Abstract
Greenhouses are usually irrigated after cropping to remove accumulated salts in the topsoil. Nitrate remained in the soil is reported to be transported to groundwater due to the irrigation, resulting in high nitrate concentration in ground or surface waters. The present study evaluated the effect of a catch crop (dent corn) on leaching losses of nitrogen and phosphorus during a fallow period (catch crop cultivation, salt removal irrigation and reductive soil disinfection) in a farmer's eggplant greenhouse in Okayama, Japan, in 2010 and 2011. Nitrogen leaching was greatly reduced owing to the nitrogen uptake by the catch crop with compared to the control (p < 0.01). Differences of nitrogen losses during the fallow period between treatments were 12.2 g m-2 in 2010 and 5.4 g m-2 in 2011, probably due to different contents of mineral nitrogen remained in the soil after eggplant harvests. On the other hand, phosphorus leaching was not significantly different between treatments (p > 0.05). The effect of phosphorus uptake by the catch crop may be masked because of the large amount of mineral phosphorus accumulated in the soil. Our results clearly showed that catch crop growth during a fallow period reduced nitrogen leaching in the eggplant greenhouse.
