Agriculture Reference
In-Depth Information
1975-1996. The average yield fluctuates around and the
annual increase in yield (0.15 %) is not significantly different from zero.
However, yields of silage maize varieties that were determined in variety
trials show an annual yield increase attributable to breeding of 0.88% in the
period 1954-1981 (Struik 1983).
The fact that the trend in the yield of new varieties is not reflected
in the actual yield data implies that the yield increase by improved
cultivation techniques, which was observed in winter wheat, did not occur
in silage maize. There are several possible explanations for this difference.
In the Netherlands, most silage maize is not grown by specialized arable
farmers, but by pig, chicken and dairy farmers, who partly rely on contract
workers for their crop management. This may lead to sub-optimal crop
management. Moreover, in the Netherlands, the maize crop was given very
high amounts of slurry and manure, especially in the first part of the period
shown in Figure 7.2. Although maize tolerates the high doses, they were
often not tuned to crop requirement but rather to the amount farmers
needed to dispose of. From 1987 onwards, however, legislation
progressively restricted the application of slurry and manure.
Apart from the factors that may explain the absence of an
increasing trend, there are also cultural and socio-economic developments
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