Response Of Winter Wheat Triticum Aestivum L Em Thell To Nitrogen And Chloride Fertilization In The Presence Of Take All Root Rot Gaeumannomyces Graminis Var Tritici Walker PDF Download

Take-all root rot (caused by Gaeumannomyces graminis var. tritici, Ggt) is one of the major diseases limiting winter wheat yields in western Oregon. Losses caused by take-all (TA) can be significantly reduced through crop management and fertilization practices. Results from field experiments in western Oregon show that the use of chloride with NH4-N is an effective tool to minimize grain yield losses in fields with TA. This study was undertaken to determine the effects of fall- and spring-applied chloride fertilizers on the components of leaf water potential, grain yield and disease severity of winter wheat with TA. Winter wheat field plots were established on a Woodburn soil (Aquultic Argixeroll) on 15 October 1980 at a site previously cropped to first-year wheat after fallow. Spring fertilizer application was on 16 March 1981. Twenty treatments were arranged in a randomized complete block design to study the effects of source, rate, method of application and timing of chloride fertilizers on grain yield, disease severity and leaf water potential components. Other comparisons included rates of P and Cu plus Zn banded in the fall, and fall and spring nitrogen rates. Grain was harvested with a plot combine on 30 July 1981, and grain yield, test weight and 1000 kernel weight were measured. Disease severity was assessed using two methods, (1) visual estimation of black root lesions on three dates, and (2) whole plant fresh weights on 2 July 1981. Leaf osmotic potentials and plant nutrient concentration were measured on four dates. Leaf water potential components (turgor, osmotic and leaf water potentials) and plant nutrient concentrations were determined during May and June on second-year wheat and once on third-year wheat from an adjacent site. A partial diurnal water curve for (NH4)2S04- and NH4Cl-treated plants was measured on 2 June 1981, on third-year wheat. Grain yields were increased by 1000 kg/ha with the addition of spring chloride as NH4CI, KCl or CaCl2. Arate of 92 kg spring Cl/ha was adequate to achieve the highest grain yield (6633 kg/ha). Grain yield was not significantly affected by rate, source or method of application of fall-applied chloride, fall or spring N rates, or by the application of P or Cu plus Zn banded with the seed at planting. Application of 368 kg spring Cl/ha as NH4Cl reduced severity of take-all and increased whole-plant fresh weight when compared to (NH4)2S04 at the same rate of N, but the differences were not statistically significant. Disease severity was not significantly affected by either rates or sources of spring chloride. Grain yields were negatively correlated to disease severity indices. Spring chloride fertilizers applied as NH4Cl or KCl significantly increased percent total N in flag leaves sampled in late spring, while the percent leaf chloride was increased with application of either KCl, NH4C1 or CaCl2. Osmotic potentials in flag leaves of second-year wheat were significantly reduced (from -21.6 to -22.6 bars) over the nil CI rate by application of spring chloride fertilizers. Ninety-two kg Cl/ha was adequate to reduce the osmotic potential. Spring chloride at 368 kg Cl/ha significantly increased turgor potentials in both secondand third-year winter wheat, and significantly decreased osmotic potentials (2 bars) in second-year wheat when compared to (NH4)2S04- treated plots at the same N rate. Potassium chloride significantly reduced leaf and osmotic potentials at the 185 kg Cl/ha rate. Potassium chloride did not increase turgor. The results of this study support the recent literature indicating that application of spring chloride in combination with ammonium-nitrogen to moderately acidic soils reduces the severity of take-all and increases yield of winter wheat.