The Role of Soil Organic Matter and Manures in Sustainable Nutrient Cycling - Sustainable Management of Soil Organic Matter - page 298

Table 4.10.5. Bivariate correlation between spring wheat yields with composted farmyard
manure (Y1) and mineral fertilization (Y2) at three fertilization levels; results of four replicates and
14 years, n= 55 (P< 0.05).

Fertilization Major axis regression Confidence limits for the slope b

Low Y1 = 5.786 + 0.815 Y2 0.596 < b < 1.092

Medium Y1 = 16.925 + 0.550 Y2 0.333 < b < 0.816

High Y1 = 15.956 + 0.620 Y2 0.416 < b < 0.868

to compensate for poor environmental conditions and yielded up to 10 dt
ha −1 more than the mineral treatments. Possible compensation mechanisms
may include increased root growth with manure fertilization (reported by
Bachinger, 1996 for CFMBD) or modified morphological characteristics
and yield components (studied by Boemer-Schulte, 1992 in this trial).
With respect to global climate change, currently there is a debate on
whether soils can be either a source or a sink of atmospheric carbon dioxide
(IPCC, 1996; GACGC, 1998). The issue of which conditions can switch a
source to a sink and vice versa is of special interest. A recent study in
the USA reported that SOM is increased by organic farming methods
(Drinkwater et al ., 1998). The authors describe organically managed soils
as a substantial carbon sink for carbon dioxide from the atmosphere. The
manure treatments in our trial contain 3.6-8.4 t ha −1 more carbon in the
topsoil than the corresponding minerally fertilized plots. These differences
are several times higher than those reported in the USA study. However, in
contrast to the American experiment, the C org differences in our trial are the
outcome of varying degrees of reduction, not of humus accumulation. Even
the soil fertilized with farmyard manure was a carbon source, though to a
much lesser extent than the minerally fertilized soil. Carbon losses could
only be avoided when farmyard manure application was combined with the
biodynamic preparations. Probably the effect of a treatment depends upon
the pre-history of the soil. We intend to investigate this matter in more
detail, although its relevance to the atmospheric carbon dioxide budget is
limited.

References

Abele, U. (1987) Produktqualität und Düngung - mineralisch, organisch,
biologisch-dynamisch. Angewandte Wissenschaft , Heft 345, Hiltrup, Münster.
Anderson, J.P.E. and Domsch, K.H. (1978) A physiological method for the
quantitative measurement of microbial biomass in soils. Soil Biology and
Biochemistry 10, 215-221.