Response of the Soil Microflora and Fauna to Spring
Plowing of Zero-till and Pasture Soils
Researchers: V.G. Thomas, Land Resource Science, University
of Guelph, Supervisor. P. Neave, Land Resource Science, University of
Guelph, Principal Researcher
- To examine the effect of plowing on the soil microflora and
fauna in zerotilled and pasture soils.
- To examine what differences exist between the pasture and zerotill
soils (plowed and unplowed) in terms of biomass, number of organisms
and their diversity.
- To help better understand the complex soil community.
- To provide further insight into agricultural management decisions.
During the project, the major activities included the establishment
of the treatments (cropping sequence and tillage), preparation of the
15N-labelled plant materials and collection of agronomic
data. Prepared plant and soil samples have been submitted to the Department
of Land Resource Science, University of Guelph for 15N/14N analysis.
Samples of the above-ground plant biomass were taken biweekly from
adjacent non--labelled areas in the macroplot area and plotted against
the model outputs as a sensitivity analysis. In general, the growth
curves generated by the simulation models accurately described growth
rates of the crops in the macroplots. This suggests that the timings
of the 15N-labelling pulses which were based on equal biomass
accumulation between labelling periods were accurately predicted.
The simulation models for wheat, soybean and tobacco also accurately
predicted total above-ground biomass accumulation during the season.
However, the models for corn and fall rye under-estimated the total
above-ground biomass production by 16% and 34%, respectively. Thus,
the total amount of 15N/14N enrichment of the
crop residues will be less than that predicted from model outputs.
The total above-ground biomass production in the microplot areas
deviated from that of the macroplot areas. This should have little effect
on the 15N/14N enrichment of the crop residues
except for corn and soybeans.
Yields of wheat grain were significantly higher (p = 0.0008) in 1990
than in 1991. Yield of wheat managed under conventional tillage practices
was not significantly different than the yield of wheat managed under
conservation tillage practices over the two growing seasons. However,
wheat yields were higher when managed under conventional tillage practices
than when managed under conservation tillage in 1990 but lower than
when managed under conservation tillage in 1991. This observation is
most likely attributable to the conservation of soil moisture by reduced
tillage in 1991 when below average rainfall was received for most of
the growing season. Similarly yields of rye grain were higher in 1990
than in 1991 (p = 0.0013) and yields were not significantly different
for either of the tillage practices. In contrast to wheat yields, conventional
tillage practices in both years suggesting that rye was not as affected
by the droughty conditions in 1991 as wheat. Corn grain yields were
similar in both years of the study with yields of corn being slightly
but not significantly higher under conservation tillage management.
Soybean yields were also similar in both years of the study with similar
yields for both tillage practices. Yields of flue-cured tobacco leaf
were significantly higher (p = 0.0163) in 1991 than 1990. Cured leaf
yields were higher when tobacco was managed under reduced tillage practices.
This suggests that the water conservation effects of reduced tillage
are nullified when a crop is irrigated as part of its recommended management.
Comparisons of the total weight of above-ground non-harvested residues
over a complete two year cycle for each of the three cropping systems
suggested that there was a significant difference between the total
above-ground residue weights for each of the two sites in the study.
This difference can be attributed to differences in the residue weights
of the different crops within each cropping system over the two years
of the study.
Tuesday, May 10, 2011 12:50:10 PM