Critical Tissue Concentration and Chloride Requirements for Wheat
- R. E. Engel ,
- P. L. Bruckner and
- J. Eckhoff
Previous research in the Pacific Northwest and Great Plains has provided evidence that wheat (Triticum aestivum L.) yields are often improved by Cl− fertilization. Published reports on critical tissue concentrations and Cl− requirements for wheat are few in number. Our objectives were to define a critical plant Cl− concentration (head emergence) for maximum yield, develop a Cl− fertilizer recommendation, and determine the effect of Cl− fertilizer on grain protein. Thirty-two field experiments (18 winter and 14 spring wheat) were conducted in Montana between 1988 and 1995. Experiments included comparisons with multiple cultivars and Cl− rates (0–90 kg ha−). Relative yield vs. plant Cl− concentration relationships were assessed from 219 cultivar × experiment episodes. Three zones of Cl− status were identified: (i) a deficiency zone, plant Cl− <1.0 g kg−1, where significant (P < 0.10) yield responses to applied Cl− occurred in 59 of 86 episodes (69%); (ii) an adequate Cl− status zone, plant Cl− ≥4.0 g kg−1, where yield responses occurred in only 2 of 44 episodes (<5%); and (iii) a critical range between these two zones, where responses were observed in 25 of 89 episodes (28%). Regression of plant Cl− concentration on soil (0–60 cm) plus fertilizer Cl− revealed that deficient, critical range, and adequate Cl− zones were associated with <7.5, 7.5 to 32, and ≥33 kg Cl− ha−1, respectively. The proposed guideline for wheat is to add sufficient Cl− to reach the upper end of the critical range (4.0 g kg−1 plant Cl−). This recommendation ensures adequate Cl− nutrition for maximum yield and kernel weight, although at some sites a slight reduction in grain protein (0.5%) may result.
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