Pg. 32-34 Effect of Phosphorus and Potassium Fertilization on Lychee Production over Three Years

Phosphorus (P) and potassium (K) were applied to lychee (litchi) trees at three sites in subtropical Queensland, Australia (lat 27°S) to determine the effects on leaf nutrient concentrations and fruit production. Applications were equivalent to 0 to 2.4 t per ha for P, and 0 to 3.2 t per ha for K. In the first two years, there was no effect of fertilizer on leaf P and K, while in year three, leaf P was related to P application at two out of two sites and leaf K to fertilizer K at one out of three sites. Thus, P and K accumulated at some sites at high rates of fertilization. In contrast, levels in control unfertilized trees fell only slightly over time. Generally, fruit production was similar over the range in leaf P of 0.18 – 0.44% and leaf K of 0. 75 – 1.37%, compared with the Australian standards of 0.14 – 0.22% and 0.70 – 1.10%, respectively. The buffering capacities of lychee soils and trees are thus indicated. These results suggest that annual applications of P and K may not be required, indicating savings for lychee growers.

Summary:

• The study investigated the effects of phosphorus (P) and potassium (K) fertilization on lychee trees at three subtropical Queensland sites over three years.
• Fertilizer application rates ranged from 0 to 2.4 t/ha for P and 0 to 3.2 t/ha for K.
• In the first two years, fertilizer had no significant effect on leaf P and K concentrations; by the third year, leaf P increased with P application at two sites, and leaf K increased with K application at one site.
• Leaf P and K concentrations in unfertilized control trees declined only slightly over time, indicating some buffering capacity.
• Fruit production showed little change across a wide range of leaf P (0.18-0.44) and K (0.75-1.37), and remained within or above Australian standards for these nutrients.
• Nutrient buffering in lychee trees and soils likely prevents rapid deficiency or toxicity effects.
• High K fertilization at one site reduced leaf calcium (Ca) and magnesium (Mg) levels, but these remained within optimal ranges.
• No symptoms of P or K deficiency were observed, even after three years without fertilizer.
• The study suggests annual P and K fertilization may not be necessary if leaf nutrient levels are above 0.18% for P and 0.7% for K, potentially saving costs for growers.
• The study compared findings with earlier research from South Africa and discussed nutrient management implications for lychee orchard fertilization guidelines.