• Authors:
    • Abbott, L. K.
    • Murphy, D. V.
    • Solaiman, Z. M.
  • Source: PLANT AND SOIL
  • Volume: 353
  • Issue: 1-2
  • Year: 2012
  • Summary: Background and aims Biochar can be produced from a wide range of organic sources with varying nutrient and metal concentrations. Before making irreversible applications of biochar to soil, a preliminary ecotoxicological assessment is desirable. Methods First, we determined the effect of biochar type and rate on early growth of wheat in a soil-less Petri dish bioassay. Second, we investigated the effect of the same biochars on seed germination and early growth of wheat in ten soils with varying texture using a glasshouse bioassay. Finally, we investigated whether these biochars had similar effects on three plant species when grown in one soil. Results Biochar type and application rate influenced wheat seed germination and seedling growth in a similar manner in both the soil-less Petri dish and soil-based bioassay. Germination and early root growth of mung bean and subterranean clover differed from that of wheat in response to the five biochars. Conclusions We recommend use of the soil-less Petri dish bioassay as a rapid and simple preliminary test to identify potential toxicity of biochars on seed germination and early plant growth prior to biochar application to soil.
  • Authors:
    • Lobell, D. B.
    • Schlenker, W.
    • Roberts, M. J.
    • Urban, D.
  • Source: CLIMATIC CHANGE
  • Volume: 112
  • Issue: 2
  • Year: 2012
  • Summary: Climate change has the potential to be a source of increased variability if crops are more frequently exposed to damaging weather conditions. Yield variability could respond to a shift in the frequency of extreme events to which crops are susceptible, or if weather becomes more variable. Here we focus on the United States, which produces about 40% of the world's maize, much of it in areas that are expected to see increased interannual variability in temperature. We combine a statistical crop model based on historical climate and yield data for 1950-2005 with temperature and precipitation projections from 15 different global circulation models. Holding current growing area constant, aggregate yields are projected to decrease by an average of 18% by 2030-2050 relative to 1980-2000 while the coefficient of variation of yield increases by an average of 47%. Projections from 13 out of 15 climate models result in an aggregate increase in national yield coefficient of variation, indicating that maize yields are likely to become more volatile in this key growing region without effective adaptation responses. Rising CO2 could partially dampen this increase in variability through improved water use efficiency in dry years, but we expect any interactions between CO2 and temperature or precipitation to have little effect on mean yield changes.
  • Authors:
    • Alves, B. J. R.
    • de Resende, A. S.
    • Barbosa, K. P.
    • Maia e Sa, Jerusa
    • Leite, J. M.
    • Schultz, N.
    • Batista, R. B.
    • de Morais, R. F.
    • Xavier, R. P.
    • Urquiaga, S.
    • Boddey, R. M.
  • Source: PLANT AND SOIL
  • Volume: 356
  • Issue: 1-2
  • Year: 2012
  • Summary: In Brazil N fertilization of sugarcane (Saccharum spp.) is low compared to most other countries. N-15-aided studies and the occurrence of many N-2-fixing bacteria associated with cane plants suggest significant contributions from biological N-2 fixation (BNF). The objective of this study was to evaluate BNF contributions to nine cane varieties under field conditions using N balance and N-15 natural abundance techniques. The field experiment was planted near Rio de Janeiro in 1989, replanted in 1999 and harvested 13 times until 2004. Soil total N was evaluated at planting and again in 2004. Samples of cane leaves and weeds for the evaluation of N-15 natural abundance were taken in 2000, 2003 and 2004. N accumulation of the commercial cane varieties and a variety of Saccharum spontaneum were persistently high and N balances (60 to 107 kg N ha(-1) yr(-1)) significantly (p < 0.05) positive. The delta N-15 of leaf samples were lower than any of the weed reference plants and data obtained from a greenhouse study indicated that this was not due to the cane plants tapping into soil of lower N-15 abundance at greater depth. The results indicate that the Brazilian varieties of sugarcane were able to obtain at least 40 kg N ha(-1) yr(-1) from BNF.
  • Authors:
    • Vrieling, A.
    • Tubiello, F. N.
    • Velde, M. van der
    • Bouraoui, F.
  • Source: Climatic Change
  • Volume: 113
  • Issue: 3-4
  • Year: 2012
  • Summary: Extreme weather conditions can strongly affect agricultural production, with negative impacts that can at times be detected at regional scales. In France, crop yields were greatly influenced by drought and heat stress in 2003 and by extremely wet conditions in 2007. Reported regional maize and wheat yields where historically low in 2003; in 2007 wheat yields were lower and maize yields higher than long-term averages. An analysis with a spatial version (10 x 10 km) of the EPIC crop model was tested with regards to regional crop yield anomalies of wheat and maize resulting from extreme weather events in France in 2003 and 2007, by comparing simulated results against reported regional crops statistics, as well as using remotely sensed soil moisture data. Causal relations between soil moisture and crop yields were specifically analyzed. Remotely sensed (AMSR-E) JJA soil moisture correlated significantly with reported regional crop yield for 2002-2007. The spatial correlation between JJA soil moisture and wheat yield anomalies was positive in dry 2003 and negative in wet 2007. Biweekly soil moisture data correlated positively with wheat yield anomalies from the first half of June until the second half of July in 2003. In 2007, the relation was negative the first half of June until the second half of August. EPIC reproduced observed soil dynamics well, and it reproduced the negative wheat and maize yield anomalies of the 2003 heat wave and drought, as well as the positive maize yield anomalies in wet 2007. However, it did not reproduce the negative wheat yield anomalies due to excessive rains and wetness in 2007. Results indicated that EPIC, in line with other crop models widely used at regional level in climate change studies, is capable of capturing the negative impacts of droughts on crop yields, while it fails to reproduce negative impacts of heavy rain and excessively wet conditions on wheat yield, due to poor representations of critical factors affecting plant growth and management. Given that extreme weather events are expected to increase in frequency and perhaps severity in coming decades, improved model representation of crop damage due to extreme events is warranted in order to better quantify future climate change impacts and inform appropriate adaptation responses.
  • Authors:
    • Zhang, F. S.
    • Yang, X. G.
    • Wang, E. L.
    • Wang, J.
    • Yin, H.
  • Source: CLIMATIC CHANGE
  • Volume: 113
  • Issue: 3-4
  • Year: 2012
  • Summary: In the North China Plain, the grain yield of irrigated wheat-maize cropping system has been steadily increasing in the past decades under a significant warming climate. This paper combined regional and field data with modeling to analyze the changes in the climate in the last 40 years, and to investigate the influence of changes in crop varieties and management options to crop yield. In particular, we examined the impact of a planned adaptation strategy to climate change -"Double-Delay" technology, i.e., delay both the sowing time of wheat and the harvesting time of maize, on both wheat and maize yield. The results show that improved crop varieties and management options not only compensated some negative impact of reduced crop growth period on crop yield due to the increase in temperature, they have contributed significantly to crop yield increase. The increase in temperature before over-wintering stage enabled late sowing of winter wheat and late harvesting of maize, leading to overall 4-6% increase in total grain yield of the wheat-maize system. Increased use of farming machines and minimum tillage technology also shortened the time for field preparation from harvest time of summer maize to sowing time of winter wheat, which facilitated the later harvest of summer maize.
  • Authors:
    • Zatta, A.
    • Zegada-Lizarazu, W.
    • Monti, A.
  • Source: PLANT AND SOIL
  • Volume: 351
  • Issue: 1-2
  • Year: 2012
  • Summary: Lately sweet sorghum (S) has attracted great interest as an alternative feedstock for biofuel production due to its high yielding potential and better adaptation to drought than maize (M). However, little is known about the response of newly developed sweet sorghum genotypes to water deficits, especially at the root level and its water uptake patterns. The objective of this study was to compare the water uptake capacity, growth and developmental characteristics at the root and canopy levels of a sweet sorghum hybrid (Sorghum bicolor cv. Sucro 506) with those of maize (Zea mays cv. PR32F73) at two water regimes. The trial was setup in a total of 20 rhizotrons (1 m(3)), where calibrated soil moisture probes were installed for monitoring and adjusting the soil moisture content to 25% (well-watered, W) and 12% (drought stress, D). DS was able to sustain its physiological activity close to that of WS plants, while maize was not. The biomass production potential of DS was reduced about 38%, while in maize the reduction was 47%. The water use efficiency (WUE), however, was increased by 20% in sweet sorghum and reduced in 5% in maize. Moreover, in contrast to maize the root length density and water uptake capacity of DS was enhanced. Root water uptake efficiency in DM was sustained close to its potential, but not in sweet sorghum. In summary, the better adaptation to drought of sweet sorghum is explained by increased WUE, sustained physiological activity and enlarged root system. It is also associated with a reduced water uptake efficiency compared to its control but maintained compared to maize.
  • Authors:
    • Filley, T. R.
    • Yang, X.
    • Zhang, X.
    • Zhang, X.
    • Ding, X.
    • He, H.
    • Zhang, B.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 124
  • Year: 2012
  • Summary: Tillage practices affect soil microorganisms, which in turn influence many processes essential to the function and sustainability of soil. In this study, the changes in soil microbial biomass and community composition in response to conventional tillage (CT, moldboard plowing and post-harvest residue removal) and no-tillage (NT) practices were examined during a maize (Zea mays L.) growing season in a clay loam soil (Typic Hapludoll) in northeastern China. Soil samples were taken in May, June, July, August, and September of 2008 at 0-5, 5-10, and 10-20. cm depths. Microbial communities were characterized by phospholipid fatty acid (PLFA) analysis. While microbial biomass increased at the beginning then decreased toward the end of the growing season in CT soils, it showed the opposite trend in NT soils. Microbial community structure showed better distinction among sampling months than between tillage practices. These results suggest that seasonal variations in soil microbial communities could be greater than changes associated with tillage treatments. However, microbial biomass accumulation was tillage dependent. On average, NT treatment resulted in 21% higher microbial biomass in 0-5. cm depth than CT treatment (P<0.05). Higher fungi to bacteria ratio was also observed under NT than CT treatment at both the 0-5 and 5-10. cm sampling depths. These data demonstrate that examining the effect of management practices on soil quality based on soil microbial communities should consider seasonal changes in the environmental properties. It is strongly recommended that NT practice should be adopted as an effective component of an overall strategy to improve soil quality and sustainability in northeastern China.
  • Authors:
    • Crosson, E.
    • Bandaru, V.
    • West, T.
    • Andrews, A.
    • Lauvaux, T.
    • Davis, K.
    • Richardson, S.
    • Miles, N.
  • Source: Journal of Geophysical Research-Biogeosciences
  • Volume: 117
  • Issue: G1
  • Year: 2012
  • Summary: This study presents observations of atmospheric boundary layer CO2 mole fraction from a nine-tower regional network deployed during the North American Carbon Program's Mid-Continent Intensive (MCI) during 2007-2009. The MCI region is largely agricultural, with well-documented carbon exchange available via agricultural inventories. By combining vegetation maps and tower footprints, we show the fractional influence of corn, soy, grass, and forest biomes varies widely across the MCI. Differences in the magnitude of CO2 flux from each of these biomes lead to large spatial gradients in the monthly averaged CO2 mole fraction observed in the MCI. In other words, the monthly averaged gradients are tied to regional patterns in net ecosystem exchange (NEE). The daily scale gradients are more weakly connected to regional NEE, instead being governed by local weather and large-scale weather patterns. With this network of tower-based mole fraction measurements, we detect climate-driven interannual changes in crop growth that are confirmed by satellite and inventory methods. These observations show that regional-scale CO2 mole fraction networks yield large, coherent signals governed largely by regional sources and sinks of CO2.
  • Authors:
    • Bernhardt, E.
    • Ardon, M.
    • Morse, J.
  • Source: Ecological Applications
  • Volume: 22
  • Issue: 1
  • Year: 2012
  • Summary: Whether through sea level rise or wetland restoration, agricultural soils in coastal areas will be inundated at increasing rates, renewing connections to sensitive surface waters and raising critical questions about environmental trade-offs. Wetland restoration is, often implemented in agricultural catchments to improve water quality through nutrient removal. Yet flooding of soils can also increase production of the greenhouse gases nitrous oxide and methane, representing a potential environmental trade-off. Our study aimed to quantify and compare greenhouse gas emissions from unmanaged and restored forested wetlands, as well as actively managed agricultural fields within the North Carolina coastal plain, USA. In sampling conducted once every two months over a two-year comparative study, we found that soil carbon dioxide flux (range: 8000-64 800 kg CO2.ha(-1).yr(-1)) comprised 66-100% of total greenhouse gas emissions from all sites and that methane emissions (range: -6.87 to 197 kg CH4.ha(-1).yr(-1)) were highest from permanently inundated sites, while nitrous oxide fluxes (range: -1.07 to 139 kg N2O.ha(-1).yr(-1)) were highest in sites with lower water tables. Contrary to predictions, greenhouse gas fluxes (as CO2 equivalents) from the restored wetland were lower than from either agricultural fields or unmanaged forested wetlands. In these acidic coastal freshwater ecosystems, the conversion of agricultural fields to flooded young forested wetlands did not result in increases in greenhouse gas emissions.
  • Authors:
    • Torbert, H.
    • Watts, D.
    • Way, T.
    • Mays, D.
    • Nyakatawa, E.
    • Smith, D.
  • Source: Journal of Sustainable Agriculture
  • Volume: 36
  • Issue: 8
  • Year: 2012
  • Summary: Soil management practices can alter the natural balance at the soil-plant-atmosphere ecosystem interface, which can significantly affect the environment. This study compared CO2 fluxes in conventional tillage (CT) and no-tillage (NT) corn (Zea mays L.) production systems receiving poultry litter (PL) and ammonium nitrate (AN) fertilizers on a Decatur silt loam soil in the Tennessee Valley region of North Alabama from Spring 2008 to Fall 2009. Soil CO2 flux in CT plots (9.5 kg CO2 ha(-1) day(-1)) was significantly greater than that in NT plots (4.9 kg CO2 ha(-1) day(-1) in summer. Soil CO2 fluxes were lowest in fall where CT plots had a mean soil CO2 emission of 0.8 kg CO2 ha(-1) day(-1), while plots under NT and grass fallow system were sinks of CO2 with fluxes -0.6 and -1.0 kg CO2 ha(-1) day(-1), respectively. Mean soil CO2 flux averaged over seasons in NT plots was 36% lower than that in CT plots. Grass fallow plots were net sinks of CO2 with a mean CO2 flux of -0.4 kg CO2 ha(-1) day(-1). Our study showed that application of PL or AN fertilizer in NT systems can significantly reduce soil CO2 emissions compared to CT systems in corn production.