Campbell et al. 1997 found that the elimination of fallow had the greatest impact on total organic C, N, and microbial biomass. Lupwayi et al. 2009, Liebig et al. 2006, and Lupwayi et al. 1999 show significantly higher soil microbial biomass and diversity (Lupwayi et al., 1998) relative to conventional tillage. The difference between the tillage systems being in the top few centimetres of soil which has more crop residue and moisture creating a suitable microbial environment. Clapperton et al. 1997 report significant differences in earthworm populations between zero tillage and conventional tillage in a 25-year wheat –fallow rotation. The difference in soil health between zero tillage and conventional tillage should be reflected in greater N and P availability which would present itself in higher yields and quality (protein).
Nutrient Runoff (Wind, Water and Tillage Erosion)
Erosion due to wind and water is a function of crop residue, soil health and weather events. Tillage affects the amount of crop residue that is available to limit erosion either from high wind, snowpack melt and high rainfall events. Tillage also affects the erodibility of the soil by increasing the amount of aggregates that are susceptible to erosion. Also, the permeability of the soil affects the amount of runoff from a field. Drought affects the amount of crop residue and tillage of a dry soil creates higher amounts of small aggregates. Elimination of fallow plays a major role in reducing erosion. Chem fallow and Chem/Till fallow are less prone to erosion than tillage fallow.
Tillage erosion is a function of thenumber of tillage passes, type of implement and terrain. Reduced tillage on hilly or rolling landscapes limits the amount of soil that moves from the hilltops. Typically, the area affected is from 20% to 30% (Govers et al. 1999).