Summer annual crops have grown in popularity in the past 10 - 15 years. The preventive plant measures taken in 2019 provided an opportunity for many farmers to raise summer annuals for the first time. Demand for summer annual feed has remained strong as farmers learn to fit it into the crop rotation, to feed it, and to market it as a valued forage.
The purpose of this article series is to discuss the different uses of the wide range of summer annuals CISCO offers and how to improve performance. As one of the CISCO forage agronomists and a beef/forage farmer, my experiences with summer annuals have been very good. They are often underutilized and undermanaged because of a lack of education on best management practices. I want to take a practical management approach with this article to help other farmers improve their experiences with summer annuals.
Summer annuals can be grown throughout the Midwest. What makes them work so well is their rapid growth, water efficiency, quick canopy, and high forage quality potential. They can be raised full-season or following another crop such as winter wheat.
First off, let’s talk soils and fertility for summer annuals. Summer annuals perform best on moderately well-drained to well-drained soils. They do not tolerate standing water. The better the soil fertility, the better the crop performance. This seems to be an obvious statement; however, it is often neglected. Soil pH of 6.0 or above is recommended. In my experience, phosphorous (P) and potassium (K) levels that are adequate for a 150 bushel per acre corn crop will raise a great summer annual crop. If soil fertility is less than desirable, pearl millet is the most capable species for handling lower fertility situations.
Nitrogen (N) is the largest fertility variable in raising summer annuals. It provides increased yield and protein content of the harvested forage. Nitrogen also promotes more rapid canopy growth, which will in turn provide quicker weed suppression by shading. The rule of thumb is to provide 1 to 1.25 pounds of N per day of growth. This applies to sorghum sudangrass, sudangrass, and teff. Pearl millet is more efficient with N and produces about 2/3 the yield of sorghum Sudangrass, so it can perform well on 0.75 to 1 pound of N per day of growth. Forage sorghum, on the other hand, needs up to 1.5 pounds of N per day of growth.
To explain this further, Sweet Six BMR sorghum sudangrass is our most popular summer annual. Under ideal conditions, it takes 45 to 50 days from emergence to reach late boot stage. This means that it requires 50-60 pounds of N per acre at planting. After the first harvest, there are an additional 30 - 35 days to the second harvest. This requires an additional 30 - 40 pounds of N per acre. Depending on the growing conditions, many producers opt-out of applying N for the final harvest because of the reduced growth caused by cooler weather.
Nitrogen sources vary widely across the Midwest. Sources can range from urea to beef pen pack manure. Ideally, summer annuals need to have a readily available source of N. Remember, there are only 45 to 60 days between plant emergence to the first harvest on most of these crops. They need N right away. A great way to help boost yield and crude protein content is to add a source of sulfur (S) with the N. The best method to manage this is to use ammonium sulfate, gypsum, or manure. The range of nitrogen to sulfur is 12:1 to 15:1. Another way to look at this is if you are putting down 60 pounds of N, then you need to add 4-5 pounds of sulfur.
Liquid manure is a great source of fertility for feeding summer annuals. I have had multiple phone calls with questions concerning how many gallons of liquid manure should be tanked onto the field before planting. This is a very vague question that can be easily answered. It depends. Is it hog, dairy, or beef manure? How “hot” (how much N) is it? This is easily answered with a manure test. Apply manure for what the crop needs. Excess N and P will end up in the watershed, resulting in a waste of your money and an excess of nutrients to the surrounding watershed. Over-application of N from manure can burn or kill seedlings - depending on the rate. Remember to use the right rate at the right time with the right placement.
Pen pack or dry feedlot manure is the least desirable source of N for a couple of reasons. One is the timing of breakdown and N release. Manure particle size, precipitation, temperature, and biological activity are a few variables that play into N release from pack manure. Summer annuals need N to be readily available. Pack manure is a great source of S, P, and K. According to the Purdue University Forage Field Guide, summer annuals remove about 15 lbs. P2O5 and 25 lbs. K2O per ton of dry matter harvested. It is important to replace crop removed nutrients for future crops.
Starting with good management begins in the winter before seed is purchased. Fertility maps, crop rotation plans, and feed requirements all need to be evaluated before choosing which summer annuals to plant. In the next article, I will explain the different types of summer annuals and their uses.