Wheat Grain and Forage Yields are Affected by Planting and Harvest Dates in the Central Great Plains

cultivars, net return is maximized when grazing is terminated at first hollow stem—the stage at which hollow Although grazing of winter wheat (Triticum aestivum L.) is a stem can first be identified above the crown (Redmon common practice in the southern Great Plains, little is known about the efficacy of wheat as a dual-purpose crop in the Nebraska Panhanet al., 1996). However, beyond an optimum leaf area dle. The objective of this study was to evaluate the effects of establishindex, excess foliage does not contribute to increased ment and harvest times on forage and grain production of wheat grain yield in taller wheat cultivars (Redmon et al., cultivars adapted to the region. Six cultivars were planted at four 1995). dates (very early, recommended early, recommended late, and very Differences in fall forage yield among winter wheat late) in each of 3 yr. Forage samples were taken from a previously cultivars has been reported as being sufficiently large nonharvested area late in the fall, at jointing, and at the boot stage. to be of importance to wheat-stocker cattle producers Grain yield at maturity was measured from each forage harvest treat(Krenzer et al., 1992). Unfortunately, selecting a winter ment and from a full-season unharvested control. In 2 of 3 yr, grain wheat cultivar on the basis of forage or grain yield alone yield was reduced an average of 25% compared with the full-season seldom results in the greatest economic return because check when plants were harvested for forage at the joint stage. No grain was produced when forage was removed at the boot stage. higher grain yielding cultivars are not always among the Forage removal during the fall averaged 1300 kg ha21 dry matter and highest forage yielding cultivars (Krenzer et al., 1996). resulted in insignificant losses in grain yield. While most of the fall Winter wheat often is planted early to maximize fall growth was too low to the ground for clipping, it could provide highforage production. Several problems can arise because value supplemental grazing on account of the high crude protein (310 g of early planting. Semidwarf cultivars, with short coleopkg21) and in vitro organic matter digestibility (800 g kg21) levels. tile lengths, may have emergence problems because of Spring grazing in this region is limited to the time prior to jointing the deeper planting depth required to place seed in if market conditions favor grain production. adequate soil moisture during late-summer (Redmon et al., 1995). Early planting also shifts the period of major soil water extraction from spring to fall (Winter and W wheat pasture provides high-quality forMusick, 1993). This can reduce grain yields compared age for grazing livestock (Horn, 1984). The forage with wheat planted near the optimum date. Early plantis high in moisture and soluble constituents during fall ing of winter wheat also predisposes plants to infection and winter and may be unable to meet the daily dry by diseases such as root and crown rot [caused by the matter (DM) intake requirements of cattle (Bos taurus fungi Bipolaris sorokiniana (Sacc. In Sorok.) Shoem. L.). At that time, crude protein concentration of wheat and Fusarium spp.] (Fenster et al., 1972). is high, sometimes exceeding 30% of DM, and fiber The great majority of research conducted on winter concentration is low. In the spring, yield and nutrient wheat grazing in the USA has been conducted in the levels of wheat forage are greatly influenced by plant southern Great Plains (Redmon et al., 1995). The potenmaturity, with crude protein concentration decreasing tial for winter wheat to be used as a dual-purpose crop and fiber concentration increasing with maturation in western Nebraska has not been evaluated. Nebraska (Bolsen, 1984). producers currently provide fall and spring forage by Numerous studies have investigated the effects of deferred grazing of summer pastures, purchased energy wheat grazing on grain yield (Redmon et al., 1995). Aland protein supplements, and stored hay and haylage. though the effects of environment, wheat physiology, Wheat hay and pasture could provide valuable fall and grazing management, and compensation of grain yield early spring supplementation for cow-calf operations in components make it difficult to draw a uniform concluthe central Great Plains, where the quantity and quality sion for the effects of grazing on grain yield, some genof pastures at these times are poor. The objective of eral trends are evident. this study was to evaluate the potential for winter wheat Grazing tall winter wheat cultivars prior to culm elonto be used for supplemental forage and grain production gation is likely to produce slight increases in grain yield in the central Great Plains. Specifically, planting dates, relative to nongrazed wheat because of reduced lodging forage harvest times, and cultivars were compared to potential. In semi-dwarf cultivars, grazing is more likely determine forage yield and quality attributes relative to to reduce grain yield. Semi-dwarf wheat cultivars regrain yield performance. quire maximum photosynthetic tissue to produce maximum grain yield (Redmon et al., 1995). For semidwarf MATERIALS AND METHODS Field studies were conducted at the University of Nebraska Panhandle Research and Extension Center, 4502 Ave. I, Scottsbluff, High Plains Agricultural Laboratory near Sidney, NE, at an NE 69361. Journal Series No. 12864 of the University of Nebraska Agricultural Research Division. Received 3 Dec. 1999. *Corresponding author ([email protected]). Abbreviations: ADF, acid detergent fiber; DM, dry matter; IVOMD, in vitro organic matter digestibility; NDF, neutral detergent fiber. Published in Crop Sci. 41:488–492 (2001).