不同施肥模式对菜—稻轮作农田土壤磷素径流损失与表观平衡的影响

采用田间小区定位试验(2015—2016年)研究了自然降雨条件下农户习惯性施肥(T1)、减量施肥(T2)及优化施肥(T3)不同施肥模式对太湖流域菜—稻轮作农田土壤磷素径流流失特征和磷素表观平衡的影响。结果表明:菜—轮作农田地表径流排水主要分布于强降雨(梅雨季、台风季)集中的水稻生长季,与降雨量呈显著线性正相关关系。磷素径流流失也集中在水稻季,各处理条件下,其流失量占周年流失总量的比例达74.75%~81.46%。农户习惯性施肥模式(T1)处理条件下,蔬菜季径流总磷平均浓度(0.55mg/L)显著高于水稻季(0.29mg/L),但磷素径流流失量(0.49kg/hm^2)却显著低于水稻季(2.13kg/hm^2)。减量施肥(T2)和优化施肥(T3)模式处理可显著降低蔬菜季、水稻季径流磷素浓度和菜—稻周年磷素径流流失量。较T1处理,T2和T3处理显著降低菜—稻周年TP径流流失量分别达22.48%和45.66%。菜—稻轮作农田土壤磷素盈余量呈现显著的施肥模式差异和季节差异,周年盈余量高达260.90kg/hm^2,且主要集中在蔬菜生长季(70.63%)。较T1处理,T2、T3处理显著降低周年磷素盈余量达38.47%~64.87%(P<0.05)。同时,虽然蔬菜产量在T2、T3处理下均显著下降,但较T2处理,T3处理对蔬菜、水稻及周年产量均无显著影响。可见,菜—稻轮作种植模式下,蔬菜季施用适量生物炭,稻季不施磷具有磷素减排、维持作物稳产和磷素表观平衡的协同效应。

Effects of Different Fertilization Modes on Phosphorus (P) Loss by Surface Runoff and Apparent P Balance in the Vegetable-Rice Rotation Fields of Taihu Lake Region, China

We performed a field plot experiment (2015-2016) to study the effects of different fertilization modes on phosphorus (P) losses by surface runoff, the apparent P balance, and vegetable and rice yield in a vegetable-rice rotation field in Taihu Lake Basin, China under natural rainfall conditions. The results showed that surface runoff events were mainly distributed in the rice growing season with heavy rainfall (rainy and typhoon season), which showed a significant positive linear correlation between the quantity of surface runoff water and rainfall capacity. And, phosphorus (TP) loss by surface runoff was also mainly distributed in the rice growing season, which accounted for 74.75%~81.46% of TP loss during the whole monitoring period including the vegetable and rice growing seasons. In T1 (conventional fertilizer application), the average TP concentration of surface runoff water in the vegetable growing season (0.55 mg/L) was significantly higher than that of rice growing season (0.29 mg/L), but TP loss (0.49 kg/hm²) was significantly lower than that of rice growing season (2.13 kg/hm²). Compared with T1, T2 (reducing application 31.17% of P compared with T1) and T3 (reducing application 49.75% of P compared with T1, in which, no P application during the rice growing season, and wheat straw biochar application during the vegetable growing season) could significantly reduce TP losses by surface runoff by 22.48% and 45.66% during the whole monitoring period, respectively. Furthermore, P surplus reached up to 260.90 kg/hm², which showed significant fertilization mode dependence and growing season dependence. In which, P surplus mainly occurred in the vegetable growing season, which accounted for 70.63% of that in the whole monitoring period. Compared with T1, P surplus in T2 and T3 decreased significantly by 38.47% and 64.87%, respectively. Moreover, compared with T1, vegetable yield decreased significantly under T2 and/or T3, but no significant difference was found between T2 and T3 in vegetable yield, rice grain yield, and annual yield of vegetable and rice grain. These results suggested that no P application during rice growing season and appropriate wheat straw biochar application during the vegetable growing season had synergistic effect of phosphorus reduction, maintaining stable crop yield and apparent P balance in the vegetable-rice rotation field.