• Authors:
    • Costa, M.
    • Castoldi, G.
    • Pivetta, L.
    • Steiner, F.
    • Costa, L.
  • Source: Revista Brasileira de Ciencias Agrarias
  • Volume: 6
  • Issue: 3
  • Year: 2011
  • Summary: The organic carbon is a major component of the soil organic matter, and its stock is influenced by the type of management system used. This study aimed to evaluate the effect of two cropping systems, with and without cover crop rotation, associated to three fertilization sources (mineral, organic and mineral+organic) in the organic and residual carbon contents of an Oxisol, in no-tillage system. Soil samples were collected at 0.0-0.10, 0.10-0.20 and 0.20-0.40 m depth in the first, second and third years of the experiment, installed in 2006. The crops sequence in the rotation system with cover crops was oat+vetch+turnip/corn/wheat/mucuna+brachiaria+crotalaria/corn/soybean, and in the following system it was wheat/corn/wheat/soybean/corn/soybean. The organic and mineral+organic fertilizers consisted in the sole application of organic fertilizers and combined with mineral fertilizer. The organic and residual carbon contents were not affected by the different cropping systems. The organic and mineral+organic fertilizers promoted increases in the organic and residual carbon contents. The system of crop succession fertilized with mineral fertilizer resulted in higher losses of soil carbon.
  • Authors:
    • Tendziagolska, E.
    • Wacawowicz, R.
  • Source: Progress in Plant Protection
  • Volume: 51
  • Issue: 3
  • Year: 2011
  • Summary: The objective of the studies was to assess the changes in weed seedbank over 5-year period. Two terms were considered in the experiment: (1) soil preparation for organic farming (2004-2005) and organic plant cultivation with crop rotation (2005-2008). Three variants of cereal crop sequence (A - oats - winter rye, B - oats - spring triticale, C - spring triticale - spring triticale) were included in two-year period of conversion. Over the three years of organic cultivation, a significant increase of weed species diversity in each examined layer was observed in comparison with seed species number determined after soil conversion. Strongly dominant species in both terms of the study was Chenopodium album, which has declined in its number over three years of the organic cultivation. Among the weed species, which did not appear during conversion but have appeared after organic cultivation Erigeron canadensis was noted in the highest number.
  • Authors:
    • Uygur, F. N.
    • Koloren, O.
    • Kitis, Y. E.
  • Source: African Journal of Agricultural Research
  • Volume: 6
  • Issue: 5
  • Year: 2011
  • Summary: Weeds are one of the most important problems in newly established orchards. Especially in organic orcharding, the importance of weed management is much more than conventional orcharding. Therefore, importance of alternative methods to chemical control of weeds is increasing. This study was conducted to quantify the effects of common vetch (Vicia sativa L.) as living mulch on weeds and evaluate the availability of common vetch in organic citrus production. The study was carried out in Mandarin orchard which was established specially for this research in research and implementation area of the Plant Protection Department of Cukurova University in Turkey, in a three-year-period. Living mulch and control plots were placed between rows in newly established mandarin orchard and plots were maintained at the same locations until the end of the experiment. In this study, effects of the living mulch application on density, cover proportion, biomass, dry weight and similarity index of weed species were investigated. Overall three-years results of the study were evaluated, living mulch application reduced weed density and cover proportion average of 42.8% and 45.9% respectively compare to control. Biomass and dry weight of weeds were also reduced by living mulch in all years of the experiment. The results indicate that living mulch application by common vetch is an important alternative weed suppression method for ecological weed management.
  • Authors:
    • Trond M. Henriksen, T. M.
    • Anne-Kristin Løes, A.-K.
    • Sjursen, H.
    • Ragnar Eltun, R.
  • Source: Acta Agriculturae Scandinavica, Section B - Soil & Plant Science
  • Volume: 61
  • Issue: 2
  • Year: 2011
  • Summary: By restricted access to manure, nitrogen (N) supply in organic agriculture relies on biological N-fixation. This study compares grain yields after one full-season green manure (FSGM) to yields with repeated use of a green-manure catch crop. At two sites in south-eastern Norway, in a simple 4-year rotation (oats/wheat/oats/wheat), the repeated use of ryegrass, clover, or a mixture of ryegrass and clover as catch crops was compared with an FSGM established as a catch crop in year 1. The FSGM treatments had no subsequent catch crops. In year 5, the final residual effects were measured in barley. The yield levels were about equal for grains with no catch crop and a ryegrass catch crop. On average, the green-manure catch crops increased subsequent cereal yields close to 30%. The FSGM increased subsequent cereal yields significantly in two years, but across the rotation the yields were comparable to those of the treatments without green-manure catch crop. To achieve acceptable yields under Norwegian conditions, more than 25% of the land should be used for full-season green manure, or this method combined with green-manure catch crops. The accumulated amount of N in aboveground biomass in late autumn did not compensate for the N removed by cereal yields. To account for the deficiency, the roots of the green-manure catch crops would have to contain about 60% of the total N (tot-N) required to balance the cereal yields. Such high average values for root N are likely not realistic to achieve. However, measurement of biomass in late autumn may not reflect all N made available to concurrent or subsequent main crops.
  • Authors:
    • Marold, R.
  • Source: Zeitschrift für Arznei- & Gewürzpflanzen Journal of Medicinal & Spice Plants
  • Volume: 16
  • Issue: 3
  • Year: 2011
  • Summary: Medicinal and spice plants are risky crops. In comparison to the agricultural main crops, there is a strong fluctuation of the yields and the expenses are much higher. The risk increases if the crops are organically cultivated due to the restrictions of the use agro-chemicals. The organic farm Marold is located in Thuringia and grows 70 minor crop species on 340 ha of predominantly loess soil. Grass-clover in the crop rotation and well prepared manure with as little as possible weed seeds ensure the nitrogen supply of the plants. Couch grass and thistle require a special strategy of weed control. Seed weeds can be controlled by prophylactic measures in the crop rotation and soil management and by maintenance of boundary ridges. The expense of manual labour can be reduced by minimising the width of the band of the row with the crop plants which can not be covered by the tools of the hoeing machine. The seeds used for drilling crops should not be infested by diseases. Umbel diseases of fennel, coriander and caraway provoke severe yield losses up to 40%. The most important pests are field mice (in biennial caraway), blossom rape beetle (in Brassicaceae) and aphids. Systematic investigations for the development of effective plant protection method for organic cultivation are required.
  • Authors:
    • Souza, R. F. de
    • Medeiros, M. A. de
    • Marouelli, W. A.
    • Resende, F. V.
  • Source: Horticultura Brasileira
  • Volume: 29
  • Issue: 3
  • Year: 2011
  • Summary: The efficient use of water and the environmental diversity are crucial to the balance and sustainability of the organic production system of tomatoes. The present study aimed to evaluate the organic production of tomato cultivated as a single crop and in consortium with coriander, under sprinkler and drip irrigation. The experiment was carried out at an organic production area on the Federal District of Brazil. The experimental design was randomized blocks with treatments arranged in a 2*2 factorial (two irrigation systems * two cropping schemes). No significant interaction between the both factors occurred, and there was no significant effect of the cropping scheme over the evaluated variables. Although the crop cycle has been reduced when tomato was drip irrigated, the fruit yield was not affected by the irrigation systems. The larger reduction in the stand of plants observed under sprinkler irrigation has been compensated by an increase in the number of fruits per plant, without a change on the fruit mass. The smaller volume of soil explored by the tomato roots associated with the higher incidence of South American tomato pinworm ( Tuta absoluta) and mainly powdery mildew ( Leveillula taurica) may have limited the yield of drip irrigated tomato. The fruit decay rate on sprinkle irrigated plants was twice the rate found on the drip irrigated system.
  • Authors:
    • Armengot, L.
    • Berner, A.
    • Sans, F. X.
    • Maeder, P.
  • Source: Weed Research
  • Volume: 51
  • Issue: 4
  • Year: 2011
  • Summary: Conservation tillage could provide environmental benefits to organic farming. However, potential weed problems often tend to discourage farmers from adopting it. The effects of tillage (reduced vs. conventional), fertilisation (slurry vs. manure compost) and the application of biodynamic preparations (with and without) on crop yield and on weed cover, diversity and biological attributes were investigated in a cropping sequence of wheat, sunflower and spelt. Total weed cover and perennial cover in reduced tillage treatments were two to three times greater than in conventional treatments. Monocotyledon cover in reduced tillage was three times that in conventional tillage in spelt, whereas the dicotyledon Stellaria media dominated in sunflower. Weed diversity was similar across treatments, regardless of cereal crop, whereas lower diversity values were observed with reduced tillage in sunflower, because of the dominance of S. media. There was virtually no effect of fertilisation and biodynamic preparations on weed parameters. Although wheat and spelt yield decreased in reduced tillage plots (14% and 8% respectively), the sunflower grain yield was unaffected. Reduced tillage could thus be useful in organic cropping systems but would require proper management of perennial and monocotyledonous weeds, which are often problematic for annual crops.
  • Authors:
    • Hyde, J.
    • Mortensen, D. A.
    • Barbercheck, M. E.
    • Smith, R. G.
    • Hulting, A. G.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 1
  • Year: 2011
  • Summary: In the mid-Atlantic region, the demand for organic dairy has provided incentives for farmers to transition their land to organic feed grain production. At the same time, interest in minimum-tillage organic production is growing. Two field experiments were conducted to assess the effects of a first year cover crop and tillage system on weed populations, cash crop yield, and net returns over the 3-yr transition period in a cover crop-soybean (Glycine max (L.) Merr.)-corn (Zea mays L.) feed grain rotation. The cover crop treatments were rye (Secale cereale L.)-hairy vetch (Vicia villosa Roth) (hereaft er RYE) and timothy (Phleum pratense L.)-red clover (Trifolium pratense L.) (hereaft er TIM). Tillage system treatments were moldboard plow (full tillage, FT) and chisel plow (minimum tillage, MT). Across both experiments, soybean yields ranged from 1190 to 3721 kg ha(-1). Corn grain yields were affected by tillage in the first experiment only, and were 59% higher in FT (9370 kg ha(-1)) compared to MT (5906 kg ha(-1)). Weed abundance was primarily affected by tillage, with densities in corn being 244% higher in MT compared to FT. Cumulative net returns in the first experiment were profit-generating in systems where TIM was the initial cover crop (mean = U.S. $ 317 ha(-1)). Mean cumulative net returns were positive in three of the four treatment combinations in the second experiment (U.S. $ 74-299 ha(-1)). Improved strategies for minimizing the costs associated with fertilization and management of weeds in minimal tillage will be necessary to improve the profitability and sustainability of reduced-tillage organic systems.
  • Authors:
    • Almeida, N. A.
    • Oliveira, I. R. de
    • Carvalho, L. M. de
    • Andrade, K. R.
  • Source: Acta Horticulturae
  • Issue: 925
  • Year: 2011
  • Summary: Fennel ( Foeniculum vulgare Miller), Apiaceae, a spice and medicinal plant from the Mediterranean region, is grown by family farmers without irrigation and under high temperature conditions of the Brazilian northeast. In this study, a field experiment was done in the semi-arid region of Sergipe state, Brazil, to evaluate the performance of fennel-bean intercrop under organic management, using a completely randomized block design with six replications and four treatments (fennel monocrop and fennel intercropped (additive model)) with two cultivars of beans ( Phaseolus vulgaris) and one cultivar of cowpea ( Vigna unguiculata). Fennel plants were obtained from seeds and transplanted into the field at the beginning of the rainy season in June, while seeds of the beans and cowpea were being sown. Umbels of the fennel were harvested in January, 210 days after transplanting the fennel into the field. The fresh and dry mass of umbels, absolute and relative yield, land equivalent ratio (LER) and essential oil content were improved under the intercrop with cowpea and one cultivar of bean. No significant differences were detected on height and canopy areas among treatments, but any decrease in yield of fennel plants associated with intercrops with cowpea or bean were small. The intercrops studies confirmed the viability of intercropping fennel with cowpeas and beans.
  • Authors:
    • Leifert, C.
    • Critchley, C. N. R.
    • Eyre, M. D.
    • Wilcockson, S. J.
  • Source: European Journal of Agronomy
  • Volume: 34
  • Issue: 3
  • Year: 2011
  • Summary: A survey of 128 plots, in 2008, of a trial where the effects of crop protection can be separated from those of fertility management, generated weed cover data within six crops (winter wheat, winter barley, spring barley, potatoes, cabbages and a grass/clover ley). The effects of the 2008 crop types, of the two preceding crops and of organic and conventional crop protection and fertility management, were assessed using mixed-effects models and constrained ordination. Cover data for 22 weed species and for monocotyledon, dicotyledon, annual, perennial and total weed cover were used. Cover of 15 weed species, and of the five weed groups, was significantly affected by 2008 crops, with cover highest in spring beans and cabbage. Nine and four weed species 2008 cover were significantly related to crops grown in 2007 and 2006 respectively, as were dicotyledon, annual and total weed cover, but not monocotyledon or perennial cover. Cover of 15 species, and the five groups, was significantly higher in plots with organic crop protection, but only eight species and annuals were significantly affected by fertility management. Crop:crop protection produced the most significant interactions with most cover in organically managed plots. Five species, perennials and total weed cover produced significant three-factor models. The greatest weed cover was in organic crop protected but conventionally fertilised spring barley and the least in totally conventional winter barley. Other factors such as crop density and mechanical weeding also affected 2008 weed cover. The ordination indicated that most of the 22 species were strongly associated with crops from all three years. The sequence of crops in the rotation had a profound effect on weed cover. Where three spring-sown, difficult to weed, crops were grown in sequence (spring beans, potatoes and vegetables, spring barley) weed cover increased. However, cover was limited in grass/clover and some cereal plots with different preceding crops. Models predicting weed cover may need to take into account crop sequences within crop rotations, as well as the more usual management inputs. (C) 2011 Elsevier B.V. All rights reserved.