The Role of Soil Organic Matter and Manures in Sustainable Nutrient Cycling - Sustainable Management of Soil Organic Matter - page 296

omitting the preparations gave lower C org values. The effect of fertilization
levels depends significantly upon their type. Whereas increasing amounts of
mineral fertilizer had no effect upon SOM content, higher levels of manure
fertilization preserved higher organic carbon contents. C org differentiation
set in during the first years of the trial between 1980 and 1983/84 (values
presented by Bachinger, 1996). In all treatments, C org levels have now been
fairly constant for > 10 years.
Bachinger (1996) investigated soil microbial parameters in 1988-1991.
As an example, the results of 1989 are shown in Table 4.10.3. The treat-
ments with high and constant humus values also had the higher biological
activity. Protease and dehydrogenase activity as well as microbial biomass
(chloroform fumigation extraction) were more pronounced in the manure
than in the mineral treatments. A further study found higher amino acid
contents in the manure compared with the mineral treatments (Scheller
et al ., 1997). This is an indication of the important role of farmyard manure
and amino acids for humus synthesis.
Crop yield (Table 4.10.4) did not show the same pattern as soil para-
meters. Whereas spring wheat gave the same yield with all types of fertilizer,
winter rye had 33% and potatoes 10% higher yields with mineral than with

Table 4.10.3. Averages of soil microbiological parameters in topsoil by type and level of
fertilization; results of 1989 (Bachinger, 1996).

Fertilization CFM CFMBD MIN Low Medium High

PA 1 0.27 b 0.26 b 0.20 a 0.25 a 0.25 a 0.23 a

C mic 2 34.9 b 37.8 b 26.1 a 30.6 a 34.1 a 34.2 a

DHA 3 109.1 b 121.9 c 75.9 a 94.5 a 103.8 a 108.6 a

a,b,c Mean values within a half-row with superscript different letters are significantly different
(P< 0.05).
1 Protease activity (mg g − 1 Tyr); method of Ladd and Butler (1972).
2 Microbial biomass (SIR; mg 100 g − 1 C); method of Anderson and Domsch (1978).
3 Dehydrogenase activity (

g 10 g − 1 TPF); method of Thalmann (1967).

µ

Table 4.10.4. Crop yield (dt ha − 1 ) by type and level of fertilization, averages of the 1992-1995
and 1996-1999 crop rotation periods.

Fertilization CFM CFMBD MIN Low Medium High

Winter rye 28.3 a 29.8 a 37.7 b 28.1 a 31.7 b 36.1 c

Spring wheat 38.9 a 39.3 a 41.0 a 36.8 a 40.2 b 42.2 c

Potatoes 247 a .9 262 b .9 271 b .9 230 a .9 262 b .9 288 c .9

a,b,c Mean values within a half-row with different superscript letters are significantly different
(P< 0.05).