This is the second article in a series of four discussing no-till farming issues. The first article discussed the benefits of no-till. This article will focus on manure management issues in a no-till system. There are a variety of issues that must be considered; including nitrogen availability, odor, cover crops and manure injection.
The biggest agronomic concern is nitrogen availability. Same day incorporation will result in 40%-75% of the nitrogen to be available for the crop, depending on manure type. If tillage occurs seven or more days after application, 15%-20% of the nitrogen is available. This would be the same as not incorporating at all, as in a no-till system. Also consider that a half inch of rain has the same effect on nitrogen availability as tillage. As long as soil tests show phosphorus or potassium levels are at optimum or below; manure application rates can be adjusted to supply the needed nitrogen. In situations where nitrogen availability falls short of the recommended level without tillage, the producer must consider the cost of tillage and loss of soil structure versus the cost of extra fertilizer.
Injecting manure saves nitrogen and reduces odor. This can only be done with liquid manure. Injection has the same nitrogen availability for crop use as immediate incorporation. To inject manure requires the expense of new equipment and/or updating spreaders. It may be more economical to hire a certified manure hauler to spread your manure. Injection may make non-farm neighbors more comfortable, and they may feel that the producer is being considerate. While planning to start injecting manure, make sure injection is compatible with your conservation plan. Most types of injection cause significant soil disturbance.
For the producers handling manure as a solid, there is no easy solution. Composting can reduce odor without significantly reducing the total amount of nitrogen. It produces fine-textured compost that can be spread thinly and is easy to plant into. To begin composting, there is an initial monetary outlay to build or convert a facility. Composting requires time to properly manage it and puts a lag time between clean out and spreading. For those not interested in composting; a fine, well decomposed manure is best for a no-till situation. It can be spread evenly; distributing nutrients evenly and creating a situation that will work well with a no-till planter.
Whether you have liquid or solid manure, if the producer’s number one concern is odor, a no-till system is probably not for them. Odor can be reduced but not eliminated by implementing some of the previous practices.
The only law that requires incorporation is Pennsylvania ’s Act 6 Nutrient Management Law. The law calls for incorporation in certain, unique situations. Manure should not leave the field where it has been spread. Proper timing, attention to the weather and cover can all play a part to prevent pollution. Proper conservation practices and planning play a key role in reducing the amount of nutrients that could be carried in runoff. By leaving the manure on top, there may be a slight increase in the amount of nutrients in runoff but reductions in leaching should offset this increase.
Cover is very important in no-till. Crop residue can help hold liquid or solid manure in place. If fall spreading is necessary, cover crops can be the answer. Cover crops can take up extra nutrients, mainly nitrogen, in the soil. They need to be planted early enough to get a good start, usually September. When they are killed in the spring, they decompose and release the nutrients for the next crop to use. Or the crops could be cut for feed eliminating the nutrient recycling. This is good if your fields are above optimum levels for phosphorus or potassium. Cover crops also provide extra cover for fields with low residue, such as corn silage or soybean fields. They create more organic matter, even when harvested, which is key in the no-till system.
The addition of manure to a no-till system improves soil quality by increasing organic matter. This additional organic matter can make a smoother transition to no-till, because the soil structure improves faster. Good soil structure allows more water infiltration. Stable soil structure is the most important part of a no-till system. Once the soil structure is stable, yields should become similar to tilled yields. The few years while the soil structure is forming usually have lower yields. Manure as an organic matter addition helps shorten the time for the soil structure to form. Tillage destroys the soil structure, so any tillage after no-tilling for a few years effectively puts the producer back where they started.
All additions in no-till are made to the top two inches of the soil and can result in a condition known as “acid roof”. Basically, the addition of pesticides, fertilizers and manure result in a lowering of the pH in the top two inches of the soil. This layer should be tested annually or more frequently if your pesticides don’t seem to be working properly. If surface pH is below 6.2 and a standard soil test doesn’t require lime, 2,000 lb/ac of lime should be surface applied. This will bring the surface pH up.
Manure will work best with no-till when the producer has a limited concern about odor, is willing to use a cover crop or has high crop residue levels, and is willing to make changes to application rates to adjust for lower available nitrogen. Each producer must make a decision based on the circumstances best for their operation. Manure application and no-till systems are compatible.
Remember to look for the next article which will be focusing on preparing to begin no-tilling and the last article which will cover making no-till work for you.