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LSP Report LS7016

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

Funding: $16,537


  1. To examine the effect of plowing on the soil microflora and fauna in zerotilled and pasture soils.
  2. To examine what differences exist between the pasture and zerotill soils (plowed and unplowed) in terms of biomass, number of organisms and their diversity.

Expected Benefits

  1. To help better understand the complex soil community.
  2. To provide further insight into agricultural management decisions.

Summary of Research Results

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.




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Created: 03-23-1996
Last Revised: Tuesday, May 10, 2011 12:50:10 PM