Pasture and Forage Minute: Considerations for Inoculants, Thinning and Heat-stressed Alfalfa
Inoculants for Corn Silage
High quality silage starts with proper harvesting and storage, but management extends into the feeding phase. Adding inoculants might be one way to help maintain quality. However, inoculants do not replace other important silage decisions such as harvesting at the right moisture and solid bunker packing.
Inoculants are simply bacterial cultures that help reduce pH faster by converting sugars to acids which reduce molds, fungi and unwanted bacteria. Generally, inoculants are more beneficial for alfalfa silage than corn silage unless that crop is harvested on the dry side or immediately after a killing frost.
Since inoculants only work if the bacteria are alive, store them properly in a cool, dry place. Wet packages can be refrigerated until use. Do not use hot water or chlorinated water to make a liquid inoculate mix, since either can kill the bacteria. Liquid inoculant mixes are usually viable for 24 to 48 hours and need to be stored less than 95°F, so protect the inoculant from heat such as hot chopper engines.
For bunker storage, it is more efficient to apply the inoculant through the chopper in the field rather than trying to pour the inoculant on the top of a silage wagon, hoping that it gets mixed. The most effective alfalfa silage inoculants contain homolactic acid bacteria whereas the heterolactic acid bacteria — such as Lactobacillius buchner — are especially useful at reducing spoilage on the face of bunker silos if the face is too wide to keep fresh, or if producers take out several days’ worth of feed from the pile at one time. However, the bacterium is slow growing and needs 45 to 60 days of storage time before being effective.
The purpose of inoculants is not to fix a train wreck or improve a perfect silage year, but they can help when things aren’t ideal. Inoculants can be used as an insurance policy to reduce the risk of spoilage and maintain quality.
Adding Grass to Thinning Alfalfa
Do you have a thinning and low producing alfalfa stand but are not quite ready to do a complete reseeding? These stands can be rejuvenated by interseeding grasses to increase hay production in subsequent years or to convert them to pasture.
Most alfalfa fields start to lose stand and production potential after cutting hay for several years. Orchardgrass is the grass most commonly interseeded into alfalfa, but other grasses like endophyte-free tall fescue, smooth or meadow brome, festulolium, and wheatgrasses also can be used. If the field will be used as pasture, a mixture of several grasses may be best since it adds diversity to your animals' diet.
Whether irrigated or dryland, interseeding after an August hay harvest can be excellent timing. It may be a little risky this year for dryland fields because several rains will be needed to start the new grass seedlings. The seeding should be done as soon as that August harvest is complete. If your alfalfa is relatively thick, you probably will need to take another cutting in about four weeks, or as soon as the alfalfa starts to form a full canopy. This allows sunlight to continue to reach new grass seedlings below the alfalfa.
The seeding rate of the grasses will vary depending on the species that is used and how thick the existing alfalfa is. With orchardgrass for example, as little as 3 lb/acre might be adequate in a relatively thick alfalfa stand or up to 6 lb/acre in a very thin alfalfa stand.
Next spring you will need to judge how well established the new grasses have become. If they seem a little weak, cut hay early to open the canopy for better light penetration.
Heat Effects on Alfalfa
With high temperatures across the state, you may have adjusted your schedule or habits to adapt to the heat. Adapting to warm conditions isn’t limited to animals, plants adjust too.
When it gets hot, alfalfa plants grow more slowly and moisture stress becomes common, even in moist soil. Production of high-quality hay is nearly impossible due to the high temperatures, especially when the heat does not subside at night. High night-time temperatures cause rapid respiration rates in alfalfa, burning off valuable nutrients that plants accumulated during the day. This often produces alfalfa hay with fine stems that contain high protein, but they also have high fiber and low relative feed value.
Another problem with heat is how fast alfalfa plants mature. When it is hot, alfalfa may begin to bloom in less than four weeks. If you use blooming as a signal to harvest, this early bloom can be misleading. During hot weather alfalfa plants need more time, not less time to rebuild nutrient reserves in their roots because they burn off nutrients instead of moving them to the roots when it is hot. So, watch the calendar along with plant maturity to determine when to cut your alfalfa fields.
If drought conditions have shut down growth completely the question may become whether or not to cut plants at all. If you can find basal bud growth occurring in a drought-stressed stand, go ahead and cut to remove the old growth and give room for new shoots to develop. If no growth is occurring, cutting may still be the answer. Regrowth will occur from the crown when moisture returns, so leaving old growth standing will just lower the quality of your harvest. It’s a good idea to leave a bit more stubble than normal to help protect the crowns and regrowth.
Finally, you might adjust the time of day when you cut hay. Some research has shown that cutting in late afternoon produces higher quality hay than cutting in the morning. However, on good drying days it may still be wiser to cut in the morning. When hay in the windrow stays above 50% moisture, plant cells continue to respire, burning away nutrients. Hay cut late in the day respires all night long, losing yield and quality. On good drying days, plant cells can dry enough to be stabilized before nightfall, reducing respiration losses.
Getting high quality hay is challenging. Both you and the weather must cooperate and even then, there are no guarantees.