Estimation of Nutrient Leaching Applying Liquid Manure in Bio-Circulation Experimental Forest Using Root Zone Water Quality Model.

Manure recycling as a fertilizer is one of solutions for the environmental problem related with livestock manure treatment as well as the ocean dumping ban act in Korea. For the manure disposal, tree plantation area is being a candidate place. However, the manure application has possibilities to cause environmental impacts. It is necessary to investigate water quality impact from manure disposal to the agricultural area. In this study, 5-year tulip tree was planted and Liquid manure (LM) has been applied during tree growing periods from 2008 to 2011. Soil moisture contents and soil water monitored in LM and no application (ctrl) plot. To investigate the leaching impact of LM under model-based of scenario, Root Zone Water Quality Model (RZWQM) was calibrated and evaluated and scenarios were constructed based on right time and rate. The right time scenarios consisted of LM application times: rainfall, application seasons and long term impacts. The right rate scenarios consisted of LM concentration (high or low concentration LM and ctrl) and whether compost or not. The nutrient concentration of soil water was higher in LM than in ctrl, in particular, when less composted LM were over-fertilized during non-growing or rainfall season. Nutrient has possibilities to leach into shallow groundwater. From the RZWQM simulation, simulated soil moisture content was well reflecting the observed one and simulated nitrogen in soil water exists between minimum and maximum value and was well reflecting the observed nitrogen trend. When LM applied in day, before and after precipitation, nutrient leaching and runoff were increasing. When LM was applied, it is necessary to determine the degree of composing and concentration and should avoid at precipitation and winter season. From this study, nutrient status and guideline for environmental management will be able to provide for establishing the agricultural water conservation in agricultural watershed.