Sulfur management for corn growth with conservation tillage

Reduction in soil disturbance associated with conservation tillage planting systems suggests that it is important to evaluate management practices for use of S for corn (Zea mays L.) grown in these planting situations. Evaluation of source, placement, and rate of S applied has not been the focus of past research. In this study, two S fertilizers [21-0-0-24 (ammonium sulfate), 12-0-0-26 (ammonium thiosulfate)] were applied at rates to supply 0, 6.7, 13.4, and 20.1 kg S ha(-1) either in contact with the seed at planting or in a band near the seed at planting. Soil texture varied from loamy fine sand to silty clay loam at the experimental sites. Corn emergence was reduced when 12-0-0-26 was placed in contact with the seed at sites with a loamy fine sand and sandy loam texture and soil was dry at time of planting. Stand reduction was most severe when 12-0-0-26 fluid material was used at rates to supply 13.4 and 20.1 kg S ha-1. Placement maintaining soil between seed and fertilizer had no negative effect on emergence. When placed in a band near the seed, both S sources had an equal effect on yield. Reduction in emergence due to 12-0-0-26 in contact with the seed had a negative effect on grain yield. Application of fertilizer S increased yield at all sites except where the texture was a silty clay loam. Optimum rate of fertilizer S was either 6.7 or 13.4 kg S ha(-1) and varied with site. The response to fertilizer S on the silt loam soil suggests that inadequate S is released from soil organic matter via mineralization in conservation tillage planting systems.