Intercropping, a mix of non-legume and legume crops, can improve crop yield and/or economic returns and reduce input costs. Field experiments (barley-pea intercrop) were conducted in 2008, 2010 and 2011 on an Oskondog...Intercropping, a mix of non-legume and legume crops, can improve crop yield and/or economic returns and reduce input costs. Field experiments (barley-pea intercrop) were conducted in 2008, 2010 and 2011 on an Oskondoga silt loam soil at Thunder Bay, Ontario, Canada, to determine the effect of intercropping barley (non-legume) and pea (legume) on grain yield, land equivalency ratio (LER), grain quality (protein concentration-PC), N uptake and economic returns. Barley and pea were grown as mono crops and in combinations as intercrops (both in the same row/and alternate rows). Nitrogen fertilizer was applied at 0, 40 and 80 kg·N·ha-1 to mono crop barley and at 0, 20 and 40 kg·N·ha-1 to barley-pea intercrop combinations. On an average of three years, application of 80 kg·N·ha-1 increased grain yield of barley by 846 kg·ha-1 as a sole crop and by 420 - 488 kg·ha-1 in the two intercropping combinations. Compared to barley and pea as sole crops, grain yield with barley-pea intercropping was greater by 266 kg·ha-1 with alternate row combination and by 223 kg·ha-1when both crops were grown in the same row. The LER values suggested 7% - 17% less land requirement for barley-pea intercropping than sole crops. Net returns from barley-pea intercropping without applied N greatly improved ($854 - $939 ha-1) compared to barley sole crop with 80 kg·N·ha-1($628 ha-1), although the net returns were highest for pea grown as a sole crop without applied N ($1141 ha-1). For barley as a sole crop, PC in grain increased with applied N. Compared to barley as sole crop with zero-N, PC in barley grain increased when barley was intercropped with pea. In barley-pea intercrop treatments, application of N fertilizer had no significant effect on PC in barley grain, although PC in pea grain was much higher than PC in barley grain. The response trends of total N uptake in grain were similar to grain yield. The findings suggest that pea or barley-pea intercropping could be an option for organic farming systems.展开更多
The present paper provides both experimental and DEM analyses of the filling and discharge of pea grains from a 3D flat-bottomed bin. In the DEM model, the fixed mean values of the experimentally determined single par...The present paper provides both experimental and DEM analyses of the filling and discharge of pea grains from a 3D flat-bottomed bin. In the DEM model, the fixed mean values of the experimentally determined single particle data, such as the particle density, Young＇s modulus, Poisson＇s ratio as well as the sliding and rolling friction coefficients were incorporated to analyse their effects on the macroscale indicators, such as the wall pressure, discharge velocities and material outflow parameters. The effect of rolling friction was studied based on the experimentally measured single particle rolling friction coefficient. This analysis is aimed at the quantitative prediction of flow parameters as related to the identification of material parameters.展开更多
Facultative bacterial endosymbionts in insects have been under intense study during the last years. Endosymbionts can modify the insect＇s phenotype, conferring adap- tive advantages under environmental stress. This s...Facultative bacterial endosymbionts in insects have been under intense study during the last years. Endosymbionts can modify the insect＇s phenotype, conferring adap- tive advantages under environmental stress. This seems particularly relevant for a group of worldwide agricultural aphid pests, because endosymbionts modify key fitness-related traits, including host plant use, protection against natural enemies and heat tolerance. Aimed to understand the role of facultative endosymbionts on the success of introduced aphid pests, the distribution and abundance of 5 facultative endosymbionts （Hamiltonella defensa, Regiella insecticola, Serratia symbiotica, Rickettsia and Spiroplasma） were stud- ied and compared in 4 cereal aphids （Sitobion avenae, Diuraphis noxia, Metopolophium dirhodum and Schizaphis graminium） and in the pea aphid Acyrthosiphon pisum complex from 2 agroclimatic zones in Chile. Overall, infections with faeultative endosymbionts exhibited a highly variable and characteristic pattern depending on the aphid species/host race and geographic zone, which could explain the success of aphid pest populations after their introduction. While S. symbiotica and H. defensa were the most frequent endosym- bionts carried by the A. pisum pea-race and A. pisum alfalfa-race aphids, respectively, the most frequent facultative endosymbiont carried by all cereal aphids was R. insecticola. Interestingly, a highly variable composition of endosymbionts carried by S. avenae was also observed between agroclimatic zones, suggesting that endosymbionts are responding differentially to abiotic variables （temperature and precipitations）. In addition, our findings constitute the first report of bacterial endosymbionts in cereal aphid species not screened before, and also the first report of aphid endosymbionts in Chile.展开更多
文摘Intercropping, a mix of non-legume and legume crops, can improve crop yield and/or economic returns and reduce input costs. Field experiments (barley-pea intercrop) were conducted in 2008, 2010 and 2011 on an Oskondoga silt loam soil at Thunder Bay, Ontario, Canada, to determine the effect of intercropping barley (non-legume) and pea (legume) on grain yield, land equivalency ratio (LER), grain quality (protein concentration-PC), N uptake and economic returns. Barley and pea were grown as mono crops and in combinations as intercrops (both in the same row/and alternate rows). Nitrogen fertilizer was applied at 0, 40 and 80 kg·N·ha-1 to mono crop barley and at 0, 20 and 40 kg·N·ha-1 to barley-pea intercrop combinations. On an average of three years, application of 80 kg·N·ha-1 increased grain yield of barley by 846 kg·ha-1 as a sole crop and by 420 - 488 kg·ha-1 in the two intercropping combinations. Compared to barley and pea as sole crops, grain yield with barley-pea intercropping was greater by 266 kg·ha-1 with alternate row combination and by 223 kg·ha-1when both crops were grown in the same row. The LER values suggested 7% - 17% less land requirement for barley-pea intercropping than sole crops. Net returns from barley-pea intercropping without applied N greatly improved ($854 - $939 ha-1) compared to barley sole crop with 80 kg·N·ha-1($628 ha-1), although the net returns were highest for pea grown as a sole crop without applied N ($1141 ha-1). For barley as a sole crop, PC in grain increased with applied N. Compared to barley as sole crop with zero-N, PC in barley grain increased when barley was intercropped with pea. In barley-pea intercrop treatments, application of N fertilizer had no significant effect on PC in barley grain, although PC in pea grain was much higher than PC in barley grain. The response trends of total N uptake in grain were similar to grain yield. The findings suggest that pea or barley-pea intercropping could be an option for organic farming systems.
文摘The present paper provides both experimental and DEM analyses of the filling and discharge of pea grains from a 3D flat-bottomed bin. In the DEM model, the fixed mean values of the experimentally determined single particle data, such as the particle density, Young＇s modulus, Poisson＇s ratio as well as the sliding and rolling friction coefficients were incorporated to analyse their effects on the macroscale indicators, such as the wall pressure, discharge velocities and material outflow parameters. The effect of rolling friction was studied based on the experimentally measured single particle rolling friction coefficient. This analysis is aimed at the quantitative prediction of flow parameters as related to the identification of material parameters.
文摘Facultative bacterial endosymbionts in insects have been under intense study during the last years. Endosymbionts can modify the insect＇s phenotype, conferring adap- tive advantages under environmental stress. This seems particularly relevant for a group of worldwide agricultural aphid pests, because endosymbionts modify key fitness-related traits, including host plant use, protection against natural enemies and heat tolerance. Aimed to understand the role of facultative endosymbionts on the success of introduced aphid pests, the distribution and abundance of 5 facultative endosymbionts （Hamiltonella defensa, Regiella insecticola, Serratia symbiotica, Rickettsia and Spiroplasma） were stud- ied and compared in 4 cereal aphids （Sitobion avenae, Diuraphis noxia, Metopolophium dirhodum and Schizaphis graminium） and in the pea aphid Acyrthosiphon pisum complex from 2 agroclimatic zones in Chile. Overall, infections with faeultative endosymbionts exhibited a highly variable and characteristic pattern depending on the aphid species/host race and geographic zone, which could explain the success of aphid pest populations after their introduction. While S. symbiotica and H. defensa were the most frequent endosym- bionts carried by the A. pisum pea-race and A. pisum alfalfa-race aphids, respectively, the most frequent facultative endosymbiont carried by all cereal aphids was R. insecticola. Interestingly, a highly variable composition of endosymbionts carried by S. avenae was also observed between agroclimatic zones, suggesting that endosymbionts are responding differentially to abiotic variables （temperature and precipitations）. In addition, our findings constitute the first report of bacterial endosymbionts in cereal aphid species not screened before, and also the first report of aphid endosymbionts in Chile.
