Science and nitrogen use efficiency

Nitrogen use efficiency (NUE) is a term maintaining its currency. Worldwide, NUE is 33%. Once a concern primarily due to groundwater quality and health concerns, rising natural gas prices have moved economic concerns to the forefront. Economics must certainly have resonated in the government NUE workshop "Roadmaps to more N efficiency" held in Germany recently and mentioned in a previous article. Climate change concerns have increased interest as well as the availability of grant funding for research. NUE is affected by many factors: fertilizer form and placement, irrigation management, climate, soil characteristics and CO2 levels.
Nitrogen loss due to denitrification is caused by microbial respiration when soil oxygen levels are depleted. It is negligible in some parts of the planet and the dominant form of loses in others. This from the University of Kentucky, somewhat buried in an article about economic concerns:

Worldwide nitrogen use efficiency is only about 33 percent, so 33 percent actually makes it into the crop. A lot of nitrogen is applied that never gets used by the crop. In the United States, the rate is 50 to 60 percent, but still half the nitrogen never makes it to the crop.

In Kentucky the biggest loss of nitrogen comes from denitrification, when nitrate is converted to nitrogen gas and dissipates into the air. By controlling denitrification, a farmer can potentially reduce the amount of nitrogen needed to produce a crop.

The other forms of reduced efficiency are leaching of nitrate and volatization of ammonia. Part of the loss to percolation can be attributed to uniformity of application and even off-target losses. Necessary to complete a zero-sum balance point of view is accounting for microbially fixed nitrogen, and changes in soil biomass,both microbial and plant roots.
Those of us who work in support of permitted land application of waste water and waste water solids are very interested in advances in understanding of NUE. Our client projects are generally held to a land treatment capacity based on a design philosophy that an NUE of 100% is a reasonable target, the legacy of a simpler time in history. With the higher level of information and better technology available today, this simplistic design standard may well be approaching the end of its useful life.

Tech Tags: soil science fertility nitrogen-use-efficiency nitrogen denitrification management research government environmental economics farm survival agriculture crop waste recycling

German science workshop news critical of precision agriculture performance

A German soil science research center reports that Precision Agriculture has not delivered on promised benefits, stating:

...worse are the actually reported effects of ..."Precision Agriculture" (PA) ...on N efficiency. Still after 15 years of implementation no results proving consistent increases in yields or decreased fertilizer application are available. Quite the contrary: some of the techniques developed in PA may even decrease fertilizer N efficiency...

The Federal Agricultural Research Center (FAL) - Institute of Plant Nutrition and Soil Science's workshop, Options for reducing the nitrogen surplus in plant production, has individual presentation pdf files available, including the one on PA.

Tech Tags: soil science fertility farm productivity dairy waste management manure efficiency environment GPS data analysis precision agriculture workshop news

Tetany animal health issue and soil, hay links

Tetany is a complex disease in that no specific condition triggers it in all cases. Gauge tetany risk using soil and tissue analysis when growing or feeding hay comprised solely of cool-season grasses. A grass-legume mix does not have this risk.

Tetany is a disease affecting ruminants and is associated with feeding or grazing bluegrass, bromegrass, fescue, orchardgrass, ryegrass, timothy and wheatgrass. It is caused by low blood levels of calcium and/or magnesium. Classic risk conditions occur when the forage grass is growing quickly in the spring and nitrogen levels are high. Less well known is that tetany can be a problem when hay is grown on soils with excessive soil potassium. Manure and potassium hydroxide cleansers are two potential sources. Lactating animals are more susceptible to tetany, thus dairies are particularly alert to the concern and tend to avoid growing or feeding grass hay exclusively. Forage guides may not mention it as a concern. A forage tissue ratio of K/(Ca+Mg) of more than 2.2 indicates a high risk of tetany and the need to supplement feed with magnesium (Mg) (see also). If an animal goes down and tetany is suspected, a veterinarian should be contacted for immediate treatment. Often an animal will recover if it can be given an injection of magnesium sulfate (Epsom salts) early on.

Preventative Mg feed supplement and the ready supply of alfalfa tends to keep the incidence of tetany to a minimum. My thought is that tetany is additionally controlled by the close knit nature of farm communities. Caring neighbors and long memories tend to interact sufficiently that tetany symptoms don't take more than an animal or two, usually the weakest anyway, before it is figured out. Perhaps this explains why analytical laboratories in my region are generally unaware of tetany or the role of soil and tissue nutrient levels. My opinion is that cooperative extension publications in the Pacific Northwest can do better in this area. Tips for preventing animal loss due to tetany should be included in the fertility guides published to help folk interpret forage test results.

See also:
Spring Mineral Considerations by Jeff Heldt (link added 03MAR06)
Controlling Grass Tetany in Livestock, by Cooperative Extension, New Mexico State University, available in pdf format

Tech Tags: soil science animal nutrition environment chemistry dairy manure farm waste recycling land treatment information