Interseeding camelina and rye in corn at different stages, row spacing and hybrid maturity

Two experiments were established in Forman and Prosper, ND.  Experiment 1: the experimental design was a randomized complete block (RCBD) arranged as a split-plot with three replicates. The treatments were a factorial combination of row spacing, cover crop, and date of cover crop interseeding. An additional no-cover crop check plot was included in each main plot. Row spacing was the main plot with cover crop and date of interseeding as the subplots. Row spacing treatments were narrow (56 cm) or wide (76 cm). Plots with a 56 cm row spacing were 2.2 m wide and 6.1 m long. Plots with a 76 cm row spacing were 3.0 m wide and 6.1 m long. All plots were planted with four corn rows to depth of 5.1 cm at a seeding rate of 79,000 live seeds/ha. The hybrid used was Dekalb brand ‘DKC 36-28’ which has a relative maturity of 86 d.  Cover crops were sown when the corn reached the V7 or the R4 growth stage. Cover crops were camelina, rye and a mix of camelina and rye. Experiment 2: The experimental design was a RCBD with four replicates; treatments were a factorial combination of corn hybrid RM and cover crop. The corn was planted in four rows spaced 76 cm apart to a depth of 5.1 cm at a seeding rate of 79,000 live seeds ha^-1. Plot dimensions were 3.0 m wide by 6.1 m long.  Dekalb brand ‘DKC 30-19’ with a RM of 80 d was used as the early maturing hybrid. Dekalb brand ‘DKC 39-27’ with a RM of 89 d was used as the later maturing hybrid. Cover crop treatments were sown when the corn reached the V7 growth stage. Both experiments were repeated in 2017 at both locations. Cereal rye at the Forman location did not survive past emergence due to dry conditions.

Cover crop biomass was sampled in early November in 2016 and 2017, and in the spring of 2017.  The rye at Forman in 2016 and the camelina at Prosper in 2017 failed due to insect damage. The cover crops did not affect corn grain yield, but the corn severely suppressed cover crop growth beneath the canopy.

Corn hybrid RM did not have a significant effect on fall cover crop biomass, but significantly affected spring biomass accumulation when the data was combined across environments. Spring biomass was 83.0 kg ha^-1 when interseeded beneath the earlier maturing (80 RM) hybrid compared with 63.1 kg ha^-1 when interseeded beneath the later maturing (89 RM) hybrid, however this small amount of biomass likely did not provide any benefit to the environment.

Corn row spacing and cover crop planting date did not significantly affect cover crop biomass when the data was combined across environments. Fall biomass accumulation among treatments ranged from 17.8-82.2 kg ha^-1, and spring biomass accumulation among treatments ranged from 33.7-826.6 kg ha^-1. The amount of cover crop biomass accumulated was very low in both the spring and the fall, and likely provided little benefit to the environment.