Across the Brazilian Cerrado, the land area under soybean-maize (double cropping) and maize-brachiaria (intercropping) systems has been expanding. In this study, we evaluated the efficiency of P fertilization and the response of residual P compartments to i) soybean monoculture in conventional (CT) or no-tillage (NT), ii) soybean in rotation systems including the maize+brachiaria consortium; and iii) soybean in succession systems including soybean-maize double cropping. These factors were combined into eight treatments in an experiment conducted at Itiquira, Mato Grosso, Brazil. Our study was laid out following a completely randomized block design with four replicates. We determined the apparent efficiency of P fertilization using the balance method for 12 years, after which residual P was evaluated in soil samples submitted to a soil P fractionation scheme using CaCl, Mehlich-3, NaOH (inorganic-Pi and organic-Po) and HCl. P occluded was estimated as the difference between total soil P and the sum of the extractable P fractions. Our data showed apparent efficiency of P fertilization about 78.3 % under soybean-fallow (CT or NT) and about 93.0–94 % under the soybean-successions. Under the rotations, the apparent efficiency of P fertilizations was about 100–123.0 % coupled to some depletion of P-Mehlich-3 and Pi-NaOH. We found positive correlations between P-Mehlich-3 and Pi-NaOH, whereas both Po-NaOH and P-Mehlich-3 showed strong negative correlations with P occluded. Overall, the rotation systems evaluated in this research appear to benefit from the transfer of P between P-Mehlich-3 and Pi-NaOH pools, coupled to the formation of Po-NaOH limiting the accumulation of P occluded. These characteristics allow reconciling productive crop grain systems with efficient P fertilizations and recycling of P in soils with high residual P pools in tropical agroecosystems.

中文翻译：

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热带农业轮作系统中有效施磷的残留池中的磷循环


在巴西塞拉多地区，大豆-玉米（双季）和玉米-臂形（间作）系统的土地面积一直在扩大。在这项研究中，我们评估了磷施肥的效率以及残留磷隔室对i）常规（CT）或免耕（NT）中的大豆单一栽培，ii）包括玉米+臂形菌群在内的轮作系统中的大豆的响应； iii) 大豆连作系统，包括大豆-玉米双季。在巴西马托格罗索州伊蒂基拉进行的一项实验中，将这些因素组合成八种处理方法。我们的研究是按照完全随机的区组设计进行的，有四次重复。我们使用平衡法测定了 12 年磷施肥的表观效率，之后使用 CaCl、Mehlich-3、NaOH（无机 Pi 和有机 Po）和土壤磷分馏方案评估了土壤样品中的残留磷。盐酸。吸留磷被估计为土壤总磷与可提取磷分数之和之间的差值。我们的数据显示，大豆休耕（CT 或 NT）下磷肥的表观效率约为 78.3%，而大豆连续种植的磷肥表观效率约为 93.0-94%。在轮作下，磷肥的表观效率约为 100-123.0%，同时 P-Mehlich-3 和 Pi-NaOH 有所消耗。我们发现 P-Mehlich-3 和 Pi-NaOH 之间呈正相关，而 Po-NaOH 和 P-Mehlich-3 均与 P 吸留呈强负相关。总体而言，本研究中评估的轮换系统似乎受益于 P-Mehlich-3 和 Pi-NaOH 池之间 P 的转移，再加上 Po-NaOH 的形成限制了 P 吸留的积累。 这些特性使得生产性作物谷物系统与有效的磷施肥以及热带农业生态系统中残留磷库高的土壤中磷的循环利用相协调。