Sulfur, manganese, molybdenum, and magnesium influences on brome‐grass forage yield and composition in southcentral alaska

Abstract

When a bromegrass stand failed to respond normally to ammonium nitrate application, an observational experiment provided indications of beneficial grass response to K₂SO₄ application and to Mn and Mg foliar sprays. A Mo foliar spray apparently depressed growth. This study was to diagnose this apparent acute S deficiency which later became common to wide areas of Alaskan grasslands. An experiment involving three S treatments (no S, elemental S, and K₂SO₄) with four other treatments (Mn, Mo, Mg, and a check) was conducted with bromegrass on Knik silt loam (Typic Cryorthent) from 1969 through 1976. All plots received adequate and uniform N, P, and K annually. Sulfur application increased bromegrass yields for both cuttings annually during this 8‐year period. The S concentration of the two cuttings increased with S application, being greater with K₂SO₄ than with elemental S. The N/S ratio also indicated that S from K₂SO₄ was more readily available than that from elemental S. Generally, S application depressed both NO₃‐N and total N concentration in both cuttings. Second‐cutting Ca and Mg concentrations exceeded those of the first cutting. When K₂SO₄ was applied, the S concentration decreased with MgO application. Soil pH decreased from 6.3 in 1969 to 5.5 in 1976 with all treatments except those where MgO had been used. Sulfur application increased the total S in the soil at the 0–5 and 5–10 cm sampling depths and the SO4‐S at all three sampling depths.

Key words:

• Nutrient uptake
• soil reaction
• subarctic

Notes

Cooperative investigation of USDA, SEA‐AR, and the Alaska Agr. Expt. Sta. Alaska Agr. Expt. Sta. Journal Paper No. J‐148.

Research soil scientist, USDA, SEA‐AR, Palmer, AK., laboratory technician, Alaska Expt. Sta., Palmer, AK., and biological technician, USDA, SEA‐AR, Palmer, AK.