Effect of Fertilizer Nitrogen Source and Chloride on Take-All of Irrigated Hard Red Spring Wheat. R. E. Engel, Assistant Professor, Southern Agricultural Research Center, Huntley, MT. D. E. Mathre, Professor, Department of Plant Pathology, Montana State University, Bozeman 59717. Plant Dis. 72:393-396. Accepted for publication 2 December 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0393.

Field experiments were conducted over 2 yr on an alkaline soil (pH 7.9) to determine the effect of several fertilizer nitrogen (N) sources and chloride (Cl) application methods on irrigated spring wheat inoculated with Gaeumannomyces graminis var. tritici. The effect of fertilizer N source and Cl on disease severity indices (root disease scores and percent white heads) was not as great as the effect on grain yield and test weight. Application of Cl generally had little effect on disease severity indices. Fertilizer N source did not affect root disease scores but did affect percent white heads. This response was not consistent over the two seasons. In 1985, percent white heads was greater for NH₄OH than for NaNO₃. In 1986, percent white heads were greater for NaNO₃ than for NH₄NO₃, NH₄OH, or Co(NH₂)₂. Disease severity indices did not appear to correlate well with yield results. Grain yield and test weight response to Cl in inoculated wheat was influenced by fertilizer N source applied. Chloride had little effect on grain production and test weight when NaNO₃ or no N was applied, but did when NH₄OH or CO(NH₂)₂ was applied. Yield and test weight improvements from Cl were as great as 869 and 517 kg/ha and 36 and 24 g/L, respectively, in 1985 and 1986. Differences in the distribution and amount of growing season moisture and indigenous soil NO₃-N levels may have confounded the results from the 2 yr of study.

Keyword(s): ammonium, band, broadcast, nitrate, sodium chloride.