181. Temperatures and the growth and development of maize and rice: a review.

• Authors:
  • Porter, J. R.
  • Rasmussen, A.
  • Sanchez, B.
• Source: Global Change Biology
• Volume: 20
• Issue: 2
• Year: 2014
• Summary: Because of global land surface warming, extreme temperature events are expected to occur more often and more intensely, affecting the growth and development of the major cereal crops in several ways, thus affecting the production component of food security. In this study, we have identified rice and maize crop responses to temperature in different, but consistent, phenological phases and development stages. A literature review and data compilation of around 140 scientific articles have determined the key temperature thresholds and response to extreme temperature effects for rice and maize, complementing an earlier study on wheat. Lethal temperatures and cardinal temperatures, together with error estimates, have been identified for phenological phases and development stages. Following the methodology of previous work, we have collected and statistically analysed temperature thresholds of the three crops for the key physiological processes such as leaf initiation, shoot growth and root growth and for the most susceptible phenological phases such as sowing to emergence, anthesis and grain filling. Our summary shows that cardinal temperatures are conservative between studies and are seemingly well defined in all three crops. Anthesis and ripening are the most sensitive temperature stages in rice as well as in wheat and maize. We call for further experimental studies of the effects of transgressing threshold temperatures so such responses can be included into crop impact and adaptation models.

182. Ecophysiological performance of maize, sorghum and brachiaria under water deficit and rehydration.; Desempenho ecofisiologico de milho, sorgo e braquiaria sob deficit hidrico e reidratacao.

• Authors:
  • Lima, J. R. S.
  • Antonino, A. C. D.
  • Falcao, H.
  • Santos, O. O.
  • Lustosa, B. M.
  • Santos, M. G.
• Source: Bragantia
• Volume: 73
• Issue: 2
• Year: 2014
• Summary: The present study evaluated the ecophysiological performance of species Zea mays (maize), Sorghum bicolor (sorghum) and Brachiaria decumbens (Brachiaria) under water deficit conditions in a greenhouse. The leaf water potential, gas exchange, chlorophyll a fluorescence and biochemical variables of photosynthetic metabolism were assessed at maximum stress and rehydration. At 90 days after emergence and under 21 days under suspension of irrigation the maize showed the highest reduction of leaf water potential (248%), stomatal conductance (87%) and photosynthesis (53%) when compared to well watered plants. Sorghum decreased by 212%, 42% and 26%, while the brachiaria showed lower values in 105%, 36% and 31%, respectively for the same parameters. However, two days of water supply were enough for all species recover the values showed by the respective controls. The species with the smallest decrease related to the variables evaluated was sorghum, which reduced 4 among 14 variables evaluated, while brachiaria and maize decreased 9 variables when under drought. The present study highlights that beyond economics, decision making by small farmers and technicians, about which species should be used under low availability of technology and high risk of water shortages should take into account also the ecophysiological performance.

183. Heterogeneous effects of warming and drought on selected wheat variety yields

• Authors:
  • Nalley, L. L.
  • Barkley, A.
  • Tack, J.
• Source: Climatic Change
• Volume: 125
• Issue: 3-4
• Year: 2014

184. Methane, carbon dioxide and nitrous oxide fluxes in soil profile under a winter wheat-summer maize rotation in the North China Plain.

• Authors:
  • Zhang, Y. M.
  • Dong, W. X.
  • Schaefer, D. A.
  • Oenema, O.
  • Ming, H.
  • Hu, C. S.
  • Wang, Y. Y.
  • Li, X. X.
• Source: PLOS ONE
• Volume: 9
• Issue: 6
• Year: 2014
• Summary: The production and consumption of the greenhouse gases (GHGs) methane (CH 4), carbon dioxide (CO 2) and nitrous oxide (N 2O) in soil profile are poorly understood. This work sought to quantify the GHG production and consumption at seven depths (0-30, 30-60, 60-90, 90-150, 150-200, 200-250 and 250-300 cm) in a long-term field experiment with a winter wheat-summer maize rotation system, and four N application rates (0; 200; 400 and 600 kg N ha -1 year -1) in the North China Plain. The gas samples were taken twice a week and analyzed by gas chromatography. GHG production and consumption in soil layers were inferred using Fick's law. Results showed nitrogen application significantly increased N 2O fluxes in soil down to 90 cm but did not affect CH 4 and CO 2 fluxes. Soil moisture played an important role in soil profile GHG fluxes; both CH 4 consumption and CO 2 fluxes in and from soil tended to decrease with increasing soil water filled pore space (WFPS). The top 0-60 cm of soil was a sink of atmospheric CH 4, and a source of both CO 2 and N 2O, more than 90% of the annual cumulative GHG fluxes originated at depths shallower than 90 cm; the subsoil (>90 cm) was not a major source or sink of GHG, rather it acted as a 'reservoir'. This study provides quantitative evidence for the production and consumption of CH 4, CO 2 and N 2O in the soil profile.

185. Transforming plant carbon into soil carbon: process-level controls on carbon sequestration.

• Authors:
  • Angers, D. A.
  • Gregorich, E. G.
  • Barker, J.
  • Grayston, S. J.
  • Feng, X. J.
  • Clemente, J. S.
  • Simpson, M. J.
  • Yanni, S. F.
  • Poirier, V.
  • Gul, S.
  • Whalen, J. K.
  • Rochette, P.
  • Janzen, H. H.
• Source: Canadian Journal of Plant Science
• Volume: 94
• Issue: 6
• Year: 2014
• Summary: Plants figure prominently in efforts to promote C sequestration in agricultural soils, and to mitigate greenhouse gas (GHG) emissions. The objective of the project was to measure the transformations of plant carbon in soil through controlled laboratory experiments, to further understand (1) root-associated CO 2 and N 2O production during a plant's life cycle, (2) decomposition of plant residues leading to CO 2 production, and (3) stabilization and retention of undecomposed plant residues and microbial by-products in the resistant soil C fraction. Experimental plant materials included transgenic near isolines of Zea mays L. and cell wall mutants of Arabidopsis thaliana, selected for their diverse residue chemistry. Phenology, morphology and above-ground biomass affected soil respiration and N 2O production in root-associated soils. Mineralization of C and N from incubated plant-soil mixtures was complemented with stable isotope tracing ( 13C, 15N) and 13C-phospholipid fatty acid analysis. Advanced chemical techniques such as nuclear magnetic resonance spectroscopy and physical separation (particle size and density separation) were used to track the transformations of plant C into stable soil C compounds. Conceptual models were proposed to explain how the plant residue chemistry * soil physico-chemical interaction affects C sequestration. Incorporating single gene mutations affecting lignin biosynthesis into agricultural and bioenergy crops has the potential to alter short- and long-term C cycling in agroecosystems.

186. Soil microaggregate and macroaggregate decay over time and soil carbon change as influenced by different tillage systems

• Authors:
  • Kwaw-Mensah, D.
  • Douelle, A.
  • Al-Kaisi, M. M.
• Source: JOURNAL OF SOIL AND WATER CONSERVATION
• Volume: 69
• Issue: 6
• Year: 2014
• Summary: Soil tillage can affect the formation and stability of soil aggregates. The disruption of soil structure weakens soil aggregates to be susceptible to the external forces of water, wind, and traffic instantaneously, and over time. The choice of tillage system or land management changes the soil physical condition and soil organic matter content, which is an essential factor in building soil aggregates. This study was conducted to investigate the effects of different tillage systems on the rate of decay of different sizes of soil aggregate fractions and other associated properties over time as subjected to a continuous wetting process. This research was conducted on a long-term tillage study, established in 2002 at the Iowa State University Agronomy Research Farm near Ames, Iowa. The soil association in this study is Clarion-Nicollet-Webster (Clarion [fine-loamy, mixed, mesic, Typic Hapluduolls], Nicollet [fine-loamy, mixed, mesic, Aquic Hapluduolls], and Webster [fine-loam, mixed, mesic, Typic Endoaquolls]). The experimental design was a randomized complete block design with four replications. Main plot treatments were five tillage systems: moldboard-plow, chisel-plow, deep-rip, strip-till, and no-till. The cropping system was corn (Zea mays L.)-soybean (Glycine max L.) rotation. Wet aggregate stability was measured using the Wet Sieving Apparatus (Eijkelkamp, Agrisearch Equipment. Art no. 08.13). Soil organic carbon (SOC) and soil total nitrogen (N) were analyzed by dry combustion using CHN Analyzer (TruSpec CHN Version 2.5x). Results show no-till with the highest carbon (C) content and the highest macro-and microaggregate stability over time. The findings also show a strong relationship between the increase in SOC content and the stability of macro-and microaggregate under continuous wetting process. Furthermore, the findings suggest that aggregate stability and moisture content are highly correlated with SOC content, and the rate of decay of both aggregate sizes (macro and micro) is highly influenced by the intensity of tillage. The implication of this research is the importance of no-till not only in increasing the stability of micro- and macroaggregates and SOC storage, but also in its effect on increasing the stability of all aggregate fractions in continuous wet conditions for extended periods of time.

187. Benefits of winter cover crops and no-tillage for microbial parameters in a Brazilian Oxisol: a long-term study.

• Authors:
  • Calegari, A.
  • Balota, E. L.
  • Nakatani, A. S.
  • Coyne, M. S.
• Source: Agriculture Ecosystems and Environment
• Volume: 197
• Year: 2014
• Summary: Soil degradation in Brazil is a concern due to intensive agricultural production. Combining conservation practice, such as no-tillage, with winter cover crops may increase microbial activity and enhance soil quality more than either practice alone. This research evaluated the benefits of long-term (23 years) winter cover crops and reduced tillage on soil microbial quality indicators in an Oxisol from Parana State, Southern Brazil. The winter cover treatments were: fallow, black oat, wheat, radish, blue lupin, and hairy vetch in conventional (plow) or no-tillage management; the summer crop was a soybean/maize rotation. Soil quality parameters included organic C, microbial biomass C and N, total and labile polysaccharide, easily extractable and total glomalin-related soil protein, and enzyme activity. Winter crops increased soil microbial quality parameters compared to fallow in both tillage systems, with greater relative increase in conventional than no-tillage. No-tillage had higher microbial biomass, polysaccharide, glomalin-related soil protein, and soil enzyme activity than conventional tillage. Including legumes in the crop rotation was important for N balance in the soil-plant system, increasing soil organic C content, and enhancing soil quality parameters to a greater extent than grasses or radish. The microbial parameters proved to be more sensitive indicators of soil change than soil organic C. Cultivating winter cover crop with either tillage is a beneficial practice enhancing soil microbial quality and also soil organic C stocks.

188. Interannual Variation in Carbon Sequestration Depends Mainly on the Carbon Uptake Period in Two Croplands on the North China Plain

• Authors:
  • Wang, Y. Y.
  • Zhao, F. H.
  • Sun, X. M.
  • Wen, X. F.
  • Bao, X. Y.
• Source: PLOS ONE
• Volume: 9
• Issue: 10
• Year: 2014
• Summary: Interannual variation in plant phenology can lead to major modifications in the interannual variation of net ecosystem production (NEP) and net biome production (NBP) as a result of recent climate change in croplands. Continuous measurements of carbon flux using the eddy covariance technique were conducted in two winter wheat and summer maize double-cropped croplands during 2003-2012 in Yucheng and during 2007-2012 in Luancheng on the North China Plain. Our results showed that the difference between the NEP and the NBP, i.e., the crop economic yield, was conservative even though the NEP and the NBP for both sites exhibited marked fluctuations during the years of observation. A significant and positive relationship was found between the annual carbon uptake period (CUP) and the NEP as well as the NBP. The NEP and the NBP would increase by 14.8 +/- 5.2 and 14.7 +/- 6.6 g C m(-2) 22 yr(-1), respectively, if one CUP-day was extended. A positive relationship also existed between the CUP and the NEP as well as the NBP for winter wheat and summer maize, respectively. The annual air temperature, through its negative effect on the start date of the CUP, determined the length of the CUP. The spring temperature was the main indirect factor controlling the annual carbon sequestration when a one-season crop (winter wheat) was considered. Thus, global warming can be expected to extend the length of the CUP and thus increase carbon sequestration in croplands.

189. Weather, Disease, and Wheat Breeding Effects on Kansas Wheat Varietal Yields, 1985 to 2011

• Authors:
  • Fritz, A.
  • Bowden, R.
  • Bergtold, J.
  • Nalley, L. L.
  • Tack, J.
  • Barkley, A.
• Source: AGRONOMY JOURNAL
• Volume: 106
• Issue: 1
• Year: 2014
• Summary: Wheat (Triticum aestivum L.) yields in Kansas have increased due to wheat breeding and improved agronomic practices, but are subject to climate and disease challenges. The objective of this research is to quantify the impact of weather, disease, and genetic improvement on wheat yields of varieties grown in 11 locations in Kansas from 1985 to 2011. Wheat variety yield data from Kansas performance tests were matched with comprehensive location-specific disease and weather data, including seasonal precipitation, monthly air temperature, air temperature and solar radiation around anthesis, and vapor pressure deficit (VPD). The results show that wheat breeding programs increased yield by 34 kg ha(-1) yr(-1). From 1985 through 2011, wheat breeding increased average wheat yields by 917 kg ha(-1), or 27% of total yield. Weather was found to have a large impact on wheat yields. Simulations demonstrated that a 1 degrees C increase in projected mean temperature was associated with a decrease in wheat yields of 715 kg ha(-1), or 21%. Weather, diseases, and genetics all had significant impacts on wheat yields in 11 locations in Kansas during 1985 to 2011.

190. Soil carbon accumulation under switchgrass barriers.

• Authors:
  • Eisenhauer, D. E.
  • Gilley, J. E.
  • Blanco-Canqui, H.
  • Jasa, P. J.
  • Boldt, A.
• Source: AGRONOMY JOURNAL
• Volume: 106
• Issue: 6
• Year: 2014
• Summary: The benefits of grass barriers or hedges for reducing offsite transport of non-point-source water pollutants from croplands are well recognized, but their ancillary benefits on soil properties have received less attention. We studied the 15-yr cumulative effects of narrow and perennial switchgrass ( Panicum virgatum L.) barriers on soil organic C (SOC), total N, particulate organic matter (POM), and associated soil structural properties as compared with the cropped area on an Aksarben silty clay loam (fine, smectitic, mesic Typic Argiudoll) with 5.4% slope in eastern Nebraska. Five switchgrass barriers were established in 1998 at ~38-m intervals parallel to the crop rows in a field under a conventional tillage and no-till grain sorghum [ Sorghum bicolor (L.) Moench]-soybean [ Glycine max (L.) Merr.]-corn ( Zea mays L.) rotation. Compared with the cropped area, switchgrass barriers accumulated about 0.85 Mg ha -1 yr -1 of SOC and 80 kg ha -1 yr -1 of total soil N at the 0 to 15 cm soil depth. Switchgrass barriers also increased coarse POM by 60%. Mean weight diameter of water-stable aggregates increased by 70% at 0 to 15 cm and by 40% at 15 to 60 cm, indicating that switchgrass barriers improved soil aggregation at deeper depths. Large (4.75-8 mm) macroaggregates under switchgrass barriers contained 30% more SOC than those under the cropped area. Switchgrass-induced changes in SOC concentration were positively associated with aggregate stability ( r=0.89***) and porosity ( r=0.47*). Overall, switchgrass barriers integrated with intensively managed agroecosystems can increase the SOC pool and improve soil structural properties.