Biosolids Application to Agriculture
Utilizing Biosolids Analysis to Meet Crop Nutrient Needs

Bulletin 879-99

3. Determine application rate by nitrogen balance.

Determine the following:

• Organic nitrogen - mineralization rates are adjusted according to digestion process and the time of year. Typically 30 to 33 percent of the organic nitrogen applied is available to the plant in the year of application, as per Table 3 and Table 4.
  
• Ammonium nitrogen - efficiency factor 0.50 if surface applied in November - February. Assume all of the ammonium nitrogen is available in year of application if incorporated or injected immediately and plants are actively growing.
  
• Nitrate nitrogen - immediately available to the plants.

Determine amount of nitrogen available from mineralization of previously applied organic nitrogen and crop. Utilize Table 2 to determine nitrogen credits from the previous crop and subtract these credits from the nitrogen requirement. Some soil testing laboratories automatically adjust nitrogen recommendations based on the previous crop. Be sure to ask the lab analyzing your soil if they have accounted for nitrogen credits in their recommendations.

The amount of ammonium nitrogen available will vary greatly depending on temperature and whether or not the biosolids are incorporated. From our analysis the following levels of nitrogen exist:

Ammonium nitrogen = 5.58 lb/ton
T.K. nitrogen = 43.76 lb/ton
Organic nitrogen = 43.76 - 5.58 = 38.18 lb/ton
Organic nitrogen = T.K. nitrogen - ammonium nitrogen