添加紫云英对稻田土壤颗粒吸附磷酸盐的影响

【目的】研究添加紫云英(Chinese milk vetch, CMV)对土壤颗粒表面磷素吸附特征的影响机制，为绿肥高效利用提供理论依据。【方法】采用土培试验方法，设置4个紫云英翻压量梯度：CMV0 (0)、CMV1(15000 kg/hm²)、CMV2 (22500 kg/hm²)和CMV3 (30000 kg/hm²)，淹水培养30天后，取土样，过250μm筛后，分为细砂粒(48～250μm)、粉粒(2～48μm)和粘粒(<2μm)，分别测定土壤有机质、全氮、全磷和有效磷含量，并分别进行磷酸盐的等温吸附和动力学吸附试验。【结果】与CMV0相比，添加紫云英显著提高了土壤颗粒中有机质、全氮、全磷和有效磷含量，尤以砂粒中的提高幅度最大，分别达到33.42%～81.04%、4.83%～15.17%、45.45%～51.52%和40.76%～60.70%；添加紫云英降低了砂粒和粘粒的比表面积，但是提高了粉粒的比表面积。土壤颗粒对磷素的吸附可用Langmuir吸附等温线方程很好地拟合，添加紫云英提高了各粒径土壤对磷的理论最...

Phosphate adsorption on paddy soil particles affected by application of Chinese milk vetch

  【Objectives】  Studying the effect of Chinese milk vetch (CMV) on phosphate (P) adsorption on soil particles could provide a theoretical basis for efficient green manure usage.  【Methods】  Paddy soil was collected from Anhui Province, and CMV was added at the rate of 0, 15000, 22500 and 30000 kg/hm2, and denoted as CMV0, CMV1, CMV2, and CMV3. The mixture was incubated for 30 days under anaerobic conditions. Each soil sample was divided into sand (48–250 μm), silt (2–48 μm), and clay (<2 μm) particles for the isothermal and kinetics adsorption experiment.  【Results】  Compared with CMV0, CMV (P<0.05) increased the content of organic matter (SOM), total nitrogen (TN), total phosphorus (TP) and available phosphorus (AP) in all the three soil particle sizes. The highest increase of 33.42%–81.04%, 4.83%–15.17%, 45.45%–51.52%, and 40.76%–60.70% was recorded in sand particles. CMV reduced the specific surface area of sandy and clay particles but increased those of silt particles. The Langmuir model described well the P adsorption of soil particles. The maximum adsorption capacity (Q_m), native adsorbed exchangeable phosphorus (NAP), zero-equilibrium P concentration values (EPC₀), adsorption constant (K_L), and soil affinity to phosphorus (K_p) in all soil particles increased under CMV. Sandy particles recorded the highest increase, with the Q_m reaching 4.02%–46.81%. In silt particles, the NAP, K_L, EPC₀, and K_p increased by 116.77%–210.78%, 29.55%–69.05%, 93.62%–141.28%, and 11.97%–28.87%, respectively. The kinetic P adsorption was well fitted with the Pseudo-second-order kinetics. The fitting results showed that the adsorption rate (k₂) and the initial sorption rate (H) of the different soil particles increased with CMV application. The highest H and k₂ increases were recorded for clay particles, increasing by 25.77%–98.20% and 25.74%–111.15%, respectively. Notably, CMV2 recorded higher H and k₂ values than CMV1 and CMV3 in all soil particles. The Q_m and EPC₀ were correlated with AP in sandy particles (P<0.01) . The NAP, EPC₀, and K_p were correlated with SOM and TP (P<0.05) ; K_L was correlated with TP in silt particles (P<0.01) . In clay particles, Q_m was correlated with TP and AP (P<0.01) ; EPC₀ was correlated with SOM, TN, TP, and SSA; K_p was correlate with SOM, TN, and SSA (P<0.05) .  【Conclusions】  The adsorption of phosphate on the soil particles was enhanced by improving TP and AP mainly with the application of CMV, especially on the sandy and silt particles. The highest values of Q_m and K_L in CMV2 were recorded for sandy and clay particles. In CMV3, the silt particles had the highest Q_m and K_L. Therefore, rational application of CMV to paddy soil combined with soil texture could help achieve scientific management of P.