Soil inorganic carbon under no‐till dryland crop rotations

Soil inorganic carbon (SIC) constitutes a large proportion of soil total carbon (STC) under dryland cropping systems in arid and semiarid regions. Information on the effect of management practices on SIC is scarce. We evaluated the effect of 1‐ to 4‐yr no‐till diversified crop rotations on SIC at the 0‐ to 120‐cm depth in Sidney and Friod, MT. The SIC increased from the soil surface to 90‐cm depth and then declined. Crop rotations did not affect SIC and STC, except at 90–120 cm in Sidney where barley (Hordeum vulgare L) and winter wheat (Triticum aestivum L) in rotation with pea (Pisum sativum L.) had higher SIC than other crop rotations. The SIC contributed from 0% of STC at 0–15 cm for most crop rotations to 78% at 60–90 cm for barley–pea rotation. Long‐term studies are needed to evaluate the effect of dryland crop rotations on SIC in the northern Great Plains.