Soil tillage and other methods of soil management may influence CO 2 emissions because they accelerate the mineralization of organic carbon in the soil. This study aimed to quantify the CO 2 emissions under conventional tillage (CT), minimum tillage (MT) and reduced tillage (RT) during the renovation of sugarcane fields in southern Brazil. The experiment was performed on an Oxisol in the sugarcane-planting area with mechanical harvesting. An undisturbed or no-till (NT) plot was left as a control treatment. The CO 2 emissions results indicated a significant interaction (p < 0.001) between tillage method and time after tillage. By quantifying the accumulated emissions over the 44 days after soil tillage, we observed that tillage-induced emissions were higher after the CT system than the RT and MT systems, reaching 350.09 g m −2 of CO 2 in CT, and 51.7 and 5.5 g m −2 of CO 2 in RT and MT respectively. The amount of C lost in the form of CO 2 due to soil tillage practices was significant and comparable to the estimated value of potential annual C accumulation resulting from changes in the harvesting system in Brazil from burning of plant residues to the adoption of green cane harvesting. The CO 2 emissions in the CT system could respond to a loss of 80% of the potential soil C accumulated over one year as result of the adoption of mechanized sugarcane harvesting. Meanwhile, soil tillage during the renewal of the sugar plantation using RT and MT methods would result in low impact, with losses of 12% and 2% of the C that could potentially be accumulated during a one year period.
Silvopastoral systems (SPS) have been widely implemented in the Colombian Amazon region to improve pastures involving a greater diversity of species, soil tillage, fertilization, and higher stocking rate, which can induce changes in soil properties and functions. This study aimed to evaluate soil chemical properties and carbon sequestration changes due to the transition from traditional pastures to silvopastoral systems. The study was conducted in the Colombian Amazon region, specifically in La Montañita and El Doncello Counties, in Caquetá, the second most important hotspot of deforestation in the entire Amazon basin. In each study site, we established a chronosequence consisting of three areas following the typical land‐use change at the region: (i) native vegetation, (ii) traditional pasture, and (iii) silvopastoral system. We found that agricultural practices involving liming and tillage, performed under the silvopastoral management, contributed to reducing soil active acidity and exchangeable acidity with soil pH increasing from 3.8 to 4.3 and H++Al3+ decreasing from 5.8 to 2.3 cmolc kg−1. These alterations favored increases in Ca2+ and Mg2+ contents mainly, increasing the base saturation from 17% in traditional pastures to 55% under silvopastoral systems. The synergic effect of the mix of grasses and trees under silvopastoral management improved soil micronutrient contents and modified soil C stocks in 20–30 cm layer. A rate of soil C accretion of 0.26 Mg ha−1 yr−1 for the 0–30 cm detected in silvopastoral systems suggests that its implementation could be a promising tool for C sequestration in tropical regions, capable of restoring soil functioning of degraded areas.
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