Organic Matter and Sustainability - Sustainable Management of Soil Organic Matter - page 26

R.H.Ellerbrocket al. FT-IR Studies onSOM

1.2

FT-IR Studies on Soil Organic
Matter from Long-term Field
Experiments

R.H. E LLERBROCK , A. H ÖHN AND H.H. G ERKE

Center for Agricultural Land Use and Landscape Research e.V.
ZALF,EberswalderStr. 84, D-15374Müncheberg, Germany

Introduction

Soil organic matter (SOM) is affected by the type of land use which, in
turn, determines the organic matter turnover, and the water, and nutrient
cycling. Körschens and Müller (1996) found significant correlations
between management practice and crop yield as well as organic carbon
(C org ) and total nitrogen (N t ) content in the soil of a 100-year-old fertiliza-
tion experiment. In addition to the SOM content, the SOM composition
can be affected by the type of land use and soil management practices. In
this chapter, SOM composition is defined as the variety and quantity of
functional groups (e.g. carboxyl and hydroxyl groups). These functional
groups play an important role in the sorption of solutes in the soil, such as
plant nutrients or contaminants (Stevenson et al ., 1982). Fourier transform
infrared (FT-IR) spectroscopy can be used for the characterization of soil
organic matter (Stevenson, 1982). Celi et al . (1997) showed that the con-
tent of carboxyl groups of SOM can be determined by FT-IR spectroscopy
via integrating the area below the absorption band of the C = O group at
1700 cm −1 . For a long-term field experiment located on a sandy soil, the
contents of the carboxyl and hydroxyl groups in the sodium pyrophosphate
extracts of soils from plots fertilized with cattle manure were found to be
higher than in those from plots that received straw + mineral nitrogen
(Ellerbrock et al ., 1999a). The hot water-extractable SOM from a sandy site
was found to be not significantly influenced in composition by the type of
fertilization (Ellerbrock et al ., 1999b). This was assumed to be caused by
the relatively low application rate of organic fertilizer (32 dt ha −1 year −1 ). In