No abstract

The influence of method of drying on concentrations of total P, extractable phosphate and two N fractions in petioles from recently matured sugarbeet leaves was studied. Method of drying had no or small effects on total P, total N and nitrate-N. However, method of drying had a marked effect on the value of extractable phosphate. Concentrations of phosphate-P extractable with water and 2% acetic acid were least with freeze-dried material and increased as temperature of oven drying was varied from 70 to 100°C.Extractable phosphate-P in tissue dried by a particular method was lower when acetic acid was the extractant. Quantity of extractable phosphate-P in oven-dried material was not influenced by substitution of ascorbic acid for stannous chloride and elimination of the H 2 O 2 oxidation step in the analytical procedure. Leaf position greatly affected concentrations of total P and acetic-acid 905

Distribution of four nitrogen fractions in tops and roots of 4‐ and 8‐week‐old barley (Hordeum vulgare L.) plants as influenced by two rates of nitrogen and three ambient temperatures during the latter half of growth period was studied in pot experiments. All plants were initially grown at 15.6 to 18.3 C for 4 weeks under two nitrogen treatments. Temperature variables were established on the plants during the last 4 weeks of growth. Temperatures tested in two sets of experiments were 7.2 to 8.9 C and 15.6 to 18.3 C, and 15.6 to 18.3 C and 26.6 to 27.7 C. Samples were analyzed for total, alcohol‐insoluble, alcohol‐soluble, and nitrate nitrogen. Highest dry matter was produced at 15.6 to 18.3 C. The 400‐mg N/pot yielded more total, alcohol‐insoluble, alcohol‐soluble, and nitrate nitrogen than the 20 mg N/pot. Yields of total and protein nitrogen in plants were approximately proportional to yield of dry matter, and percent total nitrogen in plants was inversely related to yield of dry matter. Alcohol soluble nitrogen yield was greater in plants grown at higher ambient temperatures in both experiments. In plants supplied with 400 mg N/pot, an above optimum temperature (26.6 to 27.7 C) caused a significant portion of the total nitrogen to be in alcohol‐soluble form. A large part of this alcohol‐soluble nitrogen was nitrate nitrogen. This alcohol‐soluble nitrogen is highly mobile and can be easily translocated to grain. These results corroborate field observations that temperatures above 27 C during the heading stage of barley plant restrict grain yields, even though protein percent remains high.

Groundwater quality analyses included