• Authors:
    • Mann, D.
    • Ranjan, R.
    • Kahimba, F.
  • Source: Applied Engineering in Agriculture
  • Volume: 25
  • Issue: 6
  • Year: 2009
  • Summary: Soil freezing and thawing processes and soil moisture redistribution play a critical role in the hydrology and microclimate of seasonally frozen agricultural soils. Accurate simulations of the depth and timing of frost and the redistribution of soil water are important for planning farm operations and choosing rotational crops. The Simultaneous Heat and Water (SHAW) model was used to predict soil temperature, frost depth, and soil moisture in agricultural soils near Carman, Manitoba. The model simulations were compared with three years of field data collected from summer 2005 to the summer 2007 in four cropping system treatments (oats with berseem clover cover crop, oats alone, canola, and fallow). The simulated soil temperatures compared well with the measured data in all the seasons (R 2=0.96-0.99). The soil moisture simulations were better during the summer (RMSE=9.1-12.0% of the mean) compared to the winter seasons (RMSE=17.5-19.7% of the mean). During the winter, SHAW over-predicted by 0.02 to 0.10 m 3 m -3 the amount of total soil moisture below the freeze front and under-predicted by 0.02 to 0.05 m 3 m -3 the soil moisture in the upper frozen layers. The model was revised to account for the reduction in effective pore space resulting from frozen water to improve the winter soil moisture predictions. After this revision, the model performed well during the winter (RMSE=14.4% vs. 17.5%; R 2=0.74 vs. 0.67 in vegetated treatments, and RMSE=12.9% vs. 19.7%; R 2=0.73 vs. 0.52 in fallow treatments). The modified SHAW model is an enhanced tool for predicting the soil moisture status as a function of depth during spring thawing, and for assessing the availability of soil moisture at the beginning of the subsequent growing season.
  • Authors:
    • Lovato, P.
    • Lana, M.
    • Fayad, J.
    • Comin, J.
    • Kieling, A.
  • Source: Ciencia Rural
  • Volume: 39
  • Issue: 7
  • Year: 2009
  • Summary: To eliminate herbicide use in no-tillage tomato production, an experiment was carried out to evaluate the best combination of winter cover crops for weed control and tomato production at the Ituporanga Experimental Station in Santa Catarina, Brazil. Oat ( Avena strigosa [ Avena nuda]), vetch ( Vicia villosa) and fodder radish ( Raphanus sativus) were grown in monoculture and in mixes. The tomato cv. Marcia-EPAGRI was stake-trained and grown under fertigation. The highest values in above-ground dry biomass were obtained by oat+vetch and oat monoculture, followed by vetch+radish, oat+radish, and oat+vetch+radish. Treatments with oats had the best performances in controlling resident vegetation, while vetch was associated with the worst performances. There were no significant differences between the treatments for total yield and marketable fruit production.
  • Authors:
    • Bellinder, R.
    • Brainard, D.
    • Kumar, V.
  • Source: Hortscience
  • Volume: 44
  • Issue: 3
  • Year: 2009
  • Summary: Hairy galinsoga [ Galinsoga ciliata (Raf.) Blake] has become a troublesome weed in vegetable crops. Field studies were conducted in 2006 and 2007 in central New York to determine the effects of: (1) spring-sown cover crops on hairy galinsoga growth and seed production during cover crop growth grown before subsequent short duration vegetable crops; and (2) cover crop residues on establishment of hairy galinsoga and four short-duration vegetable crops planted after cover crop incorporation. The cover crops [buckwheat ( Fagopyrum esculentum Moench), brown mustard ( Brassica juncea L.), yellow mustard ( Sinapis alba L.), and oats ( Avena sativa L.)] were planted in May and incorporated in early July. Lettuce ( Lactuca sativa L.) and Swiss chard [ Beta vulgaris var. cicla (L.) K. Koch] were transplanted and pea ( Pisum sativum L.) and snap bean ( Phaseolus vulgaris L.) were sown directly into freshly incorporated residues. Aboveground dry biomass produced by the cover crops was 4.2, 6.4, 6.8, and 9.7 mg.ha -1 for buckwheat, brown mustard, yellow mustard, and oats, respectively. Cover crops alone reduced the dry weight (90% to 99%) and seed production of hairy galinsoga (98%) during the cover crop-growing season compared with weedy controls. In 2006, only yellow mustard residue suppressed hairy galinsoga emergence (53%). However, in 2007, all cover crop residues reduced hairy galinsoga emergence (38% to 62%) and biomass production (25% to 60%) compared with bare soil, with yellow mustard providing the greatest suppression. Cover crop residues did not affect snap bean emergence, but reduced pea emergence 25% to 75%. All vegetable crops were suppressed by all cover crop residues with crops ranked as: pea > Swiss chard ≥ lettuce > snap bean in terms of sensitivity. The C:N ratios were 8.5, 18.3, 22.9, and 24.8 for buckwheat, brown mustard, yellow mustard, and oat residues, respectively. Decomposition rate and nitrogen release of brown mustard and buckwheat residues was rapid; it was slow for oats and yellow mustard residues. Spring-sown cover crops can contribute to weed management by reducing seed production, emergence, and growth of hairy galinsoga in subsequent crops, but crop emergence and growth may be compromised. Yellow mustard and buckwheat sown before late-planted snap beans deserve further testing as part of an integrated strategy for managing weeds while building soil health.
  • Authors:
    • Migliorini, P.
    • Mazzoncini, M.
    • Bigongiali, F.
    • Antichi, D.
    • Lenzi, A.
    • Tesi, R.
  • Source: Renewable Agriculture and Food Systems
  • Volume: 24
  • Issue: 2
  • Year: 2009
  • Summary: When animal husbandry is not included in organic farming systems, green manure may be crucial to preserve or increase soil organic matter content and to ensure an adequate N supply to crops. Different species, both legumes and nonlegumes, may be used as cover crops. The present research was carried out to investigate the effect of different green manure crops [oats and barley mixture ( Avena sativa L. and Hordeum vulgare L.), rye ( Secale cereale L.), brown mustard ( Brassica juncea L.), flax ( Linum usitatissimum L.), pigeon bean ( Vicia faba L. var. minor)] on the production of the following tomato crop. A field trial was conducted for two cropping seasons (2003-2004 and 2004-2005) in a commercial organic farm. The yield of tomato crop was positively affected by pigeon bean, although statistically significant differences in comparison with the other treatments were observed only in 2004-2005, when the experiment was conducted in a less fertile soil. This was probably due mainly to the effect of the pigeon bean cover crop on N availability. In fact, this species, in spite of a lower biomass production than the other cover crops considered in the study, provided the highest N supply and a more evident increase of soil N-NO 3. Also, cover crop efficiency, evaluated using the N recovery index, reached higher values in pigeon bean, especially in the second year. The quality of tomato fruits was little influenced by the preceding cover crops. Nevertheless, when tomato followed pigeon bean, fruits showed a lower firmness compared to other cover crops, and in the second year this was associated with a higher fruit N content.
  • Authors:
    • Velykis, A.
    • Arlauskiene, A.
    • Maiksteniene, S.
    • Satkus, A.
  • Source: ZEMDIRBYSTE-AGRICULTURE
  • Volume: 96
  • Issue: 2
  • Year: 2009
  • Summary: A series of experiments was carried out during the period 1997-2004 to study the effects of crop rotations with a different proportion of winter and spring crops, various legume preceding crops and cover crops and their biomass use for green manure on weed infestation in cereals on a clay loam Endocalcari-Endohypogleyic Cambisol ( CMg-p-w-can) under North Lithuania's conditions. Crop rotations with prevailing winter crops predetermined the reduction in perennial weeds in cereals. The occurrence of weeds in cereals was determined by the weed incidence in the preceding crops tested: red clover ( Trifolium pratense L.), lucerne ( Medicago sativa L.) and vetch-oats ( Vicia sativa L., Avena sativa L.) mixture and by competitive ability of cereals. The biomass of clover and vetch-oat mixture incorporated as green manure tended to increase weed incidence in cereals. Undersowing of cover crops ( Trifolium pratense L., Lolium multiflorum Lam., Dactylis glomerata L.) tended to reduce the weed emergence in cereals, compared to the crops without undersowing. Undersown red clover performed best at suppressing weeds during the cereal post-harvest period. Its positive effect persisted in the following year after incorporation of red clover biomass for green manure. The effect of post-harvest sown cover crops ( Raphanus sativus L., Sinapis alba L.) on weed incidence in cereals was lower compared to undersown crops.
  • Authors:
    • Isk, D.
    • Ngouajio, M.
    • Mennan, H.
    • Kaya, E.
  • Source: PHYTOPARASITICA
  • Volume: 37
  • Issue: 4
  • Year: 2009
  • Summary: Weed control is a major concern for organic farmers around the world and non-chemical weed control methods are now the subject of many investigations. Field studies were conducted in tomato ( Solanum lycopersicum L.) from 2004 to 2006 at the Black Sea Agricultural Research Institute experiment field to determine the weed suppressive effects of winter cover crops. Treatments consisted of ryegrass ( Lolium multiflorum L.), oat ( Avena sativa L.), rye ( Secale cereale L.), wheat ( Triticum aestivum L.), gelemen clover ( Trifolium meneghinianum Clem.), Egyptian clover ( Trifolium alexandrinum L.), common vetch ( Vicia sativa L.), hairy vetch ( Vicia villosa Roth.) and a control with no cover crop. Treatments were arranged in a randomized complete block design with four replications. To determine the weed suppressive effects of the cover crops, weed density and total weed dry biomass were assessed at 14, 28, and 56 days after termination (DAT) of the cover crops from all plots using a 50*50 cm quadrat placed randomly in each plot. After cover crop kill and incorporation into soil, tomato seedlings variety 'H2274' were transplanted. Broadleaved weed species were the most prominent species in both years. Total weed biomass measured just prior to cover crop incorporation into the soil was significantly lower in S. cereale plots than in the others. The number of weed species was lowest at 14 DAT and later increased at 28 and 56 DAT, and subsequently remained constant during harvest. This research indicates that cover crops such as L. multiflorum, S. cereale, V. sativa and V. villosa could be used in integrated weed management programs to manage some weeds in the early growth stages of organic tomato.
  • Authors:
    • Komecki, T. S.
    • Balkcom, K. S.
    • Raper, R. L.
    • Arriaga, F. J.
    • Price, A. J.
    • Reeves, D. W.
  • Source: Journal of Cotton Science
  • Volume: 13
  • Issue: 4
  • Year: 2009
  • Summary: An integral component of conservation agriculture systems in cotton ( Gossypium hirsutum L.) is the use of a high-residue winter cover crop; however, terminating cover crops is an additional expense and planting into high-residue can be a challenge. An experiment was conducted using black oat ( Avena strigosa Schreb.), rye ( Secale cereale L.), and wheat ( Triticum aestivum L.) cover crops established in early November at three locations. In mid-April each year all winter cover crops were flattened with a straight-blade mechanical roller-crimper alone or followed by three rates of glyphosate (0.84, 0.42, 0.21 kg ae/ha). Additionally, glyphosate alone at each rate and a non-treated check were included to complete the factorial treatment arrangement. Cotton was then planted 3 weeks after treatments were administered following in-row sub-soiling at E.V. Smith and direct seeding at Tennessee Valley and Robertsdale. Results showed that rolling followed by reduced glyphosate rates as low as 0.42 kg ae/ha can effectively and reliably terminate mature cereal winter cover crops; thus maintaining cotton population and protecting growth. Additionally, reduced glyphosate rates applied as low as 0.84 kg ae/ha alone can effectively terminate immature cereal covers while conserving soil moisture. Rolling mature winter cereal cover crops will likely conserve more soil moisture compared to standing covers; however, rolling immature cereal cover crops provides no benefit. In 2005 at E.V. Smith and at Tennessee Valley in 2006, increasing glyphosate rate increased cotton yield likely due to less mature cereal covers at time of treatment application. However, the inclusion of glyphosate did not increase cotton yield for any other comparison.
  • Authors:
    • Miquelluti, D. J.
    • Oliveira, O. L. P. de
    • Ferreira, E. Z.
    • Nohatto, M. A.
    • Mafra, A. L.
    • Rosa, J. D.
    • Cassol, P. C.
    • Medeiros, J. C.
  • Source: REVISTA BRASILEIRA DE CIENCIA DO SOLO
  • Volume: 33
  • Issue: 1
  • Year: 2009
  • Summary: This study was conducted to evaluate the effect of phytomass management forms of different cover crop species on soil chemical properties related to organic matter, nutrient availability, and on grapevine yields. The experiment was carried out in Embrapa Uva e Vinho, in Bento Goncalves, Rio Grande do Sul, in Southern Brazil, on a Haplic Cambisol, in a vineyard established in 1989, using White and Rose Niagara grape in a horizontal overhead trelling system. The treatments established in 2002 were three cover crops: spontaneous native species, black oat ( Avena nuda), and a mixture of white clover ( Trifolium repens) + red clover ( Trifolium pratense) + annual ryegrass ( Lolium multiflorum); and two management systems: desiccation by herbicide spraying and mechanical mowing, performed each autumn prior to cover crop resowing. The experiment had a completely randomized block design, with three replications. Soil acidity and nutrient contents were little influenced by the plant cover. In comparison with the mowed management, herbicide application increased exchangeable Ca and Mg, extracted P, and organic C levels in the soil. The grape yield in the seasons 2004 and 2006 was low in view to the cultivar potential, probably affect by climatic limitations, but was higher when black oat was used as plant cover instead of the mixture of plant covers.
  • Authors:
    • Cao, E.
    • Andrigueti, M.
    • Carvalho, P.
    • Anghinoni, I.
    • Costa, S.
    • Souza, E.
  • Source: REVISTA BRASILEIRA DE CIENCIA DO SOLO
  • Volume: 33
  • Issue: 6
  • Year: 2009
  • Summary: The potential for adopting crop-livestock systems in southern Brazil is high, especially in untilled soybean areas with cover crops in the winter season. The long-term use of this system at different grazing intensities will result in different carbon and nitrogen stocks in the soil due to the different plant and animal residues. This research was conducted to evaluate alterations in total carbon and nitrogen pools and in organic matter fractions in a soil under different grazing intensities under no-tillage. The experiment on a Rhodic Hapludult (Oxisol) was initiated in 2001, after soybean harvest. The treatments were different cattle grazing (black oat+ryegrass) pressures (10, 20 and 40 cm sward height) and an ungrazed treatment in the winter and soybean in the summer, in a randomized block design. Soil samples were taken at the beginning of the experiment (May, 2001), after three years (May, 2004) and after six years (May, 2007) to evaluate the content and stocks of organic carbon and nitrogen. Moderate grazing intensities (20 and 40 cm plant height) resulted in an increase of total carbon and nitrogen and in the organic matter particulate fraction, similarly to the ungrazed area. However, at the most intensive grazing pressure (10 cm plant height) there were losses in the stocks of these elements and reduction in soil organic matter quality.
  • Authors:
    • Kindred, D. R.
    • Wiltshire, J. J. J.
    • Sylvester-Bradley, R.
    • Hatley, D. L. J.
    • Clarke, S.
  • Source: HGCA Project Report
  • Volume: i + 47 pp.
  • Issue: 460
  • Year: 2009
  • Summary: This report describes a second year of research that tested whether soil nitrogen supplies to cereal crops can be detected using canopy sensors; the first season was reported in HGCA Project Report No. 427. Nitrogen fertiliser experiments on cereals were established at four sites in 2006-7. In the following year, commercial cereal crops (wheat, oats or barley) were grown and, at each site, plot positions as used in the previous year were marked out for testing with a reflectance sensor. Reflectance was measured four times during tillering, between December and May (dependant on site), using a Crop Circle instrument (provided by Soilessentials Ltd) which measured reflectance at 880 nm (near-infrared, NIR) and 590 nm (orange). A Normalised Difference Vegetation Index (NDVI) was calculated to give a measure of vegetation cover. Soil mineral N (SMN) data were obtained for the sites. No fertiliser N was applied in 2008 and total N uptake at harvest was taken to represent the 'soil N supply' (SNS). Data were interpreted for relationships between canopy reflectance and soil N. The best level of tillering and ground cover was achieved at High Mowthorpe, which was sown early. Boxworth and Terrington crops were smaller, and the crop at Rosemaund was very small. High levels of N applied in 2007 had large effects on SMN at Boxworth and Terrington, but maximum amounts were smaller at High Mowthorpe or Rosemaund and maximum SMN and SNS levels were small. Use of the sensor successfully detected the differences in SMN residues at Boxworth and Terrington, especially below 120-140 kg/ha, as was found in the previous year's experiments. The relationships improved with later assessment of NDVI. Change in NDVI between assessment dates showed that canopies always grew during the 2007/08 winter but change in NDVI was less useful for predicting SNS than absolute values of NDVI. Merged data from both seasons of the study showed that NDVI signals overwinter could be interpreted according to their differences from the theoretical NDVI of an unlimited crop. It was concluded that young canopies can signal soil N status where SMN is less than 120-140 kg/ha. Effects were more certain as crops grew, so canopy sensing for soil N supplies should prove more useful as the season progresses.