Root length density of cereal and grain legume crops grown in diverse rotations

The development of crop rotations to support sustainable agriculture depends on understanding how crop rotations affect above- and belowground crop characteristics. Our objectives were to investigate crop rotation effects on shoot dry weight and root characteristics of cereal and grain legume crops at anthesis, as well as on grain yield. Rotations were corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] (CS), corn-soybean-spring wheat (Triticum aestivum L.)-field pea (Pisum sativum L.) (CSSwP), corn-soybean-spring wheat-sunflower (Helianthus annuus L.) (CSSwSf), corn-field pea-winter wheat-soybean (CPWwS), and corn-oat (Avena sativa L.)-winter wheat-soybean (COWwS). Crop biomass and root samples were collected at crop anthesis for each crop within the crop rotation. Two soil cores were taken within each of the crops grown in rotation, and the two soil cores were cut into segments of 0-15, 15-30, 30-45, 45-60, 60-90, and 90-120 cm and combined for measuring root length density. Rotations were established in 2000 with plants measured in 2015 and 2016. Rotations had no significant effects on shoot dry weight at anthesis. Small grains had greater root length density than grain legumes between 0- and 60-cm soil depths. Rotation treatments had significant effects only on soybean root length density at 0- to 90-cm soil depths. Soybean following winter wheat (CPWwS and COWwS) had significantly less root length density than soybean following corn. Soybean grain yield was significantly greater following winter wheat (CPWwS and COWwS) than in other rotations. Thus, smaller root systems at anthesis in soybean following winter wheat were associated with higher grain yield at maturity.