Linking Cover Crop Residue Quality and Tillage System to CO2-C Emission, Soil C and N Stocks and Crop Yield Based on a Long-Term Experiment
2020
Otávio A. Leal | Telmo J. C. Amado | Jackson E. Fiorin | Cristiano Keller | Geovane B. Reimche | Charles W. Rice | Rodrigo S. Nicoloso | Rafael P. Bortolotto | Rai Schwalbert
Cover crops (CC), particularly legumes, are key to promote soil carbon (C) sequestration in no-tillage. Nevertheless, the mechanisms regulating this process need further elucidation within a broad comprehensive framework. Therefore, we investigated effects of CC quality: black oat (Avena strigosa Schreb) (oat), common vetch (Vicia sativa L.) (vetch), and oat + vetch on carbon dioxide-C (CO2-C) emission (124 days) under conventional- (CT), minimum- (MT) and no-tillage (NT) plots from a long-term experiment in Southern Brazil. Half-life time (t1/2) of CC residues and the apparent C balance (ACB) were obtained for CT and NT. We linked our data to long-term (22 years) soil C and nitrogen (N) stocks and crop yield data of our experimental field. Compared to CT, NT increased t1/2 of oat, oat + vetch and vetch by 3.9-, 3.1- and 3-fold, respectively: reduced CO2-C emissions in oat, oat + vetch and vetch by 500, 600 and 642 kg ha&minus:1, respectively: and increased the ACB (influx) in oat + vetch (195%) and vetch (207%). For vetch, CO2-C emission in MT was 77% greater than NT. Legume CC should be preferentially combined with NT to reduce CO2-C emissions and avoid a flush of N into the soil. The legume based-NT system showed the greatest soil C and N sequestration rates, which were significantly and positively related to soybean (Glycine max (L.) Merrill) and maize (Zea mays L.) yield. Soil C (0&ndash:90 cm depth) and N (0&ndash:100 cm depth) sequestration increments of 1 kg ha&minus:1 corresponded to soybean yield increments of 1.2 and 7.4 kg ha&minus:1, respectively.
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