A lysimeter experiment was conducted to examine the effects of plastic film mulching on the leaching rate of nitrate nitrogen (NO₃-N) from chemical fertilizer that was applied to an upland field that had been converted from paddy rice production. Leaching was monitored in two lysimeters filled with sandy loam soil, which contained low soil organic matter content, under different surface mulch conditions. One was mulched only on the ridge (ridge-mulch treatment) and another one was mulched fully, including the furrow, with black plastic film (full-mulch treatment). Chemical fertilizer was mixed into the top 0.2 m of soil in the two lysimeters before installing the mulch. After transplanting broccoli, the amount of subsurface discharge water and the NO₃-N concentrations in the discharge water were measured every day. Larger NO₃-N discharges occurred in the ridge-mulch treatment for three days after heavy rainfalls in which cumulative precipitation exceeded 10 mm, and the daily NO₃-N load was twice as large as the full-mulch treatment. The differences in the amount of subsurface discharge water and NO₃-N discharged between treatments were not significant when there was no rainfall. Cumulative NO₃-N loads for the ridge- and full-mulch treatment during the last month of the experimental period were 0.246 and 0.195 g m⁻², respectively. The effect of mulching on the reduction of NO₃-N discharge rate was higher for the full-mulch treatment. This result showed that a plastic-film mulching system would be effective as an appropriate fertilizer management to reduce nitrate-leaching losses.

Authors and Affiliations

1. Faculty of Agriculture, Kyushu University, Hakozaki 6–10–1, 812–8581, Higashi-ku, Fukuoka, Japan

   Tomokazu Haraguchi, Yoshisuke Nakano & Ken Mori

2. Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Hakozaki 6–10–1, 812–8581, Higashi-ku, Fukuoka, Japan

   Atsushi Marui

3. Department of Regional Environment Engineering, Kyushu-kyoritsu University, Jiyugaoka 1–8, 807–8585, Yahata nishi-ku, Kitakyushu , Japan

   Kozue Yuge

Corresponding author

Correspondence toTomokazu Haraguchi.

Reprints and permissions