The effect of irrigation level in the kernel dry matter accumulation period on almond yield, kernel dry weight, fruit count, and canopy size

The effect of irrigation regime in the kernel filling stage of almond was examined in a field experiment. The experiment was conducted on 9-year-old local variety (Um-El-Fahem) grafted on GF677 rootstock in Israel. Five irrigation treatments were applied during the main kernel dry matter accumulation. Irrigation rates in June varied from ~1 to ~8 mm/day and midday stem water potentials varied from ~−2.6 to ~−1.3 MPa. Seasonal irrigation varied from 394 to 801 mm. Kernel yield increased in the high irrigation treatments in the first four seasons where it decreased in the three lower irrigation treatments. Similarly, the four-season trunk cross-sectional area accumulation increased with increasing irrigation. Kernel yield increased with both midday stem water potential and irrigation rate. Kernel dry weight decreased with increasing fruit count where higher kernel weights were found in the higher irrigation treatments at similar fruit count. Kernel relative growth rates of all treatments were similar along the dry matter accumulation stage except for around 1 June where the lowest irrigation rate had significantly lower growth rate. Spurs survival analysis showed that the number of fruits per spur, fruiting spurs, and alive spurs increased with increasing irrigation.