Does Increasing the Diversity of Small Grain Cropping Systems Improve Aggregate Stability and Soil Hydraulic Properties?

Abstract

Wheat (Triticum aestivium L.) and barley (Hordeum vulgare L.) are two commonly grown cereal crops in the northern Great Plains. Adding other crops such as field pea (Pisum Sativum L.), canola (Brassica napus L.), or camelina (Camelina sativa L.) to wheat or barley cropping systems may improve soil quality. However, little is known about the effects of including oilseeds in small grain cropping systems on soil physical properties. We sampled an 8-year dryland study with 10 different cropping systems including continuous spring wheat, continuous winter wheat, continuous barley, pea–spring wheat, pea–barley, pea–winter wheat, pea–barley–camelina–spring wheat, pea–barley–canola–spring wheat, pea–winter wheat–camelina–spring wheat and pea–winter wheat–canola–spring wheat. We measured dry aggregate stability, wet aggregate stability, water retention, hydraulic conductivity, bulk density and total carbon. Continuous barley and winter wheat had a higher fraction of large dry soil aggregates, whereas the pea–barley–canola–spring wheat and pea–spring wheat cropping systems had a higher fraction of small aggregates in the 0–15 cm depth. However, wet aggregate stability, water retention, bulk density, hydraulic conductivity and soil carbon concentration were not affected by the cropping system in the 0–15 cm depth. Diversifying small grain cropping systems by adding canola or camelina oil seeds and peas generally did not affect soil physical properties at this location.