Water management of transplanted seedlings of Azadirachta indica in arid areas

Large mortality and general growth restriction of transplanted tree seedlings in the Indian arid zone prompted this study on the effects of different levels (1/4, 1/2, 3/4 and full field capacity (FC)) and intervals (1, 2, 4 and 6 weeks) of irrigation, during the first dry period (September to July), following transplantation. Results are expressed as increases in height and stem diameter over time in relation to soil moisture regime and plant water status under different treatments. Final measurements 450 days after starting irrigation treatments indicated that watering at FC at 1- and 2-week intervals brought about the maximum increase in height and stem diameter, which declined progressively with increasing intervals and decreasing level. Despite the similarity in trend, final biomass production and crown area were highest under watering at FC at a 2-week interval due to larger increase in stem and foliage weight. Limited data on root growth along a single vertical plane suggested that branching of root laterals was mostly confined to the 10–50-cm depth irrespective of irrigation treatments, while depth of rooting tended to increase at longer intervals of watering. Under the prevailing conditions, average application of 46 1 (FC) per plant at 2-week intervals led to maximum growth and biomass production with no mortality, while under the low-threshold average irrigation of 121 (1/4 FC) per plant at 2-week intervals could eliminate mortality although the biomass production was reduced by about 91%.