• Authors:
    • Zhang, F. S.
    • Yue, S. C.
    • Cui, Z. L.
    • Chen, X. P.
    • Sun, Q. P.
    • Meng, Q. F.
    • Romheld, V.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 146
  • Issue: 1
  • Year: 2012
  • Summary: Serious water deficits and excessive nitrogen (N) applications are threatening the sustainability of intensive agriculture in the North China Plain (NCP). This study examined the possibility of replacing the conventional system (Con.W/M) of winter wheat ( Triticum aestivum L.) and summer maize ( Zea mays L.), with an optimized double cropping system (Opt.W/M), a 2-year system (winter wheat/summer maize-spring maize, W/M-M), and a monoculture system (spring maize, M) based on optimal water and N management strategies. From 2004 to 2010, a long-term field experiment conducted in the NCP showed that although >70 mm of irrigation water can be saved with Opt.W/M compared with Con.W/M, annual net groundwater use under Opt.W/M was still 250 mm, 65-90% of which was consumed during the winter wheat season. When wheat production was decreased, 35% and 61% of irrigation water could be reduced in W/M-M and M compared to Con.W/M, respectively. As a result, annual groundwater use was decreased to 190 mm in W/M-M and 94 mm in M. Meanwhile, the N fertilizer rate was reduced 59% and 72% in W/M-M and M compared to Con.W/M, respectively. There were no significant differences in net economic returns between Con.W/M and W/M-M across the 6-year period. In the 6 years, no significant economic loss was observed between Con.W/M and M except in the 2008-2010 rotation. The W/M-M and M systems showed great potential to reduce water and N application and achieve groundwater use balance, and thus should be considered for economic and sustainable agricultural development in the NCP.
  • Authors:
    • Birkmose, T. S.
    • Hansen, M. N.
    • Nyord, T.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 160
  • Year: 2012
  • Summary: To provide better advice to farmers and authorities on the most efficient way to reduce ammonia volatilisation from slurry applied to fields with standing crops, various treatments and injection methods were tested in field trials. In six separate experiments conducted at Research Centre Foulum, Denmark from 2007 to 2009, pig slurry was applied to winter wheat ( Triticum aestivum L.) to determine how anaerobically digestion, solid-liquid separation of slurry and different soil injection techniques influence crop yield and ammonia emissions (NH 3). The NH 3 emission was measured by either a wind-tunnel method or by a micro-meteorological mass balance method. Both injection and solid-liquid separation were found to reduce NH 3 emission. The emission from the separated slurry did not include the emission from the solid fraction. Most effective injection techniques were found to be a winged tine or a combination of discs and a tine, which reduced NH 3 emission from approximately 20% (surface band spreading) to approximately 5% of applied Total Ammoniacal Nitrogen (TAN). The NH 3 emission from surface-applied anaerobically digested slurry was found to be almost twice that from surface-applied untreated slurry. Injection did not affect yields significantly compared with surface application in any of the experiments, but did result in a significantly increased protein content in grains compared to band application, which increased the nitrogen utilisation of slurry nitrogen. Of the techniques tested, soil injection and solid-liquid separation reduced NH 3 emissions most effectively.
  • Authors:
    • White, J. W.
    • Kimball, B. A.
    • Ottman, M. J.
    • Wall, G. W.
  • Source: Agronomy Journal
  • Volume: 104
  • Issue: 1
  • Year: 2012
  • Summary: Possible future increases in atmospheric temperature may threaten wheat (Triticum aestivum L.) production and food security. The purpose of this research is to determine the response of wheat growth to supplemental heating and to seasonal air temperature from an unusually wide range of planting dates. A field study was conducted at Maricopa, AZ, where wheat was planted from September to May over a 2-yr period for a total of 12 planting dates. Supplemental heating was provided for 6 of the 12 planting dates using infrared heaters placed above the crop which increased canopy temperature by 1.3°C during the day and 2.7°C during the night. Grain yield declined 42 g m -2 (6.9%) per 1°C increase in seasonal temperature above 16.3°C. Supplemental heating had no effect on grain yield for plantings in winter (Dec./Jan.) since temperatures were near optimum (14.9°C). However, in spring (Mar.) plantings where temperature (22.2°C) was above optimum, supplemental heating decreased grain yield from 510 to 368 g m -2. Supplemental heating had the greatest effect in the early fall plantings (Sept./Oct.) when temperature was slightly below optimum (13.8°C) and mid-season frost limited the yield of unheated plots to only 3 g m -2 whereas yield of heated plots was 435 g m -2. Thus, possible future increases in temperature may decrease wheat yield for late plantings and shift optimum planting windows to earlier dates in areas of the world similar to the desert southwest of the United States.
  • Authors:
    • Angers, D. A.
    • Rochette, P.
    • Chantigny, M. H.
    • Pelster, D. E.
    • Rieux, C.
    • Vanasse, A.
  • Source: Journal of Environmental Quality
  • Volume: 41
  • Issue: 2
  • Year: 2012
  • Summary: The use of various animal manures for nitrogen (N) fertilization is often viewed as a viable replacement for mineral N fertilizers. However, the impacts of amendment type on N 2O production may vary. In this study, N 2O emissions were measured for 2 yr on two soil types with contrasting texture and carbon (C) content under a cool, humid climate. Treatments consisted of a no-N control, calcium ammonium nitrate, poultry manure, liquid cattle manure, or liquid swine manure. The N sources were surface applied and immediately incorporated at 90 kg N ha -1 before seeding of spring wheat ( Triticum aestivum L.). Cumulative N 2O-N emissions from the silty clay ranged from 2.2 to 8.3 kg ha -1 yr -1 and were slightly lower in the control than in the fertilized plots ( P=0.067). The 2-yr mean N 2O emission factors ranged from 2.0 to 4.4% of added N, with no difference among N sources. Emissions of N 2O from the sandy loam soil ranged from 0.3 to 2.2 kg N 2O-N ha -1 yr -1, with higher emissions with organic than mineral N sources ( P=0.015) and the greatest emissions with poultry manure ( P<0.001). The N 2O emission factor from plots amended with poultry manure was 1.8%, more than double that of the other treatments (0.3-0.9%), likely because of its high C content. On the silty clay, the yield-based N 2O emissions (g N 2O-N kg -1 grain yield N) were similar between treatments, whereas on the sandy loam, they were greatest when amended with poultry manure. Our findings suggest that, compared with mineral N sources, manure application only increases soil N 2O flux in soils with low C content.
  • Authors:
    • Uddling, J.
    • Pleijel, H.
  • Source: Global Change Biology
  • Volume: 18
  • Issue: 2
  • Year: 2012
  • Summary: Although it is established that there exist potential trade-offs between grain yield and grain quality in wheat exposed to elevated carbon dioxide (CO 2) and ozone (O 3), their underlying causes remain poorly explored. To investigate the processes affecting grain quality under altered CO 2 and O 3, we analysed 57 experiments with CO 2 or O 3 exposure in different exposure systems. The study covered 24 cultivars studied in 112 experimental treatments from 11 countries. A significant growth dilution effect on grain protein was found: a change in grain yield of 10% by O 3 was associated with a change in grain protein yield of 8.1% ( R2=0.96), whereas a change in yield effect of 10% by CO 2 was linked to a change in grain protein yield effect of 7.5% ( R2=0.74). Superimposed on this effect, elevated CO 2, but not O 3, had a significant negative effect on grain protein yield also in the absence of effects on grain yield, indicating that there exists a process by which CO 2 restricts grain protein accumulation, which is absent for O 3. Grain mass, another quality trait, was more strongly affected by O 3 than grain number, whereas the opposite was true for CO 2. Harvest index was strongly and negatively influenced by O 3, but was unaffected by CO 2. We conclude that yield vs. protein trade-offs for wheat in response to CO 2 and O 3 are constrained by close relationships between effects on grain biomass and less than proportional effects on grain protein. An important and novel finding was that elevated CO 2 has a direct negative effect on grain protein accumulation independent of the yield effect, supporting recent evidence of CO 2-induced impairment of nitrate uptake/assimilation. Finally, our results demonstrated that processes underlying responses of grain yield vs. quality trade-offs are very different in wheat exposed to elevated O 3 compared with elevated CO 2.
  • Authors:
    • Steffens, D.
    • Qayyum, M. F.
    • Reisenauer, H. P.
    • Schubert, S.
  • Source: Journal of Environmental Quality
  • Volume: 41
  • Issue: 4
  • Year: 2012
  • Summary: Application of biochars to soils may stabilize soil organic matter and sequester carbon (C). The objectives of our research were to study in vitro C mineralization kinetics of various biochars in comparison with wheat straw in three soils and to study their contribution to C stabilization. Three soils (Oxisol, Alfisol topsoil, and Alfisol subsoil) were incubated at 25°C with wheat straw, charcoal, hydrothermal carbonization coal (HTC), low-temperature conversion coal (LTC), and a control (natural organic matter). Carbon mineralization was analyzed by alkali absorption of CO 2 released at regular intervals over 365 d. Soil samples taken after 5 and 365 d of incubation were analyzed for soluble organic C and inorganic N. Chemical characterization of biochars and straw for C and N bonds was performed with Fourier transformation spectroscopy and with the N fractionation method, respectively. The LTC treatment contained more N in the heterocyclic-bound N fraction as compared with the biochars and straw. Charcoal was highly carbonized when compared with the HTC and LTC. The results show higher C mineralization and a lower half-life of straw-C compared with biochars. Among biochars, HTC showed some C mineralization when compared with charcoal and LTC over 365 d. Carbon mineralization rates were different in the three soils. The half-life of charcoal-C was higher in the Oxisol than in the Alfisol topsoil and subsoil, possibly due to high Fe-oxides in the Oxisol. The LTC-C had a higher half-life, possibly due to N unavailability. We conclude that biochar stabilization can be influenced by soil type.
  • Authors:
    • Kirkegaard, J. A.
    • Ryan, M. H.
  • Source: AGRICULTURE ECOSYSTEMS & ENVIRONMENT
  • Volume: 163
  • Year: 2012
  • Summary: All available data on arbuscular mycorrhizal fungi (AMF) in Australian extensive cropping systems are reviewed in an agronomic framework. In the southern temperate and northern subtropical zones, 80-85% and 60%, respectively, of cropped area is winter cereals. In the south, non-mycorrhizal winter break crops are common and crops are often rotated with low input pastures. In the north, continuous cropping with winter crops, summer crops and long (12-18 month) plant-free fallow is common. Only here does reduced colonization by AMF cause intermittent yield reductions, perhaps reflecting low phosphorus (P) soils, high crop growth rates and dry surface soil limiting P availability. Soil temperatures below 10°C may limit the contribution of AMF to southern crops. In both zones, wheat yields are generally enhanced following fallows and non-mycorrhizal break crops, even under P limitation. AMF are unlikely to aid control of root diseases or dryland salinity adaptation; their role in soil structure and carbon sequestration requires clarification. Organic crops are highly colonized, but invariably P deficient. Thus, little evidence supports consideration of AMF in farm management and many agronomic practices that underpin sustainable productivity reduce colonization. We hope this paper stimulates dialog between mycorrhizal researchers and agronomists to target high priority research.
  • Authors:
    • Siahpoosh, M. R.
    • Dehghanian, E.
  • Source: Agronomy Journal
  • Volume: 104
  • Issue: 5
  • Year: 2012
  • Summary: Improving grain performance under water-limited conditions essentially depends on the knowledge of water-yield relationships. The current project was set up to make a field evaluation of relations among grain yield, water use efficiency (WUE), and its components, i.e., transpiration efficiency (TE), uptake efficiency (UE), and harvest index (HI) in bread wheat ( Triticum aestivum L.) genotypes. Eight bread wheat genotypes and four water levels (WLs) based on evapotranspiration (ET; WL1, supplying 100% of ET water, to WL4, supplying 25% of ET water) were included in 3-yr experiments. The experiments were conducted under a line-source sprinkler irrigation system. The results of regression analysis revealed that grain yield, WUE, HI, TE, and UE showed linear regression lines against ET. These regression lines ascended for grain yield, WUE, HI, and UE but descended for TE. The best-fit model between WUE and its components was linear and showed an ascending trend for HI and UE but descending trend for TE. The results of this experiment showed that an increase in TE could improve the WUE in wheat genotypes considering that HI is high. That is, applying selection for both TE and HI under water-stress conditions might give the best results to improve WUE in breeding programs.
  • Authors:
    • Storkey, J.
    • Stratonovitch, P.
    • Semenov, M. A.
  • Source: Global Change Biology
  • Volume: 18
  • Issue: 6
  • Year: 2012
  • Summary: Predicting the impact of climate change on the damage niche of an agricultural weed at a local scale requires a process-based modelling approach that integrates local environmental conditions and the differential responses of the crop and weed to change. A simulation model of the growth and population dynamics of winter wheat and a competing weed, Sirius 2010, was calibrated and validated for the most economically damaging weed in UK cereals, Alopecurus myosuroides. The model was run using local-scale climatic scenarios generated by the LARS-WG weather generator and based on the HadCM3 projections for the periods 2046-2065 and 2080-2099 to predict the impact of climate change on the population dynamics of the weed and its effect on wheat yields. Owing to rising CO 2 concentration and its effect on radiation use efficiency of wheat, weed-free wheat yields were predicted to increase. The distribution of the weed was predicted to remain broadly similar with a possible northward shift in range. Local-scale variation in the impact of climate change was apparent owing to variation in soil type and water holding capacity. The competitive balance was shifted in favour of the deeper rooted crop under climate change, particularly on sites with lighter soils, owing to more frequent and severe drought stress events. Although the damage niche of A. myosuroides was predicted to reduce under climate change, it is likely that weeds with contrasting physiology, such as C4 species, will be better adapted to future conditions and pose a more serious threat.
  • Authors:
    • Freney, J. R.
    • Chen, D.
    • Edis, R. E.
    • Turner, D. A.
    • Denmead, O. T.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 93
  • Issue: 2
  • Year: 2012
  • Summary: As farmers in southern Australia typically apply nitrogen (N) to cereal crops by top-dressing with ammonia (NH3) based fertilizer in late winter or early spring there is the potential for large losses of NH3. This paper describes the results of micrometeorological measurements to determine NH3 loss and emission factors following applications of urea, urea ammonium nitrate (UAN), and ammonium sulfate (AS) at different rates to cereal crops at two locations in southern Australia. The amounts of NH3 lost are required for farm economics and management, whilst emission factors are needed for inventory purposes. Ammonia loss varied with fertilizer type (urea > UAN > AS) and location, and ranged from 1.8 to 23 % of N applied. This compares with the emission factor of 10 % of applied N advocated by IPCC ( 2007). The variation with location seemed to be due to a combination of factors including soil texture, soil moisture content when fertilizer was applied and rainfall after fertilizer application. Two experiments at one location, 1 week apart, demonstrated how small, temporal differences in weather conditions and initial soil water content affected the magnitude of NH3 loss. The results of these experiments underline the difficulties farmers face in timing fertilization as the potential for loss, depending on rainfall, can be large.