Eficiência comparativa da adubação orgânica e mineral no crescimento e metabolismo do algodoeiro.

Abstract

The combination of mineral and organic fertilizers has been recommended as an alternative management, especially when the applied organic material has a high carbon: nitrogen ratio (C/N). The objective of this study was to evaluate the growth and physiological aspects of cotton under doses ofcastor bean cake and peel associated with soluble nitrogen sources. Adopted a randomized closed block design with 24 treatments and 3 repetitions. The treatments consisted of four doses ofcastor cake (0 – 0,8 – 1,6 e 2,4 t ha-1) and four doses ofcastor fruit peel (0 – 0,8 – 1,6 e 2,4 t ha-1), supplemented with three levels of soluble N at a dose of 120 kg h-1 (ausent, urea and ammonium sulfate). At 90 days were quantified: plant height, stem diameter, leafarea, dry mass (air, root and mulch), chlorophyll content, flavanoids, anthocyanin, nitrogen balance index and membrane disruption. It was observed that ammonium sulfate was a viable alternative when combined with castor cake in relation to urea. The best results for height and chlorophyll contente were obtained with the application of 1,6 t ha-1 of castor bean hulls associated with ammonium sulfate. The use of castor bean cake and peel associated with urea and ammonium sulfate did not influence the stem diameter, flavanoid, anthocyanin content and nitrogen balance index. The use of 0.8 t ha-1 of urea castor bean cake promoted the largest electrolyte leakage and lower plasma membrane instability.