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Fluid Journal : Fluid Journal 2002-2004
1 Fluid Journal Late Spring 2003 Sulfur Applications Boost Alfalfa Yields by Dr. Richard Koenig, kevin Heaton, and James Barnhill In sites marginal or deficient in sulfur, tests indicate that consistent responses to sulfur fertilization can be achieved. Summary. Alfalfa consistently responded to sulfur (S) fertilization applications in both 2001 and 2002. It appears that on marginal sites (6 ppm SO4-S), consistent responses up to 19 percent can be achieved with S fertilization. On highly deficient sites (<3 ppm SO4-S), responses have been greater and have included increases in alfalfa forage quality as well as yield. All sources of S fertilizer appear to work equally well when applied in early spring to established stands of alfalfa. Sulfur is an important component of several amino acids and has been shown to influence yield, protein content, and stand density of alfalfa. Yield responses of up to 300 percent have been reported under severe S deficiency conditions. However, more typical yield responses to S fertilization are in the range of 10 to 25 percent. In the past, crop S requirements were met by depleting soil reserves, fortuitous contributions from other fertilizers, and atmospheric deposition. With high crop yields, the production of higher analysis fertilizers containing less S and reductions in atmospheric emissions, more S deficiencies in the soil are likely to occur. High-yielding alfalfa (>5 tons/A) will more likely result in soil S deficiencies as crop 7 6 5 4 3 2 Cache 01 Yield (tons/A) Garfield 01 Weber 02 Garfield 02 No S AMS K-Mag SOP K-SuL N-SuL Sulfur Source 7 6 5 4 3 2 Cache 01 Yield (tons/A) Garfield 01 Weber 02 Garfield 02 0 25 50 Sulfur rate (lb/A) 100 Figure 2. Effect of S source on alfalfa hay yield at two locations in 2001 and 2002. Figure 1. Effect of S rate on alfalfa hay yield at two locations in 2001 and 2002.
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