Manure has value, test and take credit this spring
Manure nutrients vary based on when and how it is applied. But there are always nutrients in it, and benefits to reducing fertilizer.
Myth #1: Manure that is spread during the winter and not incorporated has very little nitrogen left for the next corn crop.
Reality: Winter-applied manure will have nitrogen value! When manure is spread during cold weather and the soil has moisture, much of the nitrogen is held in the soil and is available in the spring.
As soon as soils warm up in the spring, a portion of the nitrogen in the organic fraction is released and is readily available to the growing crop. Nitrogen will be available to the next crop, even from surface applied manure when it is applied during cooler weather.
Myth #2: Manure spread in March and April will not be available to corn in June.
Reality: Again, nitrogen in manure comes in several forms including ammonium (NH4-N) and organic. As the soil warms up in the spring, up to half of the organic nitrogen converts to nitrogen that is readily available to the growing crop. If the manure was injected, this organic nitrogen is available along with most of the readily available ammonium fraction.
Myth #3: Manure is too variable to be a reliable source of nutrients for crops.
Reality: Manure is obviously more variable than fertilizer, but it can be managed for efficient crop production. Manure tests will estimate the amount of N - P2O5 - K2O that can be credited against the fertilizer recommendations. Agitation in storage prior to hauling manure to the fields improves the uniformity of nutrients. Take several manure samples as you are emptying a storage system and see how much the nutrients vary from the first loads to the latter loads.
It is important to spread manure as uniformly as possible. If the applicator makes an effort to spread a consistent distance, drive the same speed, and avoid random skips and overlaps, then the manure nutrients will be quite consistent.
Sand-laden manure stored in a pit will vary significantly in consistency and nutrient composition from beginning to end of emptying. Using the most common method of removal, skim and haul, will result in the first portion being pumped off as a liquid, a sloppy fraction in the middle and the remaining manure removed by tractor-loader and spreader. Take three manure tests from these three different fractions to evaluate where and at what concentration the nutrients are located. Many labs will test manure.
Myth #4: Manure nitrogen is in a form that is not available to plants
Reality: Corn and other crops cannot tell if nitrogen is coming from fertilizer, livestock manure or green manure cover crops. Manure contains several forms of nitrogen (organic and ammonium), and all forms of manure nitrogen ultimately convert to available forms of N for plants.
Myth #5: Manure is good for the soil to increase organic matter and tilth, but it should not be considered a nutrient source. Full rates of fertilizer should be applied to assure good yields.
Reality: Manure is a valuable source of nutrients that should be credited against fertilizer recommendations. Straw-packed manure does have less nutrient value, but the liquid systems that are common today are a valuable source of nitrogen, phosphorous and potassium. Manure application rates have a major effect on the amount of nutrients provided to the field. Obviously there is a big difference in nutrients per acre when manure is being applied at 3, 6, or 9 thousand gallons per acre. Test soil, manure test and calibrate manure application spreaders.