• Authors:
    • Asseng, S.
    • Zhu, Y.
    • Cao, W. X.
    • Tian, L. Y.
    • Liu, L. L.
    • Liu, B.
  • Source: Global Change Biology
  • Volume: 20
  • Issue: 2
  • Year: 2014
  • Summary: Wheat is sensitive to high temperatures, but the spatial and temporal variability of high temperature and its impact on yield are often not known. An analysis of historical climate and yield data was undertaken to characterize the spatial and temporal variability of heat stress between heading and maturity and its impact on wheat grain yield in China. Several heat stress indices were developed to quantify heat intensity, frequency, and duration between heading and maturity based on measured maximum temperature records of the last 50 years from 166 stations in the main wheat-growing region of China. Surprisingly, heat stress between heading and maturity was more severe in the generally cooler northern wheat-growing regions than the generally warmer southern regions of China, because of the delayed time of heading with low temperatures during the earlier growing season and the exposure of the post-heading phase into the warmer part of the year. Heat stress between heading and maturity has increased in the last decades in most of the main winter wheat production areas of China, but the rate was higher in the south than in the north. The correlation between measured grain yields and post-heading heat stress and average temperature were statistically significant in the entire wheat-producing region, and explained about 29% of the observed spatial and temporal yield variability. A heat stress index considering the duration and intensity of heat between heading and maturity was required to describe the correlation of heat stress and yield variability. Because heat stress is a major cause of yield loss and the number of heat events is projected to increase in the future, quantifying the future impact of heat stress on wheat production and developing appropriate adaptation and mitigation strategies are critical for developing food security policies in China and elsewhere.
  • Authors:
    • Benjamin, J. G.
    • Stahlman, P. W.
    • Mikha, M. M.
    • Geier, P. W.
  • Source: Agronomy Journal
  • Volume: 106
  • Issue: 1
  • Year: 2014
  • Summary: The response of manure applications on calcareous eroded soils in the western United States is unlike the responses observed on acid soils in the eastern United States. The objectives of this study were to restore the productivity and evaluate N loss of eroded land influenced by tillage practices, N sources, and N rates. The study was initiated in 2006 on an Armo silt loam (fine-loamy, mixed, mesic Entic Haplustolls) at the Agriculture Research Center, Hays, KS. Tillage practices were no-tillage (NT) and conventional tillage (CT). Nitrogen sources were beef manure (M); urea, as commercial fertilizer (F); and no-N control (C) at two rates, low (L) and high (H). The crop rotation was grain sorghum ( Sorghum bicolor L.), forage oat ( Avena sativa L.), winter wheat ( Triticum aestivum L.), grain sorghum, proso millet ( Panicum miliaceum L.), and winter wheat. Grain yield (2006-2011) and soil inorganic nitrogen (SIN) at 0- to 120-cm depth were evaluated. Grain yields were not influenced by tillage practices, except in 2006 when NT had greater yields than CT. Manure addition increased grain yields compared with F and C treatments. Excess amounts of N and low productivity lead to leaching of the SIN down the soil profile with HF and HM. The LM exhibited less productivity and less SIN loss than HM treatment. Overall, M could be the N source that can improve the productivity of the eroded site. The benefits of increasing the productivity and the risk of N loss with HM need to be further addressed.
  • Authors:
    • Diels, J.
    • Vandorpe, A.
    • Nebiyu, A.
    • Boeckx, P.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 98
  • Issue: 3
  • Year: 2014
  • Summary: Faba bean-wheat rotation is one of the traditional cropping systems in most parts of the temperate, Mediterranean and tropical highland areas. However, the net contribution of legumes to soil nutrient balance is determined by the extent to which crop residue is removed from the field. Therefore, we assessed two possible faba bean residue management scenarios and their role in the faba bean-wheat rotation system in a two-phase field experiment. We further tested to what extent high N-2-fixing and P efficient faba bean varieties could benefit subsequently grown wheat. In the first phase, three improved faba bean varieties (Degaga, Moti, Obse) were grown at four levels of P fertilization (0, 10, 20 and 30 kg P ha(-1)) along with local faba bean and reference wheat but without any fertilization. N-2-fixation, soil N balance and P uptake were determined for the faba beans. The N balance was determined via two possible residue management scenarios: scenario-I assumed that all the aboveground biomass is exported from the fields; scenario-II assumed that all the above ground biomass except grains and empty pods is incorporated to the soil. In the second phase, the N and P benefits of faba beans to rotational wheat were assessed. Scenario-I gave a negative net N balance (kg N ha(-1)) in the range of -86.5 +/- A 5.8 (Degaga) to -9.4 +/- A 8.7 (Moti) with significant differences between varieties. Scenario-II showed that all balances were significantly (P < 0.01) improved and the varieties were positively contributing N to the system in the range of 50.6 +/- A 13.4 (Degaga) to 168.3 +/- A 13.7 (Moti) kg N ha(-1), which is equivalent to 110-365 kg N ha(-1) in the form of urea (46 % N). In the second crop phase, biomass and grain yield of wheat grown after the faba beans improved significantly (P < 0.05) by 112 and 82 %, respectively compared to the yield of wheat after wheat. Phosphorus application to the preceding faba bean varieties significantly improved total biomass and grain yield of the succeeding wheat (R-2 = 0.97). The incorporated legume root, nodule and straw clearly played a role in improving wheat yield through N addition via BNF and straw P. The study demonstrates the prospects and importance of improved faba bean germplasm and management as a key component for sustainable wheat based cropping systems in the humid tropical highlands.
  • Authors:
    • Hatfield, P. G.
    • Lenssen, A. W.
    • Barsotti, J. L.
    • Sainju, U. M.
  • Source: Nutrient Cycling in Ecosystems
  • Volume: 99
  • Issue: 1-3
  • Year: 2014
  • Summary: Sheep (Ovis aries L.) grazing, a cost-effective method of weed control compared to herbicide application and tillage, may influence N cycling by consuming crop residue and weeds and returning N through feces and urine to the soil. The objective of this experiment was to evaluate the effect of sheep grazing compared to tillage and herbicide application for weed control on soil particulate and active soil N fractions in dryland cropping systems. Our hypothesis was that sheep grazing used for weed control would increase particulate and active soil N fractions compared to tillage and herbicide application. Soil samples collected at the 0-30 cm depth from a Blackmore silt loam were analyzed for particulate organic N (PON), microbial biomass N (MBN), and potential N mineralization (PNM) under dryland cropping systems from 2009 to 2011 in southwestern Montana, USA. Treatments were three weed management practices [sheep grazing (grazing), herbicide application (chemical), and tillage (mechanical)] as the main plot and two cropping sequences [continuous spring wheat (Triticum aestivum L.; CSW) and spring wheat-pea (Pisum sativum L.)/barley (Hordeum vulgare L.) mixture hay-fallow; W-P/B-F] as the split-plot factor arranged in randomized complete block with three replications. The PON and MBN at 0-30 cm were greater in the chemical or mechanical than the grazing treatment with CSW. The PNM at 15-30 cm was greater in the chemical or mechanical than the grazing treatment in 2009 and 2011 and at 5-15 cm was greater with W-P/B-F than CSW in 2010. From 2009 to 2011, PON at 0-30 cm and PNM at 15-30 cm reduced from 2 to 580 kg N ha(-1) year(-1) in the grazing and chemical treatments, but the rate varied from -400 to 2 kg N ha(-1) year(-1) in the mechanical treatment. Lower amount of labile than nonlabile organic matter returned to the soil through feces and urine probably reduced soil active and coarse organic matter N fractions with sheep grazing compared to herbicide application and tillage for weed control. Reduction in the rate of decline in N fractions from 2009 to 2011 compared to the herbicide application treatment, however, suggests that sheep grazing may stabilize N fractions in the long-term if the intensity of grazing is reduced. Animal grazing may reduce soil N fractions in annual cropping systems in contrast to known increased fractions in perennial cropping systems.
  • 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.
  • Authors:
    • Webber, M. E.
    • Sanders, K. T.
  • Source: Environmental Research Letters
  • Volume: 9
  • Issue: 4
  • Year: 2014
  • Summary: The US food system utilizes large quantities of liquid fuels, electricity, and chemicals yielding significant greenhouse gas (GHG) emissions that are not considered in current retail prices, especially when the contribution of biogenic emissions is considered. However, because GHG emissions might be assigned a price in prospective climate policy frameworks, it would be useful to know the extent to which those policies would increase the incremental production costs to food within the US food system. This analysis uses lifecycle assessment (LCA) to (1) estimate the magnitude of carbon dioxide equivalent (CO 2e) emissions from typical US food production practices, using wheat and beef as examples, and (2) quantify the cost of those emissions in the context of a GHG-pricing regime over a range of policy constructs. Wheat and beef were chosen as benchmark staples to provide a representative range of less intensive and more intensive agricultural goods, respectively. Results suggest that 1.10.13 and 318.1 kg of lifecycle CO 2e emissions are embedded in 1 kg of wheat and beef production, respectively. Consequently, the cost of lifecycle CO 2e emissions for wheat (i.e. cultivation, processing, transportation, storage, and end-use preparation) over an emissions price range of $10 and $85 per tonne CO 2e is estimated to be between $0.01 and $0.09 per kg of wheat, respectively, which would increase total wheat production costs by approximately 0.3-2% per kg. By comparison, the estimated lifecycle CO 2e price of beef over the same range of CO 2e prices is between $0.31 and $2.60 per kg of beef, representing a total production cost increase of approximately 5-40% per kg based on average 2010 food prices. This range indicates that the incremental cost to total US food production might be anywhere between $0.63-5.4 Billion per year for grain and $3.70 and $32 Billion per year for beef based on CO 2e emissions assuming that total production volumes stay the same.
  • Authors:
    • Nalley, L. L.
    • Barkley, A.
    • Tack, J.
  • Source: Climatic Change
  • Volume: 125
  • Issue: 3-4
  • Year: 2014
  • Authors:
    • Stoddard, F. L.
    • Makela, P.
    • Simojoki, A.
    • Tammeorg, P.
    • Alakukku, L.
    • Helenius, J.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 191
  • Year: 2014
  • Summary: Poor water retention capacity (WRC) and nutrient deficiency commonly limit crop yields in sandy soils. The use of biochar as a soil amendment has been previously reported to improve these limiting factors in subtropical and temperate soils. We studied the effects of biochar on soil properties and yield formation of spring wheat ( Triticum aestivum L.) when applied together with inorganic fertiliser or meat bone meal (MBM) to an Endogleyic Umbrisol with a loamy sand texture in boreal conditions. In a two-year field experiment, biochar was applied at 0, 5, 10, 20 and 30 t ha -1 combined with three fertiliser treatments (unfertilised control, MBM and inorganic fertiliser) providing equal amounts of nitrogen (N), phosphorus (P) and potassium (K). Soil WRC and fertility as well as wheat yield, yield components and quality were analysed. Soil moisture content, leaf area index and leaf chlorophyll values (SPAD) were monitored during the experiment. Biochar increased the plant-available water content of the topsoil in the first year and reduced the bulk density in the second year after application. It also increased the contents of easily soluble K and soil organic C (SOC) in the 20 cm of topsoil, but had no effects on other soil nutrients, pH or moisture content. Biochar amendment decreased the soil NO 3--N content below control values in the first year but increased it significantly in the second year. The addition of biochar did not significantly affect the nitrogen uptake, grain yield or quality of wheat, possibly because of its low nutrient availability and the high organic matter content of the soil.
  • 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.
  • 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.