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.

Because the most soils in Saudi Arabia can not maintain water being sandy soils. This. soil characteristic leads to the loss of water by gravity. In addition, the high degree of temperature also can cause high evaporation rate for water after irrigation especially in summer. A thought was developed toward a method to increase soil bulk density that leads to raise the capability of water to maintain water. This was achieved by designing and constructing a machine for compacting and making holes in soil. These holes will act as small water tanks in soil and save water to growing seeds. This machine consisted of 44 cm diameter cylinder with 245 cm width to make 8 rows of holes on the ground with 30 cm apart. The cylinder bas 5 groups of metal cones (10 cm diameter with 10 cm height) welded on the cylinder circumference. Thus, lay out holes on the ground have a distance of 30 cm apart and 40 cm apart in the other direction. Mainly two field treatments were camed out, one with holes and one without holes. Variables such as soil moisture content and soil bulk density of soil were measured at different depths and times. The other variables such soil penetration resistance and organic matter as well as the clay percent were determined affer the 4" inigation for both treatments. The results showed that soil moisture content was higher in hole soil treatment than soil without treatment due to the coUection of clay particles and organic matter by water droplets during inigation. The collection of clay and organic matter in these holes made the holes very well sealed and increased the soil storage for water. It is obvious that the developed machine decreased the soil hydraulic conductivity that leads to an increase in soil water content.