The Role of Soil Organic Matter and Manures in Sustainable Nutrient Cycling - Sustainable Management of Soil Organic Matter - page 297

manure fertilization, compared with CFM. The biodynamic preparations
increased potato yields by 15 dt ha −1 (6%) on average over all years. Higher
levels of fertilization influenced yields positively with all crops. Basically,
the yields reflect the specific nitrogen demand of each crop at various
growth stages in combination with the different nutrient availability of
organic or mineral fertilizer in those stages. Spring wheat, cultivated in the
year after the legume crop, generally may have the benefit of a favourable
position in the crop rotation. This may explain why there was no yield
difference between manure and mineral fertilization.
The yields of all crops are not very high and varied considerably from
year to year, most likely because of the extreme site conditions: a sandy
soil and dry-warm climate with drought from May to July in most years.
Irrigation is possible, but only at low levels of 20-60 mm year −1 because of
the limited capacity of our equipment. In cereals, the occurrence of weeds
depended on fertilization, but did not explain the yield differences between
treatments (Raupp et al ., 1998). Severe pest or disease problems only arise
with potato late blight in some years, causing more severe infestation in
mineral treatments, and by colorado beetle. In spring wheat, yield stability,
i.e. fluctuation over the years, differed between organic and mineral
fertilization. Figure 4.10.1 shows the correlation between the yields of the
mineral and manure treatments (in both cases at a high fertilization level)
over the last 14 years. If the yield difference is the same over the entire yield
range, the slope of the major axis of the ellipse should be at 45 , i.e. not

significantly different from 1. However, the slope is < 1 for the medium and
high fertilization level ( P < 0.05; Table 4.10.5). Thus, under good growth
conditions, minerally fertilized wheat yielded more than manure fertilized
wheat. However, yield declined much more in years of poor conditions. In
these years, the plant-soil system with manure fertilization seems to be able

°

70

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50

40

30

Fig. 4.10.1. Bivariate correlation
between spring wheat yields with the
high level of mineral fertilization and of
composted farmyard manure (results
of four replicates and 14 years, n= 55;
confidence ellipse for P< 0.05).

20

10

10 20 30 40 50 60 70

MIN (dt ha − 1 )