With lower commodity prices and tighter margins, many growers are taking another look at the “original” fertilizer. Manure is no longer considered a waste. The value of manure nutrients in real dollars can be large, even if it is a smelly solution!
Accurate information is the most important part of calculating the value of manure and proper application rates. Have your manure and soil tested! Using the “book” values for manure nutrients when budgets are tight is not a good management plan. Variability in manure sources is tremendous, and manure testing allows you optimize manure application.
The manure samples we test at AGVISE Laboratories have a wide range of nutrient amounts. Management practices, feed rations, storage, time of year, and many other factors influence the amount of nutrients in the manure at hauling. In liquid swine manure, the highest phosphate-phosphorus content was 120 lbs/1000 gallons, the lowest value was less than 1 lb/1000 gallons. The average swine manure phosphate-phosphorus content was around 18 lbs/1000 gallons. For poultry manure, the total nitrogen ranged from 26 lbs/ton to 143 lbs/ton with an average total nitrogen around 58 lbs/ton. With so much variability, how could anyone not afford to have manure tested? Here are some points to consider when making manure applications:
Determine the nutrient value of the manure. Have the manure tested and then calculate the nutrients that will be available to crops depending on the application method and timing of incorporation. Remember to consider the cost of the micronutrients, such as zinc only, in the manure if needed for the crop. If you are applying 200 lbs/acre of potassium and the field only needs 50 lbs/acre, calculate the value based on 50 lbs/acre. Deduct application costs associated with handling and hauling manure that are above the costs of applying commercial fertilizer.
Determine the needs of the field. After having soil tests done, determine which fields would benefit most from manure application. Typically, very low testing fields benefit the most from manure applications. Manure is not like commercial fertilizer where you can order a custom blend. In many cases, several nutrients in the manure will be in excess of the crop need. Nutrients like phosphorus and potassium can be built up for future crops, but caution needs to be taken so these levels do not become excessively high. Applying manure before corn in a corn-soybean rotation takes advantage of extra phosphorus and potassium. Matching the field to the manure supply will also give the most economical use of the nutrients.
Regulations have mandated testing manure in some areas, but the current price situation for fertilizers and commodities make manure a good choice when it is available. Many growers are putting this valuable nutrient resource to good use!