不同环境温度下沼液养分在土壤中的淋失模拟研究

沼液因其养分利用率高,被广泛应用于农业生产中,而环境温度可通过影响土壤的物理化学性质,影响沼液养分的淋溶损失。试验采用土柱模拟法,研究了不同环境温度对土壤沼液养分淋溶的影响,旨在揭示不同季节土壤养分淋溶可能存在的差异,为生产中合理施用沼液提供理论依据。土柱规格为内径7.5 cm、高20 cm的聚氯乙烯(PVC)管,按每公顷施入0,130和260 kg N,设置每土柱沼液灌溉总量为0,200和400 mL。按当地年平均降雨量的70%计算实际浇灌量为1500 mL,分5次每隔6 d模拟不同降雨次数进行浇灌。沼液浇灌前用清水补足不足部分并混匀。土柱放置于20和30℃的温室培养,每次淋溶后收集土壤淋溶液,测定其全氮、硝态氮、铵态氮、全钾、全磷、速效磷和电导率。结果表明,施用沼液后淋溶液中氮、磷、钾淋失量较清水对照显著增大,其中40 mL沼液水平下,全氮含量平均增加73%,全磷含量增加880%,全钾含量增加388%,且随着沼液用量的增加淋溶液中的养分浓度呈增加趋势。环境温度的提高增加了沼液养分在土壤中的淋溶损失,30℃时淋溶液中的硝态氮、全氮、全钾、全磷、速效磷含量及电导率整体高于20℃,其中全氮平均提高14.68%,全磷平均提高33.59%,全钾平均提高24.08%。整体而言,30℃下沼液养分较20℃时更易发生淋失。因此,在农业生产中,应适当减少夏季高温时的沼液施用次数,增加春秋季节施用次数,但沼液用量不要超过130 kg N/hm²,防止沼液养分大量流失,污染周边环境。

Simulation study of nutrient leaching from soils irrigated with biogas slurry under different environmental temperatures

Biogas slurry is widely used in agriculture due to its high nutrient utilization rate in soil. However, temperature might influence nutrient leaching from the slurry by affecting the physical and chemical characteristics of soils. In this study, nutrient leaching under different environmental temperatures was analyzed using the soil column simulation method, with the aim of providing advice for slurry use in different seasons. Three simulations were investigated: 300 mL water as control, 40 mL slurry plus 260 mL water, and 80 mL slurry plus 220 mL water, with application rates equaling to 0, 130 and 260 kg N/ha respectively. 300 mL of each solution were applied per soil column (7.5 cm, height 20 cm) with irrigation periods of 30 min. Leached solutions were collected until no further leaching was observed. The soil columns were cultured under 20 and 30℃ conditions and leached every 6 days for 5 times in total. The leached solution was analyzed to determine levels of total nitrogen, NO₃-N, NH₄-N, total potassium, total phosphorus, available phosphorus and electric conductance. Results showed that NO₃-N, NH₄-N, total phosphorus, total potassium and electric conductance decreased with increased leaching times only for the water control. Compared to the control, slurry applications increased the amounts of leached nitrogen, phosphorus and potassium. With the 40 mL solution, total nitrogen, total potassium and total phosphorus increased on average by 73%, 880% and 388% respectively. The amount of leached nutrient increased with increased slurry application rates and with higher environmental temperatures. Compared with 20℃, the 30℃ leached solutions showed increased total nitrogen, total phosphorus and total potassium by 14.7%, 33.6%, and 24.1% respectively. Higher environmental temperatures thus increase the amount of nutrient leaching from soils irrigated with biogas slurry. It is thus suggested that application times should be reduced in summer and increased in spring and autumn. However, the total amount of biogas slurry should be less than 130 kg N/ha to avoid excessive leaching and pollution of surrounding environment.