UBC Theses and Dissertations
An evaluation of four tillage systems on Pineview clay, a fine textured soil in the central interior of B.C. Grevers, Mike C.J.
Pineview clay originates from a lacustrine deposit and has a clay content of approximately 55%. During the spring the soil is generally quite moist due to melting snow and rainfall, while ambient air temperatures are relatively cool. These factors cause soil warming on Pineview clay to be slow. Due to the slow soil warming process in the spring and due to the fine texture of this soil, it is important that the Pineview clay maintains a good soil structure. Little research has been carried out on Pineview clay as to the effect of tillage practices on soil structure. It was the purpose of this project to study changes in the properties of Pineview clay brought about by different tillage systems. In the first part of the project major adverse soil conditions that occur on Pineview clay were evaluated with respect to the emergence of barley. In the laboratory the effects of soil compaction and soil temperature were evaluated in terms of barley seedling emergence. The second part of the study consisted of determining the feasibility of several tillage systems and the use of a herbicide prior to tillage on Pineview clay. In the last part of the study four fall sod breaking tillage systems were evaluated in terms of their effect on soil physical properties, N transformations, crop growth and development, and economic returns. Barley seedling emergence in the laboratory was found to be affected by soil compaction and soil temperature. Between 5⁰ and 20⁰C the rate of barley emergence approximately doubled for every 5⁰C increment in soil temperature. Applying the herbicide Gramaxone prior to tillage improved soil break-up and control of sod regrowth, but the cost of this herbicide may be prohibitive. For sod breaking operations a stubble plow proved to be inadequate and a special sod breaking plow should be used. Rotovation prior to moldboard plowing improved soil break-up and control of sod re-growth. Chisel plowing resulted in a rough, mulched soil surface condition, which required many passes before a satisfactory level soil surface had been created. The four fall sod breaking systems were moldboard plowing (using a sod breaking plow) with and without prior rotovation, and chisel plowing with and without prior rotovation. The results indicate major differences due to the type of plow used (moldboard vs chisel) rather than the additional use of the rotovator prior to plowing. Moldboard plowing resulted in superior soil physical conditions, higher soil NO₃-N levels, higher crop yields and N uptake by the crop, and better economic returns than chisel plowing. The four tillage systems reached maximum profits under various fertilizer rates; $208.00/ha for moldboard plowing at 112 kg N/ha, $104.00/ha for rotovating and moldboard plowing at 56 kg N/ha, $71.00/ha for chisel plowing at 168 kg N/ha, and $39.00/ha for rotovating and chisel plowing at 0 kg N/ha.
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