Soil organic carbon changes to increasing cropping intensity and no-till in a semiarid climate
Engel, R.E., Miller, P.R., McConkey, B.G., Wallander, R. (2017). Soil organic carbon changes to increasing cropping intensity and no-till in a semiarid climate, 81(2), 404-413. http://dx.doi.org/10.2136/sssaj2016.06.0194
© Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA. All Rights reserved. Soil organic C (SOC) in the semiarid Northern Great Plains (NGP) can benefit from increasing cropping intensity. We evaluated the effect of annual cropping on stocks of SOC adjusted for equivalent mass (SOCEM; 0-30 cm) and the change in SOC adjusted for equivalent mass (DSOCEM) over 10-yr at a field site (45°40′N, 111°09′ W) near Bozeman, MT. The experiment consisted of two fallow-wheat (Triticum aestivum L.; F-W) rotations under till and no-till (NT), and five annual cropping systems under NT factored with two N levels (moderate and high), and alfalfa-perennial grass system (Conservation Reserve Program, CRP). After 10-yr, we found SOCEM of five NT annual cropping ( X = 37.4 Mg ha-1) was significantly (P < 0.01) greater than NT F-W (35.1 Mg ha-1), and till F-W (33.7 Mg ha-1). The greatest SOCEM was found in CRP (39.9 Mg ha-1). Accretion of SOCEM was observed in three systems with the largest gains occurring in the CRP (0.24 Mg ha-1 yr-1), followed by NT continuous wheat (0.13 Mg ha-1 yr-1) and NT pea (Pisum sativum L.)/oil seed-wheat (0.09 Mg ha-1 yr-1). Soil organic C loss was observed in all other systems with the largest loss in the till F-W (-0.29 Mg ha-1 yr-1). Among the cropping systems, ΔSOCEM was directly related to net primary productivity (NPP; r2 = 0.73) and total C (TC; shoot + root + rhizodeposit) inputs (r2 = 0.86). We found SOCEM was maintained at 7.0 Mg ha-1 yr-1 of net primary productivity (NPP) and 2.6 Mg ha-1 yr-1 of TC inputs with accretion and loss occurring above and below these thresholds.
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