ALBERT

Description: A measure of kind and level of thinning is developed and its relationship to other stand attributes such as number of trees, basal area, and volume removed in thinning is quantified. This measure or thinning index is based on the ratio of the quadratic mean diameter of thinned trees to the quadratic mean diameter of all trees before thinning. The thinning index is then logically incorporated into a thinning multiplier from which is derived a compatible basal-area growth projection model to generalize the previous concepts for thinning effects in systems for predicting growth and yield. Empirical tests with data from thinned and unthinned natural stands of loblolly pine, from thinned and unthinned slash pine plantations, and from thinned western larch stands show the model to provide estimates with improved properties. Hence, the thinning index and the thinning multiplier are also proposed for other situations involving effects of thinning.

Description: Growth chamber and field experiments were conducted on Southern Manitoba soils, low in available soil phosphorus, to investigate the effects of various placement methods and levels of phosphorus fertilizer on soybean (Glycine max (L.) Merrill ’Maple Presto’). It was found that soybean responded well to applied phosphorus on low-P soil in growth chamber studies. In the first growth chamber experiment, P was applied in solution to 100%, 50%, 25%, 12.5% and 1% of the total soil volume. Dry matter yields, total phosphorus uptake and utilization of fertilizer P increased at each level of applied P as the size of the phosphated band was decreased. The results were partly attributed to greater chemical availability of P in the smaller zones of P fertilizer reaction. In a second growth chamber experiment, soybeans responded differently to phosphorus banded in six different locations. Placement of the fertilizer 2.5 cm directly below the seed was more effective in increasing dry matter yield, total phosphorus uptake and fertilizer P utilization than placement 2.5 cm and 5 cm away at the same depth or placement 5 cm below the seed, whether the band was directly below, 2.5 cm away or 5 cm away. Soybean yield responses in the field were greatest with P banded 2.5 cm directly below the seed on low-P soils. Placement of P 2.5 cm below the seed resulted in grain yields that were 64% and 50% higher (at the two sites) than those obtained in control plots. Sidebanding P, 2.5 cm below and 2.5 cm away from the seed at the same level of application, improved grain yields of control plots by 40% and 39%. Seed placement and broadcast applications of P were not as effective in increasing grain yields. Broadcasting P in fall or in spring at rates of up to 52.38 kg P/ha did not result in significantly higher grain yields than those obtained in control plots. Placement of P in contact with the seed appeared to reduce seedling emergence, resulting in depressed yields when 52.38 kg P/ha were applied. Key words: Glycine max L. Merrill, ’Maple Presto’

Description: The objectives of the study were to determine the effect of soil and fertilizer potassium (K) on the yield and chemical composition of alfalfa (Medicago sativa L.), and whether fall harvesting (October) had detrimental effects on alfalfa grown under the relatively cool and short growing season of the Eastern Canadian Prairies. Vernal alfalfa was sown on five soils, two high and three low in amounts of exchangeable K. Three harvests were taken each year in June, July, and October at the full bud stage. The soils were rated on their potential potassium supplying power (PKSP). The effect of fertilizer K on increasing the availability of soil K and on the K and N composition of the forage were measured. The PKSP of the soils was not related to initial levels of exchangeable K. However, soils with low exchangeable K and low PKSP required an annual application of 200 kg K/ha to produce maximum yield. There was response to K fertilizer on only one of the soils with high exchangeable K, and then only to the first increment. At maximum yield on all soils, the K and N contents of the forage at full bud were greater than 2.0% and 3.0%, respectively. When the K content of the forage was less than 1%, severe winter injury occurred and yields decreased. With adequate K fertilizer fall harvesting had no detrimental effects on alfalfa production. Comparisons of the K and N contents of the forage indicates that increasing the concentration of K available to the crop may have a beneficial effect on N-fixation. Key words: Medicago sativa L. ’Vernal’, potential potassium supplying power, nitrogen fixation