Animal manure is a good source of organic matter for crops and can contribute a significant amount of nitrogen (5 lbs./ton), phosphorus (3 lbs./ton) and potassium (5 lbs./ton). However, on average, farmyard manure contains only 0.03 lbs. of boron (B) per ton. Nutrient content should be determined by testing the manure.
- Animal manures contain varying concentrations of most plant nutrients.
- The average boron content of animal manure is 0.03 lbs./ton.
- Assuming an application rate of 10 tons/acre, the resulting boron rate of 0.3 lbs./acre may not be sufficient for high-boron requiring crops, such as alfalfa.
- Supplemental boron applications should be based on yield goals for the specific crop and on results of soil tests and/or plant analyses.
Normal rates of manure do not usually exceed 10 tons per acre. Assuming that all of the B in the manure would be available to plants, 10 tons of manure would supply only 0.3 lbs. of B. This rate of B per year will not supply alfalfa and other crops with their total B requirements.
The B content of manure may be even lower. Early studies in Connecticut showed that a ton of mixed cattle manure might contain only 0.006 lbs. of B, or only one-tenth as much B as is in a ton of alfalfa hay. Poultry manure contained as little as 0.01 lbs. of B per ton.
In a long-running series of alfalfa experiments in Storrs, Connecticut, stable manure applied at 10 tons per acre annually reduced the prevalence of B deficiency only slightly, as shown by soil and plant tissue test results.
Treated poultry litter may be an exception
Untreated poultry manure contains about the same amount of B as other manures, but in some cases, B materials are applied to poultry manure for control of insects. Based on the maximum rate of B applied and manure produced, B-treated poultry manure will normally contain approximately 0.7 lbs. of B per ton.
If it is assumed that all of the B in the manure is available to plants, 4 tons of poultry manure (the average application rate) would supply 2.8 lbs. of B. This rate of B per year would meet most crop needs. Unboronated poultry manure, however, contains only about 0.03 lbs. of B per ton and the 4-ton rate would not supply crop needs.
Boron analyses of liquid waste management systems by Dr. Mark Flock of Brookside Laboratories, Inc. showed an average of 0.04 lbs. of B per 1,000 gallons of hog and dairy waste. This translates to 0.01 lbs. of B per ton of liquid manure and 0.06 lbs. of B per ton of fresh hog, poultry and dairy manure (wet basis). Again, these levels of B would not be sufficient to supply most crop needs.
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