Produção e eficiência agronômica de compostos obtidos com palhada de gramínea e leguminosa para o cultivo de hortaliças orgânicas

Abstract

The demand for organic fertilizers in Brazil is increasing, mainly in the South and Southeastern regions. The composting is a technique that can be used to increase the availability and the quality of organic fertilizers. This research aimed to study the usage of the composting of legumes and Napier grass (Pennisetum purpureum) as substitutes for cattle and poultry manure, traditional organic fertilizers used in the vegetables production. Featuring in Chapter I, the objective of the study was to determine the time of planting, and the age of cutting, which were more adequate for production of mass and accumulation o N in the Canavalia ensiformis e Crotalaria juncea. These species were chosen due to their high potential for biomass production, uniform seedling, upright growth, and determined growing pattern, which turn easy the handling of harvesting, and have no problems when cultivated in rotation systems with commercial crops. In Chapter II different conditions of composting and diverse proportions of the raw materials were studied, having as reference the mixture of Crotalaria (Crotalaria juncea) and Napier grass. The resulting composts were tested and the results are discussed on Chapter III. The composts were used as substrate for the production of vegetables seedlings and bed fertilizer in an organic system production of lettuce, beetroot and tomato. The speed of N release from the composts was also evaluated. The results indicate the Crotalaria as the most promising legume specie. It was observed that it is possible to obtain composts with high N levels by using only Crotalaria or mixed with Napier grass, without the need of inoculation or other additives. The composts obtained with these materials may substitute the commercial substrate Plantmax HT in the production of vegetables seedlings, and the cattle manure as bed fertilizers in the production of organically grown vegetables.