The effect of natural weed buffers on soil and nitrogen losses in Japan

In Japan, heavy rains from June to October cause severe erosion in the agricultural fields. Natural weed buffers may help conserve the soil and water. We measured the mass balances of the water, soil and nitrogen components in a plot of 159 m2 (7.2 m wide and 22.1 m long). Plant growth in the plot was dominated by the weeds Humulus scandens Merrill and Poa annua L. We also evaluated the ability of the natural weed buffer to reduce soil and nitrogen losses. ements of the mass balances of the water, soil and nitrogen components showed that 93.1% of the total water received by the plot was lost through percolation. The weed buffer captured 99.6% of the soil introduced into the plot. The plot stored 80.0% of the total nitrogen input, while 13.4% percolated through the soil and 1.8% flowed off the plot from the surface. Only 0.1% of the nitrogen was taken up by plants. e 99.6% of the soil and 80.0% of the nitrogen components were captured, we concluded that the natural weed buffer was very effective in minimizing soil and nitrogen losses. As Japanese farmers grow older and more agricultural fields in the semi-mountainous regions of Japan fall into disuse, the natural weeds that grow on those fields may become efficient tools for conserving the soil and water in these regions.