Eugene G. Krenzer

Winter wheat fall-winter forage yield and grain yield response to planting date in a dual-purpose system

Abstract Previous published research suggests that if fall–winter grazing of winter wheat is properly managed, it will not reduce grain yield. However, highly aggregated state average data suggest that fall–winter grazing is associated with lower grain yields. This study was undertaken to determine the trade-off, or substitution in production, between winter wheat fall–winter forage yield and grain yield across planting dates. Data from experiment station trials were used to estimate response functions and to determine optimal planting dates. The estimated response functions suggest relatively large differences in expected fall–winter forage yield and expected grain yield across planting date. Optimal planting date is sensitive to the value of fall–winter forage relative to the value of wheat grain. Producers will optimally plant wheat intended for dual-purpose use earlier than wheat intended for grain-only. The expected yield from the earlier planted dual-purpose wheat is lower than the expected yield of the later planted grain-only wheat as a result of the earlier planting date.

Genetic trends in winter Wheat yield and test weight under dual-purpose and grain-only management systems

Wheat (Triticum aestivum L.) cultivars of the southern Great Plains are traditionally bred in environments managed for grain production only but are commonly grown for the dual-purpose of producing winter forage and grain from the same crop. To what extent grain yield and test weight are consistently expressed in those environments requires investigation relative to long-term attempts to improve them genetically. A historical set of hard red winter (HRW) wheat cultivars was evaluated under grain-only and dual-purpose management systems to compare their agronomic performance and derived estimates of genetic progress. Separate experiments were established for each system featuring whole-plot treatments of a foliar fungicide and split-plot treatments of 12 cultivars. The study was conducted for 3 yr at the Wheat Pasture Res. Ctr. near Marshall, OK. Dual-purpose experiments were generally grazed from November through February. Yield in the grain-only system improved 18.8 kg ha -1 yr -1 , equivalent to 1.3% of the mean yield for Turkey. The rate of progress in the dual-purpose system was significantly lower at 11.3 kg ha -1 yr -1 , equivalent to 0.9% of the mean for Turkey. Management for grazing had a more profound influence on estimates of yield improvement than did management for disease protection. Linear trends in test weight were not evident under either system, nor were cultivar differences influenced by management system consistently across years. Breeding practices should emphasize selection for grain yield in both environments if future progress is to be maximized in both.

Simultaneous determination of soil aluminum, ammonium‐ and nitrate‐nitrogen using 1 M potassium chloride extraction

Abstract Determination of soil aluminum (Al), ammonium‐nitrogen (NH4‐N), and nitrate‐nitrogen (NO3‐N) is often needed from the same soil samples for lime and fertilizer recommendations, but Al has to be extracted and quantified separately from NH4‐N and NO3‐N according to present methods. The objective of this study was to develop a reliable method for simultaneous analyses of soil Al, NH4‐N and NO3‐N using a Flow Injection Autoanalyzer. Thirty‐five soil samples from different locations with wide ranges of extractable Al, NH4‐N and NO3‐N were selected for this study. Aluminum, NH4‐N and NO3‐N were extracted by both 1 M and 2 M potassium chloride (KCl), and quantified using a LACHAT Flow Injection Autoanalyzer simultaneously and separately. One molar KCl was found to be a suitable extractant for all three compounds when compared to 2 M KCl. The 1 M KCl extract proposed could aid in decreasing the costs associated with simultaneous NH4‐N, NO3‐N, and Al analyses. Results of those three compounds analyzed simultaneously were not statistically different from those analyzed separately in 1 M KCl solution. This new procedure of simultaneous determination of NH4‐N, NO3‐N, and Al increases efficiency and reduces cost for soil test laboratories and laboratory users.

Optimal Stocking Density for Dual-Purpose Winter Wheat Production

Dual-purpose winter wheat production is an important economic enterprise in the southern Great Plains of the United States. Because of the complex interactions involved in producing wheat grain and beef gain from a single crop, stocking density is an important decision. The objective of the research is to determine the stocking density that maximizes expected net returns from dual-purpose winter wheat production. Statistical tests rejected a conventional linear-response plateau function in favor of a linear-response stochastic plateau function. The optimal stocking density of 1.48 steers/ha (0.60 steers/acre) is 19% greater with a stochastic than with a nonstochastic plateau.

Quality of Farmer-Saved Wheat Seed is Variable in the Southern Great Plains

Profitable wheat (Triticum aestivum) production in the southern Great Plains is highly dependent on low input costs, as weather conditions are frequently not conducive for high yield. Many producers save seed from their own production for sowing the following year to reduce production costs, and some choose to purchase bin-run seed of unknown variety, although this practice has become much less common due to stricter enforcement of seed quality and protection laws. These seed sources are seldom tested for purity or germination; therefore, a three-year experiment was conducted in central Oklahoma to evaluate the purity and fecundity of farmer-saved seed sources as compared to commercially-available certified seed sources. Differences in forage and grain yield were observed among certified seed sources of the same variety, and whether or not a forage or grain yield advantage was associated with certified as compared to farmer-saved seed often depended on which certified source was used for the comparison. Certified seed sources generally contained less foreign material, fewer weed seeds, and had higher field germination percentage than farmer-saved seed. Overall, this experiment demonstrates that if farmers use quality control measures similar to those required for certified seed, farmer-saved wheat seed can produce forage and grain yield comparable to that of certified seed.