Phosphorus Fertilizer Requirements and Nutrient Uptake of Irrigated Dry-Season Cotton Grown on Virgin Soil in Tropical Australia

Considerable amounts of phosphorus (P) fertilizer will be required on soils in the proposed Ord Stage II area of northwestern Australia if a sustainable dry-season cotton production system is to be established, because in their virgin state the soils are known to be inherently low in P. This study aimed to determine P fertilizer requirements on these soils to optimize cotton yield as well as nutrient uptake. Five rates of P fertilizer were applied to soil recently cleared of trees and prepared for irrigation. In the second year, these same rates were imposed over the trial. We conclude that the application of 60kgha-1 of P was sufficient to allow maximum yield and quality for dry-season cotton grown in the first season on virgin soils in the Ord River Irrigation Area, whereas a total of 80kgha-1 of P was required when cotton was grown over two seasons.