Wageningen, The Netherlands
March 26, 2008
Biological soil disinfestation as
part of a narrow crop rotation can result in major increases in
asparagus yield over a period of several years. This is the
result of research performed by
Wageningen UR’s Applied Plant Research (PPO).
The biological soil disinfestation deployed at three farms in
2000 was still providing for a yield increase of over 30 percent
in 2005 and 2006. "These significant increases in yield over a
number of years show that biological soil disinfestation should
be used more often,“ says PPO scientist Jan Lamers. Biological
soil disinfestation is a major alternative for the use of Methyl
bromide throughout the temperate zone to combat soil-borne
diseases such as Fusarium spp, Verticillium and Rhizoctonia.
Soil solarisation is another good alternative for the warm
regions on earth.
The rotational rule usually applied is that asparagus crops can
only be grown on a plot once every 30 years or once every
generation of men. Due to the shortage of land and the benefits
of working close to home, the option of growing asparagus more
often has many attractions.
Narrow crop rotation results in soil exhaustion, which then
leads to a decline in life span for asparagus crops from eleven
to six years. Previous Wageningen UR research showed that soil
exhaustion with asparagus is mainly caused by two ‘strains’ of
Fusarium: Fusarium oxysporum f.sp. asparagi and Fusarium
redolens f.sp. asparagi. These fungi are spread by soil
transportation and plant material.
Applied Plant Research and Wageningen University have previously
developed a technique to disinfest the soil using green manure
and an air-tight plastic covering. Deep digging in of the green
manure and the isolation of the soil results in a low-oxygen
environment, which causes the release of substances in the
manure that control nematodes and fungi.
In 2000, PPO applied biological soil disinfestation at three
farms and in an experimental field test. Soil tests showed that
the Fusarium was significantly reduced but not completely
eliminated. The newly planted asparagus crops, however, started
to grow better on the decontaminated plots and thus elongated
their life span. And less weeds grew on the treated plots.
Although the Fusarium in the treated soil seemed to have
returned to the level of the untreated soil after several years,
the yield was still higher than in untreated plots. The
experimental field showed a yield increase of no less than 50
percent and the quality of the crops was also considerably
improved. The weight of AAA asparagus was three times as high as
the produce from untreated plots. Crop observations during the
2007 growing season show that the asparagus harvest may even be
considerably higher in 2008.
Although farm fields with little Fusarium showed less pronounced
positive changes, there were no negative effects. The method can
therefore be pronounced as safe.
Taking this major production increase over a long period of time
into account, it is clear that biological soil disinfestation
should be applied more often. Research into technical
optimisation (bird repellents and better glue for ensuring a
tight fit for the plastic, for instance) and lowering the costs
of the application make the technique even more attractive.
The research was financed by the Product Board for Horticulture
in the period 2005-2007. |
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