|Bybee-finley, K. Ann - Cornell University - New York|
|Ryan, Matthew - Cornell University - New York|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/25/2016
Publication Date: 5/2/2016
Citation: Bybee-Finley, K., Mirsky, S.B., Ryan, M.R. 2016. Functional diversity in summer annual grass and legume intercrops in the Northeastern United States. Crop Science. 56:2775-2790.
Interpretive Summary: Summer annual cover crops can serve as a means of supplemental forage for livestock as well as a means to suppress weeds and build soil health. However, little work has been done to assess this potential in the mid-atlantic region of the US. Therefore, we conducted experiments in New York and Maryland to assess the potential biomass production of grass and legume summer annual cover crops. Specifically, we wanted to know how they produce in monoculture and mixtures. As expected, legumes produced lower biomass than grasses, but in mixtures we often found biomass production higher than grass monocultures, or at least, higher forage quality. There was no strong climate effect in our study. This work will serve to inform producers on which summer annual cover crops species will perform best in the mid-Atlantic region and how to combine them based on their management objectives.
Technical Abstract: A warm-season annual intercropping experiment was conducted across the Northeastern United States with four trials in 2013 and five trials in 2014 with four crop species selected based on differences in stature and nitrogen acquisition traits: 1) pearl millet (Pennisetum glaucum L.); 2) sorghum sudangrass (Sorghum bicolor L. Moench x S. sudanense P.); 3) cowpea (Vigna unguiculata L.); and 4) sunn hemp (Crotolaria juncea L.). Crops were seeded in monoculture and in 3- and 4-species mixtures using a replacement design where monoculture seeding rates were divided by the number of species in the intercrop. Crop biomass was sampled at approximately 45 and 90 days after planting. When averaged across the 9 site-years, biomass at the first and second sampling dates, respectively, of the monoculture treatments ranged from 1,040 and 2,500 kg ha-1 (cowpea) to 3,000 and 9,300 kg ha-1 (pearl millet). In general, biomass production of the legume monocultures were lower than the grass monocultures and intercrops at both sampling dates. All intercrops had land equivalent ratios greater than one, indicating complementarity, which was likely due to resource partitioning. The pearl millet-sorghum sudangrass-sunn hemp intercrop had the greatest evenness suggesting that species selected for annual intercrops should have similar monoculture growth rates to minimize asymmetric competition.