Productivity of green cowpea in sandy soil as influenced by organic manure rates and sources

abonos orgánicos acidez acidity acidité caracteres de rendimiento carbohidratos carbohydrates composante de rendement engrais organique glucide organe végétatif des plantes organic fertilizers plant vegetative organs rendement rendimiento sandy soils sol sableux suelo arenoso vigna unguiculata unguiculata yield components yields órganos vegetativos de las plantas