Response of guava (Psidium guajava L.) trees to different pruning techniques

This investigation was initiated to shed some lights on the response of guava crop to different pruning techniques carried out at both nursery and orchard conditions. Under nursery conditions, four pruning techniques were utilized, namely, removal of 20% and 40% of the total leaves, root pruning and the combination of removal of 30% of leaves plus root pruning. The results reaveled that all pruning techniques resulted in significantly greater increases in plant height and stem diameter than the control. No clear pattern was noted regarding other growth parameters in terms of number of leaves and relative growth rate;however, root pruning resulted in greater values than the rest of the treatments. Removal of 40% of leaves associated with greater values of both fresh and dry weights compared to the other treatments. No significant differences were noted among the treatments regarding CHO, Nand C/N ratios. Under orchard conditions, techn iques of fruit thinning, twig pruning and root pruning were used. Fruit thinning experiment consisted of four treatments, namely, thinning to one fruit per cluster, thinning 25% and 50% of fruits per cluster and control. Generally, thinning technique of 50% resulted in greater yield (number and weight of fruits) compared to the other treatments. No - significant differences were noted in fruit quality (fruit weight and TSS) as well as the values of both fresh and dry weights of leaf samples among the treatments. Twig and root pruning experiments consisted of four techniques, namely, 20% and 40% twig pruning, root pruning, and a combination of root pruning plus 30% twig pruning. These experiments were carried out at different seasons (winter, summer, late summer and in other months). The data collected from winter pruning showed that all pruning techniques resulted in significantly greater increases in trunk height than control (unpruned trees). No significant differences w e re noted in trunk circumference among the treatments. Significantly greater total yield was associated with 20% twig pruning or control compared to the other treatments. Generally, 20% twig pruning gave greater values of fruit weight and TSS than the rest of the treatments. No significant differences were noted in the values of fresh and dry weights of leaves as well as the ratios of fresh/dry weights. The results obtained from summer pruning reaveled that significantly greater values of both trunk height and circumference were associated with the combination of root prunig plus 30% twig pruning than the other treatments. Generally, yield data showed no clear pattern;however, the lowest total number of fruits was noted in unpruned trees (control). Significantly greater values of fruit weight was recorded in 20% twig pruning compared to the rest of the treatments. The differences in the values of TSS, CHO, Nand C/N ratios were not significant among the treatments. Late summ e r prunmg showed no significant differences among the treatments as far as trunk height and circumfernce measurements were concerned. All pruning techniques resulted in significantly greater yield than control. Significantly greater yield was associated with 20% twig pruning compared to the other pruning techniques. The differences in values of fruit weight and TSS were not significant among the treatments;however, the greatest values were associated with 40% twig pruning and the lowest with control. Generally, 40% twig pruning resulted in the greatest values of both fresh and dry weights of leaf samples collected at different times. The differences in the values of CHO, Nand CIN ratios were not significant among the treatments. The detected levels of auxins and gibberellins in the leaves demonstrated that all pruning techniques tended to increase these levels. Generally, the aboveground pruning techniques resulted in greater increases than root pruning. Pruning carried out in mid June, mid July and mid August months showed variations in the recorded parameters. Pruning trees in mid June resulted in significantly greater number of flushes than control. Root pruning carried out in mid July resulted in significantly greater flushes compared to the other treatments. Mid August pruning showed no significant differences in the number of flushes among the treatments. Yield tended to vary among the treatments depending upon the time of pruning. No significant differences were noted in fruit quality (weight of fruit and TSS) among the treatments, regardless of month of pruning. Generally, it seems that guava at different stages of growth tended to respond to pruning techniques;however, this response varies with the time of pruning