Growth and mineral content of Italian ryegrass were affected by K and Na treatments when studied by a nutrient solution technique. Potassium influenced plant growth more than did Na. Sodium substituted partly for K in top growth when K was low in the nutrient solution. Changes in the amount of K in solution affected leaf and tiller sizes more than numbers. Visual K deficiency symptoms were delayed and were less severe when Na was high in the solution. Potassium and Na concentrations in all plant parts were directly related to K and Na treatments. Potassium concentration was higher in old blades than in young blades when plants were K deficient, regardless of Na treatment. Sodium concentration, unlike K, generally decreased with increased blade age. Potassium and Na concentrations in the stem were high, compared to other plant parts. The youngest blade that was fully open and had a ligule, blade 1, was determined to be the best plant part to sample. It was necessary to determine Na in addition to K in blade 1 in order to diagnose the K status of the ryegrass adequately. The critical K concentration was 0.8% for blade 1 tissue that contained more than 2.4% Na, dry basis. The critical K concentration was 3.5%, however, for blade 1 tissue that contained less than 0.3% Na, dry basis.

Synopsis Plant growth and the absorption of P by Italian ryegrass from nutrient solution was affected by P supply, whereas the distribution and accumulation of P within the ryegrass was largely determined by the kind of, and age of, tissue sampled. Blade 1, the youngest blade that was fully open and had a ligule, and H2PO4‐P were selected, from 6 plant parts sampled and 2 forms of P determined, as the best combination to diagnose the P status of Italian ryegrass. About 750 ppm of H2PO4‐P in blade 1 tissue was tentatively set as the critical concentration for growth of the ryegrass.

No abstract

* Weights are means of 5 replications-Measurement includes 35 blades, stems, total tops, or roots, or 15 tillers. f Letters In common within a plant part indicate no significant difference at the 5% level (4).

Alkar tall wheatgrass, Agropyron elongatum (Host.) Beauv., and Greenar intermediate wheatgrass, A. intermedium (Host.) Beauv., grown separately in nutrient solutions to which NO3‐ had been added at 0, 0.25, 0.5, 1.0, 2.0, 4.0, 8.0, 16, or 32 meq of NO3‐ per liter. Other nutrients were present in ample amounts. The two grasses were grown concurrently in full greenhouse sunlight for 36 days. Total dry matter production (tops + roots) was significantly reduced with less than 4.0 meq of NO3‐ per liter. Average maximum top weight (oven‐dry) was 2.02 g per plant for tall wheatgrass and 2.76 for intermediate wheatgrass. These top weights were obtained with 8, 16, or 32 meq of NO3‐ per liter. In a common and favorable environment, growth of intermediate wheatgrass was more rapid than that of tall wheatgrass. Accumulation and distribution of nitrate‐N varied slightly within the plants. At high NO3‐ treatments, matured blades of tall wheatgrass had the highest nitrate‐N concentration (14,600 ppm) whereas stems of intermediate wheatgrass had the highest (16,000 ppm) concentration. Immature blades had the lowest nitrate‐N concentration, about 8,200 and 9,200 ppm, respectively, for tall and intermediate wheatgrasses. Recently matured blades of intermediate wheatgrass had higher percentages of total‐N, nonsoluble‐N (protein‐N), and crude protein than did those of tall wheatgrass. Soluble‐N and nitrate‐N concentrations were generally higher in tall wheatgrass than in intermediate wheatgrass. The critical nitrate‐N concentrations for growth of these two wheatgrasses is about 500 ppm nitrate‐N in recently matured blade tissue, dry basis.