Yield and Quality of Tomato Grown with Organic and Synthetic Fertilizers

Abstract

Compost is a source of plant nutrition that can be an alternative to, or used in conjunction with, synthetic fertilizers. Field trials were conducted in 2002 and 2004 to evaluate the effect of fertilizer types on yield and quality of tomato (Lycopersicon esculentumMill.). Compost-based fertilizer (CBF), derived from maize stover, cassava peels, and poultry manure, was applied at 5 Mt·ha−1 and combined with 0, 30 and 60 kg·ha−1 of N from urea, and compared with application of an N:P:K (20:10:10) synthetic fertilizer providing 30 and 60kgha_1 of N. Microbial populations were determined in the soil at the rhizoplane (root surface), rhizosphere (soil surrounding the root surface), and bulk soil (soil away from the root zone). Application of CBF alone increased fruit yield by 145% over controls and was significantly better than other treatments in 2002. Application of combinations of CBF +urea to tomato affected growth and quality of fruit. Titratable acidity in tomato grown with CBF alone slightly decreased in relation to tomato fertilized with 30 kg·ha−1 of the NPK fertilizer and vitamin C increased by 13%, while the Ca content was 44% greater than controls. Microbial populations found at the rhizosphere, rhizoplane, and bulk soil due to application of CBF, CBF +urea (30 or 60 kg·ha−1), and CBF +urea increased two to fivefold relative to treatment with 60 kg·ha−1 of synthetic NPK fertilizer. Organic fertilizer can be combined with synthetic fertilizer at rates below those recommended for sustainable production of tomato. However, other levels of urea need to be tested to determine whether addition of lower amounts of urea will consistently support yields.