Influence of Soil and Applied Chloride on Several Wheat Parameters1

Previous field studies have indicated yield responses of small grain crops to KCl on very high K‐testing soils, which were likely due to Cl fertilization. Suggested mechanisms for the involvement of Cl range from plant disease effects to effects on plant water relations. The possibility that climatic and biological environment may interact with the Cl response could make plant and soil diagnostic relationships difficult to interpret. The objectives of this study were to determine the relationships of plant tissue and soil Cl concentrations to hard red spring wheat (Triticum aestivumL.) yield, and to examine possible interactions with plant diseases and water relationships. Field experiments at 14 locations over 3 yr were conducted on Typic Argiustolls, Pachic and Udic Haplustolls, and Pachic Udic and Udic Haploborolls. A critical plant Cl concentration of 1.5 g kg−1for whole plants at head emergence assured 96% of maximum grain yield. Soil Cl levels > 43.5 kg ha−1(60 cm) or 75 kg ha−1(120 cm) were adequate for near‐maximum wheat yield. Both soil and plant Cl tests appeared to have potential as tools for diagnosing Cl responsive situations. Root and crown samples were taken at seven locations and rated for common root rot (Cochiobolus sativus). No influence of Cl on root rot was detected. Leaf rust (Puccinia recondita) and leafspot (complex of diseases) were suppressed at only one location by Cl addition. Leaf relative water content was measured at two locations and showed significant elvation due to Cl addition at both sites. The lack of detectable disease effects at some yield responsive sites and the good correlation between plant Cl concentration and yield response suggest that the beneficial effect of Cl was more general than disease reduction.