Evaluation of three methods of teaching ninth grade algebra

This item was digitized by the Internet Archive. Thesis (Ed.M.)--Boston Universit

Ethics as a Science: Going from Is to Ought

Two beliefs which serve to prevent teaching, defining, or progress in ethics and morality are: 1. That we cannot derive an ought from an is. We supposedly cannot derive value statements from factual statements. 2. That we cannot define ethical terms in terms of non-ethical terms (naturalistic fallacy). But can we derive an ought from an is? Does it ever make sense to do so? Let\u27s take a case as it may arise. It is cold outside. I know that a chill may bring on a cold and I wish to avoid catching cold. I then conclude I ought to wear my coat. When I put on my coat, I derive an ought from an is

Soybean Residual Effects on a Following Corn Crop

The reason for the yield advantage of rotations is still speculative. Differences in soil nutrients, soil moisture, diseases, insects, weeds, and soil physical properties have all been considered to be responsible for this effect. It was not until the late \u2770s that a non-nitrogen soybean effect on the following corn crop was substantially documented. Corn after soybeans consistently performed better than second-year corn irrespective of nitrogen fertilization. In previous work done with the soybean-corn rotation, there has never been an evaluation of the potentially different effects of soybean varieties on following corn yields. This study aimed to evaluate whether such differences exist

Soybean Residual Effects on a Subsequent Maize Crop

Maize (Zea mays 1.) grown after soybean (Glycine max 1. Merr.) consistently performs better than maize that follows itself (second year maize), irrespective of nitrogen fertilization. In previous studies of the soybean-maize rotation, there never has been an evaluation of the potentially different effects of soybean genotypes on following maize. A two-year, soybean maize rotation was initiated in Ames at 1988 with the first year planted to various soybean genotypes, a maize hybrid, and oat (Avena sativa 1.). These were followed in the second year by a single maize hybrid with 0, 80, 160, and 240 kg/ha N fertilization levels. Results are based on three repetitions of this cycle. Averaged over all years and N rates, maize after nodulated soybean and oat yielded 1270 and 1570 kg/ha, 16 and 20% respectively, more than second-year maize. Second-year maize was delayed in silking by 4 days. Though soybean returned 60 to 70 kg/ha of N to the soil in vegetative residue, there seemed to be no net N contribution from soybean to maize because soybean benefited maize less at zero N than did unharvested oat. Soybean evidently returns to the soil less N than is mineralized from soil organic matter during a cropping year. Prior soybean and oat both benefited maize even under the highest nitrogen fertilization rate. BSR 201 soybean benefited maize more than did the other soybean cultivars or oat. Averaged for years and the two highest N rates, BSR 201 benefited maize 680 kg/ha (ca 11 bu/A) more than all the other nodulated soybean genotypes averaged. The BSR 201 effect, however, was not consistent, occurring in two of the three years. Work is continuing using other BSR types

Research Notes : Flavonol classes of cultivars in Maturity Groups 00-IV

Since the complementary action of Fg1 and Fg3 in producing kaempferol 2G-glucosyl-gentiobioside (Buttery and Buzzell, 1975) is associated with deleterious effects on chlorophyll concentration, photosynthetic rate and yield (Buttery and Buzzell, 1976), the bringing together of these two genes in crosses may necessitate selection against the Fg1-Fg3-genotype in the segregating material. For example, with the cross of \u27Corsoy\u27 (Fg1 fg3) x \u27Hawkeye\u27 (fg1 Fg3) at Iowa State University, visual selection was carried out against chlorophyll deficient types during inbreeding in order to develop lines for a physiological study. At the time of selection it was not known that flavonol-glycoside genes were involved. Advanced lines were later classified using thin layer chromatography (Buttery and Buzzell, 1973

For corn and soybeans - Narrow Rows

There\u27s yield advantage, but costs, too, in narrow rows as compared to 40-inch rows for corn and soybeans. Since costs of changing to narrow rows will vary from farm to farm, each farmer must decide his own best time, if ever, to change

Chlorophyll Meter Assessments of Corn Response to Nitrogen Management Practices

Environmentally sound nitrogen (N) management is necessary to simultaneously achieve high crop yields and protect surface and groundwater quality. We evaluated a hand-held chlorophyll meter as a diagnostic tool for improving management for corn (Zea mays L.). Five N fertilizer rates (0, 67, 134, 201 and 280 kg N ha-1) were evaluated in one study, and in a second study, the meter was used to evaluate the N status of corn plants grown under varying tillage (chisel plow vs no-till), crop rotation (continuous corn vs corn-soybean [Glycine max (L.) Merr.]), and N management treatments. Meter readings were taken at several plant growth stages in both studies and correlated with plant N concentrations and grain yield. The chlorophyll meter readings detected differences in corn plants receiving low and high fertilizer N rates, as well as those grown with different tillage, N fertilizer management, and crop rotation practices. We recommend taking measurements between plant growth stages V9 and V12 and conclude that chlorophyll meters can be effective tools for improving N fertilizer management