• Authors:
    • Davison, D. R.
    • Petersen, J. L.
    • Shaver, T. M.
    • Donk, S. J. van
  • Source: Transactions of the ASABE
  • Volume: 55
  • Issue: 1
  • Year: 2012
  • Summary: Reduced tillage, with more crop residue remaining on the soil surface, is believed to conserve water, especially in arid and semi-arid climates. However, the magnitude of water conservation is not clear. An experiment was conducted to study the effect of crop residue removal on soil water content, soil quality, and crop yield at North Platte, Nebraska. The same field plots were planted to soybean ( Glycine max) in 2009 and 2010. There were two treatments: residue-covered soil and bare soil. Residue (mostly corn residue in 2009 and mostly soybean residue in 2010) was removed every spring from the same plots using a flail chopper and subsequent hand-raking. The experiment consisted of eight, 12.2 m * 12.2 m, plots (two treatments with four replications each). Soybeans were sprinkler-irrigated, but purposely water-stressed, so that any water conservation in the residue-covered plots might translate into higher yields. After four years of residue removal, soil organic matter content and soil residual nitrate nitrogen were significantly smaller, and soil pH was significantly greater, in the bare-soil plots compared to the residue-covered plots. The residue-covered soil held approximately 90 mm more water in the top 1.83 m compared to the bare soil near the end of the 2009 growing season. In addition, mean soybean yield was 4.5 Mg ha -1 in the residue-covered plots, compared to 3.9 Mg ha -1 in the bare-soil plots. Using two crop production functions, it is estimated that between 74 and 91 mm of irrigation water would have been required to produce this extra 0.6 Mg ha -1. In 2010, mean soybean yield was 3.8 Mg ha -1 in the residue-covered plots, compared to 3.3 Mg ha -1 in the bare-soil plots. Between 64 and 79 mm of irrigation water would have been required to produce this extra 0.5 Mg ha -1. In both years, several processes may have contributed to the differences observed: (1) greater evaporation of water from the soil in the bare-soil treatment, and (2) greater transpiration by plants in the bare-soil treatment in the beginning of the growing season as a result of more vegetative growth due to higher soil temperatures in the bare-soil treatment.
  • Authors:
    • Muchaonyerwa, P.
    • Chiduza, C.
    • Dube, E.
  • Source: Soil & Tillage Research
  • Volume: 123
  • Year: 2012
  • Summary: A study was conducted to determine the effects of oat (Avena sativa) and grazing vetch (Vicia dasycapa) winter cover crops and fertilization regimes on soil organic matter (SOM) in an irrigated maize-based (Zea mays L.) conservation agriculture (CA) system following four years of continuous practice. Separate plots of oat and grazing vetch cover crops were grown in winter and then maize was planted in all plots in the following summer season. The four fertilization regimes used were: (i) fertilizer applied to the cover crops and the maize crop (F1), (ii) fertilizer applied to cover crops only (F2), (iii) fertilizer applied to the maize crop only (F3) and (iv) no fertilizer applied (F4). Control plots (weedy fallows) were included and the treatments were laid out in a randomized complete block design with three replications. Soil samples from 0-5, 5-20 and 20-50 cm depths were analyzed for total SOM, particulate organic matter (POM) fractions, hot water soluble C (HWC) and C-associated with water stable macro- and micro-aggregates (WSAC). While total SOM was more concentrated in the 0-5 cm soil depth across treatments, a lack of maize fertilization (F2 and F4 regimes) significantly (P
  • Authors:
    • Haghighi, B. J.
    • Miri, H. R.
    • Ebrahimi, S. M.
  • Source: Advances in Environmental Biology
  • Volume: 6
  • Issue: 4
  • Year: 2012
  • Summary: The purpose of this study was evaluating the growth and compare yield and water consumption of corn under treatments of conventional tillage, reduced tillage and no tillage during the different irrigation intervals. This study was conducted at Arsanjan city, southern Iran in 2009. The experiment was split plot in randomized completely blocks design with three tillage methods (conventional tillage without residues, minimum tillage and conservation residues, and no tillage and reserve residues) as main factor and irrigation intervals (8 days, 11 days and 14 days intervals) as sub factor with four replication. Result of this study showed that 8 days irrigation interval and conventional tillage produced the highest grain yield, biological yield, ear number, seed number and seed weight in comparison with other treatments. But, by increasing irrigation interval to 14 days and decreasing water usage, no tillage and reserve residue treatment could prevent reduction in grain yield. In general results showed that residues management by reserving residue as a surface cover and improves tillage method to minimum and no tillage can increase corn yield through improvement soil organic carbon which is the main goal in conservation agriculture. We can reach to economic corn yield by reducing irrigation times and saving water usage in warm and dry regions, so it is possible to plant corn in this area directly in residue of previous crop.
  • Authors:
    • Hellin, J.
    • Wall, P.
    • Sayre, K.
    • Erenstein, O.
    • Dixon, J.
  • Source: Journal of Sustainable Agriculture
  • Volume: 36
  • Issue: 1-2
  • Year: 2012
  • Summary: Conservation agriculture's underlying principles-minimal soil disturbance, soil cover and crop rotation-are increasingly recognized as essential for sustainable agriculture. This article summarizes three contrasting cases of adapting conservation agriculture (CA) to smallholder conditions in the (sub)tropics: a) irrigated rice-wheat systems in South Asia; b) rainfed maize/wheat and irrigated wheat systems in Mexico; and c) rainfed maize in Southern Africa. In the South Asia case, farm surveys show rapid and widespread adoption of zero tillage wheat-primarily due to a substantial cost saving (15-16%). In the other cases, uptake so far has been limited-although long-term trials show continuously higher and more stable yields both for maize and wheat. Under marginal conditions CA can generate substantial yield increases-averaging some 50% over conventional smallholder maize yields of 1 ton per ha over 6 years in on-farm trails in Southern Africa. The diverse experiences attest to the wide adaptability of CA systems, which can generate clear economic and potentially enormous environmental benefits. The case studies and wider literature however also reiterate the substantial challenges in terms of targeting, adapting and adopting CA-particularly for smallholders in the (sub)tropics. CA systems are best developed in situ through a multi-stakeholder adaptive learning process to create viable CA-based options that are technically sound, economically attractive, and socially acceptable.
  • Authors:
    • Poole, M. L.
    • Rodriguez, L. C.
    • Dunlop, M. I. A.
    • Campbell, P. K.
    • Jovanovic, T.
    • Taylor, J. A.
    • Herr, A.
    • Crawford, D. F.
    • O'Connor, M. H.
    • May, B. M.
    • Raison, R. J.
    • O'Connell, D. A.
    • Farine, D. R.
    • Braid, A. L.
    • Kriticos, D.
  • Source: GCB Bioenergy
  • Volume: 4
  • Issue: 2
  • Year: 2012
  • Summary: We provide a quantitative assessment of the prospects for current and future biomass feedstocks for bioenergy in Australia, and associated estimates of the greenhouse gas (GHG) mitigation resulting from their use for production of biofuels or bioelectricity. National statistics were used to estimate current annual production from agricultural and forest production systems. Crop residues were estimated from grain production and harvest index. Wood production statistics and spatial modelling of forest growth were used to estimate quantities of pulpwood, in-forest residues, and wood processing residues. Possible new production systems for oil from algae and the oil-seed tree Pongamia pinnata, and of lignocellulosic biomass production from short-rotation coppiced eucalypt crops were also examined. The following constraints were applied to biomass production and use: avoiding clearing of native vegetation; minimizing impacts on domestic food security; retaining a portion of agricultural and forest residues to protect soil; and minimizing the impact on local processing industries by diverting only the export fraction of grains or pulpwood to bioenergy. We estimated that it would be physically possible to produce 9.6GLyr-1 of first generation ethanol from current production systems, replacing 6.5GLyr-1 of gasoline or 34% of current gasoline usage. Current production systems for waste oil, tallow and canola seed could produce 0.9GLyr-1 of biodiesel, or 4% of current diesel usage. Cellulosic biomass from current agricultural and forestry production systems (including biomass from hardwood plantations maturing by 2030) could produce 9.5GLyr-1 of ethanol, replacing 6.4GLyr-1 of gasoline, or ca. 34% of current consumption. The same lignocellulosic sources could instead provide 35TWhyr-1, or ca. 15% of current electricity production. New production systems using algae and P. pinnata could produce ca. 3.96 and 0.9GL biodieselyr-1, respectively. In combination, they could replace 4.2GLyr-1 of fossil diesel, or 23% of current usage. Short-rotation coppiced eucalypt crops could provide 4.3GLyr-1 of ethanol (2.9GLyr-1 replacement, or 15% of current gasoline use) or 20.2TWhyr-1 of electricity (9% of current generation). In total, first and second generation fuels from current and new production systems could mitigate 26MtCO2-e, which is 38% of road transport emissions and 5% of the national emissions. Second generation fuels from current and new production systems could mitigate 13MtCO2-e, which is 19% of road transport emissions and 2.4% of the national emissions lignocellulose from current and new production systems could mitigate 48MtCO2-e, which is 28% of electricity emissions and 9% of the national emissions. There are challenging sustainability issues to consider in the production of large amounts of feedstock for bioenergy in Australia. Bioenergy production can have either positive or negative impacts. Although only the export fraction of grains and sugar was used to estimate first generation biofuels so that domestic food security was not affected, it would have an impact on food supply elsewhere. Environmental impacts on soil, water and biodiversity can be significant because of the large land base involved, and the likely use of intensive harvest regimes. These require careful management. Social impacts could be significant if there were to be large-scale change in land use or management. In addition, although the economic considerations of feedstock production were not covered in this article, they will be the ultimate drivers of industry devlopment. They are uncertain and are highly dependent on government policies (e.g. the price on carbon, GHG mitigation and renewable energy targets, mandates for renewable fuels), the price of fossil oil, and the scale of the industry.
  • Authors:
    • Ward, P. R.
    • Cordingley, N.
    • Flower, K. C.
    • Weeks, C.
  • Source: Field Crops Research
  • Volume: 132
  • Year: 2012
  • Summary: Cover crops have been successfully integrated into conservation agriculture systems in many parts of the world. They are primarily used to provide surface cover as well as to improve soil fertility and suppress weeds. Black oat (Avena strigosa Schreb.) is a widely used cereal cover crop with a rapid growth and high biomass production. It is being trialled as a cover crop for conservation agriculture systems in southwestern Australia, which has a Mediterranean climate with a short winter growing season and where terminal drought is common. Only one crop can be grown in a year and, as such, the long term benefits of including a cover crop in this system must outweigh the loss in income by not growing a cash crop. This study, which was part of a larger conservation agriculture cropping systems trial, examined the effect of different crop sequences, which included oat cover crops and grass pasture, on soil nitrogen mineralisation and weed control. A related paper in this Special Issue examined the effect of cover crops on the soil water balance. We hypothesised that the inclusion of high-biomass oat cover crops in a cereal-dominated cropping system would (i) result in less immobilisation of soil nitrogen compared with that of harvested cereals, and (ii) significantly improve the weed control. We show that soil N mineralisation following oat cover crops was similar to that following wheat and barley. Therefore, cash crops grown after oat cover crops would require similar levels of nitrogen to those grown after harvested cereals. Oat cover crops and grass pasture were found to be very effective in controlling weeds, even in continuous cereal rotations. Two consecutive years of cover crop were required for good annual ryegrass (Lolium rigidum Gaud.) control in a predominantly cereal rotation. Timing of when the cover crops were killed by herbicide was crucial for good weed control, as failure to prevent weed seed set resulted in significantly reduced weed control. Also, late killing of the cover crop reduced soil water storage. The inclusion of an oat cover crop in the rotation reduced the three-year average gross margin; however, the profitability of these crops needs to be evaluated over a longer period. To date, managed pasture, with herbicide control of weed seed set, appears to be a better option than oat cover crops because of the relatively low cost and increased soil water storage. (C) 2011 Elsevier B.V. All rights reserved.
  • Authors:
    • Carbonell-Bojollo, R.
    • Ordóñez-Fernández, R.
    • Veroz-González, O.
    • González-Sáncheza, E. J.
    • Gil-Ribes, J. A.
  • Source: Soil & Tillage Research
  • Volume: 122
  • Year: 2012
  • Summary: Conservation agriculture (CA) helps to mitigate climate change. Firstly, the modifications introduced by CA on the carbon dynamics in the soil directly result in an increase of the carbon (C) in the soil fraction. Secondly, CA drastically reduces C oxidation processes by diminishing the mechanical manipulation of the soil. Spain's position in relation to the Kyoto Protocol must be improved, as is one of the European countries in a non-compliance situation. With the aim of providing knowledge about the potential of CA as C sink in Spain, 29 articles on this subject were reviewed. According to 2010 CA uptake, the results demonstrated that conservation practices have the potential to promote the fixation in soil of about 2 Gg year(-1) more C than traditional tillage (TT) systems. As indicated by Tebrugge (2001), 3.7 Mg of CO2 are generated from 1 Mg of C through microbial oxidation processes taking place in the ground, meaning that through CA almost 7.5 Gg of CO2 could be sequestered from the atmosphere every year until the equilibrium is reached. C fixation was found to be irregular over time. C fixation rates were high in newly implemented systems during the first 10 years, reaching top values of 0.85 Mg ha(-1) year(-1) for no-tillage (NT) and 1.54 Mg ha(-1) year(-1) for cover crops (CC) implemented in-between perennial tree rows. After those first 10 years, it followed a period of lower but steady growth until equilibrium was reached. Nevertheless, C decreases of 0.16 Mg ha(-1) year(-1) in the first 10 years may be expected when practicing minimum tillage (MT). C sequestration rate resulted higher in case farmers do crop rotations in NT and MT rather than monoculture. In woody crops, studies reported higher C fixation values for native species when compared to sowed CC. Also, climate conditions seem to affect C sequestration rate in Spain. Although in NT differences observed between maritime and continental climates are not pronounced, as approximately 25% of the values recorded in both climates are equal, in the case of MT about 75% of maritime climate values result higher than the continental situation. (c) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Coquet, Y.
    • Justes, E.
    • Benoit, P.
    • Alletto, L.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 153
  • Year: 2012
  • Summary: Water drainage and herbicide degradation and leaching were studied during four years in a continuous maize field managed with two tillage systems and two types of fallow periods. The tillage systems consisted of either a conventional practice with mouldboard ploughing (28 cm-depth) or a conservation practice with superficial tillage (
  • Authors:
    • Dercon, G.
    • Kumar S.
    • Garg, A. K.
    • Manchanda, J. S.
    • Aulakh, M. S.
    • Nguyen, M. L.
  • Source: Soil & Tillage Research
  • Volume: 120
  • Year: 2012
  • Summary: Continuing cereal-based crop rotations such as rice-wheat, intensive cultivation and complete removal of postharvest crop residue (CR) for animal consumption and fuel, or its burning have reduced the organic matter content and productivity of irrigated semi-arid subtropical soils of South Asia. Identification of effective strategies for the management of tillage and CR could foster sustainable and environmentally sound agricultural systems. To this effect, a 4-year field experiment was established with annual soybean-wheat rotation under subtropical climate conditions in the Indo-Gangetic Plains of Northwestern India to evaluate the integrated effects of tillage, CR retainment, mineral fertilizers and farmyard manure (FYM) on crop production, nutrients uptake, soil moisture storage and temperature dynamics. The experimental soil was loamy sand, poor in organic C and low in available P. Sixteen treatment combinations involved recommended and 25% higher NP rates without or with 10 t FYM ha -1 and CR incorporated in conventional tillage (CT) and retained on the soil surface in conservation agriculture (CA) system. The results clearly revealed that (a) soybean yield was 2-6% higher in CA than CT in different treatments with and without CR, (b) significantly higher uptake of N and P by soybean from CR-amended treatments of both CT and CA, which reflected its effect in improving the soybean yield, (c) the current fertilizer NP recommendation of 20 kg N and 26 kg P ha -1 for soybean is not adequate and either application of 25% higher NP rate (25 kg N and 33 kg P ha -1) or additional 10 t FYM ha -1 is required for optimum crop production of ~2500 kg ha -1, (d) CA conserved more water in soil profile than CT, however, the differences in soil moisture storage in CT vis-a-vis CA were not reflected in soybean yield presumably due to frequent wetting of soil by heavy monsoonal rains, (e) the wheat yield was highest in both CT and CA systems when grown with the application of 150 kg N and 33 kg P ha -1 without CR and was 7% higher in CA (4140 kg ha -1) than CT (4048 kg ha -1), and (f) retention of CR on soil surface in winter-grown wheat under CA reduced wheat yield by 8-24% and N uptake by 3-5% as a consequence of mulching effects creating cooler environment in surface soil layer during initial 3 weeks after seeding, which led to the delayed germination and relatively poor crop growth during initial period.
  • Authors:
    • Smith, P.
    • Hillier, J.
    • Walter, C.
    • Malin, D.
    • Garcia-Suarez, T.
    • Mila-i-Canals, L.
  • Source: Environmental Modelling & Software
  • Volume: 26
  • Issue: 9
  • Year: 2011
  • Summary: Agriculture and deforestation contribute approximately one third of global greenhouse gas emissions. Major sources of emissions in this sector are from loss of soil carbon due to repeated soil disturbance under typical crop cultivation, fossil fuel use in the production of synthetic fertilisers, direct and indirect soil nitrous oxide emissions from fertiliser application, pesticide manufacture and use, and fossil fuel combustion in machinery use (e.g. tractors, irrigation, etc). Although knowledge of emissions sources aids in the determination of potential mitigation strategies (reduced or no-till methods, use of N-fixing leguminous crops in rotations, use of lower emissions fertilisers), there currently exist limited decision support and knowledge transfer tools to enable the farmer or grower to make choices appropriate to existing management practices. In this article we present a model, and open source software tool called the "Cool Farm Tool" integrating several globally determined empirical models in a greenhouse gas calculator. The software, in requiring inputs of which a farmer typically has good knowledge (and no more), has a specific farm-scale, decision-support focus. Due to its use of only readily available farm data, there is considerable scope for its use in global surveys to inform on current practices and potential for mitigation.