不同土壤湿润速率下中性紫色土磷素淋溶的动态变化

Dynamic Change of Phosphorus Leaching of Neutral Purple Soil at Different Rewetting Rate

土壤的湿润过程是一种常见的非生物胁迫形式，为探明土壤湿润速率对土壤磷素淋溶的影响，以及土壤微生物生物量与磷素淋溶形式的相关性，设置0、2、4、24、48h这5个不同土壤湿润速率，对5个长期不同施肥处理的中性紫色土进行了室内磷素淋溶模拟分析．结果表明：①土壤湿润过程中微生物生物量碳（MBC）在2h降到最低，随着湿润速率的降低，MBC逐渐升高；②缓慢的土壤湿润速率有利于增强土壤的微生物活性，有机肥配施氮磷钾肥（MNPK）的增强效果更加明显；③所有施肥处理的磷素淋溶主要发生在0、2、4h快速湿润速率下，对于施用化肥的土壤而言，缓慢湿润是减缓土壤磷素淋失的重要举措，在田间磷素管理过程中具有重要意义；④土壤淋洗出的磷以溶解态有机磷为主，所有处理的淋洗液中DTP／TP、DOP／TP变化幅度最高，分别为35．42％-85．99％、29．74％-78．58％；⑤随着湿润速率的降低，土壤微生物生物量碳与淋洗液中TP和TDP呈极显著负相关，与DOP呈显著负相关（P〈0．05）．综上所述，可以推测土壤湿润后淋洗出的磷主要来源于土壤微生物．

Re-wetting was one of the most common forms of abiotic stresses experienced by soils. To investigate the effects of soil re-wetting rate on phosphorus （P） leaching and the relationship between soil microbial biomass carbon （MBC） and forms of P in leachate, five kinds of neutral purple soils of different fertilizer treatments were analyzed using simulating lab test at re-wetting rate of 0 h, 2 h, 4 h, 24 h and 48 h. The results showed that： ① The lowest content of MBC appeared at the rate of 2 h during the soil re-wetting process, and the content of MBC increased with the reducing re-wetting rate. ②Slower re-wetting helped to enhance soil microbial activity and the enhancement effect of organic fertilizer with NPK fertilizer （MNPK） was more significant. ③ The P leaching events of all fertilizer treatments occurred mainly at rapid re-wetting rates such as 0 h, 2 h, 4 h. Slower re-wetting was an important measure to prevent P leaching especially for the soils applied with chemical fertilizers, and it was of great significance in the field management of P. ④ Dissolved organic phosphorus （DOP） was the primary leaching part in leachate, and the variation range of ratio of total dissolved phosphorus （TDP） to total phosphorus （TP） and DOP to TP was 35.42%-85.99% and 29.74%-78.58% respectively. ⑤With the reducing of re-wetting rate, significant negative correlation was observed between MBC and TP, TDP as well as DOP in the leachate （P 〈 0. 05）. To sum up, it was speculated that the P in soil leachate mainly came from soil microorganisms.