• manure cannot be spread during the growing season when annual crops are actively growing
• broadcast manure application onto perennial crops is not normally recommended due to a higher potential of runoff and the potential gaseous loss of nitrogen - the only exception is if liquid manure can be shanked directly into the soil
• spreading manure onto frozen soils is not recommended due to the possibility of runoff problems from rapid snow melt which can carry dissolved and solid manure particulate into surface waters, causing contamination

"When solid or liquid manure is broadcast onto soil, it is important to incorporate it into the soil the same day as it is applied," says Dr. Ross McKenzie, research scientist - agronomy, Alberta Agriculture and Rural Development, Lethbridge. "Incorporation is critical to reduce nitrogen losses to the air and prevent air quality concerns. The longer manure is left on the soil surface, the greater the nitrogen losses, which reduces the value of the manure as a nitrogen fertilizer. Also, the longer the manure is left on the soil surface, the greater the potential environmental concerns. Immediate incorporation of manure prevents potential runoff, making early spring or after harvest and before freeze-up in the fall the best times for manure application." 

Approximate dry matter and fertilizer nutrient composition of various animal manures

 
The best management practice (BMP) for liquid manure is to shank it directly into soil. This has the advantages of minimizing nitrogen losses and avoiding air quality concerns. In very special cases, liquid manure could potentially be applied through an irrigation sprinkler system at very low application rates; however, extreme care to prevent surface water runoff and nitrogen losses to the air, is required. Therefore, it is a practice that requires very careful management.

"It is difficult to put an exact value on manure because of the variability in nutrient content and because the nutrients are released over a period of years," says McKenzie. "Other benefits such as better soil tilth and reduced horsepower required to work the soil, are hard to quantify.

"However, if commercial nitrogen (N), phosphate (P2O5) and potassium (K2O) fertilizers have values of approximately $0.65, $0.60 and $0.40 per pound, respectively, and each ton of feedlot manure has a total N, P2O5 and K2O content of 21, 18 and 26 lb, respectively, then one ton of feedlot manure has a value of about $35. If manure is applied at 30 tons per acre, the value of nutrients applied in the manure would be about $1050 per acre. The total amounts of added N, P2O5 and K2O would be 630, 540 and 780 lb/ac. Keep in mind, however, that in the case of feedlot manure, only about a third of the N and about half of the P would become available in the year of application. A 30 ton/ac application rate should provide enough P2O5 and K2O to meet the requirements of a irrigated crops for 8 to 10 years. Then the only nutrient that would be required would be N in three to four years after manure application."

Producers within 10 to 15 kilometres of a confined livestock operation should consider using manure as a fertilizer source. The potential to purchase manure by paying for delivery and spreading has a double benefit. The confinement operator can dispose of extra manure and a nearby neighbour has the advantage of an excellent source of fertilizer for the cost of transportation. In addition, manure applied to eroded fields will also improve the physical quality of the soil. 

"When neighbouring farmers can take advantage of win-win situations like this, the whole agricultural community benefits," says McKenzie. "So - always make the most of manure!"

^{source: July 7, 2008 issue of Agrinews}