Chlorosis in macadamia as affected by phosphate fertilization and soil properties1

Publisher Website
Google Scholar
Abstract
Knowledge of macadamia (Macadamia integrifolia) nutrition has lagged behind problems associated with commercial production. To improve this knowledge, a 16‐kg pot experiment was conducted to study chlorosis in macadamia as induced by phosphate fertilization and soil properties. Six soils representing potential macadamia growing areas in Hawaii were used, which consisted of three volcanic ash or aa lava‐derived soils (low in micronutrients and in P sorption capacity) and three highly weathered soils (high in Fe and Mn oxide contents and in P sorption). Several P levels, ranging from 0.006 to 1.6 mg P/L in soil solution, were established based on P adsorption isotherms. Macadamia was grown for 15 months; dry matter production, leaf chemical composition (P, Fe, and Mn concentration) and numerical index of leaf color were used as the growth‐response indicators. Results indicate that macadamia seedlings can be expected to produce near maximum dry matter when leaf P content ranges from 0.10 to 0.14% which correspond to 0.03 to 0.05 mg P/L in the soil solution. When these P levels are exceeded, chlorosis and yield reduction may occur. Low Fe/Mn ratio in leaves, resulting from heavy P fertilization, appears to be the direct cause of chlorosis. This nutritional disorder can be corrected through Fe foliar spray which is more effective in low‐Mn than in high‐Mn plants.

This publication has 4 references indexed in Scilit: