SOIL-MOISTURE AND ROOT DISTRIBUTION IN AN APPLE ORCHARD IRRIGATED BY TRICKLERS

The soil moisture distribution at different distances from the water source in a high-yielding apple orchard planted on a 60-cm-deep heavy basalt soil underlined with gravel was studied. The soil water content was determined in three irrigation treatments which differed in discharge rates, distances between the tricklers on the lateral, and frequencyof application of an equal amount of water. The determinations were made several times during the wetting and drying processes in one irrigation cycle of each treatment. The roots of the trees perpendicular to and along the trickler line were counted in the soil profile. The results showed that the soil moisture and root system distribution covered a wider area when irrigated twice a week with 8 1/h tricklers rather than by irrigating every day or once a week with 4 1/h tricklers. Every day compared with once a week irrigation caused an appreciably narrower soil moisture distribution but a quite similar root distribution pattern. The soil-moisture-saturated level in the soil profile in all treatments, in the area under the trickler, caused water loss by drainage while irrigation continued. The loss was estimated to be 17% of the water applied. A pulsed irrigation was assumed to decrease this drainage loss by trying to supply the water in pace of the plant consumption. © 1979 Martinus Nijhoff Publishers.