Abstract

LOPEZ, Marisol; BOLIVAR, Ángela; SALAS, Manuel  and  DE GOUVEIA, María. Conservacionist practices and rotation with pigeonpea as a sustanaible alternative for the agroecosystems of savannahs of Guarico, Venezuelan. Agronomía Trop. [online]. 2006, vol.56, n.1, pp.75-109. ISSN 0002-192X.

On an acid soil of Guarico state savannas, the effect of conservation practices such as minimum tillage, acid tolerant cultivars, organic combined with inorganic fertilizers at low rates and the rotation sorghum (Sorghum bicolor (L.) Möench, pigeon pea (Cajanus cajan (L.) Millsp.), on soil productivity, grain yield and aerial biomass of pigeon pea was evaluated. Phosphorus sources evaluated were natural Riecito phosphoric rock (RFR), partially acidulated Riecito phosphoric rock (RFRPA) and industrial diammonium phosphate (FDA). Inorganic treatments were T1 (N+0P+K), T2 (N +P-RFR+K), T3 (N+ P-RFRA K+) and T4 (N+P-FDA+ K). The levels of fertilizers applied on sorghum were 100 (kg ha-1)of N+80 of P+60 of K and on pigeon pea 15 of N+60 of P+45 of K+5,7 of S+0,2 of Mo. Former treatments were applied within the following organic treatment plots: without residues (SR) and with gramineous residues (RG). After 3 years of conservation management, using low inputs and agroecological principles, increments in pigeon pea yields were evidenced, due mainly to an increase in soil productivity induced by the combined management of organic and inorganic fertilizers, among other practices. Pigeon pea grain yields increased progressively. During the first year grain yield oscillated between 672 and 882 kg ha^-1 and shoot biomass exceeded 800 kg ha^-1. During the second year variations in grain yield occurred between 700 and 863 kg ha^-1 and in shoot biomass between 750 and 890 kg ha^-1. Finally, during the third year, grain yield were between 850 and 1000 kg ha^-1 in SR and between 1000 and 1300 kg ha^-1 in RG. Highest yields were achieved by treatments where organic fertilizers (crop residues, RG) and inorganic fertilizers (RFR and RFRPA) were combined.

Keywords : Sustainable; pigeon pea; acid soil; conservationist management.

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