Excessive corn (Zea mays L.) stover removal for biofuel and other uses may adversely impact soil and crop production. We assessed the effects of stover removal at 0, 25, 50, 75, and 100% from continuous corn on water erosion, corn yield, and related soil properties during a 3-year study under irrigated and no-tillage management practice on a Ulysses silt loam at Colby, irrigated and strip till management practice on a Hugoton loam at Hugoton, and rainfed and no-tillage management practice on a Woodson silt loam at Ottawa in Kansas, USA. The slope of each soil was <1%. One year after removal, complete (100%) stover removal resulted in increased losses of sediment by 0.36-0.47 Mg ha À1 at the irrigated sites, but, at the rainfed site, removal at rates as low as 50% resulted in increased sediment loss by 0.30 Mg ha À1 and sediment-associated carbon (C) by 0.29 kg ha À1. Complete stover removal reduced wet aggregate stability of the soil at the irrigated sites in the first year after removal, but, at the rainfed site, wet aggregate stability was reduced in all years. Stover removal at rates ≥ 50% resulted in reduced soil water content, increased soil temperature in summer by 3.5-6.8°C, and reduced temperature in winter by about 0.5°C. Soil C pool tended to decrease and crop yields tended to increase with an increase in stover removal, but 3 years after removal, differences were not significant. Overall, stover removal at rates ≥50% may enhance grain yield but may increase risks of water erosion and negatively affect soil water and temperature regimes in this region.Keywords: stover removal, water erosion, soil aggregation, soil carbon, irrigation IntroductionThe demand for corn stover feedstock for bioenergy production and other competing uses is expected to increase in the near future. Corn stover has been identified as a prime feedstock for bioenergy production in the United States because of its perceived abundance and availability (Wilhelm et al., 2004; United States Department of Agriculture, 2010). Although the use of corn stover for bioenergy production and other expanded uses appears to be feasible, the magnitude at which different levels of stover removal affect soil erosion, soil properties, crop production, and other ecosystem services is not well understood in the western Corn Belt in general and Kansas in particular. This information is needed for determining the amount of stover that can be harvested for biofuel from rainfed and irrigated conditions.Removal of stover for bioenergy may negatively affect ecosystem services provided by crop residues such as erosion control (Cruse & Herndl, 2009). Even soils under no-till management may be affected if residues are removed at high rates. On silt loam and sandy loam no-till soils in Iowa, Laflen & Colvin (1981) found that a decrease in stover cover resulted in an exponential increase in sediment loss. On a silt loam in Illinois, 100% stover removal resulted in increased sediment loss from 0.1 to 1.3 Mg ha À1 (Bradford & Huang, 1994).Differences in s...

Spray application of 24 and 46 g ha−1 MON 37500 was used in efficacy studies, and vacuum infiltration or droplet application of radiolabeled MON 37500 was used in metabolism studies to evaluate temperature and soil moisture on MON 37500 efficacy and metabolism. Day/night temperatures before vs. after application of MON 37500 of 25/23 vs. 25/23, 25/23 vs. 5/3, 5/3 vs. 25/23, and 5/3 vs. 5/3 C were evaluated for the efficacy study, whereas day/night temperatures of 5/3 and 25/23 C were used for the metabolism study. Soil moisture of one-third and full pot capacities was evaluated for both studies. No Triticum aestivum injury was observed at the different temperatures or soil moistures because of rapid metabolism of MON 37500 by T. aestivum. Weed control was greater when the temperature after application was 25/23 C or soil moisture was at full pot capacity than when the temperature was at 5/3 C after application or soil moisture was at one-third pot capacity. Susceptibility to MON 37500 was greatest for Bromus tectorum, moderate for Avena fatua, and least for Aegilops cylindrica. This pattern of susceptibility for the weed species was related to their ability to metabolize MON 37500. Aegilops cylindrica metabolized more MON 37500 in the first 24 h than did A. fatua, whereas B. tectorum metabolized the least MON 37500. Cool air temperatures decreased MON 37500 metabolism in all species, whereas soil moisture had no effect.

Kochia is a troublesome weed throughout the western United States. Although glyphosate effectively controls kochia, poor control was observed in several no-till fields in Kansas. The objectives of this research were to evaluate kochia populations response to glyphosate and examine the mechanism that causes differential response to glyphosate. Glyphosate was applied at 0, 54, 109, 218, 435, 870, 1305, 1740, 3480, and 5220 g ae ha−1on 10 kochia populations. In general, kochia populations differed in their response to glyphosate. At 21 d after treatment, injury from glyphosate applied at 870 g ha−1range from 4 to 91%. In addition, glyphosate rate required to cause 50% visible injury (GR50) ranged from 470 to 2149 g ha−1. Differences in glyphosate absorption and translocation and kochia mineral content were not sufficient to explain differential kochia response to glyphosate.

Water supply frequently limits crop yield in semiarid cropping systems; water deficits can restrict yields in drought‐affected subhumid regions. In semiarid wheat (Triticum aestivum L.)‐based cropping systems, replacing an uncropped fallow period with a crop can increase precipitation use efficiency but reduce wheat productivity. Our objective was to analyze crop sequence and environmental effects on water use, components of water productivity, and net returns of winter wheat (WW) in a semiarid region. A field study was established to evaluate eight 3‐yr crop sequences, including a wheat phase followed by a feed grain phase (corn [Zea mays L.] or grain sorghum [Sorghum bicolor (L.) Moench]) and an oilseed phase (OS; spring canola [Brassica napus L.], soybean [Glycine max (L.) Merr.], sunflower [Helianthus annuus L.], or none [fallow]). Standard measurements included crop water use (WU), canopy leaf area index at anthesis, biomass, grain yield, and yield components. Net return (NR) was calculated as the difference between crop revenue and total operating costs. Replacing an uncropped fallow period with an OS crop reduced water productivity responses of WW (biomass, grain yield, and NR) by 18, 31, and 56%, respectively, relative to that of WW grown after fallow. These responses to continuous cropping corresponded to reductions in all components of a water‐limiting yield production function. The modest water productivity observed (0.28–0.62 kg m−3), relative to a reported global range of 0.6 to 1.7 kg m−3, indicates opportunity to improve wheat water productivity through management and genetic gain.

Pyroxasulfone (KIH-485) is a seedling growth-inhibiting herbicide developed by Kumiai America that has the potential to control weeds in sunflower. However, little is known about how this herbicide will interact with various soil types and environments when combined with sulfentrazone. The objective of this research was to evaluate sunflower injury and weed control with pyroxasulfone applied with and without sulfentrazone across the Great Plains sunflower production area. A multisite study was initiated in spring 2007 to evaluate sunflower response to pyroxasulfone applied PRE at 0, 167, 208, or 333 g ai ha−1. In 2008, pyroxasulfone was applied alone and in tank mixture with sulfentrazone. In 2007, no sunflower injury was observed with any rate of pyroxasulfone at any location except Highmore, SD, where sunflower injury was 17%, 4 wk after treatment (WAT) with 333 g ha−1. In 2008, sunflower injury ranged from 0 to 4% for all treatments. Adding sulfentrazone did not increase injury. Sunflower yield was only reduced in treatments in which weeds were not effectively controlled. These treatments included the untreated control and pyroxasulfone at 167 g ha−1. Sunflower yield did not differ among the other treatments of pyroxasulfone or sulfentrazone applied alone or in combination. The addition of sulfentrazone to pyroxasulfone improved control of foxtail barley, prostrate pigweed, wild buckwheat, Palmer amaranth, and marshelder, but not large crabgrass or green foxtail. The combination of pyroxasulfone and sulfentrazone did not reduce control of any of the weeds evaluated.