Green manure (GM) is a soil conditioner used to improve soil structure and fertility. This study evaluated the effect of Crotalaria spectabilis Roth (showy rattlebox), Cajanus cajan (L) Millsp (pigeonpea) and Brachiaria decumbens Stapf (brachiaria) on soil microbial and biochemical attributes of the citrus orchard. The leguminous was planted at the intercrops and, after 3 months, they were cut and applied in the intercrops. The grown brachiaria was cut and applied in the intercrops. After 5 months, the soil samples were taken from the rows and intercrops in the depth of 0-20 cm. A split-plot design was used. Significant effect (p < 0.05%) from the GM application on the bacteria counts and dehydrogenase and nitrifying activities was obtained an it increased, on average, 20, 39, and 190%, respectively. Fungi number decreased 57%. Urease and solubilizing activities and organic matter and moisture contents were not influenced by the GM application. Among the plants, significant responses were found due to the stimulating activities of dehydrogenase of 57% by pigeonpea, urease 58% by brachiaria, solubilizing 346% by showy rattlebox and nitrifying 236% by pigeonpea or brachiaria in relation to the others GM. These results suggest that GM application for successive years can stimulate microorganisms activity and to improve soil quality.
dehydrogenase; urease; nitrifying activity; solubilization
