Tag: manure

Posted on

What’s the P Index?

The P Index is the Phosphorus Index, a risk assessment tool to quantify the potential for phosphorus runoff from a field. The P Index helps to target critical source areas of potential P loss for greater management attention. It includes source and transport factors. Source factors address how much P is available (for example, soil test P level and P fertilizer and manure application amounts). Transport factors evaluate the potential for runoff to occur (for example, soil erosion, distance and connectivity to water, soil slope, and soil texture). The P Index allows for relative comparisons of P runoff risk. When the P Index is high, recommendations are made either to apply manure on a P basis or not to apply manure at all. When the P Index is low, manure can be applied on a N basis. Also, if the P Index is high, the factors that are responsible for the higher risk of P loss are identified, and this information provides guidance for management practices to reduce the risk. For example, if the P Index is high because of high soil erosion, a recommendation to implement soil conservation best management practices (BMPs) may lower the risk and allow safe manure application.

For additional information:

To find your state’s P Index, do a web search for “phosphorus index” plus your state name.

Author: Jessica Davis, Colorado State University

Posted on

What are typical values for the higher heating value of manure scraped from cattle feedyard surfaces?

The higher heating value of manure scraped from cattle feedyard surfaces depends primarily on its ash and moisture content. If the manure’s ash and water were completely removed with only the combustible fraction remaining as a residue, that (primarily organic) residue would have a higher heating value (HHV) of about 8,500 BTU per pound, as determined experimentally by Annamalai et al. (1987) and Rodriguez et al. (1998). That figure of 8,500 BTU/lb is known as a “dry, ash-free” (DAF) fuel value. To estimate the HHV of actual feedyard manure (i.e., in its “as-received” or “as-is” state), which always has some ash and some moisture in it, you can multiply the 8,500 BTU/lb figure by (1 – ash) and (1 – moisture). In this case, “ash” is the manure’s ash content expressed as a fraction (dry basis), and “moisture” is the manure’s moisture content as a fraction (wet basis). For example, a manure sample having 40% ash (dry basis) and 20% moisture (wet basis) would have an HHV of approximately: HHV(ash = 40%, moisture = 20%) = 8,500 BTU/lb x (1 – 0.40) x (1 – 0.20) = 8,500 x 0.6 x 0.8 = 4,080 BTU/lb Cattle manure (as excreted) has about 75% moisture and 15% ash, which translates to an HHV around 1,750 BTU/lb. On the feedyard surface, it generally dries out and may reach moisture contents as low as 15 to 20%. Depending on whether the corral surfaces are paved or native soil, the ash content may increase dramatically. HHV values between 2,000 and 5,000 BTU/lb are common, but they are highly variable because of moisture and ash dynamics of these outdoor facilities. Fuel value of manure generated in full confinement?under roof, on concrete?can be more tightly controlled.

Other cited literature:

Annamalai, K., J. M. Sweeten and S.C. Ramalingam. 1987. Estimation of gross heating values of biomass fuels. Transactions of the ASAE 30(4):1205-1208. Rodriguez, P.G., K. Annamalai, and J.M. Sweeten. 1988. The effect of drying on the heating value of biomass fuels. Transactions of the ASAE 41(4):1083-1087

 

Posted on

How can I prevent leaching of nitrate into groundwater from manure applications?

Nitrate contamination of groundwater occurs when excess nitrate in the soil profile moves along with water that is moving down past the root zone of the crop. In most cases, it is not possible to keep water from moving past the roots, so the only other option for preventing nitrate leaching is to avoid having excess nitrate present in the root zone during times when leaching events are likely to occur. Determine the available nitrogen content of manure prior to application, and don’t apply more available nitrogen than the crop can use. Make the applications as close to the time the crop will use the nitrogen as possible.

Although only available nitrogen is subject to leaching, organic form nitrogen will become available as it mineralizes, at which time it too can leach if not utilized by the crop. The amount of nitrogen that will mineralize prior to and during the crop season should be taken into account when calculating manure application rates. If significant mineralization from previous applications is expected, plan to have a crop present to utilize it prior to leaching events.

Posted on

Making Sense of Treatment Technology Options for Livestock Farms

Have you ever wondered whether manure should be treated on your livestock operation? What technology will work best in your situation? This webinar discusses strategies for selecting the right technology to meet your farm’s needs and reviews some proven and emerging technologies that are showing promise for the dairy industry. This presentation was originally broadcast on February 16, 2018. More… Continue reading “Making Sense of Treatment Technology Options for Livestock Farms”

Proudly powered by WordPress