Reduction of phosphorus release by liming from temporary flooded rice rotational system in greenhouse upland soil

Plastic-film greenhouse (hereafter, greenhouse) vegetable production by temporarily flooding for crop rotation with rice is used as a countermeasure to reduce salt build-up, specifically in flooded rice production systems in Korea. However, flood waters are still observed to contain large amounts of soluble phosphorus (P) enhancing fresh water eutrophication rate. We hypothesized that the addition of liming materials containing high calcium (Ca) content can convert water-soluble P (W-P) into lesser soluble forms reducing P release into off-field water bodies. An incubation study was conducted to select the best liming material, using Ca(OH)2, CaCO3, and CaSO4·2H2O (hereafter, gypsum) mixed with a salt-accumulated soil at a rate 10 g Ca kg−1. Calcium hydroxide was found to be the most effective in reducing W-P concentration in the incubation test. Thus, Ca(OH)2 was applied at rates of 0, 2, 4, and 8 Mg ha−1 before transplanting rice (Oryza sativa) into a paddy field and temporarily successively planted from vegetables grown in greenhouse. Addition of Ca(OH)2 significantly reduced total P (T-P) and dissolved reactive P (DRP) concentrations in the flooded water and T-P, DRP and unreactive P (UP) in the leachate collected at −60 cm soil depth. The reduction of P leaching and runoff loss by amending Ca(OH)2 was mainly affected by the conversion of W-P into calcium bound P (Ca-P) forms. Liming improved soil pH and other nutrient conditions. Conclusively, Ca(OH)2 could be a good material to reduce P release and restore nutrient balance in a vegetable–rice crop rotation under greenhouse condition.