DOSES DE NÍQUEL EM FEIJÃO CAUPI CULTIVADO EM DOIS SOLOS

Abstract

Ni was the last nutrient characterized like essenti al for plants. Its essentiality is due to participa - tion as constituent of urease enzyme, which makes i t extremely important for the metabolism of N. Thus , the objective of this study was to investigate the grow th, content and accumulation of urea and nutrients in cowpea bean plants ( Vigna unguiculata (L.) Walp.) ‘IPA 206’ according to nickel rate and two soil types. The experi- ment was carried out in a greenhouse at Universidad e Estadual do Norte Fluminense Darcy Ribeiro, using a 5 x 2 factorial scheme in a randomized block design wit h four replications. Treatments consisted of foliar applica- tions of five nickel concentrations (0, 20, 40, 60 and 100 mg L -1 Ni) in the form of NiCl 2 .6H 2 O and two soils, a Typic Quartzipsamment and a Tb dystrophic Red-Yello w Ultisol. Ni rates promoted Ni toxicity symptoms j ust on young leaves of bean. These symptoms were charac terized by small reddish spots that have not progre ssed during the time and did not influence on the plants development. The foliar application of Ni increase d levels of this micronutrient in stems, mature leaves, youn g leaves and pods of cowpea bean, indicating high m obility of this micronutrient in the plant, but did not alt er the urea contents, indicating no effect on the a ctivity of urease enzyme. The dry mass of the shoots and the c ontent of others nutrients were not affected by fol iar appli- cation of Ni. Plants grown in Ultisol showed higher growth and higher content of urea and Cu in mature leaves; K and B in mature leaves, young leaves and twigs an d Zn in mature leaves and stem.