ALTERNATE BEARING INFLUENCES ANNUAL NUTRIENT CONSUMPTION AND THE TOTAL NUTRIENT CONTENT OF MATURE PISTACHIO TREES

The influence of alternate bearing on nutrient utilization and total t ree nutrient content was investigated in mature pistachio (Pistacia ve ra L. cv Kerman trees). Removal of N, P and Zn in fruit and abscised l eaves of cropping ('on') trees averaged 5, 6, and 2 times, respectivel y, the removal in abscised leaflets of the non-fruiting, 'off' year tr ees. One hundred and thirty-five kg N, 131 kg K, 86 kg Ca, 39 kg Mg an d 18 kg P per hectare were removed in fruits and abscised leaves in 'o n' year trees. Tree nutrient contents and, presumably, the size of nut rient storage pools in dormant trees varied between 'on' and 'off' yea rs. There was 22% and 14% more N and P, respectively, in dormant trees following 'off' than 'on' years. The greater N and P accumulation in 'off' year trees is depleted in support of the large fruit demand for N and P during 'on' years. In contrast to N and P, there was greater K and Ca accumulation in perennial tree parts during 'on' years than du ring 'off' years. The greater K accumulation in perennial tree parts a nd approximately 30% greater removal of K in annual organs during 'on' than 'off' years suggests that K uptake could be 4 times higher in 'o n' year trees than in (non-cropping),'off' year trees.