中国北方主要农区农田氮磷淋溶特征与时空规律

中国北方黑土区、潮土区和褐土区是我国农业主产区,大水大肥问题尤为突出,氮磷淋溶是全国典型的地下水污染来源。然而,中国北方主要农区农田氮磷淋溶特征和时空规律尚不清楚。本文利用田间原位监测和文献荟萃分析方法,系统分析了中国北方主要农区285个监测点年的4种主要种植模式(春玉米、冬小麦-夏玉米、露地蔬菜、保护地蔬菜)农田氮磷淋溶特征与时空规律。研究结果表明,中国北方4个主要种植模式的平均氮和磷淋溶强度分别为:保护地蔬菜117.5 kg(N)·hm~(-2)和0.74 kg(P)·hm~(-2),露地蔬菜51.7kg(N)·hm~(-2)和0.10kg(P)·hm~(-2),冬小麦-夏玉米轮作49.9kg(N)·hm~(-2)和0.07kg(P)·hm~(-2),春玉米30.7kg(N)·hm~(-2)和0.09kg(N)·hm~(-2)。与粮田相比,蔬菜田的高水肥投入决定了其较高的氮磷淋溶量。受土壤质地以及区域间水肥管理差异的影响,同一种植模式下,总氮淋溶强度为黑土区褐土区潮土区。农田氮磷淋溶年际间变化主要受降雨强度的影响,总氮淋溶量与降雨强度呈正线性相关关系,尤其前一年无淋溶事件发生背景下,下一年的淋溶量会急剧增加。空间尺度上,潮土区和褐土区是氮素淋溶的主要风险区。值得注意的是一些蔬菜种植面积尤其是保护地蔬菜种植面积占比较大的省份表现出较高的氮磷淋溶风险。综上,北方主要农区农田氮磷淋溶风险以氮为主,磷的淋溶风险也不容忽视。潮土区和褐土区是氮素淋溶的主要风险区。区域尺度上,氮磷淋溶主要来自粮田,但菜田面积越大,氮磷淋溶风险越高。

Nitrogen and phosphorus leaching characteristics and temporal and spatial distribution patterns in northern China farmlands

The main agricultural production areas in northern China are the black soil area, fluvo-aquic soil area, and cinnamon soil area. In the areas, N and P leaching is a common cause of groundwater pollution, but the leaching characteristics and distribution patterns (temporal and spatial) are unclear. The in situ monitoring of field leakage ponds and literature data analysis were used to analyze N and P leaching characteristics at 285 monitoring sites using the four main planting patterns (spring maize, winter wheat-summer maize rotation, open-field vegetables, and greenhouse vegetables). The results showed that the average N and P leaching rates were 30.7 kg(N)·hm^-2 and 0.09 kg(P)·hm^-2 for spring maize, 49.9 kg(N)·hm^-2 and 0.07 kg(P)·hm^-2 for winter wheat-summer maize rotation, 51.7 kg(N)·hm^-2 and 0.10 kg(P)·hm^-2 for open-field vegetables, and 117.5 kg(N)·hm^-2 and 0.74 kg(P)·hm^-2 for greenhouse vegetables. Fertilizer application and irrigation, often determined by the planting pattern, were positively correlated with N leaching. Therefore, high fertilizer and water amounts used in vegetable fields resulted in more N and P leaching than observed in grain fields. In fields using the same planting pattern, the fluvo-aquic soil area had the greatest total N loss intensity, followed by the cinnamon soil area; the black soil area had the least intensity. Different soil textures resulted in different leached N amounts when the same fertilization and irrigation practices were used. Fields using the same planting pattern also had different leaching amounts because of regional differences in fertilization and irrigation practices. Annual N and P leaching was mainly affected by rainfall intensity, and total N leaching was positively correlated with rainfall intensity. If no leaching events occurred in the previous year, a sharp increase in leaching was observed in the following year. Spatially, the cinnamon and fluvo-aquic soil areas were the primary N leaching risk areas, especially, some provinces with large vegetable planting areas (particularly those with large greenhouse areas) showed high N and P leaching risks. Northern Chinese agricultural areas are primarily at risk for N leaching, but also P leaching; cinnamon and fluvo-aquic soils are the highest risk areas. Regionally, N and P leach mainly from grain fields, but as vegetable field size increases, so does the risk of N and P leaching.