Soil and water scientists with Alberta Agriculture have completed a three-year study that measured phosphorous release rates from composted cattle manure.
Soil samples were collected from three fields involved in a potato rotation.
One of the fields had received a variety of rates of compost in 1999, one in 2000 and one in 2001.
Results indicated that release rates in the zero to 15 centimetre depth range for nitrate nitrogen averaged five percent in the first year, one percent in the second and two percent in the third.
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For phosphate phosphorus the rates were three percent in the first year, 15 in the second and 25 percent in the third; and for potassium the rates were 17, 39 and 26 percent.
Overall, nutrient release rates showed a decline with increasing compost application rates. Nutrient release rates were lower and later than expected, likely due to the colder climate and shorter growing season found in southern Alberta.
No changes in organic matter were observable with these single applications of compost. The high degree of variability in soil characteristics such as texture, moisture and fertility, combined with the high degree of variability in application rate of compost across a field, made studying the field scale nutrient release rates of compost difficult.
The authors recommend more study to determine accurate nutrient release rates, specific to the southern Alberta climate. Long-term plot scale and field scale research is suggested for a variety of crops, soils and field conditions.
The full study results, including charts and graphs, are available at www.producer.com by clicking on links in the news.
