CO2 emissions and their relation to physical attributes of a fertirrigated latosol with treated sewage effluent and two levels of straw

Abstract

Sewage Treatment Effluent (STE) is an urban waste that can be used as a source of macronutrients due to its chemical composition, reducing the use of chemical fertilizers and having a more environmentally appropriate destination. In this work we investigated the effect of the application of two levels of Brachiaria straw fertirrigated, with three effluent fractions of treated sewage (FETE - frações de efluente de esgoto tratado), on the emission of CO₂ (ECO₂) and its relations with the physical-chemical attributes of the soil: temperature, humidity, total porosity of the soil, pH and free porosity of water. The experiment was conducted over 23 days of November 2013, in an area of 160 m² of eutroferric Red Latosol, devoid of vegetation and without soil preparation. The design used was random blocks, in a 2 x 3 factorial scheme, and the treatments consisted of the combination of two levels of Brachiaria brizantha straw (without straw and with straw, 10 Mg ha^-1) and three fractions of irrigation (F1: 11% of STE, F2: 60% of STE and F3:100% of STE). The results showed that the presence of straw on the soil favored higher CO₂ emissions and smaller STE blades (F1 and F2) mitigated the environmental impact of ECO₂. The presence of straw on the soil resulted in the maintenance of higher soil moisture levels, which can benefit the cycle of various crops. The presence of straw in this short assessment period did little to increase the degradation of straw used. The intermediate fractions of STE reconcile the condition of lower ECO₂ combined with more appropriate soil physical-chemical attributes in maintaining organic matter and soil moisture.