Oats grown with different nutrient treatments in temperature-controlled soil in the greenhouse produced higher yields of grain and straw when soil temperature was increased from 41° to 67°F. Yields were usually less at 80°F. than at 41°F. This relationship between growth and soil temperature was also apparent at the heading stage. At 7th leaf, however, the best temperature for growth varied with nutrient treatment. Root yields usually decreased with increase in soil temperature.Increasing soil temperature from 41° to 67°F. increased uptake of N, P and K. In many instances increases in the concentration of N, P and K in the plant contributed to these increases in uptake. The effect of soil temperature on uptake was more consistent for P than for other elements.Nitrates and native phosphorus in incubated soil samples increased with increase in temperature from 41° to 80°F. but exchangeable K values were not affected.

When grown with different nutrient treatments in temperature‐controlled soil in the greenhouse, yields of corn and bromegrass tops increased with increments in temperature from 41° to 80° F., but yields of potato tops and tubers showed a less consistent relationship with temperature. Yields of corn and bromegrass roots also increased with temperature except for a decline in bromegrass roots when temperature was increased from 67° to 80° F. Tuber yields were usually higher at soil temperatures above 41° F., but the optimum temperature varied with nutrient treatment. The nutrient composition of the crops showed few consistent trends in relation to soil temperature. The P content of bromegrass and potato tops, however, increased with rising temperatures when the plants were grown without added P. Uptake of N, P, Ca, Mg and K by the crops usually increased with increasing temperature to at least 67° F. The uptake of P by the plants without addition of the nutrient, relative to the uptake obtained with addition, increased almost invariably with each increment in temperature. Water‐use efficiency usually increased where N, P and K were added together and often decreased as soil temperatures increased.

ABSTRACT

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Established stands of three grasses and legumes, grown in a greenhouse, were subjected to flooding treatments consisting of soil moisture tensions of approximately 0, 25 and 40 centimetres of water which were equivalent to field conditions where the water table is at the soil surface, 25 and 40 centimetres below the soil surface, respectively. Herbage and root yields were measured.Grasses were more tolerant to flooding than were the legumes. The order of decreasing tolerance to flooding was: reed canary grass, timothy, brome grass, birdsfoot trefoil, Ladino clover and alfalfa. The yields of grasses tended to increase with increasing moisture levels and with durations of flooding, whereas the yields of legumes tended to decrease with increasing moisture levels and with the duration of flooding.The effect of flooding on yields was more pronounced on the first than on the second harvest. Highly significant positive correlation coefficients were obtained between total top and root weights of reed canary grass, birdsfoot trefoil, Ladino clover and alfalfa. Corresponding correlation coefficients for timothy and brome grass were negative and highly significant.Oxygen diffusion measurements indicated that, in general, the yields of legumes increased with increasing availability of oxygen whereas the yields of grasses showed a tendency to decrease. As the soil temperature under flooding conditions increased from 41° to 80°F. the forage yields usually decreased.

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Young seedlings of flax and cereals, grown in a greenhouse, were subjected to 0, 12.5, and 25.0 cm of soil moisture tension for periods of 7, 14, and 21 days The grain, straw, and root yields of all plant species, except barky, increased with increasing soil moisture content was maintained near field capacity during the growth of plants. The yields of oats, winter wheat, and fall rye decreased with increasing duration of flooding, whereas those of barley, flax and spring wheat were variable. Correlation coefficients between yields of tops and roots were positive.