holes in the soil that increase the percolation of water into the
soil and decrease runoff.
Soil organic matter is an important source of nutrients and
can help increase biodiversity, which provides vital ecological
services, including crop protection (Pimentel et al. 2005).
For example, adding compost and other organic matter reduces
crop diseases (Cook 1988,Hoitink et al. 1991) and increases
the number of species of microbes in the
agroecosystem (van Elsen 2000). In addition, in the organic
systems, not using synthetic pesticides and commercial fertilizers
minimizes the harmful effects of these chemicals on
nontarget organisms (Pimentel 2005).
In conventional crop management in New Zealand,Nguyen
and Haynes (1995) did not report any adverse effect on soil
microbial activity.These conventional systems, however,were
part of a rotation pastoral–arable system with a relatively
high level of soil organic matter (carbon content of the soil
ranged from 2.9% to 3.5%).