Influence of K on the Yield and Chemical Composition of Grasses Grown in Hydroponic Culture with 12, 50, and 75% of the N Supplied as NH₄+¹

Abstract

The role of K in NH4+ utilization by three grasses harvested at the early vegetative, late vegetative, and early heading stages of development was studied in a greenhouse hydroponic experiment. Nitrogen was supplied at 250 ppm, with 12, 50, or 75% of the N in the form of NH4+ in solutions containing 50 or 250 ppm K. Orchardgrass produced the highest dry matter yield followed by bromegrass and timothy. A high ammonium source (75%) with low K (50 ppm) resulted depression of yield, reduction in tillering, increased mortality, and significant changes in the percent K, Ca, Mg, P in the plant tissue. Provision of adequate K (250 ppm) improved NH4+ utilization, increased the yield of forage and reduced the content of total, protein, and nonprotein N in the tissue. Potassium reduced the accumulation of tissue N in soluble or nonprotein form. Nonprotein nitrogen was the same at the late vegetative and early heading stages as at the early vegetative stage of development. The reduced nitrogen fraction which ranged from 0.3 to 0.8% with 50 ppm K was lowered to a range of 0.1 to 0.5% with 250 ppm K. Significant interaction effects for K and percent NH4+ showed that K increased the utilization of NH4+ nitrogen by grass and altered the percent of each nitrogen fraction present in the tissue.

Effects of Nitrogen Form and Potassium Concentration on Growth, Flowering, and Nitrogen Utilization of Greenhouse Roses1

“…Subsequently, Maynard et al, (12) observed when K was supplied in adequate amounts, NH4-N toxicity symptoms were prevented and NH4-N did not accumulate in the tissue. Similar results have been ob tained with a number of plant species (1,11,16).…”

Effects of N, P, and K and Their Interactions on the Yield and Kernel Weight of Barley in Hydroponic Culture1

“…Each plot (polyethylene container 55 em long, 37 em wide, and 25 em deep) was subdivided in a randomized design to allow each treatment to be harvestt'd at three stages of development. The rooting medium was flooded four times daily with nutrient solutions as described previously (4,5) .…”

Effects of N and K Fertilization on the Protein, Nitrate and Nonprotein Reduced N Fractions of Timothy and Bromegrass

“…Greenhouse experiments have indicated that adequate K improves NHn utilization and reduces the accumulation of nonprotein N in forage (Macleod 1965;Macleod and Carson 1966). …”