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Changing role of cultivated land in the global carbon cycle

Buyanovsky, G.A., Wagner, G.H.
Biology and fertility of soils 1998 v.27 no.3 pp. 242-245
agricultural land, biogeochemical cycles, crop yield, soil fertility, crop residues, Triticum aestivum, crop rotation, Zea mays, Trifolium, soil organic matter, continuous cropping, biomass production, Missouri
The carbon balance is ill defined for agricultural lands so that their role in global C balance cannot be accurately estimated. Changes in agriculture in the last 50 years have resulted in a general increase in grain yields, total net annual production (TNAP), and C input to the soil. Amounts of C returned annually with crop residues on Sanborn Field, one of the oldest experimental fields in the United States, increased after 1950, and this was accompanied by C accumulation in soils. Under wheat monocrop (with mineral fertilizer), C accumulated at a rate of 50 g m-2 year-1. A 3-year rotation (corn/wheat/clover) with manure and nitrogen applications sequestered 150 g m-2 year-1 of C. Total C balance for the wheat and corn production area in the United States, approximated on the basis of these rates, indicates that at least 32 Tg C was sequestered annually during the last 40-50 years.