Balance de carbono de dos agroecosistemas en un suelo del distrito de riego del río Zulia, departamento norte de Santander-Colombia

Resumo

The use and management of soil can affect carbon dynamics, soil properties and cause greenhouse gas emissions. After changes in tillage on croplands it`s necessary to assess the effects on soil organic carbon (SOC) dynamics, in order to identify if soil is a sink or emitter of carbon dioxide to the atmosphere. This study was carried in two plots of rice cultivation, where tillage and water management changes occurred. A third plot of native forest with Cacao trees was used as a reference soil (agroforestry). For SOC balance estimation, measurement of organic carbon (OC) inputs was determined from necromass, roots, microbial biomass, and urea applications. The CO2 and CH4 emissions were also measured. Results showed that the change in the use of irrigation and tillage in rice cultivation did not cause significant differences in OC inputs to the soil, or in outputs due to carbon emissions. The content of oxidizable organic carbon in the soil shows that there is a significant effect of several factors: land use, crop stage and soil depth. For the SOC, it was found that the agroforestry system has a significantly higher content than the soil under rice cultivation, both with and without irrigation. When comparing the behavior of the total edaphic respiration in each land use, it was found that the agroforestry system expressed the lowest total respiration, contrary to the use with rice that presents greater total respiration and does not show significant differences between them. The behavior of each greenhouse gas (methane, carbon dioxide and nitrous oxide) was different depending on the type of land use and the stage of cultivation, the emission curves showed that the soil in all types of use and stages culture, behaved as emitter or source of carbon dioxide. However, for methane and nitrous oxide there are situations where the soil is a sink. The Flux of CO2 and N2O gases is significantly affected by the stage of the crop factor, while for the Flux of CH4 there is no significant effect. For N2O, the lowest emission was in the third stage and the highest emission was in the first stage, while for carbon dioxide the lowest emission was in the second stage and the highest emission was recorded in the fourth stage. For the CH4 Flux there is a statistically significant effect of the type of land use factor, with irrigated rice being the use that shows the highest CH4 Flux and the agroforestry system the use with the lowest CH4 Flux. In addition, it was found that both the irrigation and tillage management systems in rice cultivation compared to the agroforestry system were management systems with a negative difference between OC inputs and outputs, due to CO2 emissions associated with intense stimulation of crop root respiration and microbial activity. The comparison of the SOC dynamics between the agroforestry system and the rice cultivation systems showed that the agroforestry system is a carbon sink with positive OC dynamics.