Efeitos de diferentes fontes e níveis de matéria orgânica em algumas propriedades físico-hídricas do solo: uso da aproximação fractal.

Abstract

Aiming to evaluate the effects of different sources and amounts of organic matter on soil hydric and physical properties, determined by fractal theory, a field experiment was conducted at the experimental station of the State Company of Agricultural Researches of Paraiba state, Brazil, in randomized blocks with four replications and nine treatments composed of castor oil plant pie (TM1 = 3,000, TM2 = 6,000, TM3 = 10,000 and TM4 = 13,000 kg ha'1), cotton pie (TA1 = 4,000, TA2 = 8,000, TA3 = 12,000 and TA4 = 16,000 kg ha4), and the control (ST - without organic matter). The soil water retention curve was estimated through the models of Brooks and Corey, Brooks and Corey modified for the fractal dimension based on laboratory measurements of the soil water retention curve, and Brooks and Corey modified for the fractal dimension based on soil particles distribution curve determined at laboratory. The saturated hydraulic conductivity was estimated by the soil fractal dimension. It was verified that in all treatments with organic matter happened significant differences in the values of the basic infiltration velocity and of the available water, in relation to the treatment without organic matter; not having, however, significant differences in those variables and in the soil density in the treatments with organic matter. For the treatment without organic matter the soil density differed only from the treatment with cotton pie in the amount of 16,000 kg ha"1. Regarding the organic matter content, the treatments with organic matter in the amounts of 13,000 kg ha"1 of castor oil plant pie and of 12,000 and 16,000 kg ha"1 of cotton pie presented significant differences in relation to the treatment without organic matter and to the other treatments with organic matter; however, the treatments with 13,000 kg ha"1 of castor oil plant pie and with 12,000 kg ha"1 of cotton pie were statistically equals. The use of the fractal dimension in the estimates of the saturated hydraulic conductivity and of the soil water retention curve allowed evaluating those properties satisfactorily.