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ARS Home » Southeast Area » Auburn, Alabama » Soil Dynamics Research » Research » Publications at this Location » Publication #229851
Title: Nitrogen immobilization in plant growth substrates: clean chip residual, pine bark and peat moss

Author
item BOYER, CHERYL - AUBURN UNIVERSITY
item Torbert, Henry - Allen
item GILLIAM, CHARLES - AUBURN UNIVERSITY
item FAIN, GLENN - AUBURN UNIVERSITY
item GALLAGHER, THOMAS - AUBURN UNIVERSITY
item SIBLEY, JEFF - AUBURN UNIVERSITY

Submitted to: International Journal of Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/2012
Publication Date: 5/19/2012
Citation: Boyer, C.R., Torbert III, H.A., Gilliam, C.H., Fain, G.B., Gallagher, T.V., Sibley, J.L. 2012. Nitrogen immobilization in plant growth substrates: clean chip residual, pine bark and peat moss. International Journal of Agronomy. Vol. 2012, Article ID 978528, doi:10.1155/2012/978528.

Interpretive Summary: Pine bark is the substrate use by the horticulture nursery industry as a potting substrate. Competition for pine bark from various industries and high shipping costs has lead to a serious need to develop alternative substrates for the industry. However, there has been concern that N immobilization in other substrates could potentially limit their use. A study was undertaken to determine the extent of nitrogen (N) immobilization in a high wood-fiber content substrate (clean chip residual (CCR)). Control treatments of pine bark (PB) and peat moss (PM) were compared to two screen sizes (0.95 cm and 0.48 cm) of CCR in a 60 day incubation experiment. This study suggests that N-immobilization in substrates composed of CCR is similar to that of PB and can be treated similarly with fertilizer amendments in a nursery setting.

Technical Abstract: A study was undertaken to determine the extent of nitrogen (N) immobilization and microbial respiration in a high wood-fiber content substrate (clean chip residual (CCR)). Control treatments of pine bark (PB) and peat moss (PM) were compared to two screen sizes (0.95 cm and 0.48 cm) of CCR for microbial activity and N availability in a 60 day incubation experiment. Four rates of supplemental N (0, 1, 2, and 3 mg N) were added to each of the four substrates in the study. Samples were adjusted to similar moisture contents, treated with fertilizer and placed in a jar containing 10 ml water to maintain humidity. The jars were placed in a dark incubation chamber at 25° C for 60 days. Four samples of each treatment were removed at 7, 15, 30 and 60 days after treatment and evaluated for microbial activity and N content. In general, PM had very little microbial respiration over the course of the study, regardless of supplemental N rate. The smallest sized CCR (0.48 cm) had the most respiration, followed by the larger CCR size (0.95 cm) and PB. Respiration generally increased with increasing N rate. Total inorganic N (plant available N) was greatest with PM. With both screen sizes of CCR and PB, the total inorganic N was generally similar within the 0, 1, and 2 mg supplemental N treatments. A significant increase occurred with the highest rate of supplemental N. Clean chip residual and PB were also generally similar in available N when compared to PM. This study suggests that N-immobilization in substrates composed of CCR is similar to that of PB and can be treated similarly with fertilizer amendments in a nursery setting.