Author : Harsono

Summary : Field experiments were conducted to study the effect of plowing depth, mulching, and nitrogen (N) fertilizer application on some soil physical properties of loamy fine isohyperthermic matahalloysitic family of Fragic Ustropepts, and on the growth and water use of rice (IR-36)- corn (Hybrid C1) cropping system. This was conducted at the Agriculture Training Research and Development, Yogyakarta, Indonesia, from 25 October 1988 to 21 July 1989. Daily soil moisture content of the root zone and water use of rice and corn were estimated using the modified Crop Yield Water Use Simulation Model (Poesposutardjo, 1984) with mulch factor for soil evaporation and correction factor for the potential crop transpiration owing to the difference in leaf area index from the normal crops. Plowing at 20 or 30 cm depth before planting reduced bulk density and soil resistance. Bulk density gradually increased during the rice and corn cropping periods. Bulk density and soil resistance at 0-10 and 10-20 cm depths in the shallow and deep plowed plots did not significantly differ at any growth stage of the crop. Bulk density and soil resistance at 20-30 cm depth of the deep plowed plot were significantly lower with the shallow plowed at early growth stage. Mulching did not affect bulk density. Mulching reduced the estimated total soil water by 41 - 48 percent and also the soil temperature at 0-10 cm depth by 3 degree C. However, mulching increased root density. The root density of corn was higher in deep plowed than in shallow plowed plots. Mulching or deep plowing with any level of nitrogen fertilization significantly increased rice root density at 90 days after emergence (DAE). At 150 kg N/ha, deep plowing resulted in significantly higher corn root density in 30-40 cm depth than the shallow plowing at 60 DAE; mulching gave significantly higher rice density than nonmulching at 50 DAE. Nitrogen fertilizer application significantly increased root density, plant height, leaf area index, grain yield, and nitrogen content of grain.