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Winter wheat (Triticum aestivum L.) is the most common dryland crop grown in the central Great Plains. Producers in this region include fallow in the rotation to minimize yield variability due to erratic precipitation. However, fallow degrades soil quality by increasing erosion potential and loss of organic matter. Fortunately, minimum‐till production systems and residue management improve water use efficiency by plants, thus producers can crop more frequently. We evaluated eight rotations comprised of various sequences of winter wheat (W), corn (Zea mays L.) (C), proso millet (Panicum miliaceum L.) (M), sunflower (Hettanthus annum L.) (S), and fallow (F) in comparison to W‐F at Akron CO. Our goal was to identify rotations that can replace W‐F to minimize the frequency of fallow. The soil was a Weld silt loam (Aridic Paleustoll). Continuously cropping with W‐C‐M and W‐M almost doubled total grain yield compared with the conventional system of W‐ F. Other rotations such as W‐C‐F, W‐C‐S‐F, and W‐C‐M‐F yielded >60% more on an annualized basis than W‐F. Winter wheat yield increased with longer time intervals between wheat crops. Sunflower yielded the most when grown only once every 4 yr; more frequent cropping favored diseases. Sunflower reduced yield of the following crop, especially during dry years. Yield variability was highest with corn and sunflower, whereas proso millet showed the least variability. Producers can manage yield variability by diversifying crops in the rotation, as annualized yield variability of W‐M and W‐C‐M was similar to W‐F. With residue maintenance and minimum tillage, producers can crop more frequently, thus increasing land productivity while minimizing the frequency of fallow in this semiarid region. Research Question Since the 1930s, winter wheat‐fallow has been the prevalent crop rotation for the semiarid Central Great Plains. Because available water is usually the most limiting resource, producers rely on fallow to minimize the impact of erratic precipitation on grain production. However, fallow degrades soil quality by increasing erosion and loss of organic matter. Development of minimum‐till production systems has altered the water relations in our agroecosystems. Minimizing tillage leaves more crop residue on the soil surface, subsequently increasing precipitation storage and water use efficiency of crops. Thus, with minimum‐till systems, more intensive cropping is possible in the central Great Plains. This study evaluated cropping systems composed of various sequences of winter wheat (W), corn (G), proso millet (M), sunflower (S), and fallow (F), including continuous cropping. Our goal was to identify rotations that may be successful alternatives to W‐F. Literature Summary With reduced‐till systems, several crops have been successful in a wheat‐summer crop‐fallow rotation in this region, including proso millet, corn, and grain sorghum. In addition, longer rotations with three crops in 4 yr, such as W‐C‐M‐ F, are also successful and have increased land productivity by 70%. Another p...

New evidence confirms earlier postulates that root signals to shoots, including abscisic acid, nitrate flux, and cytokinins, modify whole plant growth processes including leaf expansion, stomatal behavior, and biosynthesis of photosynthetic enzymes. Root signals are thought to reflect soil water, nutrient, and mechanical attributes, as sensed by roots. Meristematic activities in root tips initiate changes in root architecture, modifying the soil volume subject to root uptake, and may provide multiple sensory and signaling capabilities. Knowledge of root signals regulating whole plant growth processes suggests new analytical and experimental tools for integrated analysis of plant phasic development, optimal growth, and ecological fitness.

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Increasing water and radiation use efficiencies (WUE and RUE, respectively) are critical to enhance crop production. Exploring genetic variability in WUE and RUE is necessary to improve these traits. The objectives of this research were to evaluate eight sorghum [Sorghum bicolor (L.) Moench] genotypes for biomass production, WUE, and RUE and to test whether the differences in WUE among sorghum genotypes were associated with increased biomass production or decreased water use under field conditions. The WUE was estimated as the slope of the regression of aboveground biomass on cumulative water use for specified sampling intervals. The RUE was estimated as the slope of the regression of aboveground biomass on cumulative intercepted photosynthetically active radiation (IPAR). Sorghum genotypes showed significant differences in biomass production, WUE, and RUE. The WUE varied from 3.39 ± 0.80 to 5.42 ± 0.80 g kg−1 in 2009 and from 4.04 ± 0.58 to 7.63 ± 0.58 g kg−1 in 2010. Similarly, RUE varied from 2.13 ± 0.33 to 3.53 ± 0.31 g MJ−1 IPAR in 2009 and from 2.08 ± 0.35 to 3.83 ± 0.33 g MJ−1 IPAR in 2010. Among the eight sorghum genotypes tested in this study, IS 27111 and IS 27150 had the largest biomass production, WUE, and RUE. The WUE was more strongly correlated to biomass production than to water use. This result implies that it is possible to improve WUE without compromising biomass production. The sorghum genotypes evaluated for biomass production, WUE, and RUE in this study offer useful plant materials for identifying the mechanisms causing differences in these traits.

Sorghum [Sorghum bicolor (L.) Moench] grain yield is severely affected by abiotic and biotic stresses during post-flowering stages, which has been aggravated by climate change. New parental lines having genes for various biotic and abiotic stress tolerances have the potential to mitigate this negative effect. Field studies were conducted under irrigated and dryland conditions with 128 exotic germplasm and 12 adapted lines to evaluate and identify potential sources for post-flowering drought tolerance and stalk and charcoal rot tolerances. The various physiological and disease related traits were recorded under irrigated and dryland conditions. Under dryland conditions, chlorophyll content (SPAD), grain yield and HI were decreased by 9, 44 and 16%, respectively, compared to irrigated conditions. Genotype RTx7000 and PI475432 had higher leaf temperature and grain yield, however, genotype PI570895 had lower leaf temperature and higher grain yield under dryland conditions. Increased grain yield and optimum leaf temperature was observed in PI510898, IS1212 and PI533946 compared to BTx642 (B35). However, IS14290, IS12945 and IS1219 had decreased grain yield and optimum leaf temperature under dryland conditions. Under irrigated conditions, stalk and charcoal rot disease severity was higher than under dryland conditions. Genotypes IS30562 and 1790E R had tolerance to both stalk rot and charcoal rot respectively and IS12706 was the most susceptible to both diseases. PI510898 showed combined tolerance to drought and Fusarium stalk rot under dryland conditions. The genotypes identified in this study are potential sources of drought and disease tolerance and will be used to develop better adaptable parental lines followed by high yielding hybrids.Electronic supplementary materialThe online version of this article (doi:10.1186/2193-1801-2-650) contains supplementary material, which is available to authorized users.

Canola oil is high in oleic acid which is commonly used for food and industrial purposes. To determine adaptability of spring canola (Brassica napus L.) to the High Plains for industrial oil production, 26 irrigated trials were conducted from 2005 to 2008. Trials were divided into five regions-1: 36-37 • N 108 • W; 2: 39-40 • N 101-103 • W; 3: 41-42 • N 102-103 • W; 4: 41-42 • N 104 • W; 5: 43-44 • N 106-108 • W. Cultural practices were based on site-specific protocols. Four cultivars, Hyola 401, Hyola 357 Magnum, SW Marksman, and SW Patriot, were planted in replicated plots in April or May under standard irrigation and harvested in July to October depending on region. Seed yield Hyola 401 and Hyola 357 Magnum were higher than SW Marksman and SW Patriot across the five regions and within Regions 1, 2, 3, and 5. Regions 1, 2 and 3 yielded significantly greater than did Regions 4 and 5. Samples from 18 trials were examined for their oil content and fatty acid distribution. The four cultivars had greater than 38% oil content; SW Marksman and SW Patriot had higher oil content than Hyola 401 and Hyola 357 Mag. Higher oil content was achieved in Regions 1, 4 and 5. Across and within regions, the percent of oleic acid did not differ for the four cultivars. The mean content of oleic acid decreased going north from Region 2 to Region 5, as did seed yield in the High Plains. Linoleic acid increased going north from Region 1. Linolenic acids showed little variation across regions. Considering yield and total oil content together, growing spring canola would be excellent in the High Plains.

Producers wishing to diversify crop production systems from the traditional winter wheat (Triticum aestivum L.)‐fallow system of the central Great Plains need information regarding the impact of sunflower (Helianthus annuus L.) on subsequent winter wheat and proso millet (Panicum miliaceum L.) yields. This study was conducted to quantify winter wheat and proso millet yield reductions due to the lower available soil water that exists when sunflower is the prior crop in rotation. Eight crop rotations—including combinations of winter wheat (W), proso millet (M), corn (Zea mays L.) (C), sunflower (Sun), and fallow (F)—were established in 1990 and evaluated for yield, available soil water at planting, and crop water use in 1995, 1996, and 1997. The experiment was conducted at Akron, CO, on a Weld silt loam (fine, smectitic, mesic Aridic Paleustoll). Available soil water at wheat and millet planting was lower where sunflower had been the previous crop than where sunflower was not the previous crop. In dry years, rotations with sunflower as the previous crop had lower wheat and millet water use than other rotations, but averaged over 3 yr, there was no effect of sunflower on wheat or millet water use. Average wheat yield in a W‐Sun‐F rotation was about 30% lower than wheat yield from W‐C‐Sun‐F, W‐M‐Sun‐F, W‐C‐F, and W‐F. Average millet yield in a M‐Sun rotation was 43% lower than millet yield from M‐W‐C. Wheat yield declined by 178.5 lb/acre (3 bu/acre) for each inch decline in available soil water at planting. Millet yield declined by 295.6 lb/acre for each inch decline in available soil water at planting. In making the decision to include sunflower in crop rotations, producers will have to consider impact on subsequent crop yields, as well as costs of production, market value of crop, impact on pest problems, and total productivity of all crops in the rotation. Research Question Sunflower production offers central Great Plains producers an opportunity to diversify from the traditional winter wheat‐fallow production system. But sunflower can leave the soil water profile in the top 72 in. very dry. The objective of this study was to determine the impact of sunflower on subsequent winter wheat or proso millet yields. Literature Summary Sunflower is adapted to the growing conditions of the central Great Plains and has an established market. But sunflower is a deep‐rooted species capable of extracting large amounts of available water from deep in the soil profile. Yield of winter wheat and proso millet are linearly related to crop water use. Consequently, the low available soil water following sunflower production may reduce yield of subsequent wheat and millet crops. Study Description A crop rotation experiment was established near Akron, CO, in 1990. The following rotations were measured in 1995, 1996, and 1997 to quantify the effect of sunflower on subsequent winter wheat and proso millet yield: wheat‐fallow (W‐F), wheat‐corn‐fallow (W‐C‐F), wheat‐sunflower‐fallow (W‐Sun‐F), wheat‐corn‐sunflower‐fallow (W‐C‐Sun‐F), whea...