植物油包膜控释尿素在香蕉各生育时期土壤中的释放特性

【目的】探讨香蕉4个不同生育时期施用的植物油包膜控释尿素（PCU）在土壤中的养分释放特征曲线和静水培养中特征曲线的差异，为应用静水溶出率法简单而准确地预测香蕉生长期PCU在土壤中的供肥速度和数量提供依据。【方法】采用田间土壤培养法测定PCU的养分累积释放率及肥效期，以静水培养为对照，研究香蕉4个生育时期内控释尿素的养分释放特性。【结果】除攻蕾期外，大田苗期、旺盛生长期、幼果期土壤中PCU的养分释放曲线不同于静水的，均由静水的“S”型变为“抛物线”型，且前42 d供肥量大，而攻蕾期的供肥量较小，后期则相反；同一PCU的初期溶出率、微分溶出率、28 d累积释放率于各生育时期土壤中的测定值均大于静水的测定结果。其中，初期溶出率大小依次为旺盛生长期＞幼果期≥大田苗期＞攻蕾期；微分溶出率表现为大田苗期＞幼果期＞攻蕾期=旺盛生长期；28 d累积释放率则为幼果期＞大田苗期=旺盛生长期＞攻蕾期；与静水法测定结果相比，大田苗期和旺盛生长期土壤中PCU的肥效期分别延长了18 d和35 d，而攻蕾期和幼果期的分别缩短了10 d和30 d。【结论】同种控释尿素，施用于香蕉不同的生育时期，相同时间内的供肥速度、供肥量不等。较静水培养法测定结果，分别在大田苗期、旺盛生长期、幼果期施用的PCU前期的供肥量大，而后期的供肥量较小；在攻蕾期施用的PCU前期供肥量小，后期的供肥量较大。

Nutrient Release Characteristics of Controlled Release Urea Coated by Vegetable Oil in the Soil at Four Stages of Banana Growing

【Objective】The difference of nutrient release curves of controlled release urea coated by vegetable oil (PCU) obtained by both in the soil incubation at four growing stages of banana and that in still pure water dissolving incubation was studied in order to prove whether still pure water dissolving incubation method being a simple method to forecast the nutrient supplying rate and amount of the PCU in the soil at different growing stages.【Method】The cumulative nutrients release rate and longevity of the PCU were determined by using soil incubation method taking the still pure water dissolving incubation method as check. The nutrient release characteristics of the PCU at four growing stages during banana growth were measured, respectively.【Result】The nutrient accumulation release curve of the PCU in the soil was different from that obtained by pure water dissolving incubation method. Except for the bud promotion stage the curves at the field seedling stage, the fast growth stage and the young fruit stage changed into “parabolic” pattern from the “sigmoid” one in the water. Within the first 42 days of incubation, the nutrient supply amount of the PCU at all of the three stages was greater while which was smaller at the bud promotion stage and it was in adverse after 42 days. The initial release rate, differential release rate and cumulative release rate of 28 days of the same PCU in the soil was bigger than those in still pure water dissolving incubation, respectively. The initial release rate was in order of the fast growth stage＞the young fruit stage≥the field seedling stage＞the bud promotion stage during banana growth. The differential release rate was in order of the field seedling stage＞the young fruit stage＞the bud promotion stage=the fast growth stage. The volume of cumulative release rate of 28 days was in order of the young fruit stage＞the field seedling stage=the fast growth stage＞the bud promotion stage. Compared with the result measured by still pure water dissolving incubation method, the longevity of the PCU in the soil applied at both of the field seedling stage and the fast growth stage was extended by 18 days and 35 days, respectively, while the longevity at the bud promotion stage and the young fruit stage was shorten by 10 days and 30 days, respectively.【Conclusion】When the same kind of controlled release urea was applied at different growing stages during banana growth, the nutrient supply of the PCU were different at each stage in the same time. The nutrient supply of the PCU was a big amount in prophase when it was applied at the field seedling stage, the fast growth stage and the young fruit stage, respectively, while that was small in later period at those stages. Nevertheless, the nutrient supply of the PCU was a small amount in prophase when it was applied at the bud promotion stage, while that was big in later period at this stage.