School of Agricultural, Earth and Environmental Sciences, University of KwaZulu-Natal, Private Bag X01, Scottsville, 3209, South Africa.
Sci Rep. 2020 May 25;10(1):8634. doi: 10.1038/s41598-020-65501-3.
There is a paucity of information on nitrogen (N) and phosphorus (P) mineralization in humic soils, which are highly weathered and have high carbon (C) (>1.8%). This study was to determine effects of liming on N and P mineralization in humic soils. Lime was applied to reduce acid saturation to 20% of the 0-10 and 10-20 cm depths of soils from Eston and Eshowe. Soils were incubated at field capacity moisture and 25 °C temperature, with destructive sampling after 0, 7, 14, 21, 28, 56, 84 and 112 days. Samples were analysed for pH, ammonium- and nitrate-N and extractable P. Phosphorus pools and soil microbial biomass C and N (SMBC and N) were analysed after 112 days only. Soil pH increased up to day 7 and decreased thereafter in Eston soil but decreased throughout the incubation in Eshowe soil. Ammonium- and nitrate-N increased with lime rate, with ammonium-N peaking after 7 and 14 days for Eston and Eshowe soils, respectively. The 0-10 cm depth had higher ammonium-N than 10-20 cm for both soils. Nitrate-N increased with corresponding decrease in ammonium-N. Extractable P decreased till day 21 and increased thereafter in Eston soil, with slight changes in Eshowe. Higher lime rate decreased Al-P, Fe-P and CBD-P and increased soluble-P, Ca-P, and SMB-C and N for both soils. The findings imply that liming humic soils increase nitrate-N and, to a lesser extent, extractable P, possibly improving productivity and exposing N to leaching.
关于腐殖质土壤中氮（N）和磷（P）矿化作用的信息很少，这些土壤高度风化，且碳（C）含量很高（>1.8%）。本研究旨在确定石灰对腐殖质土壤中 N 和 P 矿化作用的影响。在埃斯顿和埃肖韦的土壤中，施石灰将酸饱和度降低到 0-10 和 10-20 厘米深度的 20%。土壤在田间持水量和 25°C 的温度下培养，在 0、7、14、21、28、56、84 和 112 天后进行破坏性采样。分析土壤的 pH 值、铵态氮和硝态氮以及可提取磷。仅在 112 天后分析磷库和土壤微生物生物量 C 和 N（SMBC 和 N）。埃斯顿土壤的 pH 值在第 7 天之前上升，之后下降，但埃肖韦土壤的 pH 值在整个培养过程中都在下降。铵态氮和硝态氮随石灰用量的增加而增加，埃斯顿和埃肖韦土壤的铵态氮分别在第 7 天和第 14 天达到峰值。两种土壤的 0-10 厘米深度的铵态氮含量均高于 10-20 厘米深度。随着铵态氮的相应减少，硝态氮增加。埃斯顿土壤的可提取磷在第 21 天之前下降，之后增加，埃肖韦土壤则略有变化。较高的石灰用量降低了 Al-P、Fe-P 和 CBD-P，增加了可溶性-P、Ca-P 和 SMBC 和 N。研究结果表明，石灰处理腐殖质土壤会增加硝态氮，在较小程度上增加可提取磷，这可能会提高生产力并使氮更容易淋失。
