Project Details:

Nutritional guidelines for California cotton were established over 30 years ago using Acala 4-42. Yield from Acala varieties has increased 12.7 lbs/A per year due to genetic improvement since cotton production began in the San Joaquin Valley in 1918. These yield improvements have been associated with improved disease tolerance as well as a change in plant type. Modern varieties are less vegetative, initiate fruiting earlier, and place a greater percentage of biomass in bolls than old varieties. Similar results were shown for varieties grown in Mississippi during this century. Cotton is not unique in the evolution of plant types during the past 100 years. Changes in plant type and management practices have increased yields, but they have potential to influence fertility recommendations. Preliminary work by Cassman and Kerby suggests cotton response to nitrogen fertility is influenced by more than just soil supply. Earliness of fruit set, intensity of fruit set, and the ratio of vegetative mass to fruit mass are important variables which affect cotton response to nitrogen as well as nitrogen use efficiency.