紫色土丘陵区非耕作季节不同种植模式下NP流失模型

The Model of N and P Losses from Different Cropping Modes in the Purple Hilly Region During the Noncropping Season

为了解长江上游紫色土丘陵区非耕作季节N、P的流失特征,以长江上游紫色土丘陵区4种典型种植模式为研究对象,采用野外调查、室内分析和模型模拟相结合的方法,于2008年11月1日至12月31日研究了耕作季节后不同种植模式在每次降雨后的N、P流失特征及不完全混合模型的综合应用效果。结果表明,非耕作季节,紫色农耕地均表现出较大的N、P流失量,最大分别达到(0.491±0.079)kg·hm-2和(12.604±13.173)×10-3kg·hm-2。N的流失量均大于P的流失量,并且N、P主要通过地表径流流失。不同种植模式间N、P流失量有较大的差异,其中生姜种植模式的N、P流失量最大,大豆种植模式最小。不完全混合模型可很好应用于研究区域农耕地N、P流失。模型的有效系数均达到0.6以上,其中模拟N流失的有效系数高达0.958。这表明,非耕作季节农耕地N、P流失是区域农业面源污染的重要来源,不完全混合模型可成为该区域N、P流失预报和面源污染控制的重要手段。

N and P losses aroused by agriculture activities are important origins in regional water pollution, and then limit sustainable development of society and environment. However, more attentions have been given to the losses of N and P in the cropping season, but little information has been focused on those in different cropping modes and in the non-cropping season. In order to characterize the N and P losses in the purple hilly region of the upper Yangtze River during the non-cropping period, therefore, the N and P loss characteristics of 4 representative cropping modes in purple hilly region, and the application of their modeling simulation were studied just after cropping season from November 1 to December 31, 2008. Losses of N and P were relative serious in non-cropping season in the studied cropland, whose maximum values were（0.491±0.079）kg·hm-1 and（ 12.604±13.173×10-3）kg·hm-2, respectively. N losses were significantly higher than P losses in these studied croplands. Compared to infiltration flow, runoff flow was the main pathway during N and P losses. Obvious differences of N and P losses were found in different cropping modes. Ginger cropping modes had the maximum N and P losses via both runoff and infiltration, whereas soybean cropping modes exhibited the minimum values. Additionally, the semi-mixture model could be efficiently applied in forecasting N and P losses of these cropping lands in this region. The simulated effected coefficients were higher than 0.6, which reached to 0.958 for simulating N losses. The results demonstrated that the losses of N and P in non-cropping season could also be the important resources in agricultural non-point pollution in the purple hilly region at the upper reaches of Yangtze River. The incompletion mixture model could be the regional efficient model in forecasting N and P losses, which provided the potential effective way in controlling agricultural non-point pollution in this purple hilly region.