EFFECTS OF CROP RESIDUE ON MOISTURE CONDITIONS AND CRACK FORMATION IN PADDY SOILS OF GUILAN PROVINCE

摘要

The role of water and irrigation is vital in cultivation of rice in Iran. The dominant method of irrigatiing paddy in Iran is continuous flooding, which changes to periodical water application in times of water shortage. Soil cracks are the main problem in periodical irrigation. The amount of water required in this method is much more than flooding irrigation. Crop residues in paddy fields are able to prevent the establishment of cracks and to reduce their intensity. In this research, effect of different levels of rice straw on crack formation in some paddy soils of Guilan Province, Iran, is studied. The experiment was performed in split-split plots based on complete randomized blocks design, using four soil textures and three replications. The main factors evaluated were rice-stem residues in seven levels and crack treatments including three dry stages and two wet conditions. Results showed that interaction of level of rice straw and crack treatment on soil moisture content and the number of days to crack formation was statistically significant (p<0.01). Adding different levels of rice straw made a knock-on effect on moisture content with respect to control. Furthermore, it can be influential in delating crack formation. At all levels of crop residues, crack formation was observed in longer periods of time, as compared to control treatment. Nevertheless, soil moisture was higher with respect to control. The overall results showed that application of organic materials in soil could delay crack formation and its intensity.