施用方式和氮肥种类对砂姜黑土氮素迁移的影响

采用田间微区试验,在砂姜黑土中研究了施肥方式(上层12 cm土混施、土下12 cm点施、土下12 cm条施)和氮肥种类(尿素、磷酸氢二铵)对氮素垂直运移和水平迁移动态的影响。不同施用方式试验结果表明,在处理的90 d内,砂姜黑土中土壤NH_4~+-N和NO_3~–-N含量均呈现土下12 cm点施土下12 cm条施上层12 cm土混施的趋势。尿素在土下12 cm点施条件下,土壤NH_4~+-N主要集中在垂直方向6~18 cm土层和水平距离0~7 cm范围内;而NO_3~–-N的分布核心区土层超过21 cm,水平距离大于15 cm;NH_4~+-N和NO_3~–-N核心区浓度均随处理时间延长而明显下降。土下12 cm点施90 d后,尿素和磷酸铵的氮素养分在砂姜黑土中的横向移动距离为5~7 cm,垂直方向上养分主要集中在6~18 cm的土层范围;点施90 d时,磷酸铵处理在土下18 cm和水平距离12 cm处无机态氮(NH_4~+-N和NO_3~–-N)含量分别为148.9和77.4 mg/kg,其含量远大于尿素处理(96.3和53.2 mg/kg),而在施肥点两种氮肥处理土壤无机态氮含量差异更大,说明磷酸铵较尿素具有更高的保肥性。研究表明:点施延缓了NH_4~+-N向NO_3~–-N转化速率,提高了肥际养分供应浓度。结合作物生长和需肥特性,预示通过优化施肥位置和氮肥种类,采用一次施肥可以实现90 d持续供应高浓度养分以满足旱地作物生长发育的养分需求。

Effects of Different Fertilization Methods and Nitrogen Fertilizers on Nitrogen Diffusion and Migration in Lime Concretion Black Soil

Nitrogen (N) is one of the most important elements for plant growth and crop yield, however, excessive N fertilization and the relatively low N use efficiency (NUE) can results in the threat to environmental quality, but how to increase NUE has been an urgent problem still unsolved for agriculture development and environment protection, thus, it is important to study the diffusion and migration of N fertilizers to provide a theoretical basis for improving NUE and protecting the environment. A filed micro-plot experiment was carried out to study the effects of different fertilization methods and N fertilizers on the dynamics of soil N vertical diffusion and horizontal migration in lime concretion black soil, 3 fertilization methods (mixed uniformly with 12 cm top soil, placed in-hole at 12 cm depth, and placed in-furrow at 12 cm depth) and 2 nitrogen fertilizers (urea and ammonium phosphate) were designed, the concentrations of inorganic N (ammonium N and nitrate N) of different soil layers were determined at 30, 60 and 90 days after fertilization. The results showed that the concentrations of ammonium N and nitrate N in soils were in an order of placed in-hole at 12 cm depth > placed in-furrow at 12 cm depth > mixed uniformly with 12 cm top soil during 90 day treatment. With the point fertilization, the ammonium N of urea treatment was mainly concentrated in 6-18 cm along the vertical direction and in 0-7 cm alone horizontal distance, while the concentrated area of nitrate N reached the depth of 21 cm, and migrated to 15 cm away from fertilization point. Both the concentrations of ammonium N and nitrate N in soil declined obviously as the treatment time prolonged. The inorganic N of urea and ammonium phosphate point fertilization methods was mainly distributed in 6-18 cm soil, and the horizontal movement distance apart from the fertilization point was about 5-7 cm after 90 days. However, the inorganic N concentrations in soil 18 cm depth and 12 cm away from the ammonium phosphate fertilization point were 148.9 and 77.4 mg/kg, respectively, significantly higher than those of urea treatment (96.3 and 53.2 mg/kg, respectively). Moreover, the difference of inorganic N concentration between the two fertilizers was more apparent in the soil of fertilization point. It suggested that the capacity of ammonium phosphate in maintaining the high inorganic N concentration in soil under point fertilization method was better than that of urea. The results suggested that point fertilization could maintain higher inorganic N concentration in soil and reduce inorganic nitrogen losses. According to crop growth and fertilizer requirement, single basal application could supply the crop with a continuously high nutrient concentration during 90 days by optimizing the fertilizer placement and nitrogen species.