Agriculture Reference
In-Depth Information
as: elemental and functional groups composition, ratio of absorbance measured at
465 and 665 nm (E4/E6), molecular weight distribution, electrophoresis and elec-
trofocusing, pyrolysis-gas chromatography-mass spectrometry (GC-MS), infrared
and Fourier transformed-infrared (FT-IR) spectroscopy, electron spin resonance
(ESR) spectroscopy and fluorescence spectroscopy (Moral et al.
2009
). Amongst
these methods, advanced techniques such as NMR, FT-IR and pyrolysis have been
employed to achieve a better understanding of the structural changes of the OM dur-
ing composting and hence to evaluate composting efficiency and compost maturity
(Chen
2003
). However, these humification parameters depend on the type of waste
used for composting and their same value cannot be used for all type of composts.
5.3.3
Biological Parameters
Biological methods are widely used to assess the compost maturity. These param-
eters are comparatively more reliable than the other parameters.
5.3.3.1
Germination Test
The application of immature compost to arable soil may inhibit seed germination
and or reduce the root length of seedlings due to the creation of reducing conditions
in the soil and the presence of phytotoxic compounds in the compost. Based on this
fact the germination test has been developed to determine the degree of maturity, GI
was calculated using the following expression (Zucconi et al.
1981
):
GI
=
Percent seed germinationmean root length
×
They used cress seeds (
Lepidium sativum
) because of their quick response for deter-
mining the presence of phytotoxic substances in the compost. The proposed value
of GI above 50 % is an index to judge maturity of compost. Some workers also stud-
ied the plant growth test (assessment of top growth and sometimes root biomass)
and found that growth of plants inhibited by immature compost (Inbar et al.
1993
;
Iannotti et al.
1994
; Chefetz et al.
1996
). Zucconi and de Bertoldi (
1987
) discussed
the differences between the seed germination and growth tests. Germination tests
provide an instant picture of phytotoxicity, whereas growing test will be affected
by continuing changes in the stability or maturity of the compost tested: there may
be damaging effects on growth in the earlier stages, but beneficial effects later on,
with different conclusions depending up on time of assessment. According to Zuc-
coni et al. (
1981
), a GI value of 80 % has been used as an indicator of disappearance
of phytotoxicity in composts. Tiquia et al. (
1996
) used this value not only as an
indication of disappearance of phytotoxicity, but also an indication of maturity of
compost. However, Antil and Raj (
2012
) reported a lower value of GI (> 70 %) as a
maturity index of composts prepared from wide range of organic wastes. Ko et al.
(
2008
) reported that the compost having GI value > 110 % was considered mature
