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Wheat straw is a potential cellulosic feedstock for bioethanol. This study was conducted to evaluate straw yield potential and its relationship with grain yield for wheat (Triticum spp.) grown in the United States. The specific objective was to determine if differences in straw yield and harvest index (HI) exist between and within regions and/or wheat classes. Using ongoing variety performance trials in eight states, a total of 255 varietal trial entriess from five classes of wheat were surveyed for above-ground biomass. Averaged over all wheat classes and regions the HI was 0.45. Soft red winter wheat in Kentucky had, on average, the highest HI and lowest straw yield among regions and wheat classes. Soft white winter wheat under irrigation in the Pacific Northwest produced the highest straw yield. Hard red winter wheat in the southern plain states of Texas and Oklahoma had, on average, the lowest HI. Differences in the amount of precipitation and cultivars were the major contributors to the variation detected within wheat classes. The amount of wheat straw available as cellulosic feedstock in a state or wheat class can be estimated using the grain yield estimates provided by the National Agricultural Statistics Service and the class specific HI.

No abstract

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Maximizing P removal with cropping can increase regulated P‐based manuring rates or reduce soil test P in manure‐enriched soils. The potential for increased P removal with winter forage–corn silage double cropping was evaluated in a 3‐yr study at Parma, ID. Winter barley (Hordeum vulgare L.), and both winter and spring genotypes of wheat (Triticum aestivum L.) and triticale (×Triticosecale Wittmack) were fall planted at three seeding rates (112, 168, or 224 kg ha−1) and followed with silage corn (Zea mays L.). Corn alone and a noncropped treatment were included. Winter forages were harvested near boot stage. Seeding rates of 168 kg ha−1 were necessary for maximizing winter forage production but had little effect on P uptake. Winter forage production and P content were highly year dependent due largely to appreciable winterkill of spring wheat and winter barley in 1999. Winter forage P concentrations, unlike those for corn, decreased with successive harvests. Cumulative P uptake ranged as high as 65.7 kg ha−1 for winter triticale. Winter forages reduced corn yields in 2 of 3 yr and corn P uptake in 1 yr. Compared to corn alone, double cropping increased cumulative forage production from 8.4 to 15.9% and total P removal by 29.8 to 42.2%. Soil test P concentrations after 3 yr decreased more with double cropping than with corn alone. Half of the P decline was unrelated to P uptake and removal. Double cropping can increase total forage production, P removal, and hasten soil test P decline.