Tuesday, April 19, 2016

Beef Manure Management Systems - Manure Quality

Manure quality is dependent upon management practices and the manure handling system. Though we can adjust an animal’s diet through practices like phase feeding or supplementing specific amino acids, generally only 10-20% of the nitrogen and phosphorus fed to an animal is retained by the animal. The majority of the nutrients are excreted in the manure. Depending on the type of finishing site and your goals as a producer, there are different ways to evaluate manure quality.

At finishing sites, manure handling systems can be separated into 3 types: open lots (concrete lot and earthen lot), deep pit confinement barns, and bedded confinement facilities (hoop barns and monoslopes). While we start with roughly the same amount of nutrients in the manure of the animal, the way the manure is stored, treated, and handled can lead to drastically different nutrient contents. For example, though open lots and bedded confinement facilities both have solid manure, the amount of bedding used in each facility varies greatly. More bedding is used in a confinement facility to absorb liquids than in an open lot.

Beef finishing cattle on a fresh bed pack. Photo credit:  Rachel Klein, Ag & Natural Resources, ISUEO 


Another consideration is that nutrients can be lost between the time the manure is excreted and it is land applied. In the case of nitrogen, in an open lot, 50-70% of excreted nitrogen can be volatilized, or lost as a gas, while it sits between cleanings. In a bedded confinement urine is soaked up quickly with the bedding, reducing nitrogen volatilization to around 30%. In a deep pit barn since the manure is a liquid, it is easier for the free ammonia to be volatilized. However, since the manure in these storages have small surface area, losses of 15-30% of excreted nitrogen can be expected.

The amount of manure generated by each system varies as well. In general, an open lot typically generates 3.5 tons of manure per cattle per space. However, this number varies greatly due to weather conditions, management practices, site locations, and the moisture content of the manure when scraped. A deep pit systems averages about 6.5 gallons per head per day or about 10 tons of manure per space.  In a bedded confinement, around 6 tons of manure produced each year, assuming it is around 30% dry matter for bedding use.

The summary table below provides an idea of how much of the nutrients are retained in the different manure handling systems.  Deep pits have the advantage, as they hold onto more of the nutrients, but bedded confinements closely follow with the amount of nutrients retained. 

Facility Type
Total N
Lbs/space-year
P2O5
Lbs/space-year
K2O
Lbs/space-year
Open Lot (runoff not included)
66
48
54
Bedded confinement
98
57
58
Deep pit
94
59
82
Excreted
122
68
93


Which system you select is also dependent on your application goals. If you are moving manures a long ways, solid manures might be better because they are more nutrient dense, but sometimes liquid manure systems are nice because they are easier to automate.

Beef finishing cattle on an open lot. Photo credit:  Rachel Klein, Ag & Natural Resources, ISUEO