PRIMGHAR, Iowa — One of the advantages of raising pigs is the waste. Manure from swine barns is a valuable source of crop nutrients. In high yielding row crop intensive regions like northwest Iowa, the role of swine manure as a crop nutrient source has increased in value, replacing the purchase of increasingly expensive commercial fertilizer by providing the nutrient needs of crops.
Nutrients from manure are recycled to fertilize high yielding crops in an environmentally friendly, synergistic system. The nutrients in manure that crops require include nitrogen, phosphorus, sulfur and various micronutrients.
Manure will tend to improve soil organic matter. In fact, manure is a sought-after nutrient source because it usually increases yield. There are tradeoffs, for example the odor of manure. However, mitigation of manure has been researched and more options are available. One prominent technology is manure injection. Injection of liquid manure reduces emissions of ammonia and odors by up to 90% over broadcasting alone.
Access to the value of nutrients in manure is important to the pig grower. However, as the energy cost of swine diets has increased, feeding programs have dramatically changed.
Changes in ingredient composition have changed from manipulations of dietary formulations. These changes can alter the nutrient composition of the resulting manure and thus the nutrient value of the manure as fertilizer. A swine nutritionist can reduce the nitrogen (N) level in manure by 40 or 50% or they can increase the N level by 76%.
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The broader analyses producers should think about is comparing feed savings from diet manipulation to loss or gain of manure value from that manipulation. Diets that should be evaluated include low protein synthetic amino acid addition, phytase addition, and DDGS diets.
Consideration of the manure composition is important for two reasons. First, as the cost of hauling manure increases it is possible application charges could exceed nutrient value. Second, as the nutrient content in the manure changes, application rates should be adjusted for optimizing fertilizer rates for crops. Those who haul manure can check the ISU nitrogen calculator at http://extension.agron.iastate.edu/soilfertility/nrate.aspx/
Producers will also adjust manure application rates based on a representative manure nutrient test. The calculation of the value of swine manure can be calculated from a downloadable decision aid spreadsheet at extension.iastate.edu/agdm/livestock/html/b1-65.html/
The Trust Project
