Fertilizing and protective potential of castor oil cake on soil and morphological parameters of eggplant (Solanuma melongena)

Resumo

Vegetable crops are the backbone of agriculture. However, low soil fertility, pest spreading, high cost of chemical fertilizers and effects of pesticides have prompted the search for sustainable alternatives. This study investigated the action of castor oil cake doses on soil properties, rooty nematodes and eggplant parameters. The experiment was conducted on a Fisher block design (4x5). The treatments applied included the negative control, Triple 15 and different doses of castor oil cake (1; 1.9 and 2.8 t/ha). The incorporation of the oil cake changed the texture from clayey-sandy to loamy-sandy. The soil pH changed from 3.9 to 4.6. The saturation rate, the sum of exchangeable bases and the cation exchange capacity also increased by 30 to 41% respectively; 0.94 to 1.36% and 3.1 to 3.29%. Nitrogen content increased from 0.048 to 0.084%, phosphorus and potassium contents did not change. Organic matter rate increased from 0.84 to 2.92%. Analysis of variance showed a significant effect (p < 0.05). Plant mortality rates due to nematode were 25.25% for the negative control, 19.12% for the positive control (triple 15), 13% for D1 (1 t/ha of castor cake) and 0.00% for D2 (1.9 t/ha of castor cake) and D3 (2.8 t/ha of castor cake). Yields varied (from 3.58 to 6.80 t/ha) depending on the treatments.