Rory Lewandowski, OSU Extension Educator, Athens County
Early spring provides us with a window of opportunity to get a new forage stand established. The actual success in getting that new seeding established depends upon several factors including: soil fertility, species selection, weed control, timing of planting, planting depth, post planting management. Let’s look at each factor in a little more detail.
There are certain minimum, sometimes termed critical, soil fertility levels that should be met to give a new forage seeding the best chance of success. Begin with soil pH. I sometimes have people ask me, “What is the minimum soil pH that (fill in the blank with some grass or legume) can tolerate? I think this is the wrong question to ask. Many of our grass and clover species can tolerate, can survive at pH levels in the 5.5 to 5.8 range. My question is; do you want your forages to merely survive or do you want them to thrive? The better question is; what soil pH will allow this forage species to have a chance to produce up to its genetic potential?
Soil pH should be above 6.0 for pure grass species plantings. When a legume, such as one of the clover species, is added to the mix, then the minimum soil pH goal should be 6.5. If the forage seeding is to be alfalfa, then the pH goal should be 6.8. Soil pH can’t be changed very rapidly. Limestone is used to raise soil pH and is relatively insoluble, so it takes time to work its way down into the soil profile and go into soil solution where it can begin to change the soil pH. If limestone can be tilled into the rooting zone, this helps, but it can still take up to 9 months from the time of application and tillage into the root zone before the target pH is reached.
Soil phosphorous is very important to help a young forage plant get a root system established. The critical level for a pure grass stand is 15 ppm. If a legume is added to the mix, then the critical level is 25 ppm. Research has shown that depending upon the soil test level, it can require anywhere from 8-30 pounds/acre of actual P2O5 to increase the soil test level by 1 ppm. Notice that phrase actual P2O5. This is not the same as the amount of fertilizer material to apply. For example, if DAP is the fertilizer material that will be used to increase soil phosphorus, this has an analysis of 18-46-0. It contains 46% actual P2O5. So, it will require 2.17 lbs of this fertilizer for every 1 pound of actual P2O5 recommended.
Soil potassium is needed by plants to aid in disease resistance and winter hardiness. The critical or minimum level of soil potassium is based upon the cation exchange capacity (C.E.C.) of the soil and determined by the following equation: 75 + (2.5 x C.E.C.). For example, many Athens County soils are in the 10-13 range for C.E.C., so our critical soil potassium level is in the 100-110 ppm range. Research has shown that depending upon the soil test level of potassium, it will require anywhere from 6-12 pounds/acre of actual K2O to increase the soil test level by 1 ppm. Once again notice the phrase actual K2O, and make the appropriate calculations with the fertilizer material you will be using to apply the correct amount of fertilizer material to meet the recommendations.
Species selection should be given some careful thought. Rather than a pure grass seeding, consider adding a legume component that can help to meet the nitrogen requirements of the stand. If the stand will consist of about 30% legumes, then application of synthetic nitrogen fertilizer should not be necessary. Take a look at soil drainage when choosing a forage species. Alfalfa does not do well in poorly drained soils. Stand life will be reduced. A clover, grass mix might be a better choice. For example, reed canary grass is adapted to poorly drained and wet soils. Choose new and improved forage varieties. Yes, they will cost more than old varieties, but how many row crop farmers would think about planting corn and soybean genetics from 20-25 years ago? These new forage varieties have improved yield potential, are more drought, disease and insect resistance and more palatable.
Weeds can be a problem. If there are perennial and biennial weeds established in the soil where the new forage seeding is planned, they should be controlled before planting. Consider using a herbicide or herbicide mix to control weeds. Getting into all the herbicide options, rates, and planting restrictions is beyond the scope of this article. Give a call to your county’s Ohio State university Extension office and they can help you out with recommendations.
Pay attention to timing and planting depth. Our window of opportunity in this part of Ohio for a spring seeding is from anytime March weather cooperates until about April 20th. The reason for this is because it takes a forage plant about 6-8 weeks to get a root system established after germination. This should be done before we get into the stress of hot and dry weather. If you count ahead about 8 weeks from April 20th, you will see why that is used as the deadline date. The actual seeding rate, in terms of pounds/acre will vary depending upon the species and the forage mixture you are planning to plant. Some factors to keep in mind are germination percentage and seed coatings. Always check the seed germination percentage, and when the germination percentage was determined. There can be old seed in the market, which can have significantly lower germination than listed on the tag. Lower germination can be compensated for, to a certain degree, by increasing the seeding rate. Some seeds may come with a seed coating, either containing a fungicide, a rhizobium bacteria, lime, or a combination. Seed coatings change the weight of the seed and the calibration of planters. Make sure the planter is calibrated to plant more seed to make up for the seed coating.
Depth of seeding can’t be stressed enough. Planting too deep is responsible for many stand failures. Most forage seeds will do well planted at about one-quarter inch or less in depth. If you are going to error, error on being shallow rather than deeper.
Finally after the forage stand is planted, manage it to give it the best chance for success. Provide a 6-8 week period after germination before a light grazing pass or clipping is made. After the first light grazing or clipping, manage normally. Remember that if forage is being removed as a hay crop, that nutrients should be replace to maintain soil fertility.
For more information about establishing a new seeding, including forage species mixtures and specific seeding rates, contact a member of the OSU Extension Sheep Team.