• Authors:
    • Kennedy, G. G.
    • Barbercheck, M. E.
    • Walgenbach, J. F.
    • Hummel, R. L.
    • Hoyt, G. D.
    • Arellano, C.
  • Source: Environmental Entomology
  • Volume: 31
  • Issue: 1
  • Year: 2002
  • Summary: Populations of endemic soil entomopathogens (nematodes and fungi) were monitored in vegetable production systems incorporating varying degrees of sustainable practices in Fletcher, NC. Two tillage types (conventional plow and disk versus conservation tillage), two input approaches (chemically versus biologically based), and two cropping schedules (continuous tomato versus 3-yr rotation of corn, cucumber, cabbage, and tomato) were employed in large plots from 1995 to 1998. A Galleria mellonella (L.) trap bioassay was used to identify and monitor activity of Steinernema carpocapsae, Heterorhabditis bacteriophora, Beauveria bassiana, and Metarhizium anisopliae populations during the vegetable growing season (April-September). Seasonal detection of entomopathogens was significantly higher in conservation compared with conventional tillage systems. The strip-till operation did not affect levels of detection of S. carpocapsae. Pesticide use significantly reduced detection of entomopathogenic fungi. Type of ground cover significantly affected temperature in the upper 12 cm of soil; highest soil temperatures were observed under black plastic mulch and bare ground, whereas lowest temperatures were observed under rye mulch and clover intercrop. The high soil temperatures associated with certain ground covers may have reduced entomopathogen detection or survival. Although type of tillage appeared to be the primary factor affecting survival of endemic soil entomopathogens in our system, other factors, such as pesticide use and type of ground cover, can negate the positive effects of strip-tillage.
  • Authors:
    • Hoyt, G. D.
    • Walgenbach, J. F.
    • Hummel, R. L.
    • Kennedy, G. G.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 93
  • Issue: 1-3
  • Year: 2002
  • Summary: Populations of foliar insect pests and natural enemies were monitored in vegetable production systems incorporating varying degrees of sustainable practices in Fletcher, NC, USA. Two types of tillage (conventional plow and disk, strip-tillage), two input approaches (chemically-based, biologically-based) and two cropping schedules (continuous tomato (Lycopersicon esculentum Mill.), 3-year rotation of corn (Zea mays L.), cucumber (Cucumis sativus L.) and tomato) were employed from 1995 to 1998. Tomato pest pressure was relatively low in all years, resulting in a limited impact of production systems on potato aphid, Macrosiphum euphorbiae (Thomas) (Homoptera: Aphididae), and its associated parasitoids and predators. Thrips (Frankliniella spp. (Thysanoptera)) populations were significantly higher in the biological input treatments in 3 of 4 years. Lepidopterous (primarily Helicoverpa zea Boddie (Lepidoptera: Noctuidae)) damage on tomato was significantly higher in biological treatments in all years, damage by thrips and pentatomids (Hemiptera: Pentatomidae) increasing each year in the continuous tomato crop schedule. Most insect populations were significantly influenced by type of insecticide input or ground cover. Few population measurements were affected by tillage type. Foliar insect problems in commercial vegetable production may be associated predominantly with insecticide input (i.e. more damage with biologically based insecticides) and use of intercropping (i.e. more damage in systems with living mulch); however, the long term effects of tillage and crop rotation remain to be seen. (C) 2002 Elsevier Science B.V. All rights reserved.
  • Authors:
    • Hoyt, G. D.
    • Walgenbach, J. F.
    • Hummel, R. L.
    • Kennedy, G. G.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 93
  • Issue: 1-3
  • Year: 2002
  • Summary: Populations of epigeal arthropods were monitored in vegetable production systems under varying degrees of sustainable agricultural practices in Fletcher, NC (USA). Two tillage types (conventional plow and disk, strip-tillage (ST)), two input approaches (chemically based, biologically based) and two cropping schedules (continuous tomato Lycopersicon esculentum Mill., 3-year rotation of sweet corn [Zea mays L.]/cabbage [Brassica oleracea L.], cucumber [Cucumis sativus L.]/cabbage and tomato) were employed from 1995-1998. A second study with tomatoes was performed in 1997-1998 to separate effects of pesticide use, intercropping and herbicide application. Pitfall traps (48-h sample period) were used at similar to25-day intervals to monitor relative activity of carabid beetles (Coleoptera: Carabidae), staphylinid (Coleoptera: Staphylinidae) beetles and lycosid spiders (Araneidae: Lycosidae). Carabids and lycosids appeared to be more active in systems with ground cover. Trap catches of carabid species were not significantly affected by insecticide input, but trap catches of lycosids were lower in plots with conventional insecticide use. No consistent effect of tillage was found over time, although Scarites spp. were more active in minimally disturbed habitats in 1998. Two distinct patterns of seasonal activity were observed for carabid beetles and lycosid spiders. Ground cover generally enhanced abundance of carabids and lycosids, while tillage type, pesticide use and crop rotation had different effects. (C) 2002 Elsevier Science B.V. All rights reserved.
  • Authors:
    • Ball, A.
    • Pretty, J.
  • Year: 2001
  • Authors:
    • Morse, R. D.
    • Miyao, E. M.
    • Temple, S. R.
    • Lanini, W. T.
    • Mitchell, J. P.
    • Herrero, E. V.
    • Campiglia, E.
  • Source: California Agriculture
  • Volume: 55
  • Issue: 1
  • Year: 2001
  • Summary: The efficacy of no-till systems in conserving soil moisture and improving water infiltration under furrow irrigation was evaluated during 1997 and 1998 in California, USA. Two grass/legume mixtures, i.e. triticale/lana woolypod vetch (* Triticosecale/ Vicia dasycarpa [ V. villosa]) and rye/lana woolypod vetch ( Secale cereale/ V. dasycarpa), were used as cover cop mulches in no-till treatments, and compared with a winter fallow treatment with pre-plant herbicide (fallow +h) and a fallow control treatment with no herbicide (fallow -h). Tomato cv. Halley 3155 plants were transplanted in April 1997 and 1998, sprinkle irrigated during the first 6 weeks after transplanting, and furrow irrigated thereafter until 3 weeks before harvest. During 1997, soil water content between 0 and 78 inches did not differ among treatments, while soil water content during the 1997/98 winter was higher under the fallow +h than the cover crop treatments until cover crop termination. Soil water content of cover crop treatments in shallower soil layers (18 and 42 inches) was significantly lower than fallow treatments at the end of the winter. During the 1998 tomato crop season, soil water content between 0 and 90 inches was greater under the triticale and rye mulches than the fallow +h, beginning the 3rd week after furrow irrigations were started. Soil moisture in the shallower layers was also affected by cover crop mulches. In the 42-inch depth increment, there was significantly higher water content under the cover crops than under the fallow +h from about 1 month after the first furrow irrigation until 2 weeks before the last irrigation. Changes in soil water content during furrow irrigation under the fallow +h treatment appeared to be more pronounced than under the triticale or rye surface mulches. Soil compaction in the fallow +h treatment was higher than under the cover crop mulches for most of the 0.6-inch intervals, especially below 1 foot, but differences were significantly higher only for the 3, 3.6, 4.2, 17, 18, and 24-inch depth, but lower from the surface to 2.4 inches. Soil carbon was significantly higher (by 14 and 18%) under triticale and rye, respectively, compared with the fallow +h treatment. The number of earthworms was also higher in no-till (2.1 earthworms per square foot) than in the fallow treatments (0.6 earthworms). Tomato canopy growth did not reach 100% cover in either 1997 or 1998, while tomato plant growth, assessed by measuring the photosynthetically active radiation intercepted by the canopy, did not differ in the triticale, rye, and fallow +h system in either 1997 or 1998. Results showed that the no-till mulch system enhanced water infiltration and soil water conservation.
  • Authors:
    • Morse, R. D.
    • Miyao, E. M.
    • Temple, S. R.
    • Lanini, W. T.
    • Mitchell, J. P.
    • Herrero, E. V.
    • Campiglia, E.
  • Source: HortTechnology
  • Volume: 11
  • Issue: 1
  • Year: 2001
  • Summary: No-tillage processing tomato production in four winter cover crop-derived mulches was evaluated in 1997 and 1998 in Five Points, California, USA. The effectiveness of two medics, 'Sava' snail medic ( Medicago scutellata), and 'Sephi' barrel medic ( Medicago truncatula), and two cereal/legume cover crop mixtures, triticale/'Lana' woolypod vetch ( Triticum x Secale/ Vicia dasycarpa [ Vicia villosa]) and rye/'Lana' woolypod vetch ( Secale cereale/ V. dasycarpa), was compared with two conventionally tilled fallow controls (with and without herbicide) (fallow+h and fallow-h) in suppressing weeds and maintaining yields with reduced fertilizer inputs. The comparison was conducted as a split plot, with three N fertilization rates (0, 100, and 200 lb/acre; 0, 112, and 224 kg/ha) as main plots and cover crops and fallow controls as subplots. Tomato seedlings were transplanted 3 weeks after the cover crops had been mowed and sprayed with herbicide. There were no significant differences in weed cover in the no-till cover crop treatments relative to the fallow controls in 1997. Early season weed suppression in rye/vetch and triticale/vetch plots was similar to herbicide-treated fallow (fallow+h) in 1998, however, later in the 1998 season weed suppression was best in the fallow+h. Tissue N was highest in the fallow treatments in both 1997 and 1998. Yields were highest in the triticale/vetch and fallow and lowest in sephi treatments in 1997, but there were no differences among treatments in 1998.
  • Authors:
    • Ayuk, E. T.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 61
  • Issue: 1-2
  • Year: 2001
  • Summary: In recent years and in some situations the status of soil organic matter (SOM) has deteriorated considerably due to long periods of continuous cultivation and limited external inputs in the form of mineral fertilizers. Deterioration of SOM varies by agro-ecological zones, by soil types and by cropping patterns. It is more intense in East Africa, followed by coastal West Africa and Southern Africa and least intensive in the Sahel and Central Africa. It is also more serious in areas under low-input agriculture irrespective of the prevailing cropping system. The major consequence of the decrease in SOM in the tropics is lower agricultural productivity with a direct negative effect on food security. While biophysical dynamics of SOM have been extensively covered in the literature, social considerations have not received similar attention. This paper examines the social, economic and policy factors associated with the management of tropical soil organic matter. Empirical data from a range of environments in Africa show that SOM improvement options yield a positive return to land as well as labour. However, there are a number of constraints. Social constraints are related to the large quantities of organic matter that are required (case of farmyard manure), the competitive uses for the material (case of crop residues), land and labour requirements, and gender-related issues. From a policy stand point, unsecured tenure rights together with price distortions and other market failures may be important constraints. Challenges for sustainable management of SOM are identified. These include management conflicts, land tenure arrangements, the divergence in goals between individuals and society, land and labour requirements, inadequate support systems for land users, profitability issues, the role of subsidies, and the absence of national action plans. A number of opportunities are identified that could enhance the improvement or maintenance of SOM. These include: exploring the need and potential role of community-based SOM management practices; development of an integrated plant nutrient management strategy involving both organic and inorganic inputs; and development of concrete national action plans. It is argued that because externalities of SOM improvement or maintenance extend beyond the farmer's fields, SOM investment may require cost sharing between individuals and the society. Policies on subsidies need to be reconsidered. Research priorities are identified that require closer collaboration between scientists from a variety of disciplines.
  • Authors:
    • Zalom, F. G.
    • van Bruggen, A. H. C.
    • Lanini, W. T.
    • Klonsky, K. M.
    • Ferris, H.
    • Clark, M. S.
  • Source: Agriculture, Ecosystems and Environment
  • Volume: 68
  • Issue: 1
  • Year: 1998
  • Summary: The effectiveness, economic efficiency, and environmental impact of pest management practices was compared in conventional, low-input, and organic processing tomato and field corn systems in northern California. Pests, including arthropods, weeds, pathogens, and nematodes, were monitored over an 8-year period. Although both crops responded agronomically to the production-system treatments, arthropods, pathogens, and nematodes were found to play a relatively small role in influencing yields. In contrast, weed abundance was negatively correlated with tomato and corn yields and appeared to partially account for lower yields in the alternative systems compared to the conventional systems. Lower pesticide use in the organic and low-input systems resulted in considerably less potential environmental impact but the economic feasibility of reducing pesticide use differed dramatically between the two crops. The performances of the organic and low-input systems indicate that pesticide use could be reduced by 50% or more in corn with little or no yield reduction. Furthermore, the substitution of mechanical cultivation for herbicide applications in corn could reduce pest management costs. By contrast, pesticide reductions in tomato would be economically costly due to the dependence on hand hoeing as a substitution for herbicides. Based on the performance of the low-input and organic tomato systems, a 50% pesticide reduction would increase average pest management costs by 50%.
  • 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.
  • Authors:
    • Schulbach, K. F.
    • Jackson, L. E.
    • Wyland, L. J.
  • Source: The Journal of Agricultural Science
  • Volume: 124
  • Year: 1995
  • Summary: Winter non-leguminous cover crops are included in crop rotations to decrease nitrate (NO3-N) leaching and increase soil organic matter. This study examined the effect of incorporating a mature cover crop on subsequent N transformations. A field trial containing a winter cover crop of Merced rye and a fallow control was established in December 1991 in Salinas, California. The rye was grown for 16 weeks, so that plants had headed and were senescing, resulting in residue which was difficult to incorporate and slow to decompose. Frequent sampling of the surface soil (0-15 cm) showed that net mineralizable N (anaerobic incubation) rapidly increased, then decreased shortly after tillage in both treatments, but that sustained increases in net mineralizable N and microbial biomass N in the cover-cropped soils did not occur until after irrigation, 20 days after incorporation. Soil NO3-N was significantly reduced compared to winter-fallow soil at that time. A N-15 experiment examined the fate of N fertilizer, applied in cylinders at a rate of 12 kg N-15/ha at lettuce planting, and measured in the soil, microbial biomass and lettuce plants after 32 days. In the cover-cropped soil, 59% of the N-15 was recovered in the microbial biomass, compared to 21% in the winter-bare soil. The dry weight, total N and N-15 content of the lettuce in the cover-cropped cylinders were significantly lower; 28 v. 39% of applied N-15 was recovered in the lettuce in the cover-cropped and winter-bare soils, respectively. At harvest, the N content of the lettuce in the cover-cropped soil remained lower, and microbial biomass N was higher than in winter-bare soils. These data indicate that delayed cover crop incorporation resulted in net microbial immobilization which extended into the period of high crop demand and reduced N availability to the crop.