[pp.61-66]

Effects of Grass Buffer Strips using Ophiopogon japonicus on Reducing Soil and Nitrogen Losses under Different Fertiliza

Lalita SIRIWATTANANON Toshiyuki KAWAI and Machito MIHARA （Tokyo University of Agriculture / Taisei Corporation）

Abstract:
This study dealt with the effects of grass buffer strips using Ophiopogon japonicus on reducing soil and nitrogen losses from fertilized plots and the evaluation of the trapping characteristics under different depth of surface water gathered. Chemical fertilizer, conventional compost and granular compost were broadcasted on soils in both slope model plots; one had no conservation measures and the other buffer strips of Ophiopogon japonicus at slope toe. The results showed the buffer strips contributed to decrease 58.7% of soil loss and 41.7% of nitrogen loss averagely, comparing to the losses from the plots without conservation measures. In addition, the results of evaluating the trapping characteristics of Ophiopogon japonicus buffer strips showed the suitable water depth for the maximum trapping efficiency was from 0.5 to 0.7 cm deep, although there was a tendency for the suitable water depth to decrease with slope degree. It means that controlling water depth at buffer strips is important for keeping the trapping efficiency of soil and nitrogen components high. Also, the experimental results showed the finer soil particles having higher nitrogen concentration were hardly trapped.

Key Word:
buffer strips, soil erosion, soil loss, nitrogen loss

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