The soils of the Submiddle São Francisco River Valley are generally sandy, with low nutrient retention capacity. Since they are located in a semi-arid area, they are very poor in organic matter (OM) and as a consequence are deficient in nitrogen, which limits agricultural production. Thus, the use of legumes as green manure may overcome this problem because it adds carbon and nitrogen to soil. The study comprised two experiments with legumes intercropped with irrigated grape (Vitis vinifera) in a sandy Ultisol in Petrolina, State of Pernambuco (Brazil) from June 1996 to July 2002. The objective was to evaluate the effects of green manure on soil chemical characteristics and on grape yield and quality. The first experiment lasted until the fourth grape harvest. The treatments consisted of two legumes: sunnhemp (Crotalaria juncea) and jack bean (Canavalia ensiformis), submitted to two managements (sub-plot): (a) cut and left on the soil surface and (b) cut and incorporated into the soil. There was a control treatment (without green manure). In the second experiment, which began in the fifth grape production cycle, the methodology consisted of three treatments: (1) control; (2) sunnhemp and (3) jackbean combined with two subplot treatments: (a) 100 % of the fertilizer recommended by soil analysis, and (b) 50 % of the recommended fertilizer. Altogether, there were eleven legume cycles and nine harvests of table grape. The biomass production of the legumes decreased over time. Green manure improved the soil chemical characteristics, increasing OM and exchangeable Ca content, and the CEC value in the 0-10 cm soil layer. There was no consistent effect of the green manure on the yield and quality of table grape.
Vitis vinifera; cover crop; biomass; soil management; grape fruit quality
