Root distribution by depth for temperate agricultural crops

Root distribution pattern plays an important role in understanding and estimating of soil C allocation and the effect of crop roots C input on soil carbon balance in agroecosystems. A database of 96 profiles was compiled and root distribution pattern were fitted to a modified logistic dose response curve for 11 temperate crops. A slight linear decrease between the root mass: length distribution ratio and the soil depth was found for monocotyledons while an exponential decrease with depth was found for dicotyledons. These results indicated that roots were thicker at upper soil layers with the effect much larger for dicotyledons. The estimated depth at which 50% of total root was accumulated for different crops varied from 8 cm to 20 cm. Alfalfa (Medicago sativa L.) showed the deepest rooting profile with a fitted maximum rooting depth (dmax) of 177 cm but another perennial, fescue (Festuca arundinacea Shreb.), had the shallowest dmax of 78 cm. In general, cereal and pulse crop roots were distributed more evenly in soil profile while more roots were accumulated in the upper soil layers for oilseed crops. The estimated root distribution patterns from the present study could be incorporated into agroecosystem models for good representations of belowground processes and enhance the accuracy of carbon and water cycling estimation in agroecosystem.