The arcsine and square root transformations were tested on 82 weed control data sets and 62 winter wheat winter survival data sets to determine effects on normality of the error terms, homogeneity of variance, and additivity of the model. Transformations appeared to correct deficiencies in these three parameters in the majority of data sets, but had adverse effects in certain other data sets. Performing the recommended transformation in conjunction with omitting treatments having identical replicate observations provided a high percentage of correction of non-normality, heterogeneity of variance, and nonadditivity. The arcsine transformation, not generally recommended for data sets having values from 0 to 20% or 80 to 100%, was as effective in correcting non-normality, heterogeneity of variance, and nonadditivity in these data sets as was the recommended square root transformation. A majority of data sets showed differences between transformed and nontransformed data in mean separations determined using LSD (0.05), although most of these differences were minor and had little effect on interpretation of results.

Ten accessions of Avena sterilis L. (males) were tested as sources of genes for improving productivity of cultivated oats (A. sativa L.). They were mated with six A. sativa (females) cultivars from the north central USA, and populations of F2‐derived lines in F3 from these matings were evaluated for grain yield and biomass at three locations in Iowa and vegetative growth index at one location. Maximum specific combining ability (SCA) effects exceeded maximum general combining ability (GCA) effects for all traits in both males and females. The SCA sums of squares were intermediate in magnitude between the GCA sums of squares for males and females. Transgressive segregates, one LSD0.005 above the high parent, were derived from every parent for each trait. However, there was a greater percentage of significantly high transgressive segregates for biomass and vegetative growth index than for grain yield (9.8, 9.0, and 3.1%, respectively). Performances of the A. sterilis accessions and A. sativa cultivars per se generally were good predictors of mean progeny performance for each trait. However, the production of extreme progeny types was more closely associated with the mean genotypic variance of a parent, as calculated over the array of matings, than with that of parental performance per se.

No abstract

Winter wheat (Triticum aestivum L.) is grown under both conventional‐till and conservation‐till systems in the Northern Great Plains. A benefit of sowing winter wheat into standing stubble is the protection the crop receives from trapped snow and the resultant reduction in winter kill. A 5‐yr study was conducted at four locations in North Dakota to measure cultivar‐by‐tillage interactions for quality parameters of wheat and to determine whether testing under both conventional‐till and no‐till systems was advantageous. Fourteen hard red winter wheat cultivars were planted during 1984‐1985 through 1988‐1989 in a Max loam (fine‐loamy, mixed, Typic Haploborolls) at both Williston and Minot, in a Svea loam (fine‐loamy, mixed, Pachic Udic Haploborolls) at Langdon, and in a Bearden silty clay (fine‐silty, frigid, Aeric Calciaquolls) or Gardena silty loam (coarse‐silty, mixed, Pachic Udic Haploborolls) at Fargo. Significant cultivar‐by‐tillage interactions (P < 0.05 or P < 0.01) were obtained for volume weight, protein content, and flour yield when the analysis was restricted to environments in which wheat winter killed. A change in rank order of cultivars was detected only for volume weight. For the other quality parameters measured, evaluation of winter wheats grown in conventional‐till and no‐till plots resulted in similar relative performance of cultivars.

Winter wheat (Triticum aestivum L.) production in the Northern Great Plains is dependent upon adequate survival of the crown tissue for regeneration of root and shoot in early spring. Thus, the establishment of winter wheat as a viable alternative crop in North Dakota has been dependent upon the use of management practices that enhance winter survival. Objectives of this study were (i) to verify previous results associating winter injury or lack of with tillage and its associated effects on snow depth and soil temperature, and (ii) to determine the affect of tillage and cultivar selection on grain yield in an environment where winter injury frequently is experienced. Two hard red winter wheat cultivars were planted during the fall of 1981 and 1982 into conventional tillage (CT), mulch tillage (MT), and notillage (NT) plots on a Fargo clay (fine, montmorillonitic, frigid Vertic Haplaquoll) located at Fargo, ND. The experiment was repeated during the winters of 1983-1984 and 1984-1985 using MT, and short (0.05 m) and tall (0.20 m) stubble NT plots. Snow depth was greatest in conjunction with tall stubble (0.20 m) and resulted in warmer soil temperatures and a reduction in the duration of time temperatures dropped within the range responsible for winter injury. Winter injury was recorded only for the winters of 1981-1982 and 1984-1985. Percentage winter survival was greatest for NT wheat planted into tall stubble. The survival of MT wheat was intermediate between that of CT and NT wheat. The snow trapping ability of short stubble (0.05 m) and amount of winter injury recorded was similar to that for MT. The mean grain yield of CT, MT, and NT (both 0.05 and 0.20 m) wheat was 455, 2203, 2270 and 4073 kg ha _, respectively, for the two winters in which winter injury was recorded. There were no significant differences in yield harvested from tillage treatments for the two mild winters. Tillage selection (CT vs. NT) was more important in explaining the variation in percentage winter survival than was cultivar selection.