RESPONSE OF BROMEGRASS TO NITROGEN FERTILIZATION. I. GRASSLANDS MATUA PRAIRIE GRASS

ABSTRACT

“Matua prairie grass” (Bromus willdenowii Knuth) bromegrass is regarded as high quality forage particularly adapted to hay but may also be used for grazing. Little is known about the growth response to nitrogen (N) fertilization or its potential to accumulate nitrate (NO₃ ⁻). Effects of N fertilization were investigated in two greenhouse experiments. Matua was grown in pots in a complete randomized design with four replications of each N treatment. Nitrogen rates were 0, 25, 50, 100, and 200 kg N ha⁻¹ applied twice in Experiment 1 and 50, 100, 200, 300, and 400 kg N ha⁻¹ applied five times in Experiment 2. Plants were harvested twice in Experiment 1, and five times in Experiment 2. Twenty-five kg N ha⁻¹ per application did not sustain growth. Matua tolerated up to 200 kg N ha⁻¹ per application but little increase in growth occurred beyond 50 kg N ha⁻¹ per application. Over five N applications, Matua recovered about 90% of the 250 kg N ha⁻¹ that was applied in 50 kg-increments. Yield efficiency was greatest at 50 kg N ha⁻¹ per application and decreased with increasing N levels. Five applications of N at any rate tested decreased soil pH and increased accumulation of NO₃ ⁻ in the soil. Nitrate accumulated in the plant at N application rates above 50 kg ha⁻¹. Frequent low rates of N appear necessary to avoid N accumulation in soils, to promote high N use efficiency by this grass, and to avoid a potential for NO₃ ⁻ toxicity to livestock.

ACKNOWLEDGMENTS

*Approved by the Dean of the College of Agricultural Sciences and Natural Resources. Pub. No. T-4-492. **Research funded in part by a grant from Modern Forage Systems, L. H. Rosevear and Company, Barenburg USA, Wrightson Seeds, Pyne Gould Guiness LTD, Cascade International Seed Company, Peterson Seeds.