Eco-physiological indicators of the quality of a soil irrigated with treated wastewater

Abstract

The impact of treated wastewater application was evaluated in microbial metabolismo of a soil under pasture (Bermuda grass), in Lins/São Paulo State aiming to contribute to investigations on agricultural reuse. In an experimental design in blocks, with 6 treatments and 4 replicates: SI (control), A100 (drinkable water and addition of 520 kg ha^-1 year^-1 of nitrogen (N), E0, E33, E66 and E100 (treated wastewater irrigation and addition of 0, 172, 343 and 520 kg ha^-1 year^-1 of N), the indicators qCO₂, and C_mic:C_org were determined in dry (2004) and rainy season (2005). Values of qCO₂ above 2 and values of C_mic:C^org below 2% can be considered critical regarding soil quality. The results showed qCO₂ increases along the crop management, in dry but not in the rainy season, indicating metabolic activation by moisture added to the N contribution. There was no significant C_mic:C_org variation among the treatments, along crop management and seasons, indicating good microorganisms resistance to agricultural impact.

Key words:
reuse; irrigated agriculture; qCO₂; C_mic:C_org