Advantages of pre-harvest temporal flooding in a catch crop field in relation to soil moisture and nutrient salt removal by root uptake

Catch crop cultivation coupled with subsequent flood activity is an environmental friendly method of removing nutrient salts from soil in greenhouse. However, in comparison with the usual fallow period in greenhouse horticulture in Japan, a longer time is required for cultivation and soil drying after flooding. To minimize such time while retaining catch crop performance, temporal flooding was conducted in an experimental catch crop field of corn before harvest (i.e., pre-harvest temporal flooding), when crops were growing well and most nutrient salts within the soil had been taken up by the roots. Results showed that pre-harvest temporal flooding enhanced crop growth and stomatal opening; hence, evapotranspiration (mostly transpiration) was increased to a high value (3.5 times that of bare soil plot in greenhouse). Therefore, compared with the bare soil field, there was a remarkable pronounced decrease in the soil water content due to evapotranspirational water loss in the catch crop field after temporal flooding. Furthermore, the total nutrient (nitrogen) uptake by crops was also significantly accelerated in relation to pre-harvest flooding owing to the increase in crop growth. It was also found that electrical conductivity and nitrate nitrogen concentration of soil solution (at a soil-water ratio of 1:5) decreased with time owing to root uptake, and were at a fairly low level when pre-harvest flooding was conducted. These results suggest that pre-harvest temporal flooding shortens the implementation time by accelerating soil drying, and increases salt removal by root uptake; thus, this method delivers considerable advantages for practical use in catch crop cultivation.