施用腐植酸肥对氮素淋失及油麦菜生长的影响

为明确施用腐植酸肥对氮素淋失和油麦菜（Lactuca sativa var longifoliaf. Lam）生长的影响，通过盆栽试验法测定了砖红壤-油麦菜系统各处理不同形态氮淋失量、油麦菜农艺形态指标以及植株吸氮量。结果表明：可溶性有机氮占氮淋溶量的73.8％~76.8％，是氮素淋失的主要形态。常规处理铵态氮、硝态氮和可溶性有机氮淋失量最高，分别为3.9、48.3和163.2 mg/pot。随着腐植酸肥用量的增加，氮素淋溶损失逐渐降低。施用腐植酸肥增加油麦菜的生物量和氮素利用率，但是过量施用会影响生物量的积累，抑制根系的生长。综合考虑土壤氮素淋失和油麦菜生长状况，腐植酸肥施用量为650 mg/kg时较为适宜。

Effects of Applying Humic Acid Fertilizer on Nitrogen Leaching and Growth of Chinese Lettuce

This experiment was conducted to clarify the effects of humic acid fertilizer on the nitrogen leaching and Chinese lettuce(Lactuca sativa var longifoliaf. Lam)growth. With pot experimen, the leaching amounts of different form nitrogen(N), agronomic characteristics and nitrogen uptake of Chinese lettuce were determined. The results showed that dissolved organic nitrogen leaching accounted for 73.8%-76.8% of total N leaching. Among all the treatments, the highest amout of N was leached for the conventional treatment, and its ammonium, nitrate and organic nitrogen leaching was 3.9 mg/pot, 48.3 mg/pot and 163.2 mg/pot, respectively. All forms of N leaching decreased with increasing humic acid rate. Humic acid application could increase Chinese lettuce biomass and N use efficiency, but its over-application affected biomass accmulation of leaf-used lettuce and restrained the root growth. Based on N leaching and leaf-used lettuce growth, the application rate of 650 mg/kg for humic acid should be advocated in the leaf-used lettuce planting system.