EFEITO RESIDUAL DA ADUBAÇÃO FOSFATADA EM TRÊS CULTIVOS SUCESSIVOS COM FEIJÃO - CAUPI

This study aims to provide doses of P 2 O 5 rates in Regolithic Neossoil, and evaluate the phos- phorus waste (P) in the soil and leaf content in three successive cowpea - beans crops. The experiment was car- ried out at field conditions, in Areia city – PB, in the period January to December 2007 in a randomized block with six treatments (0, 100, 200, 300, 400 and 500 kg ha - 1 P 2 O 5 ) and four replications. The first crop production variables (green beans per plant (PGVP), productivity of pods (PV) and dry beans (PGS) as a function of the above treatments, and in the last two harvests, the same variables in the production function were evaluated residual phosphorus in the soil. Phosphorus content after the first crop (49.53 mg dm - 3 ), corresponding to a residue (38.33 mg dm - 3 ) was higher initially to that in soil (11.2 mg dm - 3 ) before the first crop. Foliar - P for the highest values were observed for the first crop. Already the third crop, introduced himself as one of lower con- centration of P in the leaves, 1.56 g kg - 1 . The dose of 280 kg ha - 1 P 2 O 5 gave residue in P sufficient for the maxi- mum production of green beans per plant of 252 g, the second crop soil's estimated maximum yield of pods, 6.3 to 7.3 t ha - 1 at the first and second crops were obtained with Keywords : Vigna unguiculata . Phosphorus waste. yield.