Micromorphometric analysis of aggregates of Rhodic Hapludox under different management systems/Analise micromorfometrica de agregados de um LATOSSOLO VERMELHO Distroferrico em diferentes sistemas de manejo

The aim of this work is to characterize, using a micromorphometric analysis, the aggregates of a Hapludox submitted to different management systems. This work was carried out in a Rhodic Hapludox in Dourados-MS. The experimental design was in randomized blocks with four replications and treatments arranged in subsubdivided plots. Treatments were established in two management systems (conventional and no-tillage), two doses of gypsum (zero and 2 t [ha.sup.-1]) and the use of two summer crops (soybean and corn). Aggregates were collected, in depths of 0 to 10 and 10 to 20 cm, using, in experimental proceedings, those held in diameter intervals of 9.52 and 4.76 mm, after sieving in a standard sieve set. For collecting aggregates, 40 x 40 cm trenches were opened and sieving was done in the field. Aggregate analyses were done by digital images obtained by scanner (300 dpi) of 60 aggregates arranged in a tray with untidy holes in order to preserve the principle of randomization. Images were later analyzed using the QUANTPORO program, and the analyzed characteristics of the aggregates were the area and its inter-relation with chemical attributes of the soil. The results demonstrated that no-tillage promoted the formation of larger aggregates; soybean as summer culture contributed to that structural effect in the soil; and the application of gypsum increased the aggregation in larger depths. Key words: no-tillage, digital images, aggregates. O objetivo deste trabalho e caracterizar micromorfometricamente os agregados de um Latossolo submetido a diferentes formas de manejo do solo. O trabalho desenvolveu-se em um LATOSSOLO VERMELHO Distroferrico, de Dourados, Mato Grosso do Sul. O delineamento experimental utilizado foi o de blocos casualizados com quatro repeticoes e os tratamentos foram arranjados em parcelas sub-subdivididas. Os tratamentos consistiram de dois sistemas de manejo (convencional e plantio direto), duas doses de gesso (zero e 2 t [ha.sup.-1]) e a utilizacao de duas culturas de verao (soja e milho). Os agregados foram coletados, nas profundidades de 0 a 10 e 10 a 20 cm, utilizando-se, nos procedimentos experimentais, os retidos no intervalo de diametro de 9,52 e 4,76 mm, apos peneiramento em um jogo de peneiras-padrao. As analises dos agregados foram realizadas por meio de imagens digitais obtidas via scanner (300 dpi) em 60 agregados dispostos em um tabuleiro de furos desencontrados. As imagens foram posteriormente analisadas com o programa QUANTPOR