Summary. The average air‐dry yield of weeds on fallow plots was about four times as large (2660 kg/ha) as the yield of weeds which developed among spring cereal crops (740 kg/ha). Application of fertilizers increased the number of weeds and their average weight on both irrigated and non‐irrigated plots. Treatment with MCPA reduced the weed yield to 36% on fallow plots and to 26% on weedy cereal plots. It was more effective on fertilized plots than on unfertilized plots, but irrigation made little difference to its effectiveness. The space left by the destroyed weeds was mainly occupied by Agropyron repens. Oats were better able to compete with weeds than were wheat and barley. On unfertilized and non‐irrigated plots spraying with MCPA (1‐26 kg/ha) at the beginning of shooting significantly reduced the yields of weed‐free barley. The yields of sprayed oats and wheat were also below the yields from the unsprayed although the reductions were not significant at the 5% level. However, on a number of fertilized and irrigated plots, both weedy and hand‐weeded, on which the plants had better growing conditions, MCPA resulted in a significant increase in the grain yield of barley and oats. Influence de l'irrigation, de la fertilisation et du MCPA sur la compétition entre céréales de printemps et mauvaises herbes

Kuten tunnettua, ovat itsesiittoiset viljelykasvi jalosteet samasiinnöksisiä eli homozygoottisia. Ne on yleensä kehitetty valikoimalla jossain määrin erilaisten

Some results of a preliminary test conducted at University Farm, St. Paul Minnesota have been given. The following conclusions have been made: 1. Flax plants that had grown slowly both before and after spraying and those that had grown slowly up to the time of spraying did not show as distinct stem bending or as great reduction in height as did those which grew rapidly before spraying. 2. Varietal differences in the response to methoxone and 2,4-D were apparent between Redwing, Dakota, and Minerva. Redwing was most tolerant with Dakota and Minerva more susceptible. 3. The effect of spraying oil flax with methoxone was not as severe as with 2,4-D when measured by the amount and degree of stem curvature and the reduction in height. Equivalent amounts of the effective substance in each herbicide were used.

Abstract. The effects of temperature and plant spacing on growth, on the distribution of biological mass within the plant, and on yield were studied with seven barley varieties at two temperatures, 10°C and 20°C, and two growth densities, 3 and 13 plants per pot.Vegetative development at 20°C was nearly twice as fast as at 10°C. After the plants had entered the reproductive phase, the difference in developmental rate became smaller. Plants grown at the lower temperature produced much higher total biological yields and grain yields than plants grown at the higher temperature. Percentage proportion of leaves was higher and proportion of culms lower at 20°C than at 10°C.Temperature had no significant effect on number of culms and 1000-grain weight. Number of grains per ear was higher at 10°C than at 20°C.Total biological yield per pot and grain yield per pot were larger when the plants were grown in dense populations. More culms and larger yields per individual plant were produced in sparse populations. Growth density did not affect the number of grains per ear. Length of ear and 1000-grain weight were larger in sparse than dense populations. Two-rowed barley varieties gave significantly higher total biological yields and slightly higher grain yields than multi-rowed varieties. There were no differences between the two types of barley in proportions of leaves, culms and roots. As expected, number of culms and 1000-grain weight were higher, and number of grains per ear was lower, in the two-rowed than in the multi-rowed varieties.Among the various yield components, number of culms explained most of the yield. The number of grains per ear explained a smaller proportion, and 1000-grain weight a larger proportion, of the yield of the two-rowed varieties than of that of the multirowed varieties. In both types of barley there was a significant positive correlation between number of culms and 1000-grain weight. The number of grains per ear was not correlated with the number of culms; neither was it correlated with 1000-grain weight. There were differences between the two-row and multi-row types in correlations between culm numbers, leaves and roots. The distribution of biological yield between various plant parts in different phases of development did not affect the grain yield.

No abstract