SOIL MICROBIAL RESPIRATION IN AGROECOLOGICAL TRANSITIONAL AREAS

Polycultures such as the Agroforestry Systems (AFS) are alternatives to the conventional agricultural production methods. Crops diversity can positively influence soil microorganisms, improving its fertility. The objective of this study was to determine the rate of soil microbial respiration under different systems of land use. Soil samples were collected in a polycultive area (pumpkin, okra and cassava) and of ASF at Settlement Chico Mendes III and São João Forest, both at Paudalho, Pernambuco. The collections occurred in the months of July 2017 (rainy season) and in March 2018 (dry season). The soil samples (50 g) were transferred to glass pots containing 15 mL of distilled water with the addition of 10mL of KOH (0.5 N). For control (white) KOH was set in the pot, without soil. The pots were closed and sealed with parafilm and incubated for 15 days. The KOH solution was titrated with HCl N using phenolphthalein (1 %) and orange methyl (0.1 %). Later, 5 g of each sample was placed in Petri dishes and dried for three hours in oven at 100 °C. The results were expressed in: mg CO2 g-1 dry soil h-1. The design was completely randomized (DIC) with three treatments (land use systems) and five replicates (soil samples) for basal respiration evaluation (RB). The results were submitted to analysis of variance and the mean was compared by Tukey test at 5 % significance. The average microbial soil respiration in rainy season was 20.94, 21.30 and 31.62 mg CO2 g-1 dry soil h-1 and dry season was 36.48, 49.67 and 60.22 mg CO2 g-1 dry soil h-1 for polycultive, AFSs and Forest, respectively. There were no statistical differences between the means in the rainy season, but in the dry period the polycultive differed from the forest and ASF was statistically equal to the forest and the polycultive. In the dry season, the polycultive area had no mulch, with a predominance of grasses close to the crops contributed by the low RB value, since the incorporation of organic matter in the environment influences the microbial activity of the soil. The RB values of the rainy season indicate that the two multi-crop areas showed a similar forest of microbial activity, demonstrating the importance of diversified production systems, and that this activity may be influenced by changes in land cover.