Beijing Key Laboratory of Farmland Soil Pollution Prevention-Control and Remediation, College of Resources and Environmental Sciences, China Agricultural University, No. 2 Yuanmingyuan Xilu, Haidian, Beijing, 100193, PR China.
School of Agriculture, Sun Yat-sen University, Shenzhen, 518107, PR China.
J Environ Manage. 2024 Jun;360:121167. doi: 10.1016/j.jenvman.2024.121167. Epub 2024 May 14.
Organic amendment substitutes mineral fertilizers has been proven to increase the organic matter content of soils, which in turn may induce phosphorus (P) mobilization by triggering the redox reaction. However, under flooded conditions according to local agricultural practices, as one of the factors restricting the decomposition of organic matter, the role ammonium plays in P transformation and leaching from soils with different organic matter remains unclear. To address the knowledge gap, the calcareous soils were collected from a long-term field trial (>13 years) containing two treatments with equal P inputs: a long-term mineral fertilization and a long-term organic amendment. Both long-term mineral fertilized soil and long-term organic amended soil were split into ammonium applications or no ammonium applications. A series of column devices were deployed to create flooded conditions and monitor the P leaching from the collected soils. The K-edge X-ray absorption near-edge structure and sequential extraction method were employed jointly to detect soil P fractions and speciation, and the P sorption/desorption characteristics of soil were evaluated by Langmuir fitting. The results showed a reduction of cumulative leached P from soils by 33.2%-43.3% after ammonium addition, regardless of previous long-term mineral fertilization or organic amendment history. A significant enhancement of soil labile P pool (indicated by the HO-P fraction and NaHCO-P fraction) after ammonium addition results in the reduction in soil P leaching. The reduced P sorption capacity coupled with the transformation from hydroxyapatite to β-tricalcium phosphate indicated that the phosphate retention is attributed to the precipitation formation rather than phosphate sorption by soil. The present study highlights that the ammonium addition could affect the phosphate precipitation transformation. This may be attributed to the effect of ammonium addition on the calcium and magnesium ion content and molar ratio in this soil, thereby regulating the form of soil phosphate precipitation. The mechanisms revealed in this study can support developing optimized agricultural management practices to alleviate soil P loss.
有机肥料替代矿物肥料已被证明可以增加土壤的有机质含量，这反过来又可能通过触发氧化还原反应来诱导磷（P）的活化。然而，根据当地农业实践，在淹水条件下，作为限制有机质分解的因素之一，铵在不同有机质土壤中 P 转化和淋失中的作用尚不清楚。为了弥补这一知识空白，从一个长期田间试验（>13 年）中收集了含有两种等量磷投入的处理的钙质土壤：长期矿物施肥和长期有机施肥。长期矿物施肥土壤和长期有机施肥土壤均分为铵施用量或无铵施用量。一系列柱状装置被部署以创造淹水条件，并监测收集土壤中的 P 淋失。采用 K 边 X 射线吸收近边结构和连续提取法联合检测土壤 P 形态和形态，通过 Langmuir 拟合评估土壤 P 吸附/解吸特性。结果表明，无论先前是否进行长期矿物施肥或有机施肥，添加铵后土壤累积淋失 P 减少了 33.2%-43.3%。添加铵后，土壤中易解吸磷库（以 HO-P 分数和 NaHCO-P 分数表示）显著增加，导致土壤 P 淋失减少。减少的 P 吸附能力加上羟基磷灰石向 β-磷酸三钙的转化表明，磷的保留是由于沉淀形成而不是土壤对磷的吸附。本研究强调了铵的添加会影响磷酸盐的沉淀转化。这可能归因于铵添加对土壤中钙和镁离子含量和摩尔比的影响，从而调节了土壤磷酸盐沉淀的形式。本研究中揭示的机制可以支持制定优化的农业管理实践，以减轻土壤 P 损失。
