GROWTH, YIELD, AND WATER-USE RESPONSES OF PEACH TO REPEATED ROOT PRUNING IN A SUBHUMID CLIMATE

The objectives of this 7-year study were to determine the effect of re peated root pruning and irrigation on peach (Prunus persica L, Batsch) tree growth and soil water use. Root pruning began in the year of pla nting, Peach trees trained to a freestanding ''Y'' were root-pruned at flowering for 4 years (1985 to 1988) and subsequently at flowering an d monthly through July for 3 years (1989 to 1991). Irrigation was with held, or applied the full season or only during stage 3 of fruit growt h on root-pruned and non-root-pruned trees. Root pruning limited soil water availability throughout most of the growing season when irrigati on was withheld; however, when irrigation was applied, there was no di fference in soil water availability, The root length density of peach roots was greatest in the 0 to 30-cm depth, was promoted by irrigation , and was reduced by root pruning in the 0 to 90-cm root zone. Full-se ason irrigation increased vegetative growth over the nonirrigated trea tments. Root pruning had no effect on vegetative growth measured as fr esh pruned material. The treatments had no effect on leaf nutrient con tent, except that root pruning reduced Zn in five consecutive years. F ruit yield was reduced 1 in 5 years by root pruning, and full-season i rrigation reduced yield in 3 of 5 years. Repeated root pruning restric ted the lateral spread of the root zone and the use of soil resources, yet on the deep soil of this site, restricting the lateral extent of the root zone did not reduce vegetative tree growth.