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Monitor Soil Nutrients for Best Use of Litter

by 5m Editor
14 September 2009, at 9:49am

US - Poultry litter can be a valuable source of crop nutrients but it is vital to monitor soil nutrients regularly to avoid the pitfalls of over-application.

Poultry litter can provide a significant supply of nutrients for crop production here in southeast Kansas, according to The Morning Sun.

Although southeast Kansas itself is not a large producer of poultry litter, you do not have to go very far east or south to find a good quantity of litter. Litter has been spread on fields and pastures in those areas for so long, they can no longer use it on most of that land because of a buildup of phosphorus in the soil. This build-up has lead to a risk of severe phosphorus runoff into lakes and streams of that area which can lead to serious water quality problems. The states of Oklahoma, Arkansas and Missouri have been forced to prohibit the use of litter in areas where the phosphorus has built up to high levels through this practice. This is a good thing for us here in south-east Kansas.

Nutrient concentration in poultry litter can be highly variable and depends mainly upon production conditions and storing and handling conditions. A laboratory analysis is the best way to determine just exactly what the nutrient content really is. Generally speaking, the three main nutrients would occur at about the same level in most poultry litter. An analysis of 60-60-60 [nitrogen-phosphorus-potassium] might be a good average for poultry litter being brought into the area.

There is a question of how quickly nitrogen and phosphorus becomes available after the litter is applied. Nitrogen primarily occurs in the organic form in litter and must undergo mineralisation in the soil to be available to the growing plant. A portion of this organic nitrogen may become part of the soil organic matter pool and become unavailable to the crop in the short term.

Field and laboratory studies suggest that 45 to 50 per cent of the nitrogen in litter becomes available to the plant in the first year. This value can vary depending on the composition of the litter and also whether it has been weathered or composted. For example, litter that has a high level of bedding material is going to be lower in nitrogen content.

Nitrogen lost from the volatile ammonium fraction at the moment of application to the soil surface can also reduce plant available nitrogen. Ammonium volatilisation is typically higher during windy and warm days. Incorporation of the litter immediately after spreading to conserve nitrogen is a critical part of this process.

The availability of phosphorus has been determined to be comparable to its availability in commercial fertilizer. Generally speaking, the phosphorus uptake by the crop will be less than either nitrogen or potassium. This means that if you are basing your application on the phosphorus requirement for corn or wheat, it is likely that there will have to be additional nitrogen applied along with potassium since the litter will not fit the requirement. Conversely, if you are applying the litter to fill the need for nitrogen for the crop, then the amount of phosphorus applied will most likely exceed the need and the same could be true for potash.

It is likely that farmers in the area will be using increasing amounts of litter as time goes by. To avoid accumulating too much phosphorus in the soil over time, it would be very wise to monitor those levels through soil tests. Over a period of years it is possible that we could run into the same problem here as they have in the areas where the litter is coming from.

As a side note, the Morning Sun article concludes that there are a few farmers in the area who are producing organically grown products and they are using litter as their only source of nitrogen, phosphorus and potassium. This is because they cannot apply any type of commercial fertilizer and still retain their organic status. And as I stated above, this requires using much more litter and this certainly could rapidly lead to excessive amounts of phosphorus in runoff and ultimately, regulation by the state. The need to monitor soil test levels in these cases cannot be overstated. It is a complicated world we live in now days.