Chloride and Liming Effects on Soil Nitrogen Form and Take-all of Wheat1
- N. W. Christensen and
- Marcia Brett2
Little is known about how chloride (Cl) functions in suppressing take-all root rot of wheat (Triticum aestivum L.). A field experiment was conducted to determine the effects of liming and CI application on ammonium (NH+4 and nitrate (NO−3-N) concentrations in soil as they correlate with development of the disease. ‘Hill 81’ soft white winter wheat was grown on a limed (pH 6.6) and unlimed (pH 5.5) Aquultic Argixeroll fertilized with a factorial combination of 30 kg N ha−1 as NH4NO3, (NH4)2SO4, or NH4Cl banded at planting and 140 kg N ha−1 as Ca(NO3)2, (NH4)2SO4, or NH4Cl topdressed in the spring. Soil was sampled to 10 and 20 cm depths and analyzed for NH+4-N, NO−3-N, Cl, and pH at weekly intervals for 10 weeks following spring application of N. Take-all was assessed at 0, 6, and 11 weeks after spring fertilization. Take-all severity, NH+4-N and NO−3-N concentrations, NH+4-N:NO−3-N ratios, and grain yield were all influenced by a highly significant interaction between liming and spring-topdressed Cl. Liming hastened disappearance of NH+4-N and increased appearance of NO−3-N in soil. Chloride slowed disappearance of NH+4-N and appearance of NO−3-N in unlimed soil but not in limed soil. A “critical” NH+4-N:NO−3-N ratio for take-all suppression of 3:1 was estimated from data in the literature. Takeall severity was negatively correlated (r2=0.84) with the length of time the NH+4-N:NO−3-N ratio remained above the estimated critical ratio. Chloride increased grain yield from 3.5 to 4.7 Mg ha−1 on the unlimed soil but had no effect on yield on the limed soil. Results suggest that Cl may reduce take-all severity and increase grain yield on moderately acid soils in western Oregon by reducing nitrification and maintaining a favorable NH+4-N:NO−3-N ratio for disease suppression.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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