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Pangolagrass Performance under Different Levels of Nitrogen Fertilization in Hawaii¹

Pangolagrass was grown on a Humic Latosol at 650 m elevation in an area of 170 cm average annual rainfall with relatively dry summers. Five levels of nitrogen from 0-640 kg ha^–1 yr^–1 were applied as (NH₄)₂SO₄ over a year period. Average annual dry matter (DM) yields ranged from 3,780 kg (control) to 18,000 kg/ha, and response to succeeding increments of N ranged from 30 units of DM per unit of N for the first increment (160 kg) down to 10 units for the 480-640 kg increment. Yields were depressed when average night temperatures were 15C and during dry periods, but yields were significantly increased by fertilization even during these periods. Percentage crude protein fluctuated with season, being highest during the cooler months. Crude protein levels were influenced only slightly by low rates of fertilization but were raised by the higher N rates to levels sufficient to insure efficient utilization by livestock. The average production of forage under clipping indicated feeding capacities ranging from 1.1 animals (360 kg steers or heifers) per ha for the control to 7.5 animals per ha for the highest N level.

Recovery of applied N increased from 36% for the first increment to 64% for the third increment, with a somewhat lower recovery for the final increment. Soil pH was reduced by 0.10-0.15 units for each ton of (NH₄)₂SO₄ applied. Liming the soil raised pH from 5.6 to 6.3 but did not influence yields of DM or crude protein. Critical levels for potash sufficiency were established at 0.11 meq/100 g of soil or 1.0% of the dry forage.

Key Words: Nitrogen recovery • Potassium requirement • Soil pH

² Assistant Agronomist and Associate Soil Scientist, Hawaii Agricultural Experiment Station, University of Hawaii, Kula, Hawaii 96790.

Received for publication December 19, 1968.