Selecting seeding rates for diverse summer annual forage crop mixtures

Selecting seeding rates for diverse summer annual forage crop mixtures

Summary

Often planted as a result of bad weather, diverse annual forage crop mixtures are more productive than monocultures, use resources more efficiently, and reduce the risk of a subsequent crop failure. A warm-season forage crop mixture 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 three- and four- species mixtures using a replacement design where monoculture seeding rates were divided by the number of crops in the mixture. Crop biomass was sampled at approximately 45 and 90 days after planting (DAP). 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. Weed biomass tended to decrease with an increase in crop biomass. It also decreased with an increase in species richness. All intercrops had land equivalent ratios (LER) greater than one, indicating complementarity.

Since seeding rates are based on species, climate, and management practice, another experiment was conducted in 2013 and 2014 measured differences in seeding rates and seeding rate ratios in the same four species for species in monoculture, biculture, and three-and four-species mixtures. Crop and weed biomass and density were also measured, but the data has not yet been analyzed. Besides yield, other factors like seed cost and potential milk production will also be examined. The goal is to provide optimal seeding rates for mixtures that maximize the land’s productivity, the plants’ forage quality, and the farmer’s profitability.

Objectives/Performance Targets

This project has five objectives:

1. 1. Quantify the effects of functional diversity of crop mixtures on productivity and weed suppression.

Data regarding the crop performance across the nine site-year environments has been written up and will be submitted to Journal of Crop Science as an article titled Functional Diversity in Summer Annual Grass and Legume Intercrops in the Northeastern United States. It is our goal to submit a journal article regarding the weeds data from this experiment to Weeds Science in the following semester. Below are the crop biomass results by composition for each site-year for the two sampling dates (Figures 1 and 2).

2. 2. Model the intraspecific and interspecific competition of the different species in each mixture based on their biomass-density relationship.

No progress has yet been made in this objective.

3. 3. Determine the effect of environment on annual forage crop mixtures and optimal seeding rates.

As stated in Objective 1, data about the effects of environment on annual forage crop mixtures has been analyzed for crop performance. While we do not anticipate major differences in forage quality, these data have not yet been analyzed.

4. 4. Conduct forage quality analysis on the diverse summer annual forages.

Forage quality data from my MS research project containing treatments of the four species in monoculture, three species, and four species mixture in three different locations in the Northeast and mid-Atlantic area: Beltsville, MD; Aurora, NY; and Willsboro, NY were analyzed for ADF, NDF, in vitro digestibility, and crude protein, but only preliminary analyses has been performed (Table 1).

5. 5. Perform an economic analysis of the suggested practice and examine the potential for widespread adoption.

No progress has been made in this objective because the forage quality analyses has not been completed.

• Figures and tables for end of year report 2015

Accomplishments/Milestones

This past year has been irregular due to personal health issues. While the SARE program has been flexible with the necessary changes to my project, many portions of my research and analyses have taken longer than expected. The greatest achievements for this project are submitting a manuscript to the Journal of Crop Science about crop performance of annual forage mixtures and completing the forage quality analysis. I am scheduled to speak about the weeds portion of my MS field work at NEWSS in January 2016. I am looking forward to spending time writing up the differences in forage quality between the mixtures over the growing season. I learned that forage crop mixtures do not differ in biomass production from grass monocultures, but we do expect them to have a higher forage quality since the mixtures include legumes.

Impacts and Contributions/Outcomes

Information gained as a result of the SARE project has been very useful providing support to an OREI grant application. One journal article so far will be submitted and I am looking forward to presenting my results at the NEWSS conference this winter. I expect that as more of my analyses gets completed that my work will have impact beyond the scientific community to the producers themselves.

Collaborators: