• Authors:
    • van Groenigen, K. J.
    • van Kessel, C.
    • Oenema, O.
    • Velthof, G. L.
    • van Groenigen, J. W.
  • Source: European Journal of Soil Science
  • Volume: 61
  • Issue: 6
  • Year: 2010
  • Summary: Agricultural soils are the main anthropogenic source of nitrous oxide (N2O), largely because of nitrogen (N) fertilizer use. Commonly, N2O emissions are expressed as a function of N application rate. This suggests that smaller fertilizer applications always lead to smaller N2O emissions. Here we argue that, because of global demand for agricultural products, agronomic conditions should be included when assessing N2O emissions. Expressing N2O emissions in relation to crop productivity (expressed as above-ground N uptake: "yield-scaled N2O emissions") can express the N2O efficiency of a cropping system. We show how conventional relationships between N application rate, N uptake and N2O emissions can result in minimal yield-scaled N2O emissions at intermediate fertilizer-N rates. Key findings of a meta-analysis on yield-scaled N2O emissions by non-leguminous annual crops (19 independent studies and 147 data points) revealed that yield-scaled N2O emissions were smallest (8.4 g N2O-N kg-1N uptake) at application rates of approximately 180-190 kg Nha-1 and increased sharply after that (26.8 g N2O-N kg-1 N uptake at 301 kg N ha-1). If the above-ground N surplus was equal to or smaller than zero, yield-scaled N2O emissions remained stable and relatively small. At an N surplus of 90 kg N ha-1 yield-scaled emissions increased threefold. Furthermore, a negative relation between N use efficiency and yield-scaled N2O emissions was found. Therefore, we argue that agricultural management practices to reduce N2O emissions should focus on optimizing fertilizer-N use efficiency under median rates of N input, rather than on minimizing N application rates.
  • Authors:
    • Sun, O. J.
    • Wang, E.
    • Luo, Z.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 139
  • Issue: 1-2
  • Year: 2010
  • Summary: Adopting no-tillage in agro-ecosystems has been widely recommended as a means of enhancing carbon (C) sequestration in soils. However, study results are inconsistent and varying from significant increase to significant decrease. It is unclear whether this variability is caused by environmental, or management factors or by sampling errors and analysis methodology. Using meta-analysis, we assessed the response of soil organic carbon (SOC) to conversion of management practice from conventional tillage (CT) to no-tillage (NT) based on global data from 69 paired-experiments, where soil sampling extended deeper than 40 cm. We found that cultivation of natural soils for more than 5 years, on average, resulted in soil C loss of more than 20 t ha-1, with no significant difference between CT and NT. Conversion from CT to NT changed distribution of C in the soil profile significantly, but did not increase the total SOC except in double cropping systems. After adopting NT, soil C increased by 3.15 +- 2.42 t ha-1 (mean ± 95% confidence interval) in the surface 10 cm of soil, but declined by 3.30 ± 1.61 t ha-1 in the 20-40 cm soil layer. Overall, adopting NT did not enhance soil total C stock down to 40 cm. Increased number of crop species in rotation resulted in less C accumulation in the surface soil and greater C loss in deeper layer. Increased crop frequency seemed to have the opposite effect and significantly increased soil C by 11% in the 0-60 cm soil. Neither mean annual temperature and mean annual rainfall nor nitrogen fertilization and duration of adopting NT affected the response of soil C stock to the adoption of NT. Our results highlight that the role of adopting NT in sequestrating C is greatly regulated by cropping systems. Increasing cropping frequency might be a more efficient strategy to sequester C in agro-ecosystems. More information on the effects of increasing crop species and frequency on soil C input and decomposition processes is needed to further our understanding on the potential ability of C sequestration in agricultural soils.
  • Authors:
    • ERS
  • Volume: 2010
  • Year: 2010
  • Authors:
    • Barfoot, P.
    • Brookes, G.
  • Source: AgBioForum
  • Volume: 13
  • Issue: 1
  • Year: 2010
  • Summary: This article updates the assessment of the impact commercialized agricultural biotechnology is having on global agriculture from an environmental perspective. It focuses on the impact of changes in pesticide use and greenhouse gas emissions arising from the use of biotech crops. The technology has reduced pesticide spraying by 352 million kg (-8.4%) and, as a result, decreased the environmental impact associated with herbicide and insecticide use on these crops (as measured by the indicator the environmental impact quotient) by 16.3%. The technology has also significantly reduced the release of greenhouse gas emissions from this cropping area, which, in 2008, was equivalent to removing 6.9 million cars from the roads.
  • Authors:
    • Armstrong, R.
    • Nuttall, J.
  • Source: Australian Journal of Soil Research
  • Volume: 48
  • Issue: 2
  • Year: 2010
  • Summary: Subsoil physicochemical constraints can limit crop production on alkaline soils of south-eastern Australia. Fifteen farmer paddocks sown to a range of crops including canola, lentil, wheat, and barley in the Wimmera and Mallee of Victoria and the mid-north and Eyre Peninsula of South Australia were monitored from 2003 to 2006 to define the relationship between key abiotic/edaphic factors and crop growth. The soils were a combination of Calcarosol and Vertosol profiles, most of which had saline and sodic subsoils. There were significant correlations between EC e and Cl - ( r=0.90), ESP and B ( r=0.82), ESP and EC e ( r=0.79), and ESP and Cl - ( r=0.73). The seasons monitored had dry pre-cropping conditions and large variations in spring rainfall in the period around flowering. At sowing, the available soil water to a depth of 1.2 m (theta a) averaged 3 mm for paddocks sown to lentils, 28 mm for barley, 44 mm for wheat, and 92 mm for canola. Subsoil constraints affected canola and lentil crops but not wheat or barley. For lentil crops, yield variation was largely explained by growing season rainfall (GSR) and theta a in the shallow subsoil (0.10-0.60 m). Salinity in this soil layer affected lentil crops through reduced water extraction and decreased yields where EC e exceeded 2.2 dS/m. For canola crops, GSR and theta a in the shallow (0.10-0.60 m) and deep (0.60-1.20 m) layers were important factors explaining yield variation. Sodicity (measured as ESP) in the deep subsoil (0.80-1.00 m) reduced canola growth where ESP exceeded 16%, corresponding to a 500 kg/ha yield penalty. For cereal crops, rainfall in the month around anthesis was the most important factor explaining grain yield, due to the large variation in rainfall during October combined with the determinant nature of these crops. For wheat, theta a in the shallow subsoil (0.10-0.60 m) at sowing was also an important factor explaining yield variation. Subsoil constraints had no impact on cereal yield in this study, which is attributed to the lack of available soil water at depth, and the crops' tolerance of the physicochemical conditions encountered in the shallow subsoil, where plant-available water was more likely to occur. Continuing dry seasonal conditions may mean that the opportunity to recharge soil water in the deeper subsoil, under continuous cropping systems, is increasingly remote. Constraints in the deep subsoil are therefore likely to have reduced impact on cereals under these conditions, and it is the management of water supply, from GSR and accrued soil water, in the shallow subsoil that will be increasingly critical in determining crop yields in the future.
  • Authors:
    • Grant, C.
    • Khakbazan, M.
    • Mohr, R.
  • Source: López-Francos A. (comp.), López-Francos A. (collab.). Economics of drought and drought preparedness in a climate change context. Zaragoza : CIHEAM / FAO / ICARDA / GDAR / CEIGRAM / MARM, 2010 (Options Méditerranéennes : Série A. Séminaires Méditerranéens;
  • Issue: 95
  • Year: 2010
  • Summary: The objective of this paper was to study the impact of drought and adaptation measures on the economics of production for some major crops grown in Western Canada. Crop yields, yield variability, and crop losses were analyzed to quantify drought impacts and statistical models were developed to estimate the relationship between yield and growing season precipitation for wheat, canola, oats, and barley. The linear and quadratic precipitation terms were found to have the correct sign and to be significantly related to yield (p
  • Authors:
    • Honeycutt, C. W.
    • Griffin, T. S.
    • Larkin, R. P.
  • Source: Plant Disease
  • Volume: 94
  • Issue: 12
  • Year: 2010
  • Summary: Seven different 2-year rotations, consisting of barley/clover, canola, green bean, millet/rapeseed, soybean, sweet corn, and potato, all followed by potato, were assessed over 10 years (1997-2006) in a long-term cropping system trial for their effects on the development of soilborne potato diseases, tuber yield, and soil microbial communities. These same rotations were also assessed with and without the addition of a fall cover crop of no-tilled winter rye (except for barley/clover, for which underseeded ryegrass was substituted for clover) over a 4-year period. Canola and rapeseed rotations consistently reduced the severity of Rhizoctonia canker, black scurf, and common scab (18 to 38% reduction), and canola rotations resulted in higher tuber yields than continuous potato or barley/clover (6.8 to 8.2% higher). Addition of the winter rye cover crop further reduced black scurf and common scab (average 12.5 and 7.2% reduction, respectively) across all rotations. The combined effect of a canola or rapeseed rotation and winter rye cover crop reduced disease severity by 35 to 41% for black scurf and 20 to 33% for common scab relative to continuous potato with no cover crop. Verticillium wilt became a prominent disease problem only after four full rotation cycles, with high disease levels in all plots; however, incidence was lowest in barley rotations. Barley/clover and rapeseed rotations resulted in the highest soil bacterial populations and microbial activity, and all rotations had distinct effects on soil microbial community characteristics. Addition of a cover crop also resulted in increases in bacterial populations and microbial activity and had significant effects on soil microbial characteristics, in addition to slightly improving tuber yield (4% increase). Thus, in addition to positive effects in reducing erosion and improving soil quality, effective crop rotations in conjunction with planting cover crops can provide improved control of soilborne diseases. However, this study also demonstrated limitations with 2-year rotations in general, because all rotations resulted in increasing levels of common scab and Verticillium wilt over time.
  • Authors:
    • Holzapfel, C. B.
    • Kutcher, H. R.
    • Gan, Y.
    • Brandt, S. A.
    • May, W. E.
    • Lafond, G. P.
  • Source: Canadian Journal of Plant Science
  • Volume: 90
  • Issue: 5
  • Year: 2010
  • Summary: Differences in response to nitrogen (N) fertilizer will affect the production economics of field crops. Currently, there is limited information comparing the agronomic and economic performance of juncea canola (Brassica juncea L.) and sunflower (Helianthus annuus L.) to napus canola (Brassica napus L.) and flax (Limon ustitatissimum L.) in Saskatchewan under no-till practices. A study of these species was carried out at five Saskatchewan locations over 3 yr and included eight nitrogen rates. All four species had a curvilinear increase in grain yield as N rate increased with the largest yield response observed in napus canola to as much as 200 kg N ha I. The majority of the increase in flax grain yield occurred as the N rate increased from 10 to 90 kg ha(-1), while most of the increase in grain yield of juncea canola and sunflower occurred as N increased from 10 to 70 kg ha(-1). Biplot analysis indicated that grain yield variation was reduced at and above 50 kg N ha(-1) in flax, napus canola and juncea canola, but not in sunflower. Analysis indicated that a wide range of N rates would provide a similar adjusted gross return within each crop with the exact N range being determined by crop price and nitrogen cost. The N rate affected the kernel weight of sunflower but not the kernel weight of other crops. The protein concentration of all the species increased as N rate increased. Seed oil concentration tended to decrease as the N rate increased, but this was not consistent. In conclusion, higher yielding cultivars of sunflower and juncea canola are needed before they will replace a large acreage of flax or napus canola; however, in the drier regions of the Saskatchewan there is potential to expand sunflower production.
  • Authors:
    • Jauhiainen, L.
    • Peltonen-Sainio, P.
  • Source: Agricultural and Food Science
  • Volume: 19
  • Issue: 4
  • Year: 2010
  • Summary: The balance between applied and harvested nitrogen (yield removed nitrogen, YRN %) is a recognized indicator of the risk of N leaching. In this study we monitored the genetic improvements and environmental variability as well as differences among crop species (spring cereals and rapeseed) in YRN in order to characterize changes that have occurred and environmental constraints associated with reducing N leaching into the environment. MTT long-term multi-location field experiments for spring cereals (Hordeum vulgare L., Avena sativa L. and Triticum aestivum L.), turnip rape (Brassica rapa L.), and oilseed rape (B. napus L.) were conducted in 1988-2008, covering each crop's main production regions. Yield (kg ha(-1)) was recorded and grain/seed nitrogen content (N(grain), g kg(-1)) analyzed. Total yield N (N(yield), kg ha(-1)) was determined and YRN (%) was calculated as a ratio between applied and harvested N. A mixed model was used to separate genetic and environmental effects. Year and location had marked effects on YRN and N(yield). Average early and/or late season precipitation was often most advantageous for N(yield) in cereals, while in dry seasons N uptake is likely restricted and in rainy seasons N leaching is often severe. Elevated temperatures during early and/or late growth phases had more consistent, negative impacts on YRN and/or N(yield) for all crops, except oilseed rape. In addition to substantial variability caused by the environment, it was evident that genetic improvements in YRN have taken place. Hence, YRN can be improved by cultivar selection and through favouring crops with high YRN such as oat in crop rotations.
  • Authors:
    • Meca, A. V.
    • Popescu, N.
  • Source: Annals of the University of Craiova - Agriculture, Montanology, Cadastre Series
  • Volume: 40
  • Issue: 2
  • Year: 2010
  • Summary: Within our country conditions the wheat, rye, barley, oilseed rape and pea-oat fodder are sown in autumn. They may be grown after crops that are harvested during summer or perennial crops or pastures that are included is crop rotation schemes. In the conditions of our country, crops that are harvested during the summer are: pea-oat fodder, pea, early potato, barley and wheat. After harvesting these crops, there must be done, immediately, the summer plowing because the soil is still moist, resulting a good quality plowing. Any delay conducts to diminishing the yields. Usually, the summer plow is made at 18-20 cm depth. Deeper plow are not necessary on most soil types from our country. Twenty cm deeper plow is need only on clayey soil that easily compacts, when the soil is highly infested by weeds, covered by high straw or when in the last year there was made a shallow plow. Summer plow, no matter the depth must be done along with harrow after plow. During the fall, till drilling, the soil has to be harrowed in order to destroy weeds and to maintain soil loosened.