Soil C, N and crop yields in Alabama's long-term ‘Old Rotation' cotton experiment     

C. C. Mitchell  J. A. Entry 《Soil & Tillage Research》1998,47(3-4):331-338

The Old Rotation cotton experiment at Auburn, Alabama, is the oldest, continuous cotton experiment in the world (cf. 1896). Long-term cropping systems provide a unique opportunity to observe the effects of 100 years of cropping on soil organic carbon (SOC). The objective of this paper was to summarize limited data on SOC and N cycling in this historic experiment. Soil organic C has been measured on the 13 plots (6 cropping systems) in 1988, 1992 and 1994. Long-term planting of winter legumes with no other source of N applied resulted in higher SOC (9.5 g C kg⁻¹) in the plow layer (0–20 cm depth) compared to continuous cotton with no winter cover crops (4.2 g C kg⁻¹). A 3-year rotation of cotton–winter legumes–corn–small grain–soybean resulted in 12.1 g C kg⁻¹. There was a significant (P<0.05), quadratic cotton yield response (R²=0.54) to increasing SOC. Winter legume cover crops supplied between 90 and 170 kg N ha⁻¹. Where no N has been applied in fertilizer or from a legume crop, annual N removal in the cotton crop is around 13 kg ha⁻¹, about the same as that fixed in precipitation.  相似文献   

Effects of rice and rye straw extracts on the growth of a cyanobacterium, <Emphasis Type="Italic">Microcystis aeruginosa</Emphasis>     

Phil-Goo Kang  Bomchul Kim  Myron J. Mitchell 《Paddy and Water Environment》2017,15(3):617-623

This study investigated the effect of extracts with time (a range of extraction periods: 0.2 days to maximum 150 days) of rice and rye straw on the growth of Microcystis aeruginosa (a cyanobacterium). The effect was assessed by an effective concentration 50 (EC₅₀) of extracts measured by a carbon (C) content, when 50% normalized maximum growth yield (50% inhibition effect) of M. aeruginosa occurred. We found that extracts of rice and rye straw inhibited the growth of M. aeruginosa. Extracts from the earliest incubation phase (0.2 days) for rice straw and the 40-day extract for rye straw showed the most inhibitive EC₅₀ value of 28.0 mg C L^?1 and 18.9 mg C L^?1, respectively. The inhibition effect was positively related to the extraction period of the rye straw, but inversely of the rice straw. Our results suggested that the long-term decomposition of extracts during straw extraction be linked with the formation of allelochemicals. These results provided information on how allelochemicals derived from agricultural by-products affect algal growth in aquatic ecosystems.  相似文献   

Modelling the potential effects of climate factors on Dubas bug (Ommatissus lybicus) presence/absence and its infestation rate: A case study from Oman     

Khalifa M Al Kindi  Paul Kwan  Nigel R Andrew  Mitchell Welch 《Pest management science》2019,75(11):3039-3049

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Plant Growth-regulating Properties of Some Nicotinium Compounds     

Mitchell JW  Wirwille JW  Weil L 《Science (New York, N.Y.)》1949,110(2854):252-254

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Sectional notes     

M. A. Lindsay  E. Marx  E. R. Bennett  C. L. Fitch  A. A. Henderson  Mitchell Jenkins  G. S. Ralston 《American Journal of Potato Research》1941,18(4):116-119

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Sectional notes     

L. M. Ware  Geo D. Ruehle  J. G. Richard  J. C. Campbell  E. V. Hardenbueg  C. A. Henderson  Robert Schmidt  J. Mitchell Jenkins  John Noonan 《American Journal of Potato Research》1941,18(5):149-154

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Sectional notes     

E. Marx  B. A. Brown  Frank W. Hussey  Marx Koehnke  E. V. Hardenburg  Robert Schmidt  Earl B. Tussing  Mitchell Jenkins  John Noonan  H. L. Bailey  Chas D. Gaines 《American Journal of Potato Research》1940,17(6):155-162

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Calibration of a common shortwave multispectral camera system for quantitative agricultural applications     

Barker  J. Burdette  Woldt  Wayne E.  Wardlow  Brian D.  Neale  Christopher M. U.  Maguire  Mitchell S.  Leavitt  Bryan C.  Heeren  Derek M. 《Precision Agriculture》2020,21(4):922-935

Unmanned aerial systems (UAS) for collecting multispectral imagery of agricultural fields are becoming more affordable and accessible. However, there is need to validate calibration of sensors on these systems when using them for quantitative analyses such as evapotranspiration, and other modeling for agricultural applications. The results of laboratory testing of a MicaSense (Seattle, WA, USA) RedEdge? 3 multispectral camera and MicaSense Downwelling Light Sensor (irradiance sensor) system using a calibrated integrating sphere were presented. Responses of the camera and irradiance sensor were linear over many light levels and became non-linear at light levels below expected real-world, field conditions. Simple linear corrections should suffice for most light conditions encountered during the growing season. Using an irradiance sensor or similar system may not properly account for light variability in cloudy or partly cloudy conditions as also identified by others. A simple stand for aiding in reference panel imaging was also described, which may facilitate repetitive, consistent reference panel imaging.

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Increased crop diversity reduces the functional space available for weeds     

R J Pakeman  R W Brooker  A J Karley  A C Newton  C Mitchell  R L Hewison  J Pollenus  D C Guy  C Schöb 《Weed Research》2020,60(2):121-131

There is a drive to improve the sustainability of agricultural systems including the biodiversity component. Cultivar mixtures offer yield benefits from the same land area, but the mechanisms behind this overyielding have not been completely worked out. One potential mechanism is improved competition with weeds. We use an experimental approach of varying barley (Hordeum vulgare L.) genotypic and phenotypic diversity to test the hypothesis that increases in diversity have an impact on weed growth strategies and community assembly, or if responses are driven by barley performance. There was no effect of increasing barley mixture diversity on weed traits, either in terms of species means or the community-weighted mean. However, Functional Richness of the weed community decreased with increasing barley mixture diversity mainly as a result of reduced specific leaf area Functional Richness. This pattern was driven by a reduction in species richness of the weed community rather than by reduced variation within species. Whilst barley phenotype had different impacts on weed traits, there were no specific mixtures of phenotypes or genotypes that had consistent effects on community assembly or weed species responses. The competitive exclusion of weed species could have agronomic and environmental benefits, through better targeting or less frequent use of herbicides. Growing crop mixtures is one of many strategies available to improve agricultural sustainability and resilience, and one that has clear benefits.  相似文献   

Sorption behavior of mixtures of glycerol and starch     

Enrione JI  Hill SE  Mitchell JR 《Journal of agricultural and food chemistry》2007,55(8):2956-2963

Glycerol is often added to starches to plasticize the product, but the presence of glycerol may also affect the water content of the samples. To evaluate the effect of glycerol on the sorption properties of starches, waxy maize, rice, and wheat starch were thermomechanically extruded in the presence of glycerol. Sorption isotherms of these extruded samples were ascertained using dynamic vapor sorption (DVS). BET and GAB modeling showed a monolayer (mo) significantly higher for waxy maize than for rice and wheat. Glycerol inclusion changed the model values, indicating reduction in sorption energy at the monolayer and restructuring of the multilayer. An interaction factor (xi) based on weight fraction models was calculated. Differences in xi were obtained when glycerol was added, varying from approximately 0.9 for 5% glycerol to approximately 0.8 for 20% glycerol, supporting the hypothesis of interactions between starch and this polyol.  相似文献