摘要
摘要:磷素的吸附和解吸特性对土壤磷素迁移及其环境效应具有重要影响, 过量磷肥施入易造成土壤磷素固定和流失, 但合理间作可促进磷素吸收利用, 减少固定, 研究间作和不同施磷量条件下红壤磷素吸附解吸特性的平衡效应对促进红壤磷的高效利用, 兼顾环境效应具有重要意义。本研究采取2因素裂区区组试验, 主因素为种植模式, 分别为与玉米||大豆(IM)、单作玉米(MM); 副因素为施磷水平, 分别为P0 [0 kg(P₂O₅)?hm^?2]、P60 [60 kg(P₂O₅)?hm^?2]、P90 [90 kg(P₂O₅)?hm^?2]、P120 [120 kg(P₂O₅)?hm^?2] 4个施磷水平, 通过田间试验, 研究间作和施磷量对红壤磷素吸附解吸平衡效应的影响; 应用结构方程模型(SEM)和邻接树法(ABT)定量分析间作和施磷水平对磷吸附和解吸的相对贡献, 揭示间作影响红壤磷素吸附解吸的关键因子。结果表明: 1) Langmuir 等温吸附方程最适合红壤对磷的吸附特征拟合, 土壤磷吸附量随平衡溶液磷浓度的增加呈先增加再趋于饱和的趋势, 土壤磷吸附量随施磷量的增加逐渐降低。2)种植模式和施磷水平以及交互作用极显著(P<0.01)影响红壤磷素的吸附量和解吸量。间作处理较单作磷素吸附量和解吸量分别增加22.9%和9.2%(P<0.05); 不同施磷水平下, 间作磷吸附量较单作显著增加13.0%、19.4%、41.5%和23.9% (P<0.05); 磷解吸量在P0和P60处理间作较单作显著增加90.2%和194.4% (P<0.05), 而在P90和P120处理间作较单作减少52.1%和34.1% (P<0.05)。3)不同种植模式与施磷水平下, 土壤磷吸附量与土壤pH、有机质、树脂磷、有效磷、全磷以及磷吸附饱和度呈极显著负相关(P<0.01), 与游离氧化铁、游离氧化铝和磷吸持指数呈极显著正相关(P<0.01), 土壤磷解吸量与标准需磷量呈极显著负相关(P<0.01)。红壤磷素的吸附和解吸主要受pH、有机质和游离氧化铁的影响, 间作通过改变土壤的pH、有机质和游离氧化铁含量影响红壤磷吸附量和解吸量。玉米||大豆间作具有较好的土壤磷缓冲能力, 低磷水平下促进磷素大量解吸供植物吸收利用, 高磷水平下促进磷素吸附有效减缓磷素的损失。
关键词:磷/
吸附/
解吸/
玉米||大豆间作/
施磷量/
红壤
Abstract:The migration and environment effect of phosphorus in soil are affected by its’ adsorption and desorption. Although the excessive application of phosphorus fertilizer causes phosphorus fixation and loss, reasonable intercropping promotes the absorption and utilization and decreases fixation of phosphorus. This study investigated the adsorption and desorption of phosphorus in red soil under intercropping and phosphorus application, it is signicant for promoting the efficient utilization of red soil phosphorus and balancing environmental effects. In this study, a two-factor split-plot block experiment was adopted through field trials, in which the first factor was the planting pattern, namely maize||soybean intercropping and maize monoculture; the second factor was phosphorus application levels: P0 (0), P60 [60 kg (P₂O₅)·hm^?2], P90 [90 kg (P₂O₅)·hm^?2], and P120 [120 kg (P₂O₅)·hm^?2]. This study aimed to explore the effects of intercropping and application of phosphorus on the adsorption and desorption of phosphorus in red soil, and to quantitatively analyze the relative contribution of intercropping and phosphorus application to phosphorus adsorption and desorption by using the structural equation model, and to reveal the key intercropping effect factors on the adsorption/desorption of phosphorus in red soil by using the aggregated boosted tree methods. Results showed that: 1) the Langmuir isothermal adsorption equation was most suitable for fitting phosphorus adsorption in red soil. The adsorption amount of soil phosphorus increased first and then tended toward saturation with the increase in phosphorus concentration in the equilibrium solution, while the adsorption amount of phosphorus decreased gradually with the increase in phosphorus application. 2) Phosphorus adsorption and desorption in red soil were significantly affected by planting pattern, phosphorus application, and the interaction between planting pattern and application of phosphorus (P<0.01). Compared with monoculture, the maize||soybean intercropping increased the adsorption and desorption of phosphorus by 22.9% and 9.2%, respectively (P<0.05). Under four application rates of phosphorus, compared with monoculture, the adsorption of phosphorus in intercropping increased significantly by 13.0%, 19.4%, 41.5%, and 23.9% (P<0.05), respectively. The desorption of phosphorus increased significantly by 90.2% and 194.4% in P0 and P60 intercropping (P<0.05), but decreased by 52.1% and 34.1% in P90 and P120 intercropping, respectively (P<0.05). 3) Under different planting patterns and phosphorus application levels, the adsorption of soil phosphorus had a significant negative correlation with soil pH, organic matter, resin phosphorus, available phosphorus, total phosphorus, and degree of phosphorus saturation (P<0.01), and a significant positive correlation with free iron oxide, free alumina, and phosphate sorption index (P<0.01). However, the desorption of phosphorus from red soil had a significant negative correlation with a standard phosphorus requirement (P<0.01). The adsorption and desorption of phosphorus in the red soil were mainly affected by pH, organic matter, and free iron oxide. Intercropping of maize and soybean changed soil pH and contents of organic matter and free iron oxide, resulting in differences in the phosphorus adsorption and desorption from that of maize monoculture in red soil, improving the soil phosphorus buffering capacity. At a low phosphorus level, intercropping can accelerate a large amount of phosphorus desorption for plants to absorb and utilize; at high phosphorus levels, intercropping can promote phosphorus adsorption and effectively slow down the loss of phosphorus.
Key words:Phosphorus/
Adsorption/
Desorption/
Intercropping of maize and soybean/
Phosphorus application level/
Red soil



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