• Authors:
    • Machado,S.
    • Pritchett,L.
    • Petrie,S.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: Winter wheat ( Triticum aestivum L.)-summer fallow (WW-SF) using conventional tillage (CT), the predominant cropping system in eastern Oregon, has increased soil erosion and depleted soil organic carbon (SOC). This research evaluates no-tillage (NT) systems designed to reduce these negative impacts on soil. In this long-term experiment (2004-2010), WW-SF using CT was compared with annual winter wheat (WW-WW), annual spring wheat (SW-SW), annual spring barley ( Hordeum vulgare L.) (SB-SB), winter wheat-chemical fallow (WW-CF), winter wheat-winter pea ( Pisum sativum L.) (WW-WP), and winter wheat-spring barley-chemical fallow rotation (WW-SB-CF), using NT. Measurements included, phenology, plant population, grain yield and yield components, residues, SOC, soil moisture, and precipitation. Water-use efficiency (WUE) was derived from precipitation and yield data. Under annual cropping, WW-WP and SB-SB produced higher yields than WW-WW and SW-SW. Grain yields in rotations with fallow (WW-SF, WW-CF, and WW-SB-CF) were not significantly different. On an annual basis, SB-SB and WW-WP produced the highest and lowest yields, respectively. The WUEs of fallow rotations, SB-SB, and SW-SW, were not different but were higher than WUEs of WW-WP and WW-WW. Residue cover and SOC were highest under annual cropping systems and lowest following peas in WW-WP and SF in WW-SF. We conclude that rotations with fallow using NT (WW-CF and WW-SB-CF) can replace the traditional WW-SF system without yield penalty.
  • Authors:
    • Morrison,Geoffrey M.
    • Yeh,Sonia
    • Eggert,Anthony R.
    • Yang,Christopher
    • Nelson,James H.
    • Greenblatt,Jeffery B.
    • Isaac,Raphael
    • Jacobson,Mark Z.
    • Johnston,Josiah
    • Kammen,Daniel M.
    • Mileva,Ana
    • Moore,Jack
    • Roland-Holst,David
    • Wei,Max
    • Weyant,John P.
    • Williams,James H.
    • Williams,Ray
    • Zapata,Christina B.
  • Source: Climatic Change
  • Volume: 131
  • Issue: 4
  • Year: 2015
  • Summary: Jurisdictions throughout the world are contemplating greenhouse gas (GHG) mitigation strategies that will enable meeting long-term GHG targets. Many jurisdictions are now focusing on the 2020-2050 timeframe. We conduct an inter-model comparison of nine California statewide energy models with GHG mitigation scenarios to 2050 to better understand common insights across models, ranges of intermediate GHG targets (i.e., for 2030), necessary technology deployment rates, and future modeling needs for the state. The models are diverse in their representation of the California economy: across scenarios with deep reductions in GHGs, annual statewide GHG emissions are 8-46 % lower than 1990 levels by 2030 and 59-84 % lower by 2050 (not including the Wind-Water-Solar model); the largest cumulative reductions occur in scenarios that favor early mitigation; non-hydroelectric renewables account for 30-58 % of electricity generated for the state in 2030 and 30-89 % by 2050 (not including the Wind-Water-Solar model) ; the transportation sector is decarbonized using a mix of energy efficiency gains and alternative-fueled vehicles; and bioenergy is directed almost exclusively towards the transportation sector, accounting for a maximum of 40 % of transportation energy by 2050. Models suggest that without new policies, emissions from non-energy sectors and from high-global-warming-potential gases may alone exceed California's 2050 GHG goal. Finally, future modeling efforts should focus on the: economic impacts and logistical feasibility of given scenarios, interactive effects between two or more climate policies, role of uncertainty in the state's long-term energy planning, and identification of pathways that achieve the dual goals of criteria pollutant and GHG emission reduction.
  • Authors:
    • Northupl,B. K.
    • Rao,S. C.
  • Source: Crop Economics, Production & Management
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: Continuous winter wheat ( Triticum aestivum L. em Thell.) is the foundation for most US Southern Great Plains (SGP) agriculture. Inorganic N fertilizers are important to wheat production, but increasing N prices have caused producers to reconsider growing legumes during summer fallow for green N. This study was conducted during 2008 to 2012 to determine the potential for using lablab [ Lablab purpureus (L.) Sweet cv. Rio Verde] to support wheat under conventional and no-till management compared with soybean [ Glycine max (L.) Merr. cv. Laredo] and three inorganic fertilizer treatments (none, 40, and 80 kg N ha -1). Legume seeds were inoculated and sown after wheat harvest each year, grown from June to August, and terminated in early September. Wheat was then sown with or without preplant tillage and grown to maturity. Grain yield, N concentration, and N accumulated in grain were analyzed to define N treatment, tillage system, and year effects. The amount and distribution of precipitation during 2008 to 2012 varied from 53 to 92% and 63 to 160% of the long-term averages for wheat (688 mm) and legume (162 mm) phases. Tillage effects were nonsignificant ( P<0.76), but N treatment * year interactions were significant for grain yield, N concentration, and N accumulated in grain ( P<0.01). The legumes resulted in some single-year increases in grain yield, but the overall yield response was inconsistent. The legume treatments reduced N concentration in wheat grain compared with the unfertilized control. These results show that neither legume was an effective short-term (≤4-yr) N source for systems of continuous wheat production in the SGP.
  • Authors:
    • Sainju,U. M.
    • Allen,B. A.
    • Caesar-Tonthat,T.
    • Lenssen,A. W.
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: Little is known about the long-term management impact on soil C and N contents in the northern Great Plains. We evaluated the 30-yr effect of tillage and cropping sequence combination on dryland crop biomass yield and soil bulk density, soil organic carbon (SOC), soil inorganic carbon (SIC), soil total nitrogen (STN), NH 4-N, and NO 3-N contents at the 0- to 120-cm depth in a Dooley sandy loam (fine loamy, mixed, frigid Typic Argiboroll) in eastern Montana. Treatments were no-till continuous spring wheat ( Triticum aestivum L.) (NTCW), spring till continuous spring wheat (STCW), fall and spring till continuous spring wheat (FSTCW), fall and spring till spring wheat-barley ( Hordeum vulgare L., 1984-1999) followed by spring wheat-pea ( Pisum sativum L., 2000-2013) (FSTW-B/P), and spring till spring wheat-fallow (STW-F, traditional system). Mean annualized crop biomass returned to the soil was 23 to 30% greater in NTCW, STCW, FSTCW, and FSTW-B/P than STW-F. At 0 to 7.5 cm, bulk density was 13 to 21% greater in STW-F, but SOC, SIC, and STN were 12 to 98% greater in STCW than other treatments. Ammonium-N and NO 3-N contents were 25 to 74% greater in FSTCW than other treatments. At other depths, SOC, SIC, STN, NH 4-N and NO 3-N contents varied among treatments. Reduced tillage with increased crop residue returned to the soil increased soil C and N storage in NTCW and STCW, but increased tillage intensity increased mineral N content in FSTCW compared with STW-F. Improved management practices, such as NTCW and STCW, may be adopted to improve dryland soil C and N stocks.
  • Authors:
    • Siebers,M. H.
    • Yendrek,C. R.
    • Drag,D.
    • Locke,A. M.
    • Acosta,L. R.
    • Leakey,A. D. B.
    • Ainsworth,E. A.
    • Bernacchi,C. J.
    • Ort,D. R.
  • Source: Global Change Biology
  • Volume: 21
  • Issue: 8
  • Year: 2015
  • Summary: Heat waves already have a large impact on crops and are predicted to become more intense and more frequent in the future. In this study, heat waves were imposed on soybean using infrared heating technology in a fully open-air field experiment. Five separate heat waves were applied to field-grown soybean ( Glycine max) in central Illinois, three in 2010 and two in 2011. Thirty years of historical weather data from Illinois were analyzed to determine the length and intensity of a regionally realistic heat wave resulting in experimental heat wave treatments during which day and night canopy temperatures were elevated 6°C above ambient for 3 days. Heat waves were applied during early or late reproductive stages to determine whether and when heat waves had an impact on carbon metabolism and seed yield. By the third day of each heat wave, net photosynthesis ( A), specific leaf weight (SLW), and leaf total nonstructural carbohydrate concentration (TNC) were decreased, while leaf oxidative stress was increased. However, A, SLW, TNC, and measures of oxidative stress were no different than the control ca. 12 h after the heat waves ended, indicating rapid physiological recovery from the high-temperature stress. That end of season seed yield was reduced (~10%) only when heat waves were applied during early pod developmental stages indicates the yield loss had more to do with direct impacts of the heat waves on reproductive process than on photosynthesis. Soybean was unable to mitigate yield loss after heat waves given during late reproductive stages. This study shows that short high-temperature stress events that reduce photosynthesis and increase oxidative stress resulted in significant losses to soybean production in the Midwest, U.S. The study also suggests that to mitigate heat wave-induced yield loss, soybean needs improved reproductive and photosynthetic tolerance to high but increasingly common temperatures.
  • Authors:
    • Thapa,R.
    • Chatterjee,A.
    • Johnson,J. M. F.
    • Awale,R.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: Nitrogen losses associated with fertilizer application have negative economic and environmental consequences, but urease and nitrification inhibitors have potential to reduce N losses. The effectiveness of these inhibitors has been studied extensively in irrigated but not in rainfed systems. This study was conducted at Glyndon, MN, under rainfed conditions to assess the impact of urease and nitrification inhibitors on NH 3 volatilization, N 2O emissions, and NO 3- concentrations below the spring wheat ( Triticum aestivum L.) rooting zone. Urea (U), urea with urease and nitrification inhibitors (SU), and urea with nitrification inhibitor only (UI) were applied at 146 and 168 kg N ha -1 along with the control treatments. Cumulative NH 3 volatilization was reduced by 26%, N 2O emissions measured 18 d after planting were reduced by 50% with SU, but no significant reduction was observed with UI compared to U. We did not observe a significant effect of higher N rate on N 2O emissions, but lower N application rate (146 kg N ha -1) significantly reduced NH 3 volatilization by 26% compared to 168 kg N ha -1. Nitrate concentration below the rooting zone was reduced by applying N at lower rate and also through the use of SU and UI instead of U. Soil inorganic N intensity was significantly related with cumulative N 2O emissions. Nitrogen source and rate did not influence grain yield and protein content. This single-growing season study under rainfed conditions suggests that fertilizer N-stabilizers can be successfully used to minimize N losses without compromising grain yield and protein content.
  • Authors:
    • Veenstra,J. J.
    • Burras,C. L.
  • Source: Soil Science Society of America Journal
  • Volume: 79
  • Issue: 4
  • Year: 2015
  • Summary: Despite a large body of scientific research that shows that soils change on relatively short time scales under different management regimes, classical pedological theory states that we should expect these changes to occur only in the surface few centimeters and that they are not of adequate magnitude to suggest fundamental changes in pedon character over short periods of time. In fact, rarely, do the scientists that make these comparisons report on any properties deeper than 30 to 45 cm in the soil profile. With this study, we evaluate soil transformation to a depth of 150 cm after 50 yr of intensive row-crop agricultural land use in a temperate, humid, continental climate (Iowa, United States), by resampling sites that were initially described by the United States soil survey between 1943 and 1963. We find that, through agricultural land use, humans are accelerating soil formation and transformation to a depth of 100 cm or more by accelerating erosion, sedimentation, acidification, and mineral weathering, and degrading soil structure, while deepening dark-colored, organic-matter rich surface horizons, translocating and accumulating organic matter deeper in the soil profile and lowering the water table. Some of these changes can be considered positive improvements, but many of these changes may have negative effects on the soils' future productive capacity. © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA. All rights reserved.
  • Authors:
    • Veum,K. S.
    • Kremer,R. J.
    • Sudduth,K. A.
    • Kitchen,N. R.
    • Lerch,R. N.
    • Baffaut,C.
    • Stott,D. E.
    • Karlen,D. L.
    • Sadler,E. J.
  • Source: Journal of Soil and Water Conservation
  • Volume: 70
  • Issue: 4
  • Year: 2015
  • Summary: The Conservation Effects Assessment Project (CEAP). was initiated in 2002 to quantify the potential benefits of conservation management practices throughout the nation. Within the Central Claypan Region of Missouri, the Salt River Basin was selected as a benchmark watershed for soil and water quality assessments. This study focuses on two objectives: (1) assessing soil quality for 15 different annual cropping and perennial vegetation systems typically employed in this region, and (2) evaluating relationships among multiple measured soil quality indicators (SQIs). Management practices included annual versus perennial vegetation, and varying grass species composition (cool-season versus warm-season), tillage intensity (no-till versus mulch-till), biomass removal, rotation phase, crop rotation (corn [Zea mays L.]-soybean [Glycine max L. Merr] versus corn-soybean-wheat [Triticum aestivum L.]) and incorporation of cover crops into the rotation. Soil samples were obtained in 2008 from 0 to 5 cm (0 to 2 in) and 5 to 15 cm (2 to 6 in) depth layers. Ten biological, physical, chemical, and nutrient SQIs were measured and scored using the Soil Management Assessment Framework (SMAF). Across SQIs, biological and physical indicators were the most sensitive to management effects, reflecting significant differences in organic carbon (C), mineralizable nitrogen (N), beta-glucosidase, and bulk density. In the 0 to 5 cm layer, perennial systems demonstrated the greatest SMAF scores, ranging from 93% to 97% of the soil's inherent potential. Scores for annual cropping systems ranged from 78% to 92%: diversified no-till, corn soybean wheat rotation with cover crops (92%) > no-till, corn-soybean rotation without cover crops (88%) > mulch-till corn-soybean rotation without cover crops (84%). Conversely, in the 5 to 15 cm layer, no-till cropping systems scored lower for overall soil function (58% to 61%) than mulch-till systems (65% to 66%). In the 0 to 5 cm layer, biological soil quality under the diversified no-till system with cover crops was 11% greater than under no-till without cover crops, and 20% greater than under mulch-till without cover crops. The effect of rotation phase was primarily reflected in 64% lower mineralizable N following corn relative to soybean. Additionally, soil nutrient function was significantly affected by biomass removal. The results of this study demonstrate that the benefits of conservation management practices extend beyond soil erosion reduction and improved water quality by highlighting the potential for enhanced soil quality, especially biological soil function. In particular, implementing conservation management practices on marginal and degraded soils in the claypan region can enhance long-term sustainability in annual cropping systems and working grasslands through improved soil quality.
  • Authors:
    • Wang,Jinzhou
    • Wang,Xiujun
    • Xu,Minggang
    • Feng,Gu
    • Zhang,Wenju
    • Lu,Chang'ai
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 102
  • Issue: 3
  • Year: 2015
  • Summary: Straw has been commonly incorporated to maintain soil fertility and crop productivity in China, but effects of long-term straw incorporation on crop yield, soil organic carbon (SOC) and total nitrogen (TN) have not been thoroughly evaluated. Thus, this study analyzed data collected in long-term (> 10-year) trials across the major agricultural zones of China. Across the trials, relative to straw removal, straw return significantly increased crop yield, SOC and TN (by 7.0, 10.1 and 11.0 %, respectively). In some trials with winter wheat in northern China, straw return reduced yield by 0.6-7.1 %. The effects of straw return on SOC and TN were not significantly affected by experimental duration, land use type and cropping system, but positively and linearly related to the inputs of straw-C and -N, respectively. Interestingly, SOC and TN responses to straw return were decoupled in upland and upland-paddy soils in China, but not in paddy soils. Mean values of straw-C sequestration efficiency (7.7, 10.3 and 9.4 %, under corn, wheat and rice, respectively) indicate that 100 % straw return could increase SOC by 281.7 Tg C in 18 years (the mean experimental period of the considered studies) in China. Our analyses demonstrate that straw return is an effective practice for sustaining crop productivity and soil fertility in large parts of China, but site-specific factors should be considered.
  • Authors:
    • Wegner,B. R.
    • Kumar,S.
    • Osborne,S. L.
    • Schumacher,T. E.
    • Vahyala,I. E.
    • Eynard,A.
  • Source: Soil Science Society of America Journal
  • Volume: 79
  • Issue: 4
  • Year: 2015
  • Summary: Excessive removal of crop residue has been shown to degrade soil organic carbon (SOC), and hence soil quality. Our objective was to assess the impacts of corn (Zea mays L.) residue removal and cover crops on various soil quality indicators. The experiment was conducted on a silty clay loam soil with and without a cover crop following three residue removal treatments. The low residue removal (LRR) treatment consisted of harvesting corn grain, leaving all other plant materials on the soil surface. Medium residue removal (MRR) consisted of harvesting grain, then chopping, windrowing and baling the remaining residue. The high residue removal (HRR) consisted of cutting the stalks 0.15 m from the ground and removing essentially all above-ground biomass. Crop residue removal significantly impacted measured soil properties including SOC, but cover cropping had minimal effects. The LRR treatment resulted in higher SOC concentrations and increased aggregate stability compared with other treatments. Residue removal significantly impacted the microbial activity as measured by hydrolysis of fluorescein diacetate (FDA). This study confirmed that HRR rates lead to SOC decomposition and adversely affect soil properties and soil quality. Soil conservation and emerging uses for crop residues must be balanced. Therefore, before making any decision to harvest crop residues, it is essential to have accumulated more C in the residue and supplemental cover crops than is needed to maintain equilibrium SOC levels. © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA. All rights reserved.