The regularity of boron nutrient requirement of cotton and foliar application of boron fertilizer were studied by field plot experiment and laboratory analysis.The results showed that more B was absorbed in and the highest requirement for boron in boll stage,56.20%of overall absorption.Spraying boron fertilizer was better in boll stage than flowering stage.On the whole growing season,0.7% boron fertilizer sprayed one time at flowering stage,0.5% boron fertilizer sprayed two times in flowering stage and boll...