Determining the Optimum Quality Harvest Stage of Male-Sterile BMR Forage Sorghum

View the project final report

Commodities

• Agronomic: sorghum (milo), sorghum (sweet), sorghum sudangrass

Practices

• Crop Production: crop improvement and selection, cropping systems, crop rotation
• Production Systems: integrated crop and livestock systems, organic agriculture

Short season BMR sorghum has been tested and produces high yields and quality to replace corn silage (1,10). It has many advantages over corn silage especially for organic farms. In balanced rations, BMR sorghum sp. can produce the same milk as corn silage but with higher components and greater feed conversion efficiency (1).
Sorghum sp. stalks will lodge as the grain head fills – a major limit to farmer adoption. Male sterile – either sorghum or sorghum-Sudan - gave some of the highest yields in PI’s trials and had the best standability with no maturing seed to bring the plant down and had higher digestibility than their seeded counterparts. Photosynthetic energy in male-sterile continues to build in the plant cells and is not translocated to the seed sink. Unfortunately, with no grain we have no indicator for the optimum time to harvest male-sterile types. Sorghum breeders cannot tell farmers the optimum harvest time for a crop without seeds. This knowledge is critical to determine varietal season length for our farms and for the farmers to harvest at the optimum time to support profitable milk production.
A BMR male-sterile sorghum will be planted on Dutch Hollow farm. From the boot stage and continuing for 6 weeks, 6 replicate samples each week will be ensiled in vacuum-sealed bags. Cumberland Valley Analytical Lab will analyze for quality components. Utilizing CNCPS model, the data will determine the optimum harvest window. This information will be disseminated through contacts with multipliers in agribusiness, Extension, and consultants.

The project seeks to both quantify and qualify the forage nutritional quality component changes of a male sterile bmr sorghum from boot stage to 35% dry matter silage stage to determine the optimum harvest window. Lyons et al 2019 Dairy Science(10), clearly determined the components for a fertile seeded BMR brachytic dwarf sorghum. Because there is no pollination in the male-sterile, there is no carbohydrate sink to pull photosynthetic nutrients from the cells in the rest of the plant and convert them to starch in the seed. This has the potential to dramatically shift both the amounts and the components of the digestible portion of the plant. This could have a significant impact on the makeup and profitability of utilizing the forage as a major component of the dairy ration. The analysis of changing forage quality components over time will tell us when is the optimum time to harvest; how big the harvest window is for dairy forage; and if there is any stoppage or loss of nutrients past a certain point in the fall with this crop. As farms, especially organic farms, increasingly switch to male-sterile genetics, this project will significantly increase their success in utilizing the forage.