Crop rotation for management of plant-parasitic nematodes in forage corn production

Corn (Zea mays L.) is an important silage source for dairy cattle production in the southeastern United States. Silage corn is often grown continuously, which frequently results in severe pressure from plant-parasitic nematodes such as sting nematode (Belonolaimus longicaudatus). Crop rotation is one of the few nematode management options available in forage production. The research objective was to assess summer-planted rotation crops, preceding spring silage corn, for management of plant-parasitic nematodes. Rotation crops included field corn, pearl millet [Cenchrus americanus (L.) Morrone]-with or without fertilizer-, sorghum-sudangrass [Sorghum bicolor (L.) Moench x Sorghum sudanense Piper], and sunn hemp (Crotalaria juncea L.), which was either incorporated into soil or harvested. Rotation crops were assessed in a 3-year field study in central Florida. Sunn hemp treatments significantly reduced sting nematode soil abundances relative to corn by 84%, 90%, and 84% before spring corn planting in 2019-2020 and 2020-2021 and at rotation crop termination in 2021-2022, respectively. Abundances of other plant-parasitic nematodes were not consistently influenced by rotation. Biomass of winter rye (Secale cereale L.)-a bridge cover crop between summer and spring crops-was consistently increased following sunn hemp with significant increases of 87%, 106%, and 186% relative to following corn in 2019-2020, 2020-2021, and 2021-2022, respectively. Similarly, sunn hemp significantly increased spring corn yield by 70% and 136% relative to double-cropped corn in 2020-2021 and 2021-2022, respectively. Overall, rotation with sunn hemp improved plant-parasitic nematode management in forage corn production relative to rotations with only gramineous crops. Summer rotation with sunn hemp manages sting nematode populations before spring silage corn better than grasses.Nematode management by sunn hemp leads to improved spring silage corn yield and winter rye growth.Diversifying forage rotations by including sunn hemp improves forage production systems.