Enhancing nutrient cycling by coupling cover crops with manure injection
Coupling winter small grain cover crops (CC) with liquid manure injection may increase manure nutrient capture. The objectives of this research were to quantify manure injection effects using target swine (Sus scrofa) manure N rates of 112, 224, and 336 kg N ha–1 on CC plant density, fall and spring shoot biomass, N, P, and K uptake and subsequent corn (Zea mays L.) yield. A winter rye (Secale cereale L.)–oat (Avena sativa L.) CC was established before fall manure injection. Manure injection lowered mean CC plant density 25% because of CC mortality in the injection zone. Fall CC dry matter (DM) was 26% lower in the manure treatments than the no manure CC control, although no difference was detected for N (9.4 kg ha–1) or P (1.4 kg ha–1) uptake. No difference was detected for spring DM between CC no manure and manure treatments. Shoot DM, N, P, and K uptake increased 29, 41, 31, and 25% from the CC manure 112 to CC manure 224 with no increase above CC manure 224. Cover crop N uptake was higher in CC manure vs. no manure (60.1 vs. 35.6 kg ha–1). Cover crop P and K uptake were also higher in CC manure vs. no manure (9.2 vs. 6.6 kg P ha–1 and 41.3 vs. 30.0 kg K ha–1). Corn grain yield was unaffected by CC and responded positively to manure application (11,022 with manure vs. 9,845 kg ha–1 without manure). Coupling manure injection and cover crops can increase nutrient capture without lowering corn yield.