Sulphur (S) is an essential element for plant and animal nutrition, but widespread deficiencies of S
occur world wide. Current recommendations for nitrogen (N):S ratios are 15 to 18:1 and 10 to
12:1 for plant and animal nutrition, respectively; but recent information suggests these may not
predict animal response. Sorghum is an important crop, particularly in drier climatic regions but
little is known concerning S-nutrition for sorghum growth or utilization of S-fertilized forages.
Sorghum "Pioneer 947" was grown on a Lucy loamy sand (loamy, siliceous, thermic Arenic
Kandiudult) in King William County, VA, with and without S fertilization (0 vs. 138 kg S ha-1 as ammonium sulphate) in a randomized block design with four replications. Sulphur fertilization
decreased (P < 0.05) soil pH and increased soil S in the 0 to 25 cm (P < 0.08) and 25 to 50 cm
(P < 0.05) soil layers. An increase in Mehlich-I extractable soil P, Mn (P < 0.05) and soil N03-N
(P < 0.06) at surface 25 cm layer occurred with S-fertilization. At harvest, S-fertilization increased
(P < 0.05) S and water soluble carbohydrates and decreased (P < 0.05) N:S ratio and P concentration
in whole plants. Sorghum leaves were higher (P < 0.05) in N, S, Ca, Mn and Cu in S fertilized
compared to non-S fertilized sorghum. Sulphur fertilization decreased (P < 0.05)
concentration of hydrocyanic acid (HCN) in the upper three leaves. A greenhouse experiment was
conducted with the Lucy soil and 'Pioneer 947' sorghum to further investigate effects of fertilization
(0, 70, and 140 kg S ha -1) as ammonium sulphate in a completely randomized design
with five replications. Sulphur application decreased soil pH, and extractable soil K linearly
(P < 0.01), and increased extractable soil S linearly (P < 0.01).
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