As dairy farms have increased in size, a higher proportion of livestock manure is stored in pits or lagoons. This has the advantage of allowing the farmer to spread manure when he wants to (subject to winter application restrictions that differ by state) rather than when he has to, as in the case of daily spreading.
Another change with increased herd size is a move from stanchions and tie stall barns to free stall barns. This has resulted in a significant reduction in the amount of used bedding – straw, sawdust, etc. – in the manure. Less fibrous material in the manure (particularly straw) makes it easier to apply to alfalfa and grass fields instead of most or all being applied to annual crops such as corn. This is convenient for farmers but presents potential problems, including the offensive odors in liquid manure.
Following are some ideas to consider as you head for the fields this summer, manure spreader or tanker in tow.
Where should I spread?
One of the best places for summer manure applications is grassland. With judicious use of summer manure applications, farmers can supply the necessary nitrogen for second and subsequent harvests of grass as well as most and perhaps all the phosphorus, potassium and other nutrients needed by the crop.
Manure also can also be used for first-cut grass, but often these fields are still too soft when it’s time to apply nitrogen – which should be at first green-up. Plus, there’s already plenty of other fieldwork to do at that time of year.
Depending on the nutrient analysis of dairy manure and forages, you also may need to apply sulfur, which is an essential nutrient. Because of greatly reduced industrial air pollution in the past generation, the amount of sulfur we get from rain and snow is a fraction of what it once was. (Is it too clever to state that sulfur depositions have declined precipitously?) If you need sulfur, a good way to apply it is as an early-spring topdress of ammonium sulfate on grass or mostly grass hay fields, either applied straight or as a 50-50 blend with urea, which, for cost reasons, is my preference.
We need to lose the idea that manure (or nitrogen, for that matter) is harmful to alfalfa. It’s not; in fact, one of the main reasons we don’t recommend fertilizing alfalfa with nitrogen fertilizer is because it’s not economical – the small yield increase wouldn’t be enough to pay for the fertilizer. (Many years ago when I was doing some farm consulting in Hungary, their fertilizer prices were so low that their agronomists were recommending the application of urea to straight alfalfa.)
When applying manure we’re operating under a different set of economic and practical guidelines because one way or another we’ve already paid for the nutrients in the manure. The nitrogen in manure won’t hurt the alfalfa while the potassium and other nutrients should increase yields where soil fertility levels are inadequate. Alfalfa-grass fields, especially those that have been established for two years or more, are excellent candidates for summer manure applications. The damage we do to alfalfa during manure application isn’t from the nutrients in the manure but from wheel traffic (more on this in the next section). That’s why you might want to avoid topdressing manure on first-, and perhaps second-year stands.
Read more: Use caution when topdressing manure
Timing may not be everything, but it’s up there
One of the challenges of topdressing manure on hay land, especially alfalfa, is the need to get the job done as soon as possible after the crop is harvested. Modern manure spreaders have wide tires and the weight of a loaded spreader can damage the crown buds and new shoots of alfalfa.
The longer you wait, the more the damage. There’s been plenty of research on this topic, including at least two trials at Miner Institute in Chazy, New York. It’s estimated that the yield of the alfalfa plants run over by a manure spreader wheel decreases by 5 percent for every day of delay between harvest and manure application. So, if you wait a week after harvest before manure application you’ve lost over a third of the yield of those squashed plants.
Application timing isn’t quite as important with grass because there aren’t any crowns to crack or buds to damage, but consider this: While alfalfa grows from crown buds, grass regrows from the cut stems. So “painting” several inches of regrowth with a coat of liquid or slurry manure could result in some of these manure solids remaining stuck to the plant until it’s harvested. Fortunately, most manure pathogens are killed by the ensiling process – more by the high acidity than the temperatures of fermentation – but some pathogens may survive.
Research at Miner Institute found that topdressing manure three and seven days after first-cut alfalfa-grass harvest resulted in significantly higher ash concentrations, with the highest ash level found after the seven-day delay. And the damage to the alfalfa with a seven-day delay was severe enough that we could still see the wheel tracks several weeks after application. Opinions differ on how much damage wheel traffic does to alfalfa crowns, but I’ve dug up enough plants with crowns split down the middle, resulting in the development of tap root diseases, that I’m a believer. Some crown and shoot damage is likely even if manure is applied the same day the crop is harvested, which is why I don’t recommend manure application on newer stands.
Be a considerate neighbor
You may think that manure is the sweet smell of success, but that doesn’t mean that your non-farming neighbors do! You have to apply livestock manure, but perhaps not on the field next to your neighbor’s house on a Friday afternoon or on a summer weekend. In fact, you might make a good impression by asking in advance if there are a few days (graduations, weddings, family reunions, etc.) when your neighbor(s) would most appreciate your spreading somewhere else.
This is from a fellow who lived next door to a dairy farm for many years. Most farmers have enough options as to when and where to spread that they can still get the job done while being a good neighbor. Even when spreading on weekdays, try to apply manure near residential areas in the morning. Morning applications will have the chance to dry (with the resulting decrease in odors) by the time the nine-to-five set gets home from work. Spreading in the morning is also good because early in the day the air is rising, taking manure odors with it, while late in the day the air is settling. Being a good neighbor also applies to any manure spills. The best idea is to prevent them, but accidents happen. If they do, clean them up as soon as possible. Coating a muffler or catalytic converter with manure and then parking the car in the garage equals no joy!
Read more: Manure management: from compost to energy