Evaluating Rotations of Cover Crops and Summer Annual Forages for Yield, Nutritional Value, Effect on Soil Nutrient Profile, and Economic Sustainability as Forage for Beef Cattle

Date: 
Aug 2019

Issue

In addition to protecting Iowa’s water quality and preserving valuable topsoil and nutrients, cover crops can provide an additional forage source to Iowa beef producers. While the long-term benefits of cover crops such as reducing soil erosion and improving soil organic matter are well documented, it can be difficult to put a dollar value on those returns on investment. Producers may be more inclined to use cover crops if they can realize a short-term benefit in addition to the long-term conservation benefits. One logical potential short-term benefit that could incentivize this practice is the utilization of cover crops as a forage resource to stretch the feed supply, extend grazing and increase carrying capacity. However, a more complete understanding is needed for utilization of alternative forages by beef cattle across the state.

Since 2012, Iowa has lost another 125,000 acres of permanent pasture while beef cow numbers have rebounded to just over 938,000 head, according to the 2017 Census of Agriculture. This data shows a continuing trend of beef cattle producers maintaining or increasing production on fewer and fewer acres of permanent pasture. If Iowa producers can use cover crop forages as beef cattle feed resources, cover crops will be more attractive as a practice with multiple benefits.

Objective

The objective of this study is to evaluate potential yield, nutritional value, effect on soil nutrient profile and economic sustainability of cover crops used in rotation with various summer annual forage species. This project will demonstrate and aid in development of best management practices of rotating winter cover crops and summer annuals to optimize forage production while improving soil and water quality.

Approach

To achieve these objectives, this study will:

  • Evaluate nutrient content and potential yield of various cover crops and summer annuals used in rotation as conservation practices and forage resources for beef cattle. Forage samples will be taken to determine forage yield and nutritional value of the cover crops and the annual species.  
  • Determine soil nutrient loss when cover crops and annuals are mechanically harvested. Soil samples will be taken at the beginning of the study to establish a baseline for soil phosphorus, potassium, pH and organic matter. Nutrient content of forage samples will be used to calculate estimated nutrient removal with forage harvest.
  • Demonstrate integration of winter cover crops in rotation with summer annuals to optimize forage production for beef cattle. 
  •  Educate producers through extension and outreach efforts, sharing findings  through a variety of formats and events. 

Project Updates

December 2020

Nitrogen was applied to the appropriate plots of summer annual crops in early July. Summer annual forages were sampled and harvested twice per farm, once in August and again in September. Data were collected to calculate forage yield and samples were sent to a commercial forage laboratory for analysis of digestibility and nutrient content. Following harvest and termination of the summer forages, the 2020/2021 winter cover crops were seeded and will be sampled again in the spring of 2021 for digestibility, nutrient content, and yield. The team has found that annual forages can be high-quality forage sources.

Table 1 below provides a forage quality summary during the 2020 growing season for annual forages included in the study. The team continues to capture photographs at various stages of growth and has recorded some video footage that could be used in future programming. Activities and travel were somewhat limited this summer and fall due to the coronavirus pandemic.

Outreach included an Iowa Learning Farm webinar on Nov. 20 and two CropsTV presentations recorded in December, both available through the ISU Extension Store. Additionally, video footage of the forage plots was used in a social media video about controlling cow costs. Upon request by “Wallace’s Farmer,” the team submitted an article scheduled to run in December.

July 2020

The research team met virtually in March and April to plan and develop a protocol for the 2020 growing season. Nitrogen was applied to the appropriate plots of winter cover crops as spring growth began to turn green. Winter cover crops were harvested in approximately mid-May. Data was collected to calculate forage yield and samples were sent to a commercial forage laboratory for analysis of digestibility and nutrient content.

The 2020 summer annuals were planted and will be sampled during summer/fall of 2020 for digestibility, nutrient content and yield. The research team compiled and analyzed data from the 2019 summer annuals and submitted a progress report of the McNay site to be included in the Iowa State Research and Demonstration Farms annual progress reports. The team has taken several photographs of the plots and has recorded some video footage that could be used in future programming.

Activities and travel were somewhat limited this spring due to the coronavirus pandemic. The project was approved as essential research so activities can move forward this summer with the use of appropriate guidelines such as physical distancing and appropriate hygiene.

December 2019

In the first six months of the project, primary activities included seeding summer annuals at each of the three research farms and collecting samples of the summer annual forage to be analyzed for digestibility, nutrient content and yield. Samples were sent to Dairyland Labs for nutritional analysis and measurements taken to analyze for yield estimation. Annual crops were harvested, and the remaining stands terminated. Winter cover crops were then seeded at each of the three research farms in fall 2019. Those forages are still standing, and samples will be collected this spring to be analyzed for digestibility, nutrient content and yield. The warm season seed for the initial summer annual seeding was donated by Millborn Seed and Barenburg. Seed for the winter cover crop seeding was purchased from Millborn Seed.

Outreach during this period included presentations at the McNay Research Farm Field Day and the Neely Kinyon Farm Field Day.

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