EFFECTS OF SULFUR DEFICIENCY ON NON-PROTEIN NITROGEN, SOLUBLE SUGARS, AND N/S RATIOS IN YOUNG CORN (ZEA MAYS L.) PLANTS

• Published in: Plant and soil 1976-04, Vol.44 (2), p.423-437
• Main Authors: RENDIG, V. V., OPUTA, C., McCOMB, E. A.
• Format: Article
• Language: English
• Subjects: Acid soils; Agricultural soils; Alfalfa; Corn; Loam soils; Nitrogen; Plant growth; Plants; Sugars; Sulfur
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1007/BF00015893

The concentrations of several N fractions, soluble sugars and N/S ratios were determined in Golden Bantam sweet corn and hybrid field corn grown in nutrient solutions and/or soil with various SO₄-S levels provided. When the level of SO₄-S supplied was less than that needed for maximum growth, higher-than-normal concentrations of amide (asparagine) N and lower-than-normal soluble sugar concentrations were found in the plants. An inadequate S supply appears to limit the plants capacity to synthesize protein to a much greater extent than it inhibits the nitrogen uptake mechanism. Total N/total S ratios (grammole basis) varying from over 100 to less than 15 were found in plants grown with different levels of sulfate supplied. When SO₄-N, NO₃-N, and the large amount of amide-N which accumulates under conditions of S deficiency are excluded, the ratio in young corn plants is generally between 22-50. The precision of the N/S ratio as an indicator of S adequacy for growing crops might be improved by a better understanding of the nature of the forms in which N and S occur in plants, and the effects of soil and plant factors other than S level. The percentage of amide-N shows promise as an indicator of S nutrient status. Data available indicates that added S will increase yields of corn plants if their amide-N level exceeds 500 ppm. Amide-N concentration correlates with N/S ratios, and it is much more readily determined than the latter. Its usefulness as a S nutrition indicator should be checked under field conditions.