A field experiment was conducted to investigate the dynamics of ammonium nitrogen (NH4+-N) in the soil during an entire rice-growing season. The NH4+-N dynamics were measured in paddy soils from two N application methods, namely, urea deep placement (UDP) and broadcast prilled urea (PU). The pore water samples from a 10 cm soil depth were collected using a “rhizon sampler.” The samples were collected at 0, 7, 10, 14, 20, and 22 cm from the urea briquette (UB) placement point at 7, 14, 21, 35, 64, and 83 days after transplanting (DAT) of rice. The NH4+-N in the floodwater sample was measured for a week after each split application of PU. UDP retained NH4+-N at the placement site (7–10 cm depth) until 64 DAT. A small amount of NH4+-N moved horizontally up to 14 cm from the placement site. It’s movement to the soil surface and floodwater was very low to negligible. In contrast, PU produced more NH4+-N in both the floodwater and in the soil surface. Therefore, broadcast urea had significantly (p < 0.05) higher ammonia volatilization (~15% of applied N) compared to UDP (<1%). UDP significantly (p < 0.05) increased grain yields, N uptake, and N recovery compared to broadcast urea. These results confirm that a single application of UDP could meet plants’ N demand throughout the rice-growing period, particularly for short- and medium-duration rice varieties.

中文翻译：

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尿素施用方法对湿地水稻土中NH4-N的迁移和滞留的影响

进行了田间试验以研究整个水稻生长季节土壤中铵态氮 (NH4+-N) 的动态变化。NH4+-N 动力学是通过两种施氮方法在稻田土壤中测量的，即尿素深施 (UDP) 和撒播造粒尿素 (PU)。使用“根采样器”收集 10 厘米土壤深度的孔隙水样品。在水稻移栽后 (DAT) 7、14、21、35、64 和 83 天，在距尿素压块 (UB) 放置点 0、7、10、14、20 和 22 cm 处收集样品。在每次分开应用 PU 后，测量洪水样品中的 NH4+-N 一周。UDP 将 NH4+-N 保留在放置位置（7-10 厘米深）直到 64 DAT。少量 NH4+-N 水平移动至距放置位置 14 cm 处。它移动到土壤表面，洪水非常低，可以忽略不计。相比之下，PU 在洪水和土壤表面产生更多的 NH4+-N。因此，与 UDP (<1%) 相比，广播尿素具有显着 (p < 0.05) 更高的氨挥发（~ 应用 N 的 15%）。与播撒尿素相比，UDP 显着（p < 0.05）增加了谷物产量、氮吸收和氮回收。这些结果证实，单次施用 UDP 可以满足整个水稻生长期对氮的需求，特别是对于中短稻品种。05) 与播撒尿素相比，增加了谷物产量、氮吸收和氮回收。这些结果证实，单次施用 UDP 可以满足整个水稻生长期对氮的需求，特别是对于中短稻品种。05) 与播撒尿素相比，增加了谷物产量、氮吸收和氮回收。这些结果证实，单次施用 UDP 可以满足整个水稻生长期对氮的需求，特别是对于中短稻品种。