• Authors:
    • Samu, F.
    • Sunderland, K.
  • Source: Entomologia Experimentalis Et Applicata
  • Volume: 95
  • Issue: 1
  • Year: 2000
  • Summary: A review of the literature showed that spider abundance was increased by diversification in 63% of studies. A comparison of diversification modes showed that spider abundance in the crop was increased in 33% of studies by `aggregated diversification' (e.g. intercropping and non-crop strips) and in 80% of studies by `interspersed diversification' (e.g., undersowing, partial weediness, mulching and reduced tillage). It is suggested that spiders tend to remain in diversified patches and that extending the diversification throughout the whole crop (as in interspersed diversification) offers the best prospects for improving pest control. There is little evidence that spiders walk in significant numbers into fields from uncultivated field edges, but diversification at the landscape level serves to foster large multi-species regional populations of spiders which are valuable as a source of aerial immigrants into newly planted crops. There are very few manipulative field studies where the impact of spiders on pests has been measured in diversified crops compared with undiversified controls. It is encouraging, however, that in those few studies an increased spider density resulted in improved pest control. Future work needs are identified.
  • Authors:
    • Nacci, S.
    • Ramos, M. C.
    • Pla, I.
  • Source: Soil Science
  • Volume: 165
  • Issue: 5
  • Year: 2000
  • Summary: In the vineyards of the Anoia-Alt Penedes region of NE Spain, erosion problems arising from a combination of soil and climate characteristics and their relief have been accelerated in the last few decades as a consequence of new cropping/planting patterns and soil management practices involving continuous tillage, which leaves the soil bare most of the time. In the rain-fed vineyards of the area, rainfall water conservation in situ has also become a problem that influences the production of high quality wine. The determination of the actual and potential erosion processes required for rational selection, design, and application of soil and water conservation practices requires identification and quantification of the hydrological properties and processes that induce runoff and soil erosion. Laboratory studies in 10 representative surface soils of the region, using simulated rainfall, proved that erosion losses were highly related to the surface sealing susceptibility of the soils, which reduced minimum rainfall water intake rates to 1 to 7 mm h(-1) or less after only 10 minutes of rainfall. This susceptibility was highly correlated with the high silt and low organic matter content of the soils. In most of the soils, surface protection by a cover was found to increase the minimum rainfall water intake rate 50 to 200 times. A simple laboratory test, based on the measurement of saturated hydraulic conductivity and the time to reach its minimum value, measured efficiently the sealing susceptibility of the studied soils and the relative effect of a protective cover. The minimum value of saturated hydraulic conductivity was highly correlated to runoff and soil erosion losses in soil boxes under simulated rainfall.
  • Authors:
    • Gurin, A. G.
  • Source: Sadovodstvo i Vinogradarstvo
  • Issue: 1
  • Year: 2000
  • Summary: In Russia, strips of shelter plants are sometimes grown between the rows of strawberries, so that at the end of the growing season the first frosts will kill off the tops of these plants which then fall and cover the strawberry plants like a mulch, and help to retain a protective snow cover through the winter. An account is given of the performance of oats, barley, rape, and mustard sown as shelter plants between the rows of Redgauntlet strawberries, with details of the snow accumulation and of the strawberry yields. The shelter plants did depress the growth of the strawberry plants somewhat, but had little or no effect on fruit yields, and also significantly reduced weed growth.
  • Authors:
    • González, J. F.
    • Ramiro, A.
    • Beltrán, F. J.
    • Encinar, J. M.
  • Source: Fuel Processing Technology
  • Volume: 55
  • Issue: 3
  • Year: 1998
  • Summary: Pyrolysis/gasification of grape and olive bagasse by CO2 under different experimental conditions has been studied. Variables investigated were particle size, temperature, type and concentration of additive and chemical washing with sulfuric and phosphoric acid solutions. Compounds like H2, CH4, CO and methanol, acetone, furfuryl alcohol, furfural, naphthalene, phenol and o-cresol were identified as components of gas and liquid fractions obtained from pyrolysis/gasification processes. Particle size had no influence, while temperature was a significant variable yielding increases of fixed carbon and gas content. In most of cases, a temperature between 600 to 700°C lead to a maximum liquid production. The principal additive used was ZnCl2, concentration of this salt exerted a positive effect on hydrogen production, about 5 to 8 times higher than that obtained in the absence of additive. As far as structural characteristics of activated carbon are concerned, the increase of temperature, ZnCl2 and acid solution concentrations (during chemical washing) lead to an increase of the specific surface area.
  • Authors:
    • Potter, J. W.
    • Cerkauskas, R. F.
    • McKeown, A. W.
    • Van Driel, L.
  • Source: Canadian Journal of Plant Science
  • Volume: 78
  • Issue: 2
  • Year: 1998
  • Summary: A 6-yr (1987-1992) experiment, continuous on the same site, evaluated potential problems for yield, nematodes and diseases with tomatoes (Lycopersicon esculentum Mill.) grown in a strip-till system. Treatments consisted of conventional tillage (CT) and strip tillage (ST), rye (Secale cereale L.), wheat (Triticum aestivum L.) and perennial ryegrass (Lolium perenne L.) cover crops and a 2-yr rye-tomato rotation. Results of the first 5 yr indicated a decrease in tomato yield over time for both tillage treatments and cover crops. However, yield rebounded overall for treatments in 1992 with the highest yield in the rye-tomato rotation. We suspect this was a result of high populations of root-knot nematodes which collapsed over the winter of 1991/1992. Tomato yields were lower following wheat and perennial ryegrass than rye. In only 1 yr out of 6, strip-tillage reduced yield compared with conventional tillage. Bacterial speck/spot symptoms on foliage, although minor, were significantly greater in ST than in CT plots during the last 3 yr. No major trends in incidence and severity of bacterial and fungal diseases and of disorders of fruit were evident during the 5-yr period and neither fruit yield nor quality were significantly affected by these factors. Root-knot nematodes (Meloidogyne hapla Chitwood) were numerically less in the rye-tomato rotation than in other treatments; both root-knot and root lesion nematodes (Pratylenchus penetrans [Cobb]) tended to be less numerous under CT than under ST. Strip-tillage is feasible for machine harvest processing tomatoes. However, we are concerned about the tendency of tomatoes grown under reduced tillage to have lower yields than those grown under conventional tillage. More work is required on the interactions of cultivars, cover crops and nematodes in soil conservation systems.