Abstract
The root zone of the plant must be well supplied with both water and oxygen. Water potential should be kept close to saturation but if a low water tension is maintained, particularly in clay soil, plants will suffer most of the time from a sub-optimal level of oxygen supply in the root zone. The diffusion rate of gases in air is about 10,000 times greater than in water. Thus, it is obvious that the rate of gas diffusion decreases as the water content of the soil increases. These two requirements are apparently contradictory and the assessment of optimum level of soil aeration in the root environment is essential for better crop establishment and growth. Influence of irrigation treatments (three depths of irrigation of 2, 4 and 6 r cm and four IW/CPE ratios of 0.45, 0.60, 0.75 and 0.90) on the soil oxygen diffusion rate (ODR) during various growing phases of peanut crop ( Arachis hypogaea L.) were studied on a lateritic sandy loam soil (ultisols) for two consecutive seasons. The rate of ODR decreases as water content of the soil increases after irrigation and then increases gradually with the lapse of time. However, it starts decreasing with decrease in soil moisture after 96 h of irrigation.