SOIL CHEMICAL ATTRIBUTES USING ORGANIC COMPOST IN LETTUCE-CARROT INTERCROPPING

Abstract

Indiscriminate use of fertilizers is responsible for problems as leaching and surface runoff, making more negative the energy balance in agroecosystems. The organic soil management using biological practices avoids waste and optimizes the exploration of natural resources. Two experiments, with intercropped lettuce and carrot and fertilized with organic compost (0 t ha^-1, 12 t ha^-1, 24 t ha^-1, and 48 t ha^-1), were conducted in Seropédica, Rio de Janeiro State, Brazil, during the year 2000, to observe P, K, Ca, and Mg levels, and pH in an Ultisol. Twenty treatments were evaluated using a complete randomized block design, with four replications. The treatments were combined as plots split in time, using doses of organic compost as main plots, and five collecting times as split plots. Soil was sampled at 0-10 cm, before and during the experimental period: 15 days before installation (DBI), 0, 6, 57, and 101 days after planting (DAP), in the first experiment, and 8 DBI, 1, 6, 60, and 116 DAP, in the second. P and K reflected the compost doses, independently of compost type, while Ca and Mg were dependent on compost quality. The period of maximum availability of P, K, Ca, and Mg occurred at 6 DAP, for both experiments. Highest correlations occurred between P and Ca, P and Mg, and K and Ca, which were associated with organic compost quality.

KEY-WORDS: Nutrients dynamics; phosphorus; potassium; organic manure.