• Authors:
    • Lares, M. T.
    • Liebig, M. A.
    • Merrill, S. D.
    • Tanaka, D. L.
    • Krupinsky, J. M.
    • Hanson, J. D.
  • Source: Agronomy Journal
  • Volume: 99
  • Issue: 4
  • Year: 2007
  • Summary: Crop sequence is an important management practice that may lower the risk for leaf spot diseases of spring wheat ( Triticum aestivum L.). Field research was conducted near Mandan, ND, to determine the impact of crop sequences on leaf spot diseases of hard red spring wheat early in the growing season. Spring wheat was evaluated for disease severity following crop sequence combinations of 10 crops [buckwheat ( Fagopyrum esculentum Moench)], canola ( Brassica napus L.), chickpea ( Cicer arietinum L.), corn ( Zea mays L.), dry pea ( Pisum sativum L.), grain sorghum [ Sorghum bicolor (L.) Moench], lentil ( Lens culinaris Medik.), oil seed sunflower ( Helianthus annuus L.), proso millet ( Panicum miliaceum L.), and hard red spring wheat. Spring wheat leaves with distinct lesions were collected for determination of lesion number and percentage necrosis data, which were used to estimate leaf spot disease severity. Pyrenophora tritici-repentis (Died.) Drechs., the cause of tan spot, and Phaeosphaeria nodorum (E. Muller) Hedjaroude, the cause of Stagonospora nodorum blotch, were the major leaf spot diseases and consistently present throughout the growing season. The frequency of isolation following alternative crops was generally lower compared with spring wheat following wheat. Leaf spot diseases on spring wheat were impacted by crop sequencing. Spring wheat following crop sequences with alternative crops for 1 or 2 yr had lower levels of disease severity compared with a continuous spring wheat treatment early in the growing season. Disease severity was apparently not related to the percentage of crop residue coverage on the soil surface associated with various crop sequence combinations. New alternative crops preceding spring wheat reduce levels of leaf spot diseases.
  • Authors:
    • Worth, D.
    • Desjardins, R. L.
    • Dyer, J. A.
    • Vergé, X. P. C.
  • Source: Agricultural Systems
  • Volume: 94
  • Issue: 3
  • Year: 2007
  • Summary: In order to demonstrate the impact of an increase in production efficiency on greenhouse gas (GHG) emissions, it is important to estimate the combined methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) emissions per unit of production. In this study, we calculated the GHG emissions from the Canadian dairy industry in 2001 as a fraction of the milk production and per dairy animal. Five regions were defined according to the importance of the dairy industry. N2O and CO2 emissions are directly linked with areas allocated to the dairy crop complex which includes only the crop areas used to feed dairy cattle. The dairy crop complex was scaled down from sector-wide crop areas using the ratios of dairy diet to national crop production of each crop type. Both fertilizer application and on-farm energy consumption were similarly scaled down from sector-wide estimates to the dairy crop complex in each region. The Intergovernmental Panel on Climate Change (IPCC) methodology, adapted for Canadian conditions, was used to calculate CH4 and N2O emissions. Most of the CO2 emission estimates were derived from a Fossil Fuel for Farm Fieldwork Energy and Emissions model except for the energy used to manufacture fertilizers. Methane was estimated to be the main source of GHG, totalling 5.75 Tg CO2 eq with around 80% coming from enteric fermentation and 20% coming from manure management. Nitrous oxide emissions were equal to 3.17 Tg CO2 eq and carbon dioxide emissions were equal to 1.45 Tg. The GHG emissions per animal were 4.55 Mg CO2 eq. On an intensity basis, average GHG emissions were 1.0 kg CO2 eq/kg milk. Methane emissions per kg of milk were estimated at 19.3 l CH4/kg milk which is in agreement with Canadian field measurements.
  • Authors:
    • Li, F.
    • Ma, Q.
    • Wang, Z.
    • Li, X.
  • Source: Soil & Tillage Research
  • Volume: 95
  • Issue: 1
  • Year: 2007
  • Summary: The effects of cultivation and overgrazing on soil quality in arid regions have been rarely addressed. This study investigated the roles of cropping and grazing in soil organic C pools and aggregate stability at 0-20 cm depth by comparing conventional grazing (non-fenced ever), intensive grazing (fenced for 22 years) and cropping (cultivated for 40 years) in the arid Hexi Corridor of northwestern China. Total soil organic C (TOC) under non-fenced grazing was 21.6 g kg-1 (or 52.9 Mg ha-1), which was 19.9% (or 13.2% mass per area) lower than that under fenced grazing, because of lower stable organic C fraction (0.25 mm) in total aggregates and mean weight diameter were 15% and 0.28 mm under cropping, significantly lower than 65% and 3.11 mm under non-fenced grazing and 65% and 2.84 mm under fenced grazing. The aggregates of >1 mm were almost entirely demolished under cropping when subjected to wet sieving. Reduction of soil carbohydrates under cropping was closely related to the decline in aggregate water-stability. The negative effects of cropping on soil organic C pool and aggregate water-stability may suggest that cropping on this arid grassland is not sustainable unless no-tillage is adopted. In favor of increasing soil carbohydrates and maintaining soil aggregation, fenced-grazing would be a better option than cropping and non-fenced grazing for the management of arid grasslands.
  • Authors:
    • Lemke, R.
    • Malhi, S.
  • Source: Soil & Tillage Research
  • Volume: 96
  • Issue: 1/2
  • Year: 2007
  • Summary: An 8-yr (1998-2005) field experiment was conducted on a Gray Luvisol (Boralf) soil near Star City, Saskatchewan, Canada, to determine the effects of tillage (no-tillage - NT and conventional tillage - CT), straw management (straw retained - R and straw not retained - NR) and N fertilizer (0, 40, 80 and 120 kg N ha -1, except no N to pea ( Pisum sativum L.) phase of the rotation) on seed and straw yield, mass of N and C in crop, organic C and N, inorganic N and aggregation in soil, and nitrous oxide (N 2O) emissions for a second 4-yr rotation cycle (2002-2005). The plots were seeded to barley ( Hordeum vulgare L.) in 2002, pea in 2003, wheat ( Triticum aestivum L.) in 2004 and canola ( Brassica napus L.) in 2005. Seed, straw and chaff yield, root mass, and mass of N and C in crop increased with increasing N rate for barley in 2002, wheat in 2004 and canola in 2005. No-till produced greater seed (by 51%), straw (23%) and chaff (13%) yield of barley than CT in 2002, but seed yield for wheat in 2004, and seed and straw yield for canola in 2005 were greater under CT than NT. Straw retention increased seed (by 62%), straw (by 43%) and chaff (by 12%) yield, and root mass (by 11%) compared to straw removal for barley in 2002, wheat in 2004, and seed and straw yield for pea in 2003. No-till resulted in greater mass of N in seed, and mass of C in seed, straw, chaff and root than CT for barley in 2002, but mass of N and C were greater under CT than NT for wheat in 2004 and for canola in 2005 in many cases. Straw retention had greater mass of N and C in seed, straw, chaff and root in most cases compared to straw removal for barley in 2002, pea in 2003 and wheat in 2004. Soil moisture content in spring was higher under NT than CT and with R than NR in the 0-15 cm depth, with the highest moisture content in the NT + R treatment in many cases. After eight crop seasons, tillage and straw management had no effect on total organic C (TOC) and N (TON) in the 0-15 cm soil, but light fraction organic C (LFOC) and N (LFON), respectively, were greater by 1.275 Mg C ha -1 and 0.031 Mg N ha -1 with R than NR, and also greater by 0.563 Mg C ha -1 and 0.044 Mg N ha -1 under NT than CT. There was no effect of tillage, straw and N fertilization on the NH 4-N in soil in most cases, but R treatment had higher NO 3-N concentration in the 0-15 cm soil than NR. The NO 3-N concentration in the 0-15, 15-30 and 30-60 cm soil layers increased (though small) with increasing N rate. The R treatment had 6.7% lower proportion of fine (38.0 mm) dry aggregates, and 4.5 mm larger mean weight diameter (MWD) compared to NR treatment. This suggests a lower potential for soil erosion when crop residues are retained. There was no beneficial effect of elimination of tillage on soil aggregation. The amount of N lost as N 2O was higher from N-fertilized (580 g N ha -1) than from zero-N (155 g N ha -1) plots, and also higher in CT (398 g N ha -1) than NT (340 g N ha -1) in some cases. In conclusion, retaining crop residues along with no-tillage improved some soil properties and may also be better for the environment and the sustainability of high crop production. Nitrogen fertilization improved crop production and some soil quality attributes, but also increased the potential for NO 3-N leaching and N 2O-N emissions, especially when applied in excess of crop requirements.
  • Authors:
    • Lupwayi, N.
    • Haq, A.
    • Arshad, M.
    • Soon, Y.
  • Source: Soil & Tillage Research
  • Volume: 95
  • Issue: 1/2
  • Year: 2007
  • Summary: Information on which management practices can enhance soil organic matter (SOM) content and quality can be useful for developing sustainable crop production systems. We tested the influence of 12 years of no-till (NT) versus conventional tillage (CT), and four crop sequences on the organic C pools of a Grey Luvisolic sandy loam soil in northwestern Alberta, Canada. The crop sequences were: continuous wheat ( Triticum aestivum L.), field pea ( Pisum sativum L.)-wheat-canola ( Brassica rapa L.)-wheat, red clover ( Trifolium pratense L.) green manure-wheat-canola-wheat/red clover and fallow-wheat-canola-wheat. Soil samples from 1992, when the study was initiated, and 1996, 2000 and 2004 were analysed for total organic C (TOC), the light fraction (LF) and its C content, and water-soluble and mineralizable C. Total organic C in the top 15 cm of soil was higher in the red clover rotation than either the pea or fallow rotation by 1996. The tillage effect became significant only in 2004 with NT having a higher TOC than CT. The LF dry matter (DM) increased from 6.9 g kg -1 soil in 1992 to a range of 10-13 g kg -1 in 2000 and 2004. It was higher under NT than CT in 2 of 3 years and in the red clover rotation than the pea or fallow rotation in 1 of 3 years. The LF C content exhibited a similar trend as LF DM. The water-soluble and mineralizable C pools were not affected by tillage but decreased with time. Among crop rotations, the red clover rotation tended to result in higher levels of hot water-soluble and mineralizable C. It is concluded that tillage had a greater influence than crop rotation on the LF DM and LF C (as indicators of C storage), whereas the converse effect applied to mineralizable C and, to a lesser degree, hot water-soluble C (as indicators of SOM quality).
  • Authors:
    • Kashevarov, N. I.
  • Source: Kormoproizvodstvo
  • Issue: 3
  • Year: 2007
  • Summary: An overview of growing conditions of annual and perennial fodder crops and forage conservation in different zones of Siberia during 1986-2005 is given. Recommended planting systems for main annual and perennial crops and grass mixtures as well as their characteristics are summarised in 5 tables. New stable and highly productive multispecies cropping systems were developed, with a focus on Siberian cultivars. Achievements of Siberian research institutes in silage conservation and in selection of new rape, maize, barley, oat, field bean and clover cultivars are presented.
  • Authors:
    • Kruzhkov, N. K.
  • Source: Kormoproizvodstvo
  • Issue: 10
  • Year: 2007
  • Summary: In trials in Orel province, Russia, in 1986-89, catch crops of spring rape were sown immediately after harvesting of winter wheat and barley crops in the following rotations: (1) vetch + oat mixture - winter wheat - barley - oats; (2) peas - winter wheat - maize - barley; (3) clover - winter wheat - potatoes - barley - oats undersown with clover; and (4) fallow - winter wheat - potatoes - buckwheat - barley. The rape was harvested for fodder or ploughed in as a green manure prior to the subsequent crop being sown. Green matter yields of 16-23.4 t/ha were obtained from the rape depending on sowing date and weather conditions. Results showed that after rape was harvested for fodder, yields of subsequent crops were reduced, significantly so in some cases (by 12% for the vetch + oats mixture, by 9.5% for potatoes and by 8.1% for silage maize). However, if the rape was ploughed in as a green manure, the yield of subsequent crops increased; for example, by 8.8% in barley, 9.7% in maize and 10.5% in peas. In terms of fodder units produced per ha, in all cases rape as a catch crop increased values by 7.4-18.9% when harvested for fodder and by 3.8-6.5% when ploughed in.
  • Authors:
    • Griffin, T. S.
    • Larkin, R. P.
  • Source: Crop Protection
  • Volume: 26
  • Issue: 7
  • Year: 2007
  • Summary: Brassica crops used in crop rotations and as green manures have been associated with reductions in soilborne pests and pathogens. These reductions have been attributed to the production of volatile sulfur compounds through a process known as biofumigation, and to changes in soil microbial community structure. In this study, selected Brassica crops, including canola, rapeseed, radish, turnip, yellow mustard, and Indian mustard, were evaluated for control of various soilborne potato pathogens and diseases in culture, in greenhouse trials, and in field trials on commercial potato farms. In in vitro assays, volatiles released from chopped leaf material of Brassica crops and barley inhibited growth of a variety of soilborne pathogens of potato, including Rhizoctonia solani, Phytophthora erythroseptica, Pythium ultimum, Sclerotinia sclerotiorum, and Fusarium sambucinam, with Indian mustard resulting in nearly complete inhibition (80-100%). All Brassica crops and barley reduced inoculum levels of R. solani (20-56% reduction) in greenhouse tests, and radish, rapeseed, and Indian mustard reduced subsequent potato seedling disease by 40-83%. In an on-farm field trial at a site with a substantial powdery scab problem, Indian mustard, rapeseed, canola, and ryegrass grown as green manure rotation crops reduced powdery scab in the subsequent potato crop by 15-40%, and canola and rapeseed reduced black scurf by 70-80% relative to a standard oats rotation. At another field site where common scab was the primary disease problem, an Indian mustard green manure reduced common scab by 25%, and rapeseed, yellow mustard, and 'Lemtal' ryegrass also reduced black scurf relative to a standard ryegrass rotation. Disease reductions were not always associated with higher glucosinolate-producing crops, and were also observed with non- Brassica crops (barley and ryegrass), indicating other mechanisms and interactions are important, particularly for control of R. solani. Overall, Indian mustard was most effective for reducing powdery scab and common scab diseases, whereas rapeseed and canola were most effective in reducing Rhizoctonia diseases. These results indicate that Brassica crops have potential for use as green manures for the control of multiple soilborne disease problems.
  • Authors:
    • Dosdall, L. M.
    • Moyer, J. R.
    • Clayton, G. W.
    • Harker, K. N.
    • Blackshaw, R. E.
    • O'Donovan, J. T.
    • Maurice, D. C.
    • Turkington, T. K.
  • Source: Crop Protection
  • Volume: 26
  • Issue: 3
  • Year: 2007
  • Summary: In western Canada, the move to integrated weed management (IWM) with reduced dependence on herbicides is being driven by low crop prices, weed resistance to herbicides, and environmental concerns. A rational step when implementing IWM is to determine if herbicide application is required in the first place. Crop yield loss models have been developed to assist with this decision. However, the weed economic threshold will be influenced considerably by management practices. Field studies showed that enhancing crop competitiveness through planting competitive varieties at relatively high seeding rates and through strategic fertilizer placement including sub-surface banded or point-injected nitrogen can reduce the impact of weeds on crop yield and the amount of weed seed entering the soil seed bank. Enhancing crop competitiveness also improved herbicide performance, especially when herbicides were applied at reduced doses. The inclusion of an early-cut silage crop in a rotation dramatically reduced wild oat ( Avena fatua L.) populations in barley ( Hordeum vulgare L.) while growing sweet clover ( Melilotus officinalis (L.) Lam) as a green manure in rotation with cereal and oilseed crops showed tremendous potential to suppress weeds. Other studies demonstrated that weed management should not be considered in isolation since it can influence the severity of alternative pests, for example, damage due to Delia spp. in canola ( Brassica napus L.). Further studies are required to examine the cumulative long-term effects of integrating the various weed management practices on all components of the crop ecosystem including weeds, diseases and insects.
  • Authors:
    • Schumacher, K. D.
    • Striewe, L.
  • Source: Agrarwirtschaft
  • Volume: 56
  • Issue: 1
  • Year: 2007
  • Summary: The international cereal production is expected to decrease by 1% in 2006/07, the second year in a row. Wheat production is expected 589 million tonnes, 5% less the previous year and the lowest harvest for the last three years. Droughts in Australia, the USA and Canada are one reason, however China, Ukraine and other Black Sea neighbouring countries reported higher production in 2006/07. In the USA 110 ethanol production units were established, most are maize (corn) based others on sorghum. A doubling of the capacity in 2007 alone is projected. The EU cereal harvest was also reduced with droughts in Spain and Portugal. Prices are predicted to rise further, the export licences established in the Ukraine have driven European prices up and Ukrainian producers suffered because of price drops within their country, due to oversupply. The global oilseed production can currently match demand, however, it is expected that demand will grow faster than supply. The global oilseed production in 2006/07 of 395 million tonnes consisted mainly of soyabeans (227), oilseed rape (47), cotton (44), peanuts (32) and sunflowers (31 million tonnes). The soyabean area in Brazil is decreasing from 23 million ha to 21 million in 2006/07, however Argentina has increased the area by 0.5 to 15.7 million ha. Globally demand is again rising faster than supply and inelastic demand caused by government subsidies for bio-fuel will lead to less cereals being available for food consumption.