Water deficits and rooting volume modify peach tree growth and water relations
Proebsting, E.L.; Jerie, P.H.; Irvine, J.
Journal of the American Society for Horticultural Science 114(3): 368-372
To compare the effects of water deficits and restricted root volume, 1- and 2-year-old peach trees (Prunus persica L.) with roots divided among four 2.5-liter pots were irrigated daily with 30% (deficit irrigation) or 100% (non-deficit) replacement of water used the day before. The water was applied to one, two, or all four pots during the period of rapid terminal growth. After 7 weeks, all trees received 100% replacement of water used the previous day. After terminal growth ended, the root:shoot ratio of the 2-year-old trees was adjusted by 1) tripling available soil volume, 2) removing two-thirds of lateral branches, 3) both 1 and 2, 4) treatment 3 defoliated, or 5) left unchanged. Deficit irrigation reduced midday leaf water potential, leaf conductance, and terminal growth equally, regardless of irrigated soil volume, whereas in non-deficit irrigated trees these factors were proportional to the irrigated soil volume. After deficit irrigation ended, terminal growth resumed at rates above those of the trees with non-deficit irrigation applied to all four pots and proportional to the severity of growth reduction during deficit irrigation. Pruning and defoliation increased leaf conductance within 3 days. Increased soil volume increased leaf conductance after 4 weeks. Deficit irrigation nearly eliminated flowering for the following year. Tripling the soil volume overcame the effect of deficit irrigation on flowering, but pruning did not. Defoliation inhibited flowering. The effect of restricted irrigated soil volume was similar to that of deficit irrigation. Increasing root:shoot ratios by adjusting the soil volume or by pruning the shoot always increased leaf conductance.