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ARS Home » Pacific West Area » Pendleton, Oregon » Columbia Plateau Conservation Research Center » Research » Publications at this Location » Publication #80977

Title: DISEASES IN WHEAT IN LONG-TERM AGRONOMIC EXPERIMENTS AT PENDLETON, OREGON

Author
item SMILEY, R.
item COLLINS, H.
item Rasmussen, Paul

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Long-term experiments provide insights into agricultural sustainability that are unlikely to be identified in short-term (1-5 year) experiments because of insufficient time for soil microorganisms to respond to new environments created by tillage, crop rotation, fertilizer use, or crop residue removal. We investigated the incidence and severity of wheat diseases caused primarily by soilborne pathogenic fungi in four long-term (27-60 year old) cropping system experiments. Take-all and eyespot were associated with increasing precipitation while root and crown rots were favored by drought. Eyespot and crown rot increased with nitrogen (N) fertility, and were inversely proportional to soil acidity. Surface residue from previous crops increased crown rot. Root rot increased with increasing residue in a winter wheat/summer fallow rotation but not in a wheat/legume rotation. Burning of crop residue suppressed root rot but enhanced eyespot and take-all. Crop rotation effects on diseases appeared related to soil microflora effects on pathogen survival. Diseases were least prevalent where N was organic rather than inorganic, but soil acidity was also less with organic N. Diseases were generally less damaging in rotations that included crops other than wheat. Soilborne plant pathogenic fungi tended to suppress wheat yield by 3-12%.

Technical Abstract: Wheat disease incidence and severity were evaluated for three years in four long-term (27-60 yr. old) cropping system experiments. Take-all and eyespot were associated with increasing precipitation; Rhizoctonia root rot and Fusarium crown rot were favored by drought. Eyespot and crown rot increased with nitrogen (N) fertility, and were inversely proportional to soil pH. Residue from previous crops increased crown rot. Rhizoctonia increased with increasing residue in a winter wheat/summer fallow (W/F) rotation but not in a wheat- pea (W/P) rotation. Burning of crop residue suppressed Pythium root rot and Rhizoctonia root rot at high N fertility, but enhanced eyespot and take-all. Crop rotation effects on diseases appeared related to soil microflora influence on pathogen survival. Rhizoctonia was most damaging in W/F, Pythium in W/F and annual wheat (W/W), and eyespot and crown rot in W/W. Diseases were least prevalent where N was organic rather than inorganic, but soil pH was also higher with organic N. Diseases were generally less damaging in W/P than in W/W or W/F rotation. Soilborne plant pathogenic fungi appeared to suppress wheat yield by 3-12%. Long-term experiments provided insights to crop management and seasonal effects that are unlikely to be identified in short-term experiments.