Carbon cycling in area under no-till and application of sewage sludge

Abstract

The experiment has as main aim to assess C sequestration, changes in the amount of microbial C, the quality of SOM and CO2 emissions resulting from application of sewage sludges from a long-time in area under no-till. Another aim of the study is to evaluate the nutrition and yield of the crops (black-oat and soybean) and the soil fertility resulting from sewage sludge application. The treatments consist of two types of sewage sludge (centrifuged and biodigested) and four rates applied on the surface (0, 2, 4 and 8 Mg ha-1).Two control treatments will also be evaluated: one with a conventional application of dolimitic lime and another in the forested area adjacent to the experimental area, which serve as a reference of the soil potential in accumulate C. Soil samples will be taken after black-oat cropping in 2012 and 2014. Organic C, microbial C and soil bulk density will be determined. Basic chemical and micronutrients analysis will be held in samples taken in first sampling. In the samples taken in the second sampling, physical and chemical fractionation of SOM will be carried out. The accumulation of nutrients, dry matter production and C input by black-oat crop and the nutrition, yield, C export and C input by soybean crop will be determined. During the experiment the flow of CO2 from the soil will be quantified. The average annual increment of C in soil and the C balance between the beginning and end of the experiment will be calculated. The data will be submitted to ANOVA and regression analysis, being adjusted to polynomial or exponential equations as a function of the regression parameters significance, F value and adjusted coefficient of determination (R2). The results obtained in each treatment will be compared with the control treatments using the Dunnett test.