NITROGEN AVAILABILITY FROM COMPOSTS AND BLENDS OF COMPOSTS AND FERTILIZERS

A study was conducted to compare the nitrogen (N) availability of blends of biosolids compost or municipal refuse-biosolids cocompost with urea(U) or NH₄NO₃(N) fertilizers to fertilizer alone on growth and N uptake of tall fescue (Festuca arundinacea L.). Blends which provided 0, 16.7, 33 or 50 % of the N kg^-1 application rate as compost N and 100, 83.3, 67 or 50% as fertilizer N were added to Sassafras soil (Typic Hapludults). Study 1 had a 150 mg N kg^-1 application rate and study 2 had 120 mg N kg^-1. Compost N mineralization was assumed to be 10% and comparisons were made on a fertilizer N equivalency basis.
Yield and N uptake from blends of biosolids compost or municipal refuse-biosolids co-compost and NH₄NO₃ were not different from the equivalent NH₄NO₃ treatment.
In study 2 which compared blends of biosolids compost and either urea (U) or NH₄NO₃(N) to fertilizer alone, yield and N uptake were not different from the equivalent fertilizer treatment with one exception.
Yield and N uptake from 50% NH₄NO₃ -50% biosolids compost blend were greater than the equivalent 66 mg NH₄NO₃-N kg^-1 treatment.
Compost fertilizer equivalent based on a 10% organic nitrogen mineralization rate was accurate in blends with fertilizer.
Greater yield and N uptake than predicted were seen when NH₄NO₃ content in the fertilizer compost blend was below 88 mg N kg^-1 and did not mask the additional benefit of compost amendment.
When an approximate N mineralization rate for compost is known, it is possible to formulate blends with fertilizer that will predictably support crop growth.

International Symposium on Composting & Use of Composted Material in Horticulture

L. J. Sikora

fertilizer equivalents, N mineralization rate, blends

https://doi.org/10.17660/ActaHortic.1998.469.37