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【目的】华北平原棉区中等肥力棉田经济最佳施氮量为300 kg/hm2左右,这一结果仅从产量效应得出,未充分考虑棉花对氮肥的回收利用和土壤中氮肥的残留。探讨低肥力土壤施氮量及施氮比例对棉花产量及氮肥利用率的影响,以及低、中、高肥力土壤条件下等量施氮效应,旨在为棉花减氮增效提供理论依据。【方法】田间试验选择了高(S1)、中(S2)、低(S3)三个肥力水平的地块,其全氮含量分别为0.83、0.74、0.60 g/kg。低肥力地块设置低氮(N1 113 kg/hm~2)、中氮(N2 225 kg/hm~2)、高氮(N3 338 kg/hm~2)3个氮肥用量;中肥力和高肥力地块设低氮量处理,氮肥两次追施在苗期与初花期进行,氮肥比例为1∶2;此外,设置低肥力土壤低氮量,氮肥追施在苗期与初花期进行,氮肥分配比例为1∶1。在吐絮70%时采集棉株和土壤样品,用~(15)N技术分析了棉株氮素吸收来源、籽棉产量、棉株氮肥回收率和土壤氮肥残留率。【结果】低氮处理,土壤肥力对棉花籽棉产量无显著影响,随土壤肥力提升,棉株吸收氮素来源于肥料的比例下降,相对增加了对土壤氮素的吸收。棉花植株~(15)N回收率随施氮量增加显著下降,随土壤肥力提高呈下降趋势,低肥力土壤与中肥力土壤间棉花植株~(15)N回收率差异不显著,但显著高于高肥力土壤。高肥力土壤~(15)N残留率高于低肥力土壤和中肥力土壤。~(15)N损失率随施氮量和土壤肥力提高显著增加。低土壤肥力低氮量条件下氮肥分配比例1∶2处理籽棉产量高于1∶1处理。低肥力土壤条件下,中氮处理籽棉51N积累量相对高于高氮和低氮处理,籽棉产量较优。【结论】在较低土壤肥力条件下,施氮225 kg/hm2籽棉产量和氮回收率均优于施氮338 kg/hm~2,氮肥损失率较低,减氮增效是可行的。高肥力土壤条件下减少氮肥投入可减少肥料的浪费。
【Objective】 The optimal nitrogen application rate for mid-level fertility cotton fields in North China Plain is about 300 kg / hm2. This result is only obtained from the yield effect. The cotton recycling to nitrogen and residual nitrogen in soil are not fully considered. The effects of nitrogen application rate and nitrogen application rate on cotton yield and N use efficiency in low fertility soil and the same amount of nitrogen application under low, medium and high fertility soil conditions were discussed to provide the theoretical basis for cotton nitrogen efficiency synergy. 【Method】 The field plots selected three plots with high (S1), medium (S2) and low (S3) fertility levels, and their total nitrogen contents were 0.83, 0.74 and 0.60 g / kg, respectively. The low fertility plots were set up with three nitrogen application rates of low nitrogen (N1 113 kg / hm2), medium nitrogen (N2 225 kg / hm2) and high nitrogen (338 kg / hm2) The plot was set to treat with low amount of nitrogen and the topdressing of nitrogen was carried out twice at seedling stage and early flowering stage. The ratio of nitrogen fertilizer was 1: 2. In addition, the low nitrogen content of low fertility soil was set up, nitrogen topdressing was carried out at the seedling stage and early flowering stage, Distribution ratio of 1: 1. Cotton plants and soil samples were collected at 70% boll flow. The sources of nitrogen absorption, seed cotton yield, cotton plant nitrogen recovery rate and soil nitrogen fertilizer residual rate were analyzed by ~ (15) N technique. 【Result】 Low N treatment and soil fertility had no significant effect on cotton seed and cotton yield. With the increase of soil fertility, the proportion of nitrogen absorbed by the cotton plant decreased from fertilizer and increased the absorption of soil nitrogen. The recovery rate of ~ (15) N in cotton plants decreased significantly with the increase of nitrogen application rate, but decreased with the increase of soil fertility. The recovery rate of ~ (15) N in cotton plants was not significantly different between low and medium fertility soils, but significantly higher Highly fertile soil. The residual rate of ~ (15) N in high-fertility soil was higher than that in low-fertility soil and middle-fertility soil. ~ (15) N loss rate increased with the increase of nitrogen application and soil fertility. Under the condition of low soil fertility and low nitrogen, the ratio of nitrogen fertilizer allocation 1: 2 was higher than the 1: 1 treatment. Under low-fertility soil conditions, the 51N accumulation of seed cotton treated with medium-nitrogen was relatively higher than that of high-nitrogen and low-nitrogen treatments, and the yield of seed cotton was superior. 【Conclusion】 Under low soil fertility conditions, the yield and nitrogen recovery rate of 225 kg / hm2 nitrogen fertilizer were better than that of nitrogen application rate of 338 kg / hm2, and the nitrogen loss rate was low. It is feasible to reduce nitrogen and increase efficiency. Reduce the fertilizer waste by reducing the input of nitrogen fertilizer under high-fertility soil conditions.