• Authors:
    • Haar, M.
    • Lindquist, J.
    • Wortman, S.
    • Francis, C.
  • Source: Renewable Agriculture and Food Systems
  • Volume: 25
  • Issue: 4
  • Year: 2010
  • Summary: While weed management is consistently a top priority among farmers, there is also growing concern for the conservation of biodiversity. Maintaining diverse weed communities below bioeconomic thresholds may provide ecosystem services for the crop and the surrounding ecosystem. This study was conducted to determine if weed diversity, density and biomass differ within and among organic and conventional crop rotations. In 2007 and 2008, we sampled weed communities in four long-term crop rotations near Mead, Nebraska using seedbank analyses (elutriation and greenhouse emergence) and above-ground biomass sampling. Two conventional crop rotations consisted of a corn ( Zea mays) or sorghum ( Sorghum bicolor)-soybean ( Glycine max)-sorghum or corn-soybean sequence and a diversified corn or sorghum-sorghum or corn-soybean-wheat ( Triticum aestivum) sequence. Two organic rotations consisted of an animal manure-based soybean-corn or sorghum-soybean-wheat sequence and a green manure-based alfalfa ( Medicago sativa)-alfalfa-corn or sorghum-wheat sequence. Species diversity of the weed seedbank and the above-ground weed community, as determined by the Shannon diversity index, were greatest in the organic green manure rotation. Averaged across all sampling methods and years, the weed diversity index of the organic green manure rotation was 1.07, followed by the organic animal manure (0.78), diversified conventional (0.76) and conventional (0.66) rotations. The broadleaf weed seedbank density in the tillage layer of the organic animal manure rotation was 1.4*, 3.1* and 5.1* greater than the organic green manure, diversified conventional and conventional rotations, respectively. The grass weed seedbank density in the tillage layer of the organic green manure rotation was 2.0*, 6.1* and 6.4* greater than the organic animal manure, diversified conventional and conventional rotations, respectively. The above-ground weed biomass was generally greatest in the organic rotations. The broadleaf weed biomass in sorghum and wheat did not differ between organic and conventional rotations (CRs), but grass weed biomass was greater in organic compared to CRs for all crops. The above-ground weed biomass did not differ within CRs, and within organic rotations the grass weed biomass was generally greatest in the organic green manure rotation. The weed seedbank and above-ground weed communities that have accumulated in these rotations throughout the experiment suggest a need for greater management in long-term organic rotations that primarily include annual crops. However, results suggest that including a perennial forage crop in organic rotations may reduce broadleaf weed seedbank populations and increase weed diversity.
  • Authors:
    • Zekaite, V.
  • Source: Vagos
  • Issue: 88
  • Year: 2010
  • Summary: Field experiments, designed to study weed incidence in Poaceae and Fabaceae monocrops and their mixtures as influenced by an organic cropping system, were carried out during 2007-2009 at the Experimental station of the Lithuanian Research Centre for Agriculture and Forest in Perloja on a Hapli-Albic Luvisol. Short-lived weeds prevailed in the crops. They accounted for 93-95% of the total weeds. The highest counts of weeds were recorded at the beginning of the growing season when the conditions for their emergence were the most conducive ones. In 2007 and 2009 the weather conditions during cereal tillering stage were wet and warm, which created optimal conditions for weed emergence and the weed count per m -2 was 257-264. In the third ten-day period of April 2008, re-current night frosts inhibited cereal and weed emergence, which resulted in 43.6-51.7% lower emergence. With increasing crop competitive power (milk maturity stage), weed emergence tended to decline and was by 17.9-9.8% lower compared with the weed count at tillering stage. Weed air dry weight decreased proportionally, however, only at crop hard maturity stage, with the reduction in crop competitive power, weed air dry weight increased by 31.6%. Due to the weather conditions, weed air dry weight in the wet year 2007 was by 35-55% higher than that in 2008 and 2009. Lupines, oats and wheat and its mixture with peas performed best in suppressing weeds. A strong linear correlation was established between weed number and precipitation and weigh (r=0.901, r=0.758); between plant density and precipitation amount (r=0.745).
  • Authors:
    • Pitchai, G. J.
    • Kumar, V. S.
  • Source: Asian Journal of Soil Science
  • Volume: 5
  • Issue: 2
  • Year: 2010
  • Summary: Maize is the third most important cereal crop after wheat and rice grown in virtually every suitable agricultural region of the globe. Maize being an exhaustive crop responds well to higher levels of NPK. The use of organic sources had significant effect on macro and micronutrients and thus it helps in sustenance of the soil fertility. For the study, a field experiment was conducted in Malayalathanpatty village, Madurai to evaluate the response of maize (Super 900M) with different organic sources like vermicompost, sewage sludge, green leaf manures and composted coir pith combined with inorganic fertilizers. There were ten treatment combinations replicated thrice in RBD in Annaiyur soil series (Entic Haplustert). The results showed that the highest grain yield of 4402 kg ha -1 was recorded in treatment that received vermicompost @ 5 t ha -1 with 75 per cent RDF and it was found to be superior to over other treatments.
  • Authors:
    • Anderson, R. L.
  • Source: Renewable Agriculture and Food Systems
  • Volume: 25
  • Issue: 3
  • Year: 2010
  • Summary: Weeds are a major obstacle to successful crop production in organic farming. Producers may be able to reduce inputs for weed management by designing rotations to disrupt population dynamics of weeds. Population-based management in conventional farming has reduced herbicide use by 50% because weed density declines in cropland across time. In this paper, we suggest a 9-year rotation comprised of perennial forages and annual crops that will disrupt weed population growth and reduce weed density in organic systems. Lower weed density will also improve effectiveness of weed control tactics used for an individual crop. The rotation includes 3-year intervals of no-till, which will improve both weed population management and soil health. Even though this rotation has not been field tested, it provides an example of designing rotations to disrupt population dynamics of weeds. Also, producers may gain additional benefits of higher crop yield and increased nitrogen supply with this rotation design.
  • Authors:
    • Six, J.
    • Lee, J.
    • Temple, S. R.
    • Rolston, D. E.
    • Mitchell, J.
    • Kaffka, S. R.
    • Wolf, A.
    • De Gryze, S.
  • Source: Ecological Applications
  • Volume: 20
  • Issue: 7
  • Year: 2010
  • Summary: Despite the importance of agriculture in California's Central Valley, the potential of alternative management practices to reduce soil greenhouse gas (GHG) emissions has been poorly studied in California. This study aims at (1) calibrating and validating DAYCENT, an ecosystem model, for conventional and alternative cropping systems in California's Central Valley, (2) estimating CO2, N2O and CH4 soil fluxes from these systems, and (3) quantifying the uncertainty around model predictions induced by variability in the input data. The alternative practices considered were cover cropping, organic practices, and conservation tillage. These practices were compared with conventional agricultural management. The crops considered were beans, corn, cotton, safflower, sunflower, tomato, and wheat. Four field sites for which at least five years of measured data were available, were used to calibrate and validate the DAYCENT model. The model was able to predict 86% to 94% of the measured variation in crop yields and 69% to 87% of the measured variation in soil organic carbon (SOC) contents. A Monte-Carlo analysis showed that the predicted variability of SOC contents, crop yields and N2O fluxes was generally smaller than the measured variability of these parameters, in particular for N2O fluxes. Conservation tillage had the smallest potential to reduce GHG emissions among the alternative practices evaluated, with a significant reduction of the net soil GHG fluxes in two of the three sites of 336 ± 47 (mean ± standard error) and 550 ± 123 kg CO2-eq ha-1 yr-1. Cover cropping had a larger potential, with net soil GHG flux reductions of 752 ± 10, 1072 ± 272 and 2201 ± 82 kg CO2-eq ha-1 yr-1. Organic practices had the greatest potential for soil GHG flux reduction, with 4577 ± 272 kg CO2-eq ha-1 yr-1. Annual differences in weather or management conditions contributed more to the variance in annual GHG emissions than soil variability did. We concluded that the DAYCENT model was successful at predicting GHG emissions of different alternative management systems in California, but that a sound error analysis must accompany the predictions to understand the risks and potentials of GHG mitigation through adoption of alternative practices.
  • Authors:
    • Bosede, A.
  • Source: African Journal of Agricultural Research
  • Volume: 5
  • Issue: 5
  • Year: 2010
  • Summary: An assessment of fertilizer use and other integrated practices was carried out with two hundred farmers selected by stratified random sampling from twenty villages in Kano and Katsina States of Nigeria. The farming system was mixed farming (legume-cereal-livestock mixture), as a strategy both to address nutrient management as well as their livelihoods (both food and income security). The major crops comprised maize, sorghum, millet, rice, soybean, groundnut and cowpea. The average farm size was 7.4 ha and livestock comprised an average of 14 goats, 15 poultry birds, 7 sheep and 9 cattle. An average of 63 kg fertilizer was applied per ha of land relative to about 649 kg of fertilizer requirement per hectare of the crops grown, very low relative to Asia and some other African countries such as South Africa, Malawi, Benin and Ethiopia. The livestock mix provided substantial farmyard manure for fertilizing the soils and supplemented farm drought animals/animal traction while the crop residues (legumes and cereals) provided feeds for the livestock. It was found that fertilizer use multiplies the returns on farmers' output by a factor of 2.1-14.6, which was relatively higher than previous findings (IFDC, 2002) for the same crops in Nigeria, but crop yields were comparatively less for other Sub-Saharan and Asian countries. The observed higher response coefficient could be explained by the use of organic/farmyard manures and other soil conservation practices. Farmers exploit land and the natural fertility of the soil through continuous cropping and poor fertilization (organic and inorganic). Critical environmental issues emanating from these are soil nutrient depletion, soil degradation by erosion, weed and pest invasion, all culminating in sustained low productivity. It was therefore concluded that sustained growth in agricultural productivity without environmental exploitation and degradation cannot be achieved unless efforts to enhance farmers' fertilizer use and organic fertilization are taken seriously. Efforts should be put in place to correct fertilizer market inadequacies, particularly to monitor the quality standard and guarantee farmers' access to fertilizers, as well as encourage National research and extension programs to emphasize economic use of basic local materials for effective fertilization of farmers' fields, reduced vulnerability to nutrient loss and drought, and increased agricultural productivity.
  • Authors:
    • Maeder, P.
    • Niggli, U.
    • Wiemken, A.
    • Burger, D.
    • Berner, A.
    • Krauss, M.
  • Source: Soil Use and Management
  • Volume: 26
  • Issue: 1
  • Year: 2010
  • Summary: To promote conservation tillage in organic farming systems, weed control and ley removal within arable-ley rotations need to be optimized. A long-term field trial was thus established in Frick, Switzerland in 2002 on a clayey soil and with a mean precipitation of 1000 mm/year. The tillage experiment distinguished between conventional tillage with mouldboard ploughing (CT, 15 cm depth) and reduced tillage (RT), including a chisel plough (15 cm) and a stubble cleaner (5 cm). Results of a 2-year grass-clover ley (2006/2007) and silage maize (2008) are presented. Due to dry conditions, mean grass-clover yields were 25% higher in RT than in CT, indicating better water retention of RT soils. Clover cover and mineral contents of the fodder mixture were also higher in RT. The ley was successfully removed in autumn 2007 in RT plots, and a winter pea catch crop was sown before maize. In CT, ploughing took place in spring 2008. Maize yields were 34% higher in RT than in CT, despite a two- to three-fold higher but still tolerable weed infestation. Maize in RT plots benefited from an additional 61.5 kg of easily decomposable organic N/ha incorporated into the soil via the pea mulch. Measurement of arbuscular mycorrhizal colonization of maize roots indicated a similar mechanical disturbance of the topsoil through the reduced ley removal system compared with ploughing. It is suggested that RT is applicable in organic farming, even in arable-ley rotations, but long-term effects need further assessment.
  • Authors:
    • Di Tizio, A.
    • Campiglia, E.
    • Mancinelli, R.
    • Marinari, S.
  • Source: Applied Soil Ecology Volume 46, Issue 1, September 2010, Pages
  • Volume: 46
  • Issue: 1
  • Year: 2010
  • Summary: Carbon sequestration in soil is an important means for reducing net emissions of CO(2) into the atmosphere. We hypothesized that organic cropping systems (ORG) would reduce soil CO(2) emission and increase C storage compared to conventional cropping systems (CONV). The objectives of this study were to: (i) analyze the ORG and CONV systems in terms of soil CO(2) emission and soil C balance and (ii) establish if the soil in the ORG and CONV systems represents a source or a sink of C. A3-year crop rotation (durum wheat-Triticum durum Desf., tomato - Licopersicum esculentum Mill., and pea - Pisum sativum L) was carried out in both cropping systems, but the crop rotation was implemented with common vetch (Vicia sativa L.) before tomato planting and sorghum (Sorghum bicolor (L) Moench.) before pea sowing and both green manured only in the ORG system. It was found that the soil CO(2) emission rate at peak times (in spring or at the end of summer - beginning of autumn) in the ORG system was higher than the CONV system. The peak of CO(2) was attributed to the fact that at this time the soil temperature and the relative soil water content (RWC) were probably in the optimal range for soil respiration (17.2 degrees C and 36.4% of RWC) and the difference between ORG and CONV was probably due to the green manuring of the cover crops in the ORG system. However, even if the cropping systems had a temporary impact on the rate of soil CO(2) emissions, the soil C output calculated as the average of cumulative CO(2) emission over the 3-year period did not show significant differences between the ORG and CONV systems (8.98 Mg C-CO(2) ha(-1) vs. 8.06 Mg C-CO(2) ha(-1)). On the other hand, the C input in the ORG system was higher than in the CONV (9.46 Mg C ha(-1) vs. 5.57 Mg C ha(-1)) as well as the C input/output ratio (1.10 vs. 0.72). The 3-year average of TOC content and C stock were higher in the ORG than in the CONV system (1.24% vs. 1.10% and 27.4 Mg C ha(-1) vs. 23.9 Mg C ha(-1), respectively). However, the decrease of TOC and C stock over 3 years period suggested that further studies over a longer period are needed to verify if C limitation for soil microbial growth and nitrogen limitation for crop growth in the organic system could hinder soil C accumulation over a longer period. (C) 2010 Elsevier B.V. All rights reserved.
  • Authors:
    • Moscatelli, M. C.
    • Lagomarsino, A.
    • Marinari, S.
    • Di Tizio, A.
    • Campiglia, E.
  • Source: Soil & Tillage Research
  • Volume: 109
  • Issue: 2
  • Year: 2010
  • Summary: The scientific literature regarding the use of C and N mineralization kinetics as a tool to highlight the effects of different cropping systems on soil C and N release is scarce. In this study we aimed to assess the effectiveness of these parameters in evaluating soil C and N potential release in organic (ORG) and conventional (CONV) three-year cropping systems. A long-term field study was established in 2001 at the University of Tuscia experimental farm (Viterbo, Italy) in a randomized block design. The soil is classified as Typic Xerofluvent or Dystric Fluvisol. In the CONV system the Good Agricultural Practice is adopted, whereas the ORG system is managed following the Regulation 2092/91/EEC. Both systems had a three-year crop rotation (pea - Pisum sativum L.; durum wheat - Triticum durum Desf.; tomato - Licopersicum esculentum Mill.). One of the main differences between the two systems is the soil N fertilization program: organic fertilizers (Guano: 6% N, 32% organic carbon and DIX10: 10% N, 42% organic carbon, both produced by Italpollina. Italy) and mineral nitrogen fertilizers (NH(4)NO(3)) were applied to ORG and CONV fields.respectively. Moreover, the rotation in the ORG system included common vetch (Vicia sativa L) and sorghum (Sorghum vulgare L) as green manure crops. Our results supported the hypotheses in that the two systems differed significantly on potentially mineralizable C (C(o)) in 2008 and on potentially mineralizable N (N(o)) as nitrate form (N(0)-NO(3)(-)) in 2006 (318 mu g C-CO(2) g(-1) 28 d(-1) vs. 220 mu g C-CO(2) g(-1) 28 d(-1); 200 mu g N-NO(3)(-) g(-1) vs. 149 mu g N-NO(3)- g(-1) in ORG and CONV, respectively). The reduction of N(o) in soil during the crop rotation period could reflect the N microbial immobilization since a negative correlation between microbial biomass N:total N ratio and No as ammonium form (N(0)-NH(4)(+))(P < 0.001) as well as a positive correlation between N0-NH4+ and C:N ratio of microbial biomass (P < 0.05) were observed. Moreover, a lower potential mineralization rate of N was observed in soil with Guano (25%) than in soil with DIX10 (35%); nevertheless the former fertilizer might cover a longer period of crop N demand as a more gradual release of N0 was observed. In this work we demonstrated that the use of mineralization kinetics parameters can offer a potential to assess the mineralization–immobilization processes in soils under different climatic and management conditions. Moreover, they can be used to evaluate the most suitable N release pattern of organic fertilizers used in various cropping systems.
  • Authors:
    • Narwal, S. S.
  • Source: Allelopathy Journal
  • Volume: 25
  • Issue: 1
  • Year: 2010
  • Summary: To make our modem agriculture successful, the use of new agricultural technology in a short span of 35-40 years have caused havoc by contaminating our soil, environment and food with toxic pesticides residues. Modem agriculture is exploitive of growth resources and has caused very serious problems such as environmental pollution through (i). contamination of underground drinking water resources, food and fodder with pesticides and nitrates, which are harmful to 0 human beings and livestock, (ii). poor soil health/soil Sickness leading to low soil productivity and (iii). poor quality of life. These problems may be overcome with the adoption of Organic Agricultural practices. The definition of Organic Agriculture used in this paper is "Organic Agriculture consists of those practices, which reduces the use of outside inputs viz., fertilizers and pesticides etc on the farm". Therefore, various types of allelopathic strategies may be used for (a) maintenance of soil fertility (use of crop rotations, Biological Nitrogen Fixation, crop mixtures, crop residues and leaf litter etc.), (b) weed management (cover crops, crop residues as mulches, intercropping, crop rotations, phytotoxic or, allelopathic varieties and natural herbicides etc.), (c) insects pest management (cropping systems, resistant varieties, insecticidal allelochemicals etc.), (d) nematodes management (plant materials, oilseed cakes, nematicidal compounds etc.), (e) diseases management (cropping systems, crop residues, organic amendments etc.) and (f) use of allelochemicals as growth regulators. Therefore, research efforts are needed to utilise inhibitory allelopathic effects of plants for natural control of crop pests (weeds, insects, nematodes, pathogens), so that use of present pesticides could be minimized or eliminated for developing Sustainable Organic Agriculture, keeping the environment clean for our future generations and reducing the cost of Organic food.