• Authors:
    • Pan, G.
    • Ogle, S.
    • Siebner, C.
    • McConkey, B.
    • Katterer, T.
    • Grace, P. R.
    • Goidts, E.
    • Etchevers, J.
    • Dodd, M.
    • Cerri, C. E. P.
    • Andren, O.
    • Paustian, K.
    • vanWesemael, B.
  • Source: Plant and Soil
  • Volume: 338
  • Issue: 1-2
  • Year: 2011
  • Summary: As regional and continental carbon balances of terrestrial ecosystems become available, it becomes clear that the soils are the largest source of uncertainty. Repeated inventories of soil organic carbon (SOC) organized in soil monitoring networks (SMN) are being implemented in a number of countries. This paper reviews the concepts and design of SMNs in ten countries, and discusses the contribution of such networks to reducing the uncertainty of soil carbon balances. Some SMNs are designed to estimate country-specific land use or management effects on SOC stocks, while others collect soil carbon and ancillary data to provide a nationally consistent assessment of soil carbon condition across the major land-use/soil type combinations. The former use a single sampling campaign of paired sites, while for the latter both systematic (usually grid based) and stratified repeated sampling campaigns (5-10 years interval) are used with densities of one site per 10-1,040 km2. For paired sites, multiple samples at each site are taken in order to allow statistical analysis, while for the single sites, composite samples are taken. In both cases, fixed depth increments together with samples for bulk density and stone content are recommended. Samples should be archived to allow for re-measurement purposes using updated techniques. Information on land management, and where possible, land use history should be systematically recorded for each site. A case study of the agricultural frontier in Brazil is presented in which land use effect factors are calculated in order to quantify the CO2 fluxes from national land use/management conversion matrices. Process-based SOC models can be run for the individual points of the SMN, provided detailed land management records are available. These studies are still rare, as most SMNs have been implemented recently or are in progress. Examples from the USA and Belgium show that uncertainties in SOC change range from 1.6-6.5 Mg C ha-1 for the prediction of SOC stock changes on individual sites to 11.72 Mg C ha-1 or 34% of the median SOC change for soil/land use/climate units. For national SOC monitoring, stratified sampling sites appears to be the most straightforward attribution of SOC values to units with similar soil/land use/climate conditions (i. e. a spatially implicit upscaling approach).
  • Authors:
    • Schwartz, R. C.
    • MacDonald, J. C.
    • Tolk, J. A.
    • Baumhardt, R. L.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 3
  • Year: 2011
  • Summary: Cattle (Bos taurus) grazing intensifies production of the dryland wheat (Triticum aestivum L.)-sorghum [Sorghum bicolor (L.) Moench]-fallow (WSF) rotation in the U. S. Southern High Plains. Stubble-mulch (SM) tillage controls weeds and counteracts soil compaction. No-till (NT) increases soil water at planting and dryland crop yields, but added grazing effects are unknown. Our objectives were to quantify dryland winter wheat and sorghum yield responses to grazing and tillage practices. At the USDA-ARS Conservation and Production Research Laboratory, Bushland, TX, we established all WSF rotation phases in triplicate ungrazed and grazed paddocks beginning 1999 on a Pullman clay loam (fine, mixed, superactive, thermic Torrertic Paleustoll) using SM tillage. During spring 2004, NT or SM tillage were superimposed within grazing main plots. Cattle gain, soil water aft er fallow, and crop yield were compared during 2005 to 2009 using a split-plot randomized complete block design. Cattle, stocked at 1.8 Mg ha(-1), grazed sorghum stover and growing wheat an average of 29 d for a mean gain of 147 kg ha(-1). Soil water at planting was unaffected by grazing, but increased from 14 to 28 mm with NT. Although grazing seldom reduced yield of wheat or sorghum, NT in ungrazed plots increased crop yields sufficiently (0.96-2.6 Mg ha(-1)) in 2008 and 2009 to off set any value added by grazing. We conclude that cumulative grazing effects in NT plots reduced soil water storage and depressed yield. We recommend post-wheat-harvest SM tillage to disrupt soil compaction and restore grazed soil productivity.
  • Authors:
    • Rangel, D.
    • Jacobson, A. R.
    • Laba, M.
    • Darnault, C.
    • Otten, W.
    • Radulovich, R.
    • Camargo, F. A. O.
    • Baveye, P. C.
  • Source: Soil Science Society of American Journal
  • Volume: 75
  • Issue: 6
  • Year: 2011
  • Summary: When the Soil Science Society of America was created, 75 yr ago, the USA was suffering from major dust storms, causing the loss of enormous amounts of topsoil as well as human lives. These catastrophic events reminded public officials that soils are essential to society's well-being. The Soil Conservation Service was founded and farmers were encouraged to implement erosion mitigation practices. Still, many questions about soil processes remained poorly understood and controversial. In this article, we argue that the current status of soils worldwide parallels that in the USA at the beginning of the 20th century. Dust bowls and large-scale soil degradation occur over vast regions in a number of countries. Perhaps more so even than in the past, soils currently have the potential to affect populations critically in several other ways as well, from their effect on global climate change, to the toxicity of brownfield soils in urban settings. Even though our collective understanding of soil processes has experienced significant advances since 1936, many basic questions still remain unanswered, for example whether or not a switch to no-till agriculture promotes C sequestration in soils, or how to account for microscale heterogeneity in the modeling of soil organic matter transformation. Given the enormity of the challenges raised by our (ab)uses of soils, one may consider that if we do not address them rapidly, and in the process heed the example of U.S. public officials in the 1930s who took swift action, humanity may not get a chance to explore other frontiers of science in the future. From this perspective, insistence on the fact that soils are critical to life on earth, and indeed to the survival of humans, may again stimulate interest in soils among the public, generate support for soil research, and attract new generations of students to study soils.
  • Authors:
    • Robertson,G. P.
    • Hamilton,S. K.
    • Jasrotia,P.
    • Bhardwaj,A. K.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 140
  • Issue: 3-4
  • Year: 2011
  • Summary: Intensively cropped agricultural production systems should be managed to improve soil quality and ecological processes and ultimately strengthen system capacity for sustained biological productivity. We examined the long-term changes (>20 years) in soil quality and productivity with incorporation of ecological management principles in a set of intensively managed row crop systems of the upper Midwest, USA. Replicated experimental treatments include corn (maize)-soybean-wheat cropping systems under four different management regimes: (a) conventional tillage and fertilizer/chemical inputs ( Conventional), (b) no tillage with conventional fertilizer/chemical inputs ( No-till), (c) conventional tillage with 30% of conventional fertilizer/chemical inputs and a leguminous cover crop ( Reduced Input), and (d) conventional tillage with no fertilizer/chemical input and a leguminous cover crop ( Organic). Effects of these treatments on soils were compared by developing a soil quality index (SQI) from 19 selected soil health indicators. An old field community maintained in early succession provided a benchmark for comparison. Reduction in tillage or fertilizer ( No-till, Reduced Input and Organic) resulted in increased SQI and improved crop production. The No-till (SQI=1.02) and Reduced Input (SQI=1.01) systems outperformed Conventional management (SQI=0.92) in nitrogen availability and use efficiency, soil stability and structure improvement, and microbial nitrogen processing. Improvements in soil quality corresponded with increased primary production and crop yield in these systems, illustrating the value of an ecologically defined SQI for assessing the long-term effects of fertility and tillage management regimes in agricultural production systems.
  • Authors:
    • Beres, B. L.
    • Carcamo, H. A.
    • Dosdall, L. M.
    • Yang, R. C.
    • Evenden, M. L.
    • Spaner, D. M.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 6
  • Year: 2011
  • Summary: Most semiarid regions of the northern Great Plains are prone to wheat stem sawfly (Hymenoptera: Cephidae, Cephus cinctus Norton) attack. As an alternative to the wheat ( Triticum aestivum L.)-fallow system, our objective was to determine if continuous cropping infested wheat stubble would inhibit wheat stem sawfly (WSS) emergence. Adult sawfly emergence from undisturbed stubble was compared to stubble harrowed with heavy tine or rotary drum harrows before recropping. Adult emergence from a control of "no recropping" was compared to direct seeding infested stubble with (i) air drills configured with knife-type openers spaced 23 or 30 cm apart, (ii) an air drill configured with high disturbance shovel-type sweep openers, and (iii) a low disturbance air drill equipped with disc openers. Pre-seed heavy tine harrowing reduced adult sawfly emergence but usually required a high tension setting. No-till planting into infested spring wheat stubble also lowered WSS emergence compared to leaving the field fallow. A system of heavy tine harrows and an air drill equipped with knife openers spaced 30 cm apart reduced WSS adult emergence in spring by 50 to 70%. Grain yield was optimized in spring wheat with air drills equipped with narrow knife openers; in winter wheat optimal yield was obtained with the low disturbance disc drill configurations. Our results indicate incremental benefits from continuous cropping rather than fallowing fields infested with WSS, which is a sustainable alternative to conventional tillage. A systems approach is recommended that integrates these practices with diversified nonhost crop phases and resistant cultivars.
  • Authors:
    • Ortega-Farias, S.
    • Selles, G.
  • Source: ISHS Acta Horticulturae
  • Issue: 889
  • Year: 2011
  • Summary: These proceedings contain 79 papers on irrigation systems for horticultural crops. Specific topics covered include the following: improvement of water use for agriculture at catchment level under drought conditions; impact of climatic change on irrigated fruit tree production; effects of the irrigation regime and partial root zone drying on grape cv. Vermentino in Sardinia, Italy; effects of canopy exposure changes on plant water status in grape cv. Syrah; water use by drip-irrigated early-season peach trees; soil water content variations as water stress indicator in peach trees; reduction in the number of fruits in peach (T204) due to postharvest deficit irrigation; effects of irrigation management and N fertilizer on the yield and quality of apple cv. Gala; canopy temperature as an indicator of water status in citrus trees; effects of root anatomy on sap flow rate in avocado trees; influence of rootstock on the response of avocado cv. Hass to flooding stress; methods of selection for drought tolerance in potato; and drip irrigation for the establishment of strawberry transplants in southern California.
  • Authors:
    • Evett, S. R.
    • O'Shaughnessy, S. A.
    • Colaizzi, P. D.
    • Howell, T. A.
  • Source: Agricultural Water Management
  • Volume: 98
  • Issue: 10
  • Year: 2011
  • Summary: The use of digital infrared thermography and thermometry to investigate early crop water stress offers a producer improved management tools to avoid yield declines or to deal with variability in crop water status. This study used canopy temperature data to investigate whether an empirical crop water stress index could be used to monitor spatial and temporal crop water stress. Different irrigation treatment amounts (100%, 67%, 33%, and 0% of full replenishment of soil water to field capacity to a depth of 1.5 m) were applied by a center pivot system to soybean ( Glycine max L.) in 2004 and 2005, and to cotton ( Gossypium hirsutum L.) in 2007 and 2008. Canopy temperature data from infrared thermography were used to benchmark the relationship between an empirical crop water stress index (CWSI e) and leaf water potential (Psi L) across a block of eight treatment plots (of two replications). There was a significant negative linear correlation between midday Psi L measurements and the CWSI e after soil water differences due to irrigation treatments were well established and during the absence of heavy rainfall. Average seasonal CWSI e values calculated for each plot from temperature measurements made by infrared thermometer thermocouples mounted on a center pivot lateral were inversely related to crop water use with r2 values >0.89 and 0.55 for soybean and cotton, respectively. There was also a significant inverse relationship between the CWSI e and soybean yields in 2004 ( r2=0.88) and 2005 ( r2=0.83), and cotton in 2007 ( r2=0.78). The correlations were not significant in 2008 for cotton. Contour plots of the CWSI e may be used as maps to indicate the spatial variability of within-field crop water stress. These maps may be useful for irrigation scheduling or identifying areas within a field where water stress may impact crop water use and yield.
  • Authors:
    • Stoffella, P. J.
    • He, Z. L.
    • Pereira, B. F. F.
    • Melfi, A. J.
  • Source: Agricultural Water Management
  • Volume: 98
  • Issue: 12
  • Year: 2011
  • Summary: The effects of irrigation with reclaimed wastewater (RWW) were compared with well water (WW) on citrus ( Citrus paradisi Macfad. * Citrus aurantium L.) nutrition. The deviation from the optimum percentage (DOP) index of macro- and micro-nutrients were used to evaluate the nutritional status: optimal (DOP=0), deficiency (DOP0). After 11 years of RWW irrigation the influence on nutrient concentration in plants decreased in the order: B > Zn > Mn=Ca > Cu > Mg > P > K. Reclaimed wastewater irritation positively affected citrus nutrition as it rendered the concentration of macro-nutrients, i.e. P, Ca, and K. closer to their optimum levels (SigmaDOP macro=7). However micro-nutrients tended to be excessive in plants (SigmaDOP micro=753) due to imbalanced supply of these elements in the RWW, particularly, for B and Cu. Citrus groves with long-term RWW irrigation may exercised caution in monitoring concentrations of B and Cu to avoid plant toxicity and soil quality degradation.
  • Authors:
    • Nalley, L. L.
    • Popp, M.
  • Source: Journal of Agricultural and Applied Economics
  • Volume: 43
  • Issue: 3
  • Year: 2011
  • Summary: Arkansas cropping pattern changes at the county level were estimated under various scenarios involving a likely decline in water availability, the development of a biomass market for renewable energy production, and the potential of a widely used carbon offset market. These scenarios are analyzed separately and jointly to determine which of the three scenarios is expected to have the largest impact on net (emissions - sequestration) greenhouse gas (GHG) emissions, renewable fuels feedstock supply, and producer net returns. Land use choices included conventional crops of rice, cotton, soybean, corn, grain sorghum, pasture, and hay. Specialty crops of loblolly pine and switchgrass were modeled for their respective potential to sequester carbon and provide feedstock for renewable fuels. GHG emissions were measured across an array of production methods for each crop. Soil and lumber carbon sequestration was based on yield, soil texture, and tillage. Using the concept of additionality in which net GHG emissions reductions compared with a baseline level were rewarded at a carbon price of $15 per ton along with $40 per dry ton of switchgrass, baled at field side, revealed that irrigation restrictions had the largest negative impact on producer net returns while also lowering net GHG emissions. Introducing the higher carbon price led to minor positive income ramifications and greatly reduced net GHG emissions. Biomass production returns were higher than the returns from the carbon offset market, however, at the cost of greater net GHG emissions. The combination of all factors led to a significant increase in switchgrass and pine production. In this scenario, approximately 16% of the total income losses with lower nonirrigated yields were offset with returns from biomass and carbon markets. Lowest statewide net GHG emissions were achieved given least irrigation fuel use and a greater than 15% increase in carbon sequestration with pine and switchgrass.
  • Authors:
    • Lenssen, A. W.
    • Sainju, U. M.
  • Source: Soil Science Society of America Journal
  • Volume: 75
  • Issue: 2
  • Year: 2011
  • Summary: Forages grown in rotation with or without cereals to sustain dryland soil water content and crop production may influence N dynamics. We evaluated the effect of alfalfa ( Medicago sativa L.) and durum ( Triticum turgidum L.)-annual forage cropping sequences on above-(stems+leaves) and belowground (roots) biomass N, dryland soil total N (STN), particulate organic N (PON), microbial biomass N (MBN), potential N mineralization (PNM), NH 4-N, and NO 3-N contents at the 0- to 120-cm depth in northeastern Montana from 2002 to 2005. Cropping sequences were continuous alfalfa (CA), durum-barley ( Hordeum vulgare L.) hay (D-B), durum-foxtail millet ( Setaria italica L.) hay (D-M), durum-Austrian winter pea ( Pisum sativum L.)/barley mixture hay (D-P/B), and durum-fallow (D-F). From 2002 to 2005, total above- and belowground biomass N was 20 to 97 kg N ha -1 greater under CA than other treatments. In 2005, STN, PON, and PNM were 7 to 490 kg N ha -1 greater under CA than D-M, D-B, and D-P/B at 0 to 30 cm but varied by treatment at other depths. In contrast, MBN at 0 to 15 cm and NH 4-N content at 30 to 90 cm were 23 to 37 kg N ha -1 greater under D-B than D-M and D-F. The NO 3-N content at 0 to 120 cm was 65 to 107 kg N ha -1 greater under D-P/B than other treatments. Even though haying removed a greater amount of N, alfalfa increased surface soil N storage and mineralization and reduced the potential for N leaching compared with durum-annual forages, probably due to increased root growth or N 2 fixation. Durum-pea/barley hay, however, increased N mineralization and availability in subsoil layers, probably due to greater root N concentration or downward movement of water-soluble N.