Soil carbon fluxes and balances of crop rotations under long-term no-till
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arbon Balance and Management Open Access
RESEARCH
Soil carbon fluxes and balances of crop rotations under long‑term no‑till João Paulo Gonsiorkiewicz Rigon* and Juliano Carlos Calonego
Abstract Background: A field study with the same crop rotations was conducted to test the hypothesis that the soil Carbon fluxes and balances could vary according to the crop species and also mitigate carbon dioxide ( CO2) emission. This study aimed to assess the CO2 emission from crop rotations according to C and N inputs from crop residue, the influences on soil organic carbon (SOC) and total soil nitrogen (TN) stocks, identifying the soybean production systems with positive C balance. Triticale (x Triticosecale) or sunflower (Helianthus annuus) are grown in the fall/winter; sunn hemp (Crotalaria juncea), forage sorghum (Sorghum bicolor), pearl millet (Pennisetum glaucum), or fallow are the spring treatments, and soybean as a main crop in summer. Results: We found that high C inputs from crop residues modify the C dynamics in crop rotations by reducing the C output ( CO2) and increasing C sequestration in the soil. In general, the higher SOC, C stocks, and TN in soil surface were due to higher C and N inputs from sunn hemp or forage sorghum crop residues in spring. These crops also produced lower accumulated CO2 emissions and, when rotating with triticale in the fall-winter season resulted in a positive C balance, making these soybean crop rotations more efficient. Conclusion: Our study suggests the ideal crop species choice in a rotation can mitigate the C O2 emissions by increasing C and N input from crop residues and consequently SOC and C stocks. In particular, crop rotation comprises an important tool to achieve a positive C balance, mitigate CO2 emissions and provide an additional ecosystem service to soybean cultivation option. Keywords: Cover crop, Cropping system, Crop straw, C and N inputs Background Soil comprises one of the largest reserves of Carbon (C) in the biosphere, and depending on the soil management used, it can be considered an important sink and act directly in reducing carbon dioxide (CO2) emissions to the atmosphere [1], mitigating the impact of current and future climate change [2–4]. In Brazil, the agricultural sector is currently the largest source of global greenhouse gas (GHG) emissions, with a 34% share [5]. However, the potential for agricultural mitigation is often ignored [6]. Thus, soil conservation *Correspondence: [email protected] College of Agricultural Sciences‑Department of Crop Science, São Paulo State University (UNESP), Lageado Experimental Farm, Botucatu, SP, Brazil
management such as no-till and crop rotations, mainly adding cover crops, are some strategies when combined can increase soil organic carbon (SOC) [7], nutrient cycling and mitigate GHG emission in agricultural systems [8–10]. Carbon dioxide emissions, as well as SOC increases, also depend on the crop rotations used in the agricultural system, which are affected by the quality of crop residue left on the soil
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