Manure is a wonderful nutrient source for crops, and though it will not completely replace the need for commercial fertilizer, manure can save money by having to purchase less fertilizer. However, getting the most from manure applications can be complex. Soil needs, timing, crop needs, and application methods and rates can all impact how manure should be used as a fertilizer.
Soil Needs
Manure provides many nutrients for crops, including nitrogen (N), phosphorus (P), and potassium (K). When manure is readily available, balancing application for P use is the best economically because the crops use all nutrients. However, this will most likely lead to the need for commercial N.
Often, N is balanced before P and K because N needs are highest in corn. Balancing for N alone will lead to oversupplying the soil with P and K. Nitrogen exists in organic and inorganic forms. Organic N is not available to plants, while inorganic N is broken down and available to plants as ammonium and nitrate. Application methods can impact N availability.
Manure Application
Broadcasting (spreading with a spreader) or injecting manure both have their benefits. Spreading manure is cheaper and can be done much faster. However, spreading manure can lead to less N efficiency. Ammonium losses are higher in broadcasted manure because ammonium is converted to ammonia gas. Nitrogen availability ranges from 20 to 40% throughout the year. Availability increases to 50 to 55% when injected. Though injecting manure can lead to more N and reduce odor, injecting requires more time, horsepower, and fuel.
Application rates should meet the demand of the crop to be grown. Maximum lbs of plan-available N should range from 80 to 195 lbs per acre, depending on the prior plant harvested from the land. On the other hand, soybeans use approximately 3.5 lbs of N per bushel harvested, meaning manure application can be 210 lbs per acre with a 60 bu/acre soybean yield.
Environmental Stewardship
Each state has its own laws and regulations for manure application. Be sure to review your state’s Nutrient or Waste Management plans. Over-application of manure can impact soil and water health. Whether balancing application rates for P or N, applying over soil needs will likely not lead to greater crop yields. Test soil regularly to determine the proper soil nutrient needs.
No one knows better than you that the future of your farm depends on balancing practices and profits that sustain your land, resources and family. The stakes are evolving based on weather patterns, technology, market demand and more. What actions are you taking to remain resilient?
