沼肥灌施配合机械深松对柑橘园土壤团聚体组成、有机质含量及矿化特征的影响

为探讨沼肥灌施配合机械深松对柑橘果园土壤团聚体组成、有机碳含量及其矿化的影响,本研究通过柑橘果园沼肥定位试验,设置常规施肥(CK,柑橘专用复合肥施用量为2 500 kg·hm^-2)与沼肥灌施(T1、T2、T3和T4,施用量分别为45、135、180和270 t·hm^-2)共5个处理,研究了不同沼肥灌施量条件下柑橘果园土壤有机碳的分布特征,并结合室内培养试验测定了其土壤有机碳矿化量。结果表明,与CK相比,柑橘果园灌施沼肥处理表层土壤团聚体平均重量直径(MWD)均显著增加,T1、T2、T3和T4的增幅分别为76.9%、35.8%、26.9%、33.6%。各处理土壤有机碳含量为10.09~14.38 g·kg^-1,其中以T3最高,其次是T4。各处理土壤有机碳含量在各粒级团聚体间存在差异,在CK、T3和T4中以0.25~2 mm团聚体为主要载体;在T1和T2中以>5 mm团聚体为主要载体。有机碳矿化试验表明,各处理土壤在前15 d矿化速率较快,累积矿化量达到168.42~190.84 mg CO₂-C·kg^-1,占整个培养期总矿化量的一半以上(58.46%~62.09%)。结合动力学方程模拟结果可知,T3和T4中可矿化碳和易矿化碳含量占土壤总有机碳的比例低于其他处理,表明沼肥灌施配合机械深松有助于柑橘果园土壤有机碳的累积。本研究结果可为柑橘果园沼肥合理施用提供科学依据。

Effects of Biogas Fertilizer Combined With Mechanical Deep Application on Aggregates Distribution,Soil Organic Carbon Content and Mineralization Characteristics in Citrus Orchard

This study aims to explore the effect of biogas fertilizer combined with mechanical deep application on aggregates distribution, soil organic carbon content and mineralization characteristics in Citrus orchard. Five treatments were designed as the regular fertilizing as control (CK, chemical fertilizer, 2500 kg·hm^-2), and four biogas fertilization treatments (T1, T2, T3 and T4), with the amount of 45, 135, 180, and 270 t·hm^-2 to detect the distribution of SOC. Moreover, mineralization characteristic was determined by laboratory culture test. The result showed that the mean weighted diameter (MWD) of soil aggregates was significantly increased by biogas fertilization, as compared with CK, with the increase amplitude of 76.9%, 35.8%, 26.9% and 33.6%, respectively. The content of soil organic carbon was from 10.09 to 14.38 g·kg^-1 in treatments, with T3 being the highest, followed by T4. The distribution of organic carbon in soil aggregates was different among treatments; the soil aggregates in diameter of 0.25-2 mm was the main organic carbon carrier in CK, T3 and T4; and soil aggregates in the diameter of >
⁵ mm was the main organic carbon carrier in T1 and T2. The SOC mineralization rates were higher at the initial stage (15 d) from 168.42 to 190.84 mg CO₂-C·kg^-1 among treatments, leading the SOC mineralization was more than half of the total cumulative amount (58.46%~62.09%). Combined with the simulated results of kinetic equation, the ratio of potential mineralization of organic carbon (C₀) and easy mineralization of organic carbon (C₁) in total soil organic carbon was low in T3 and T4, indicating that the organic carbon of orchard soil could be increased by mechanical deep application of biogas fertilizer. This study could provide a scientific basis for rational application of biogas fertilizer in Citrus orchard.