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Title: FALL FORAGE BIOMASS AND N COMPOSITION OF WINTER WHEAT POPULATIONS SELECTED FROM GRAIN-ONLY AND DUAL-PURPOSE ENVIRONMENTS

Author
item Mackown, Charles
item CARVER, BRETT - OKLA STATE UNIV.

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/15/2004
Publication Date: 1/3/2005
Citation: Mackown, C.T., Carver, B.F. 2005. Fall forage biomass and N composition of winter wheat populations selected from grain-only and dual-purpose environments. Crop Science. 45:322-328.

Interpretive Summary: Each year millions of stocker calves graze wheat pastures in the southern Great Plains to add weight before feedlot finishing. Often on more than 50% of these grazed pastures, the stockers are removed in time to allow the wheat to produce a grain crop. This dual-purpose (grazing plus grain) use of wheat offers producers economic advantages not enjoyed by producers that grow wheat as a grain-only crop. Traditionally, the wheat cultivars used for dual-purpose were developed in grain-only systems. Forage traits for 24 sets of populations (each with unique pedigree) were used to test benefits of tailoring breeding programs for dual-purpose wheat. Forage biomass and forage total nitrogen and nitrate were measured at the start of fall grazing of mass selected sub-populations derived from grain-only and dual-purpose management systems. Selection in the dual-purpose system appears to offer equal or slightly less fall forage biomass without greatly changing forage total nitrogen and nitrate concentrations. Forage nitrate, however, was affected greatly by genetic background, indicating that a breeding program could reduce undesirable high levels of nitrate in fall wheat pastures. These results will be useful to wheat breeders seeking to develop cultivars suitable for dual-purpose and grain-only use in the southern Great Plains.

Technical Abstract: Winter wheat (Triticum aestivum L.) is the foundation of agricultural enterprises in the southern Great Plains and is grown primarily as grain-only (GO) and dual-purpose (DP, grazing plus grain) crops. Traditionally, cultivars are developed in GO systems. Because of genotype by system interactions, the DP environment may compromise yield gains accrued in GO-developed cultivars. Forage traits for 24 sets of populations (each with unique pedigree) were used to test benefits of tailoring breeding programs for DP wheat. Forage biomass and forage total N and nitrate were measured at the start of fall grazing of mass selected sub-populations derived from GO and DP management systems. Nearly always, the effect of selection environment was consistent across genetic backgrounds. Effect of selection environment on forage biomass of each nursery was significant at P = 0.09 and P = 0.07 in 2001 with DP-derived populations yielding about 5% less than those from GO; in 2002, selection effect was not significant (P = 0.38 and 0.30). Selection environment had a significant effect on forage total N but not nitrate levels. Total N in DP selections was slightly greater (2.5%, P < 0.05) than those from NS and GO selections. Forage nitrate was affected by genetic background; mean nitrate-N among the 24 backgrounds ranged from 1.3 to 3.1 mg/g in 2001 and 0.4 to 1.3 mg/g in 2002. Selection in the DP system appears to offer equal or slightly less fall forage biomass without greatly changing forage total N and nitrate concentrations.