Direct Effects of Rice Stubble Management on some Physical Properties of Soil

摘要

RICE stubble management is widely practiced in cropping systems and often utlized as a means of reducing stubble loads on the soil surface. However, the short-term effects of these management regimes on soil surface properties are largely unknown. Therefore, this study was carried out at the Experimental Farm of Tani El-Nataf, Sakha Agriculture Research Station, Kafr El-Sheikh Governorate, Egypt, to investigate the direct effects of three methods of rice stubble management {no-tillage (NT), notillage+ stubble burning (NT + SB) and conventional tillage (CT)} on soil bulk density and related moisture content, t otal p orosity, p ore s ize distribution and infiltration rate, in two successive agricultural seasons, i.e., 1996-97 and 1997-98.Burning treatment (NT + SB) has a positive significant effect on the values of soil bulk density. This effect was restricted to the surface soil layer (0-5 cm) in the two seasons. In contrast, conventional tillage (CT) treatment has a negative significant influence on the soil bulk density values. Significant (P < 0.05) decreases of approximately 3-4% in total porosity and 6.5 - 5.5 % in the quickly drainable pores in the surface soil layer (0-5cm) were achieved in the burnt plots relative to unburnt plots (NT treatment). However, burning had no significant effect on the lower soil layers. In contrast, plowing praciice (CT treatment) has a positive significant effect on the values of total porosity as well as quickly drainable pores. The increasing inthe total porosity and > 30 mu. pores after CT treatment in the surface layer ranged between 6.2 10 6.8 % and 9.1 to 10.5 %, respectively. Furthermore, this positive impact of conventional tillage treatment was extended to include all investigated soil depths. The statistical analysis obviously indicates that the decline in both basic infiltration rate and cumulative infiltration after burning treatment (NT + SB) was of negative significant values, as the basic I.R.reduced from 2.32 to 0.43 cm hr~(-1) in the first season and from 2.76 to 0.43 cm hr~(-1) in the second one. Also, cumulative infiltration decreased by 72.9 to 79.3% in the two seasons. On the other hand, increasing the basic infiltration rate or cumulative infiltration after (CT) treatmentis of positive significant value. The micromorphological investigation on the surface and subsurface soil before and after burning of rice stubble certainly submitted the occurrence of macropore blockage mechanism due to the precipitating or infilling byresidual ash.