Swine Manure Broadcast Application Combined With Cover Crop Seeding; And Subsequent Rainfall Pattern Effect On Gemrination of Cover Crop Seeds.

The cover crop slurry seeding methodology developed by Harrigan et al. (2006) consists of shallow injection of a manure/seed mixture into the soil, creating enriched microsites that promote seed-manure interaction. To achieve the goals of this methodology, most manure applicators need to optimize their equipment (include seed dropping tubes, or upgrade their equipment for mixing and planting of seeds and manure). For farmers accustomed to doing broadcast applications of manure, these changes may represent technical and economical challenges. Studying surficial slurry seeding as an alternative to the original methodology (broadcast manure application + cover crop broadcast planting, instead of the shallow combined injection), might represent a simpler and less expensive version of the original slurry seeding. The objectives of this study were: 1) to evaluate the effect of surficial seeding carrier solution (manure or water), 2) to evaluate the effect of timing of a first and second rainfall event after seeding, on germination of surficial slurry seeded cover crops, and 3) to analyze the success of surficial slurry seeding as a variation of the slurry seeding concept. Mini plots of 7.5 x16 cm were constructed simulating a crack in the soil, similar to the one caused by aeration systems in the back of most manure applicators. Treatments for each species varied between seeding solution (manure vs. water as the surficial slurry seeding carrier), and either single or double rainfall patterns at different times (1, 1+5, 3+7, 7, 7+11 days after seeding). Four cover crops were selected for this experiment (annual ryegrass, crimson clover, daikon radish, and cereal rye). Seeding rates were calculated based on weight, using recommended aerial/surficial seeding rates for each of the studied cover crops (annual ryegrass 22.4 kg∙ha^-1; cereal rye 67.3 kg∙ha^-1; crimson clover 22.4 kg∙ha^-1; radish 11.2 kg∙ha^-1). Manure (and water) application for each mini plot was calculated based on an average application of 60800 L/ha. Reductions in germination percentages (around 50% less), for all species were found when manure was used as solution for surficial slurry seeding compared to water treatments. All manure treatments for all species ranged between 30 and 65% germination, while water seeded treatments ranged from 50 to 100% germination. Even when rainfall is 1 day after application, germination is reduced by manure. If rainfall occurs at 7 days after application there is no benefit in germination with either manure or water. Double rain events beginning 3 days after seeding, increased germination, however, germination with manure was always substantially less than with water. Species don’t appear to be differentially sensitive to manure in this field experiment. Ideally any slurry seeding process should try to approach the methodology developed and implemented by Harrigan et al. (2006), but if constraints are present, surficial slurry seeding can be an option to increase nutrient capture and reduce nutrient losses from manure applications.