and N fertilizer dosage were 13028 kg/hm2 and 162 kg/hm2, respectively.   【Conclusions】  The practice of returning straw to the black soil in Jilin has been in existence for a long time. Although inter-annual conditions and cultivars affect maize yield, nitrogen fertilizer remains important for high and stable maize yield. Using the appropriate quantity of N fertilizer was beneficial to increasing dry matter accumulation and distribution of maize from the silking to filling stage, thereby increasing maize yield. The optimal N application rate to maintain maize yield at 12–13 t/hm2 was 160–165 kg/hm2.