J. Eriksen et Jv. Mortensen, Soil sulphur status following long-term annual application of animal manure and mineral fertilizers, BIOL FERT S, 28(4), 1999, pp. 416-421
In agricultural systems with low S inputs, crops rely on the release of S f
rom organic forms in the soil. In the Askov long-term experiments, started
in 1894 on both sandy and loamy soils, soil S status following long-term ap
plication of animal manure and mineral fertilizers was investigated in the
growing season of 1995. In a field trial with oil-seed rape (Brassica napus
, L.) soil analysis, leaf tissue analysis, yield and S removal in plant mat
erial was used to characterize differences in availability of soil S. One h
alf of all plots received 63 kg S ha(-1) as gypsum. Long-term fertilization
with animal manure or NPK fertilizer increased the content of soil organic
C in both soils and of organic S in the sandy soil compared with unfertili
zed plots. Although dry matter yields were unaffected, the S uptake in harv
ested crop parts increased considerably after S application. The amounts of
N and S in harvested seeds and straw were closely related, but the N:S rat
io decreased when S was applied. Soil and plant analyses both indicated tha
t critical levels of S concentrations were reached, and that S application
was capable of raising S concentrations well above the critical level. Beca
use no additional mineralization from residual organic S took place, it was
concluded that the residual S effect from long-term annual applications of
animal manure or mineral fertilizers did not significantly increase the le
vel of soil S available for crops with a short growing season, such as oil-
seed rape.