Carbon balance in soybean and intercropped corn production systems in a long-term experiment

Abstract

Studies show that global climate changes are accelerated by the emission of greenhouse gases (GHG) from human activities. The main GHG is CO2, with agricultural activity being responsible for around 40% of all CO2 emitted in Brazil. The soil, when properly managed, constitutes an important reservoir of carbon (C), which is sequestered in organic matter. In accounting for C inputs and outputs via biomass production and CO2 emission, conservation systems, with the use of intercropped species, can provide a positive C balance in agriculture. Thus, the objective of this work is to evaluate the carbon balance in a long-term experiment with a succession involving soybean cultivation in the spring-summer crop and corn in the autumn-winter intercropped with different species of cover crops. The present proposal is the continuation of a long-term experiment started in 2006, registered in the Global Network of Long-Term Agricultural Experiments, organized by Rothamsted Research. The experiment was set up in a randomized complete block design, with four replications, with the treatments being composed of four production systems: I) Soybean / Corn (without intercropping); II) Soybean / Corn + Urochloa ruziziensis; III) Soybean / Corn + Crotalária spectabilis; IV) Soybean / Corn + U. ruziziensis + C. spectabilis, totaling 16 plots. The balance of C in the systems will be evaluated, with analysis of C input by residues from the aerial and root parts of plants, and C losses by the accumulated annual emission of C-CO2 from the soil to the atmosphere. Corn and soybean yields will be determined, correcting grain moisture to 13%. With the data on grain yield and accumulated C-CO2 emission, it will be possible to calculate the relative emission of C-CO2 per unit of mass of grain produced. At the end of this work, it is expected to obtain conclusive results on the carbon dynamics in different soybean and corn production systems, in which we hypothesize that intercropped systems provide a positive, or even neutral, final carbon balance in relation to the system without intercropping.