Cover Crops and Soybeans

Charles Benbrook (benbrook@hillnet.com)
Wed, 13 Oct 1999 08:15:15 -0700

In response to the Brazilian farmer's query, posted by Steve, likely
generic explanations of the benefits of cover crops and reduced fertilizer
rates in soybean production arise from the impact of the cover crop on
leaching of N and other nutrients in wet years; water holding capacity in
dry years; soil microbial biocontrol; and nutrient cycling in all years, to
varying extents. The break down of the cover crop is no doubt stimulating
microbial activity. This may be causing an increase in mycchorizae that
are essential to make P available to the soybean plant, and also helps some
with N cycling, limiting losses to leaching and/or volatization. The
late-season breakdown of the microorganisms that thrived earlier in the
year provides an often needed late-season boost to yields.

There may also be complex soil microbial biocontrol mechanisms at play,
either triggering a stronger immune response via systemic acquired
resistance, or reducing damaging pathogen pressure via competitive forces
or production of antibiotics, or other mechanisms. With the more
biological active/diverse soil, the odds are greater that strong defensive
mechanisms will arise/exert themselves and that pest pressure will not
reach damaging and uncontrollable levels.

chuck

Charles Benbrook CU FQPA site www.ecologic-ipm.com
Benbrook Consulting Services Ag BioTech InfoNet www.biotech-info.net
5085 Upper Pack River Road IPM site www.pmac.net
Sandpoint, Idaho 83864
208-263-5236 (Voice) 208-263-7342 (Fax)

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