Synopsis Yield response to additional K for grass increased up to a tissue content of 2% and levelled off between 2 and 3%. Percent protein, nonprotein and nitrate N in the forage increased with N fertilization but decreased with K fertilization. Significant interaction effects showed that adequate K (50 pounds/acre) insured a balanced N metabolism in forages heavily fertilized (100 to 200 pounds/acre) with N.

The role of P and K on the utilization of N by Herta barley (Hordeum distichon L.) was studied in a greenhouse hydroponics experiment. Nitrogen was supplied at concentrations of 10, 50, 100, and 200 ppm, potassium at 10, 50, and 200 ppm and phosphorus at 25, and 100 ppm in factorial combination. Adequate concentrations of P and K were required to obtain response to increasing concentrations of N. Interaction effects of NK and NP on tillering and on yield and kernel weight of grain were highly significant. Although both P and K were essential for normal growth and development, K had the greater influence on the utilization of N in vegetative growth and on yield of grain. Plants harvested at the early vegetative, mid‐vegetative (heading), and mature stages of development showed a yield response to N, P, and K. Percentages of N, P, and K in tissue below which final yield of grain decreased were 4.0, 0.70, and 4.0, respectively, for plants sampled at heading. These critical nutrient levels obtained from nutrient culture were higher than for barley grown in soil culture.

Alfalfa, red clover, ladino clover, alsike clover, and birdsfoot trefoil were germinated in soil (pH 6.5) or in inert silica (8 mesh) and allowed to root in a [Formula: see text] Hoagland and Snyder's nutrient solution (pH 4.5) with 0, 0.5, 1, 2, 4, and 10 p.p.m. of added aluminum. Each species, germinated in silica, was also rooted in an unlimed acid soil (pH 4.6) and the same soil limed to a pH of 6.5.Concentration of aluminum ion remaining in solution was 0, 0.1, 0.2, 0.5, 1.0, and 2.0 p.p.m. Saturation extracts of the unlimed and limed soil contained 0.45 and 0.0 p.p.m respectively of aluminum ion in solution. The pH of the nutrient solutions with 0.5, 1, and 2 p.p.m. of added aluminum increased to 5.0 or higher in 24 hours while that with 4 and 10 p.p.m. of added aluminum remained relatively constant.Seedling weight and chemical composition of the tops and root portions varied significantly between species. Alfalfa and red clover showed the most vigorous rate of establishment, and yields were higher with 0.1 and 0.2 p.p.m. concentration of aluminum ion than with the zero treatment. Significant restriction of top and root growth of all species occurred with less than 1.0 p.p.m. of aluminum ion while 2.0 p.p.m. was toxic to root growth. Growth restrictions were more severe at 21 days after seeding than at the 28- or 32-day stages. Yield of tops and roots growing into unlimed acid soil were 73 and 71% respectively of those growing into limed soil. Aluminum taken up by the plant was concentrated in the roots and only with the concentration of aluminum at 2.0 p.p.m. was the content in the tops increased significantly. Phosphorus in the roots, which increased significantly with aluminum ion concentration, was apparently immobilized by aluminum. Percent Ca in the roots increased and in the tops decreased with increasing concentrations of aluminum. Content of K and Mg also varied with aluminum concentration.

Alfalfa plants 'were grown in the g-reenh-ouse to three develop.-mer-r^tal stages'

In t'itro digestibility (IVD)