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Cabbage (<i>Brassica oleracea</i> L.) production in Virginia is concentrated in the mountainous southwest region of the state where soil erosion and soil-moisture deficits are major problems associated with row-crop agriculture. The objectives of this study were to assess the applicability of conservation tillage systems for cabbage production. Four tillage systems (conventional tillage, CT; no-tillage, NT; and two types of strip tillage—Ro-till, RT, and chisel plow, CP) and three planting dates (early, mid and late) were compared in 1985 and 1986. Plants were set with a locally adapted no-till transplanter into a cover crop of cereal rye (<i>Secale cereale</i> L.). Under unusually rainy conditions in 1985, cabbage yields with NT were lower than with CT; while with dry weather prevailing in 1986, NT and CT yields were equal for all planting dates. Yields in strip tillage systems were equal or higher than NT and CT with ample or deficit soil moisture. RT out-yielded both CT and NT in 1986. Yield was positively correlated with soil moisture content in 1986, but not in 1985. Once-over resetting was done in all plots resulting in no differences in plant numbers among tillage treatments. Head size was affected by tillage systems and was highly correlated with yield. These data indicate that (i) conservation tillage systems are viable alternatives to CT for production of cabbage, and (ii) available water resources and soil drainage should be important considerations in selection of the most productive tillage system. / M.S.

Broccoli is increasingly being grown as an alternate crop in many tobacco producing regions. Many of these regions, especially in Virginia, are quite susceptible to soil erosion losses. In order to reduce erosion and reap the other benefits of conservation tillage, a strip tillage machine named FOR2 was designed, developed and tested. FOR2 prepares the seedbed and places the seed in one pass through the field. This thesis reports the qualitative and quantitative evaluation of FOR2 based on result from two experiments. The first experiment evaluated broccoli emergence under three different tillage treatments, one of which was FOR2. The second experiment assessed the influence of adjustable machine parameters on the prepared soil condition in terms of aggregate size distributions, The parameters that were varied included pre-planting irrigation amount, tiller depth, tiller RPM, and tractor speed. The analysis revealed that the FOR2 machine produced commercially acceptable stands of broccoli with 77% germination. It was also determined that the percentage of aggregates in the seedbed greater than 0.297 mm was significantly influenced by the irrigation level and the tiller RPM. Tiller depth and tractor speed had no significant effect on the response. / M.S.

The global adoption and diffusion of conservation tillage has made considerable progress over the last 20 years. No-till and zero-tillage could be seen as representing the current technological end-point of the conservation tillage movement. This thesis uses descriptive statistics and both logit and duration regressions to analyse the influence of cross-sectional and time-dependent factors on the probability of no-till adoption by growers in Australia’s southern grain growing regions. Cross-section and time-series data on individual adoption decisions was gathered through interviews and employed in conjunction with generic time series data from various government agencies in a duration analysis modelling framework. Descriptive statistics suggest that weed management and herbicide resistance are important considerations for growers in their tillage decisions, predominantly due to the substitution of herbicides for the physical weed control provided by cultivation. Logit and duration regressions identify a number of significant factors influencing growers’ adoption decisions. These include growers’ perceptions of herbicide efficacy and sowing timeliness in no-till systems; the declining price of glyphosate relative to diesel; average annual rainfall and growers’ proximity to other adopters and opportunities to observe the beneficial effects of no-till. The results suggest that research and development of integrated weed management practices that are compatible with no-till systems is highly important if no-till systems are to be sustained in Australia’s southern wheatbelt. Such research and development should acknowledge the high value which growers place on locally generated information and the channels used to acquire such information, namely local extension events and consulting services. This thesis shows how duration analysis, with its ability to take account of both cross sectional and time-varying factors, can provide a statistical modelling framework better suited to the study of adoption decisions than traditional cross sectional methods based on logit and tobit analyses.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Bibliography: p. 182-197. The objectives of this study are: selection and construction of four narrow sowing points, evaluation of these points in terms of draught requirements and wear rates, comparison of the points in direct drilling systems and their effects on soil physical properties.

Thesis (PhD)--University of South Australia, 1998

Bibliography: p. 182-197. / xxii, 197 p. : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The objectives of this study are: selection and construction of four narrow sowing points, evaluation of these points in terms of draught requirements and wear rates, comparison of the points in direct drilling systems and their effects on soil physical properties. / Thesis (Ph.D.)--University of Adelaide, Dept. of Agronomy & Farming Systems (Agricultural Technology), 1997

Thesis (PhD)--University of South Australia, 1998

Thesis (Ph. D.)--Auburn University. / Abstract. Vita. Includes bibliographical references.