Decomposition of organic materials and its effect on transport of nitrogen, phosphorous and water in unsaturated soil

Abstract

A simultaneous transport of water, phosphorous, and nitrogen and organic matter decomposition were studied experimentally and numerically. Greenhouse experiments were achieved for collecting data of organic carbon, nitrogen, phosphorous and water contents. A numerical model (LEACHM) was used for simulating these data. Simulated results were compared with experimental data. The experiments were conducted in one-end open PVC columns (0.056-m ID and 0.30-m high) using unsaturated sandy soil under the atmospheric condition of Buridah, Al-Qassim, KSA. Municipal solid wastes (fermented partially) were mixed with the sandy soil. A 0.05-m mixed soil layer was located at six different depths (6 treatments) within the soil columns. Two replicates were assigned for each treatment. The soil or the mixed layer had initial water content of 0.0802 m 3 /m 3 . The initial carbon in the soil and mixed layer were 0.117 and 0.451%, respectively. The experiment lasted two months with application distilled water periodically at the open end of soil columns. Both predicted and measured final water showed nonlinear distributions. The model overestimated slightly the water content in comparison to the observed data. The stored water in a soil column decreased as the depth of mixed layer increased. The predicted and observed concentrations of organic carbon,NO − , and available phosphorous behaved similarly. The beak concentrations of the aforementioned variables occurred at the depth of the mixed layer. The organic matter decomposition was limited because the soil water content was low and the duration of experiment was short. The results of the study could encourage using the LEACH as a tool for organic matter management strategy and monitoring the fate and transport of plant nutrient as N and P in soil.