© 1996 Heron Publishing—Victoria, Canada
Assessment of nitrogen, phosphorus, and potassium uptake capacity and root growth in mature alternate-bearing pistachio (Pistacia vera) trees
R. C. Rosecrance, S. A. Weinbaum and P. H. Brown
Pomology Department, University of California Davis, Davis, CA 95616, USA / Received November 1, 1995
Summary
We examined interrelationships between crop load, nitrogen (N), phosphorus (P), and potassium (K) uptake, and root growth
in mature, alternate-bearing pistachio (Pistacia vera L.) trees. Pistachio trees bear heavy (on-year) and light (off-year) fruit crops in alternate years. Uptake and partitioning
of N, P, and K among tree parts were determined during (a) spring flush (mid-March to late May), (b) nut fill (late May to
early September), and (c) postharvest–leaf senescence (late September to early December). Nutrient uptake occurred primarily
during nut fill in both on-year and off-year trees. In on-year trees, N and K uptake increased by 35 and 112%, respectively,
during nut fill compared with off-year trees. During this period, nutrients were allocated largely to embryo development in
on-year trees and to storage in perennial tissues in off-year trees. Nutrient uptake was negligible between harvest and leaf
senescence. Although root growth was reduced during nut fill in on-year trees compared with off-year trees, there was no relationship
between root growth and the uptake of N, P or K from the soil. Our data support the hypothesis that sink demand regulates
the uptake and distribution of N, P, and K in pistachio trees.
Keywords:
cropy yield, nutrient use efficiency, sink demand.
