• Authors:
    • Khizar, A.
    • Abbasi, M. K.
  • Source: Ecological Engineering
  • Volume: 39
  • Issue: February
  • Year: 2012
  • Summary: Application of organic amendments to soil is an important management strategy for enhancing the restoration of degraded soils and providing better soil conditions to below-ground soil microbial composition and above-ground plant community development. This study was conducted to investigate the effect of organic amendments (poultry manure - PM; white clover residues - WCR), a mineral N fertilizer (urea N - UN), or mixtures of these fertilizers on microbial activity and nitrogen (N) mineralization through both soil analysis (laboratory incubation) and aboveground maize (Zea mays L) growth (pot experiment). In the incubation experiment, soil was amended with PM, WCR, PM + WCR, UN, UN + PM, UN + WCR, and UN + PM + WCR at the rate equivalent to 200 mg N kg(-1) soil. Pot experiment was conducted in a glasshouse using same amendments to examine the response of maize seedlings to these treatments. Organic amendments and UN applied alone or in mixtures increased soil microbial biomass compared to the control. Among N amendments, the highest evaluation of CO2-C (47.7 mg kg(-1) day(-1)), microbial biomass C (434 mg kg) and microbial biomass N (86 mg kg(-1)) were recorded in the UN + PM + WCR while the lowest values were recorded in UN. It is estimated that 9-18% of the applied N had been assimilated into microbial N pool after 105 days. Mineralization of N was higher in the fertilized soil and ranged between 85 and 192 mg N kg(-1) compared with 46 mg N kg(-1) in the control. The net cumulative N mineralized (NCNM) ranged between 43 and 169 mg kg(-1) while the net cumulative N nitrified (NCNN) ranged between 16 and 69%. Combined application of UN + PM + WCR exhibited the highest NCNM and NCNN. On average, percentage conversion of added N into NO3--N was: 21% from organic sources, 40% from UN and 52% from UN + organic sources. The apparent recovery of added N (ANR) from PM, WCR and PM + WCR was 20, 24 and 45%, respectively, while UN, UN + PM, UN + WCR and UN + PM + WCR exhibited 50, 57, 64, and 73% ANR, respectively. Results obtained from the pot experiment (on maize) were consistent with the total mineral N (TMN) released from different amendments and highly significant correlations existed between TMN and plant dry matter yield (r(2) = 0.92) and TMN and N uptake of plants (r(2) = 0.89). The present study demonstrates the existence of substantial amount of N reserve present in organic substrates, which can be transformed into inorganic N pool and can be taken into account as potential sources in the management of the nutrient poor soils and crop growth. (C) 2011 Published by Elsevier B.V.
  • Authors:
    • Akbarpour, M.
    • Taki, M.
    • Abdi, R.
  • Source: International Journal of Natural and Engineering Sciences
  • Volume: 6
  • Issue: 3
  • Year: 2012
  • Summary: The aim of this study was to examine the energy use patterns and energy input-output analysis of some field crops and vegetables in the Esfahan province of Iran. The data were collected using a face-to-face questionnaire method. The results indicated that total energy input for wheat, corn silage, cucumber and tomato production was to 69373, 109659, 152553 and 147108 MJ ha -1, respectively. Among all inputs involved, fertilizer and machinery had the highest energy values per 1 hectare for field crops; furthermore, diesel fuel had the highest share of total energy consumption for vegetable productions. The value of energy ratio for cultivating wheat, corn silage, cucumber and tomato crops were calculated at 0.74, 2.55, 0.46 and 0.73, respectively. The results of CO 2 emission analyzes showed that the total amount of CO 2 emission for wheat, corn silage, cucumber and tomato production was 2.07, 4.35, 4.99 and 4.66 tones ha -1, respectively. In the research area, greenhouse operators are still increasing the amount of inputs used in vegetable production. However, the timing of any applications and use of the inputs are not significant issues for the Iranian greenhouse producer. This inevitably leads to problems associated with energy use such as global warming, nutrient loading and pesticide pollution, as indicated above. Therefore, there is a need to develop a new policy to force producers to use all inputs on time and enough undertake more energy-efficient practices.
  • Authors:
    • Grant, T.
    • Carre, A.
    • Eady, S.
  • Source: Journal of Cleaner Production
  • Volume: 28
  • Issue: June
  • Year: 2012
  • Summary: Most agricultural products are produced on farms where there is a mix of activities, resulting in a range of co-products. This raises the issue of how best to model these complex production systems for Life Cycle Assessment, especially where there are benefits imparted by one activity in the mixed farming system to another. On the mixed farm studied, there were significant two-way reference flows (representing 288 t CO2-e/year or 10% of the total farm emissions) between activities producing distinct products (wool, meat, grain) and these were modelled using system expansion. Cropping and sheep activities were modelled as separate sub-processes in the farming system, with unique inputs and outputs identified for each. Co-production from the sheep activity was modelling using allocation, comparing biophysical and economic relationships. Using an economic allocation resulted in different estimates of global warming impact for sheep co-products, with figures varying by 7-52%. When compared to biophysical allocation, economic allocation shifted the environmental burden to the higher value co-products and away from the high resource use products. Using economic allocation, for every kilogram of wool produced there was an estimated 28.7 kg of CO2-e emitted. Amongst the live animal products, the stud rams had the highest estimated carbon footprint (719 kg CO2-e/ram). Amongst the crops, estimates of emissions for the cereal grains averaged 202 kg CO2-e/tonne grain, canola 222 kg CO2-e/tonne and lupins 510 kg CO2-e/tonne, when modelled to include the benefits of the mixed farming system. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.
  • Authors:
    • James, A.
    • Solah, V.
    • Biswas, W.
    • Gunady, M.
  • Source: Journal of Cleaner Production
  • Volume: 28
  • Year: 2012
  • Summary: A life cycle greenhouse gas (GHG) assessment of 1 kJ of strawberries, button mushrooms (Agaricus bisporus), and romaine/cos lettuces (Lactuca sativa) transported to retail outlets in Western Australia (WA) was examined and compared. The study included pre-farm, on-farm, and post-farm emissions. The pre-farm stage included GHG emissions from agricultural machinery and chemical production, and transport of raw materials (spawn, peat, and compost) in mushrooms. The on-farm stage included GHG emissions from agricultural machinery operation, chemical use, water for irrigation, waste generated, as well as electricity and energy consumption. The post-farm stage included transport of produce to Distribution Center (DC), storage in DC, and transport to retail outlets. The 'hotspots' or the stages that emit the highest GHG were determined for strawberries, button mushrooms and romaine/cos lettuces. The results have shown that the life cycle GHG emissions of strawberries and lettuces were higher than mushrooms due to intensive agricultural machinery operations during the on-farm stage. Mushrooms, however have significantly higher GHG emissions during pre-farm stage due to transport of peat, spawn, and compost. (C) 2011 Elsevier Ltd. All rights reserved.
  • Authors:
    • Robertson, M. J.
    • Pannell, D. J.
    • Kragt, M. E.
    • Thamo, T.
  • Source: Agricultural Systems
  • Volume: 112
  • Year: 2012
  • Summary: Carbon sequestration in agricultural soil has been identified as a potential strategy to offset greenhouse gas emissions. Within the public debate, it has been claimed that provision of positive incentives for farmers to change their land management will result in substantial carbon sequestration in agricultural soils at a low carbon price. However, there is little information about the costs or benefits of carbon sequestration in agricultural soils to test these claims. In this study, the costeffectiveness of alternative land-use and land-management practices that can increase soil carbon sequestration is analysed by integrating biophysical modelling of carbon sequestration with wholefarm economic modelling. Results suggest that, for a case study model of a crop-livestock farm in the Western Australian wheatbelt, sequestering higher levels of soil carbon by changing rotations (to include longer pasture phases) incur considerable opportunity costs. Under current commodity prices, farmers would forego more than $80 in profit for every additional tonne of CO2-e stored in soil, depending on their adoption of crop residue retention practices. This is much higher than the initial carbon price of $23 t(-1) in Australia's recently legislated carbon tax. This analysis does not incorporate the possibility that greenhouse gas emissions may increase as a result of including longer pasture phases. Accounting for emissions may substantially reduce the potential for net carbon sequestration at low carbon prices.
  • Authors:
    • Rimmington, G. M.
    • Chen, X.
    • Zheng, Y.
    • Luo, L.
    • Wang, Y.
    • Jiang, L.
    • Zhao, X.
    • Lai, L.
  • Source: PLOS ONE
  • Volume: 7
  • Issue: 10
  • Year: 2012
  • Summary: The variation of different ecosystems on the terrestrial carbon balance is predicted to be large. We investigated a typical arid region with widespread saline/alkaline soils, and evaluated soil respiration of different agricultural and natural ecosystems. Soil respiration for five ecosystems together with soil temperature, soil moisture, soil pH, soil electric conductivity and soil organic carbon content were investigated in the field. Comparing with the natural ecosystems, the mean seasonal soil respiration rates of the agricultural ecosystems were 96%-386% higher and agricultural ecosystems exhibited lower CO2 absorption by the saline/alkaline soil. Soil temperature and moisture together explained 48%, 86%, 84%, 54% and 54% of the seasonal variations of soil respiration in the five ecosystems, respectively. There was a significant negative relationship between soil respiration and soil electrical conductivity, but a weak correlation between soil respiration and soil pH or soil organic carbon content. Our results showed that soil CO2 emissions were significantly different among different agricultural and natural ecosystems, although we caution that this was an observational, not manipulative, study. Temperature at the soil surface and electric conductivity were the main driving factors of soil respiration across the five ecosystems. Care should be taken when converting native vegetation into cropland from the point of view of greenhouse gas emissions.
  • Authors:
    • Khamseh, A. R. M.
    • Ghotbi, M.
    • Dehaghi, M. A.
    • Rouhi, H. R.
    • Ghotbi, M.
    • Wahsha, M.
  • Source: International Journal of AgriScience
  • Volume: 2
  • Issue: 1
  • Year: 2012
  • Summary: Growing cover crops with allopathic characteristics is a way to biologically control the weed P. aegyptiaca. Allelochemicals are present in almost all plants and in many plant tissues including leaves, stems, flowers, fruits, seeds and roots. This experiment was conducted to compare effects of allopathic crops on the germination rate of P. aegyptiaca seeds. Weed infestations were tested in Polyethylene (PE) bags and pot experiments. 27 crops, of different families, were grown in 2-Kg pots containing sterile soil infested with 0.6 g of seed. The control pots contained only 0.6 g of P. aegyptiaca seeds. Two month-old plants were incorporated into the soil from the surface and then tomato seedlings ( Lycopersicum esculentum Mill.) were planted in the pots. Cotton (Malvaceae family) was among the cultured plants, used as a trap crop to thoroughly eradicate the threat of P. aegyptiaca. The most significant reduction in broomrape shoot and capsule number was demonstrated in those pots that contained cotton and sorghum, and in those that contained tomato; tomato dry weight significantly augmented. The results from the PE bags were in parallel with those of the pots. The germination rates of P. aegyptiaca (%) next to the plants in PE bags ranged from 8.333% to 55.333% respectively in millet and pepper. Except for sunflower, vetch, soy bean, chick pea, sainfoin, alfalfa, zucchini and sesame, which demonstrated catch crop, activity, the other cultivated plants; corn, oat, beet, sugar beet, triticale, caster-oil plant, millet, fiber flax, pepper, cotton and sorghum were determined as trap crops for the weed P. aegyptiaca.
  • Authors:
    • de Ridder, N.
    • Vanlauwe, B.
    • Pypers, P.
    • Guto, S. N.
    • Giller, K. E.
  • Source: Agronomy Journal
  • Volume: 104
  • Issue: 1
  • Year: 2012
  • Summary: Soil fertility gradients develop on smallholder farms due to preferential allocation of inputs. A multi-location on-farm trial was conducted in Meru South, Central Kenya whose overall aim was to test minimum tillage and crop-residue retention practices in socio-ecological niches across heterogeneous smallholder farms. We identified three soil fertility classes together with the farmers, namely: good, medium, and poor. In each soil fertility class, two tillage (minimum or regular) and two crop residue (removed or retained) practices were tested for four consecutive seasons. Maize (Zea mays L.) grain yields in the good fields were above 2.5 Mg ha(-1) across cropping seasons and cumulated yields were not influenced by tillage or crop residue management. The grain yields in the medium fields ranged between 1.3 and 5.4 Mg ha(-1) and were greater with crop residue retention. In the poor fields, grain yield was
  • Authors:
    • Samar, S. M.
    • Shahabian, M.
    • Talaie, A.
    • Emdad, M. R.
  • Source: Archives of Agronomy and Soil Science
  • Volume: 58
  • Issue: 3
  • Year: 2012
  • Summary: This work examines the effects of two deficit irrigation strategies, conventional deficit irrigation (DI) and partial root-zone drying (PRD), on mature navel orange trees. The study carried out during two consecutive years (2008 and 2009) in a semi-arid climate on a silty-clay-loam soil in the north of Iran. Both DI and PRD trees were irrigated at two levels, 75 and 50% (DI75, PRD75, DI50 and PRD50) of the full irrigation (FI). In DI, irrigation water was applied to both sides of the tree rows, similar to FI. In PRD, irrigation water was applied alternately to only one side, at each irrigation event. Results showed that DI treatments reduced fruit yield by ~30% compared with FI, but PRD treatments caused no reduction in fruit yield. No negative impact was detected in fruit quality after applying DI and PRD treatments. Shoot growth decreased in all DI and PRD treatments in both years. In DI, stomatal resistance was higher (50%) than in FI, but it was not significantly affected in PRD. The irrigation water use efficiency of PRD trees increased to nearly twice that of FI. According to these two years' results, we recommend PRD as an acceptable deficit irrigation strategy in the region.
  • Authors:
    • Jarsjo, J.
    • Tornqvist, R.
  • Source: Water Resources Management
  • Volume: 26
  • Issue: 4
  • Year: 2012
  • Summary: In many semi-arid and arid regions of the world, water saving strategies need to be implemented in the agricultural sector in order to increase the resilience to water scarcity. We investigate basin-scale hydrological impacts of possible irrigation technique improvements, considering extensive cotton fields in the Aral Sea drainage basin (ASDB), Central Asia. We use a distributed hydrologic model that combines basin-scale, calibrated discharge and evapotranspiration quantifications with experimental results of (on-farm) water application needs for different irrigation techniques. This allows for quantification of how return flows contribute to river discharge through coupled groundwater-surface water-systems at the basin scale, under different regional climatic conditions. Results show that an implementation of improved irrigation techniques can yield water savings that increase the discharge to the Aral Sea by between 1 and 6 km(3)/year. Such water savings could contribute to mitigation of the acute water scarcity in the lower ASDB. The basin-scale water savings are about 60% lower than corresponding on-farm reductions in irrigation water application, since water is re-used and, hence, return flows decrease when less water is applied. Spatial analysis of regional differences in climatic conditions shows that implementation of more efficient irrigation systems would result in much larger (up to a factor 4) water savings in the more arid downstream regions than in the colder, upstream mountainous regions.