19802015
  • Authors:
    • Cheng,Xiaoli
    • Yang,Yuanhe
    • Li,Ming
    • Dou,Xiaolin
    • Zhang,Quanfa
  • Source: Plant and Soil
  • Volume: 366
  • Issue: 1-2
  • Year: 2013
  • Summary: Over recent decades, a large uncultivated area has been converted to woodland and shrubland plantations to protect and restore riparian ecosystems in the Danjiangkou Reservoir area, a water source area of China's Middle Route of the South-to-North Water Transfer Project. Besides water quality, afforestation may alter soil organic carbon (SOC) dynamics and stock in terrestrial ecosystems, but its effects remain poorly quantified and understood. We investigated soil organic C and nitrogen (N) content, and delta C-13 and delta N-15 values of organic soil in plant root-spheres and open areas in an afforested, shrubland and adjacent cropped soil. Soil C and N recalcitrance indexes (RIC and RIN) were calculated as the ratio of unhydrolyzable C and N to total C and N. Afforestation significantly increased SOC levels in plant root-spheres with the largest accumulation of C in the afforested soil. Afforestation also increased belowground biomass. The C:N ratios in organic soil changed from low to high in the order the cropped, the shrubland and the afforested soil. The RIC in the afforested and shrubland were higher than that in cropped soil, but the RIN increased from the afforested to shrubland to cropped soil. The delta N-15 values of the organic soil was enriched from the afforested to shrubland to cropped soil, indicating an increased N loss from the cropped soil compared to afforested or shrubland soil. Changes in the delta C-13 ratio further revealed that the decay rate of C in the three land use types was the highest in the cropped soil. Afforestation increased the SOC stocks resulted from a combination of large C input from belowground and low C losses because of decreasing soil C decomposition. Shifts in vegetation due to land use change could alter both the quantity and quality of the soil C and thus, have potential effects on ecosystem function and recovery.
  • Authors:
    • Iqbal,Javed
    • Nelson,Jim A.
    • McCulley,Rebecca L.
  • Source: Plant and Soil
  • Volume: 364
  • Issue: 1-2
  • Year: 2013
  • Summary: Novel fungal endophyte (Neotyphodium coenophialum; Latch, Christensen and Samuels; Glenn, Bacon, and Hanlin) genotypes in symbiosis with tall fescue (Lolium arundinaceum; Schreb. Darbysh.) have been recently introduced to agricultural seed markets. These novel endophytes do not produce the full suite of toxins that the 'common toxic' form does, and therefore, may not have the same consequences on plant and soil processes. Here, we evaluated the effects of endophyte presence and genotype on ecosystem processes of tall fescue stands. We quantified the effects of the presence of the common toxic endophyte (CT), two novel endophyte genotypes (AR-542, AR-584), no endophyte (endophyte free, E-), and a mixture of all endophyte statuses (mix) within a single genotype of tall fescue (PDF) on various soil and plant parameters. Endophyte presence and genotype affected tall fescue cover and plant species diversity: cover-CT, AR-542, AR -584, mix > E- and species diversity-E- > AR-542, AR -584 > CT, mix. Most measured soil parameters had significant endophyte effects. For example, higher fluxes of soil CO2 and N2O were measured from stands of AR-542 than from the other endophyte treatments. These results indicate that endophyte presence and genetic identity are important in understanding the ecosystem-scale effects of this agronomically important grass-fungal symbiosis.
  • Authors:
    • Sheng,Min
    • Lalande,Roger
    • Hamel,Chantal
    • Ziadi,Noura
  • Source: Web Of Knowledge
  • Volume: 369
  • Issue: 1-2
  • Year: 2013
  • Summary: Evidence shows that tillage modifies soil properties, especially phosphorus (P) dynamics. Our objective was to disentangle long-term effects of P-fertilization and tillage on arbuscular mycorrhizal fungal (AMF) proliferation and community structure. Changes in the community structure of AMF and in the density of their hyphae and spores induced by moldboard plow (MP) or no till (NT), and fertilization with 0, 17.5, or 35 kg P ha(-1) were sought in the 0-15 cm and 15-30 cm soil layers after soybean harvest, at a long-term (17 years) experimental site in a humid continental zone of eastern Canada. The relationships among AMF, soil and plant attributes were examined. The 0-15 cm and 15-30 cm soil layers had different properties under NT, but were similar under MP, after 17 years, and MP increased soil available P levels. Phosphorus fertilization increased P levels in soil and in soybean. Treatment effects on AMF spore and hyphal density at 0-15 cm were greater than that at 15-30 cm, whereas effects on AMF community structure did not change with soil depths. At 0-15 cm, P-fertilization increased AMF spore density and reduced AMF hyphal density, and MP reduced AMF spore density. A total of eight AMF phylotypes were detected. Phosphorus fertilization reduced AMF phylotype richness and Shannon diversity index. Soil P availability increased under MP and hence the influence of P-fertilization treatments on the frequency of AMF phylotype detection varied with tillage system; it declined with P-fertilization under MP, but increased under NT. Phosphorus fertilization shifts resource partitioning in AMF propagules rather than in their hyphae, and degrades the genetic diversity of AMF in soil; tillage increases soil P availability and hence aggravates the impact of P-fertilization.
  • Authors:
    • Huffman, T.
    • Coote, D. R.
    • Green, M.
  • Source: Canadian Journal of Soil Science
  • Volume: 92
  • Issue: 3
  • Year: 2012
  • Summary: Agricultural soils that are covered by vegetation or crop residue are less susceptible to degradation by wind and water erosion, organic matter depletion, structural degradation and declining fertility. In general, perennial crops, higher yields, reduced tillage and continuous cropping provide more soil cover than annual crops, lower yields, intensive tillage, residue harvesting and fallowing. This study presents a model for estimating the number of days in a year that the soil surface is protected and demonstrates its application on the Canadian prairies over the period from 1981 to 2006. Over the 25-yr study period, the average soil cover on Canadian prairie soils increased by 4.8% overall. The improvement came primarily as a result of widespread adoption of no-till and a decline in the use of summerfallow, but the gains were offset to a great deal by a shift from higher-cover crops such as wheat, oats and barley to more profitable but lower-cover crops such as canola, soybeans and potatoes. The implication of these trends is that, even though protection of prairie agricultural soils has improved over the past 25 yr, soil cover could decline dramatically over the next several decades if crop changes continue, the adoption of conservation tillage reaches a peak and residue harvesting for biofuels becomes more common.
  • Authors:
    • Huffman, T.
    • Green, M.
    • Coote, D.
  • Source: Canadian Journal of Soil Science
  • Volume: 92
  • Issue: 3
  • Year: 2012
  • Summary: Agricultural soils that are covered by vegetation or crop residue are less susceptible to degradation by wind and water erosion, organic matter depletion, structural degradation and declining fertility. In general, perennial crops, higher yields, reduced tillage and continuous cropping provide more soil cover than annual crops, lower yields, intensive tillage, residue harvesting and fallowing. This study presents a model for estimating the number of days in a year that the soil surface is protected and demonstrates its application on the Canadian prairies over the period from 1981 to 2006. Over the 25-yr study period, the average soil cover on Canadian prairie soils increased by 4.8% overall. The improvement came primarily as a result of widespread adoption of no-till and a decline in the use of summerfallow, but the gains were offset to a great deal by a shift from higher-cover crops such as wheat, oats and barley to more profitable but lower-cover crops such as canola, soybeans and potatoes. The implication of these trends is that, even though protection of prairie agricultural soils has improved over the past 25 yr, soil cover could decline dramatically over the next several decades if crop changes continue, the adoption of conservation tillage reaches a peak and residue harvesting for biofuels becomes more common.
  • Authors:
    • Hussain, I.
    • Olson, K. R.
  • Source: Pakistan Journal of Botany
  • Volume: 44
  • Issue: 2
  • Year: 2012
  • Summary: Adoption of conservation tillage resulted in changes in soil properties, soil organic matter, soil nutrients. These soil variables were strongly correlated and could not be explained independently by the univariate analysis. The objectives of the study were to use the factor analysis for the identification of the factor pattern in soil properties and to examine the changes in factor scores in no-till (NT), chisel plow (CP) and moldboard plow (MP) tillage systems at different depths after 8 years of the tillage application and planting of corn and soybean on a sloping and previously eroded with a root restricting fragipan Grantsburg soil. The soil samples from the 0 to -5 and -5 to -15 cm soil depths were analyzed for the Ca, Mg, K, P, aggregate stability, particulate organic C, N and humified organic C and N. With factor analysis, 13 highly correlated soil variables were grouped into three different uncorrelated factors, which accounted for the 78% total variance of the data. The soil organic factor had high variable loading on aggregate stability, soil organic C and N contents in soil, POM and humified organic fractions. This factor varied between tillage and represented the accumulation of soil organic matter and its effect on aggregation because of the adoption of tillage. The soil exchange factor had high variable loading for the extractable Ca, Mg and CEC, and varied with tillage and depth because of mixing due to plowing and stratification due to use of no-till treatment. The soil nutrient factor had high variable loading on soil K and P and soil pH and varied between tillage treatments. The nutrient factor scores were also affected by fertilizer application and its mixing by plowing in CP and MP. No-till, which lacks mixing, resulted in decrease in availability of nutrients. This technique enables us to combine the correlated soil variables into three different groups and assess the impact of soil management systems, soil depths and sampling years on these factors. In the NT, lack of tillage, resulted in stratification of exchangeable bases, reduced availability of nutrients. However, it contributed to the maintenance of soil organic matter and soil aggregation. The mixing of soil with plowing resulted in the uniform nutrient availability and exchange capacity of soil in plow layer with the CP and MP systems. The plowing affected soil aggregation adversely due to decomposition of soil organic matter and making soil more susceptible to erosion. The crop yield of maize and soybean were higher with NT system than with CP and MP systems.
  • Authors:
    • Karkee, M.
    • McNaull, R. P.
    • Birrell, S. J.
    • Steward, B. L.
  • Source: Transactions of the ASABE
  • Volume: 55
  • Issue: 1
  • Year: 2012
  • Summary: As the demand for biomass feedstocks grows, it is likely that agricultural residue will be removed in a way that compromises soil sustainability due to increased soil erosion, depletion of organic matter, and deterioration of soil physical characteristics. Since soil erosion from agricultural fields depends on several factors including soil type, field terrain, and cropping practices, the amount of biomass that can be removed while maintaining soil tilth varies substantially over space and time. The RUSLE2 soil erosion model, which takes into account these spatio-temporal variations, was used to estimate tolerable agricultural biomass removal rates at field scales for a single-pass crop grain and biomass harvesting system. Soil type, field topography, climate data, management practices, and conservation practices were stored in individual databases on a state or county basis. Geographic position of the field was used as a spatial key to access the databases to select site-specific information such as soil, topography, and management related parameters. These parameters along with actual grain yield were provided as inputs to the RUSLE2 model to calculate yearly soil loss per unit area of the field. An iterative technique was then used to determine site-specific tolerable biomass removal rates that keep the soil loss below the soil loss thresholds (T) of the field. The tolerable removal rates varied substantially with field terrain, crop management practices, and soil type. At a location in a field in Winnebago county, Iowa, with ~1% slope and conventional tillage practices, up to 98% of the 11 Mg ha -1 total above-ground biomass was available for collection with negligible soil loss. There was no biomass available to remove with conventional tillage practices on steep slopes, as in a field in Crawford county, Iowa, with a 12.6% slope. If no-till crop practices were adopted, up to 70% of the total above-ground biomass could be collected at the same location with 12.6% slope. In the case of a soybean-corn rotation with no-till practices, about 98% of total biomass was available for removal at the locations in the Winnebago field with low slopes, whereas 77% of total biomass was available at a location in the Crawford field with a 7.5% slope. Tolerable removal rates varied substantially over an agricultural field, which showed the importance of site-specific removal rate estimation. These removal rates can be useful in developing recommended rates for producers to use during a single-pass crop grain and biomass harvesting operation. However, this study only considered the soil erosion tolerance level in estimating biomass removal rates. Before providing the final recommendation to end users, further investigations will be necessary to study the potential effects of continuous biomass removal on organic matter content and other biophysical properties of the soil.
  • Authors:
    • Kennedy, T. F.
    • Connery, J.
  • Source: The Journal of Agricultural Science
  • Volume: 150
  • Issue: 2
  • Year: 2012
  • Summary: The control of barley yellow dwarf virus (BYDV) and its aphid vectors in minimum tillage (MT) and conventionally tilled (CT) winter barley by insecticide seed and foliar spray treatments was investigated in 2001, 2002 and 2003. Similar investigations were undertaken on winter wheat in 2004, 2005 and 2006. Aphids numbers in autumn and BYDV in spring on barley and wheat were significantly lower on MT relative to CT crops, in two of the six seasons. An insecticide spray at Zadoks growth stage (GS) 25 significantly reduced aphids and virus in both MT and CT crops in three of the six seasons of the study. An additional spray at GS 22 provided no benefit. Aphids were significantly fewer in three of the six seasons on crops grown from insecticide treated seeds, relative to untreated seeds. Both MT and CT barley sprayed at GS 25 had significantly fewer aphids than the seed treatment in one of the three seasons. Seed-treated MT and CT barley had significantly less BYDV than controls but significantly more than crops sprayed at GS 25. CT wheat grown from insecticide-treated seed had significantly less BYDV than controls. Overall, CT barley grown from insecticide-treated seed had 6-fold more BYDV than the sprayed crop, while untreated barley had 22-fold more than the spray treatment. In MT barley, the comparable values were 3- and 10-fold respectively. BYDV was almost exclusively the MAV strain. The grain yield for insecticide-sprayed CT barley was significantly greater in two of three seasons than that for untreated plots. In general, MT and CT barley receiving an insecticide spray had greater grain yield than barley grown from insecticide-treated seed, with differences being significant in one of three seasons. It is concluded that BYDV in MT and CT cereals is better controlled by applying a pyrethroid insecticide spray between GS 23 and 25, in autumn, than by treating the seed with a nitroguanidine-type insecticide. In MT crops, a single spray between GS 23 and 25 will give effective control of MAV-type BYDV.
  • Authors:
    • Ruzibaev, E.
    • Akramkhanov, A.
    • Lamers, J. P. A.
    • McDonald, A.
    • Mirzabaev, A.
    • Ibragimov, N.
    • Kienzler, K. M.
    • Egamberdiev, O.
  • Source: Field Crops Research
  • Volume: 132
  • Year: 2012
  • Summary: Rainfed and irrigated agricultural systems have supported livelihoods in the five Central Asian countries (CAC) for millennia, but concerns for sustainability and efficient use of land and water resources are long-standing. During the last 50 years, resource conserving technologies were introduced in large parts of the rainfed areas while the irrigated areas were expanded largely without considering resource conservation. In more recent years, the use of conservation agriculture (CA) practices has been reported for the different agricultural production (AP) zones in CAC, albeit centering on a single AP zone or on single factors such as crop yield, implements or selected soil properties. Moreover, conflicting information exists regarding whether the current practices that are referred to as 'CA' can indeed be defined as such. Overall information on an application of CA-based crop management in Central Asia is incomplete. This discussion paper evaluates experimental evidence on the performance of CA and other resource conserving technologies in the three main AP zones of CAC, provides an overview of farmer adoption of production practices related to CA, and outlines technical and non-technical challenges and opportunities for the future dissemination of CA practices in each zone. Agronomic (e.g. implements, crop yields, duration. and crop residues), institutional (e.g. land tenure) and economic (e.g. short vs. long-term profitability) perspectives are considered. At present, adoption of CA-based agronomic practices in the rainfed production zone is limited to partial crop residue retention on the soil surface or sporadically zero tillage for one crop out of the rotation, and hence the use of single CA components but not the full set of CA practices. In the irrigated AP zones, CA is not commonly practiced and many of the pre-conditions that typically encourage the rapid spread of CA practices appear to be absent or limiting. Further, our analysis suggests that given the diversity of institutional, socio-economic and agro-ecological contexts, a geographically differentiated approach to CA dissemination is required in the CAC. Immediate priorities should include a shift in research paradigms (e.g. towards more participatory approaches with farmers), development of commercially available reduced and no-till seeders suitable for smaller-scale farm enterprises, and advocacy so that decision makers understand how different policies may encourage or discourage innovations that lead towards more sustainable agricultural intensification in the CAC.
  • Authors:
    • Ahuja, L. R.
    • Saseendran, S. A.
    • Green, T. R.
    • Ma, L. W.
    • Nielsen, D. C.
    • Walthall, C. L.
    • Ko, J. H.
  • Source: Climatic Change
  • Volume: 111
  • Issue: 2
  • Year: 2012
  • Summary: Agricultural systems models are essential tools to assess potential climate change (CC) impacts on crop production and help guide policy decisions. In this study, impacts of projected CC on dryland crop rotations of wheat-fallow (WF), wheat-corn-fallow (WCF), and wheat-corn-millet (WCM) in the U.S. Central Great Plains (Akron, Colorado) were simulated using the CERES V4.0 crop modules in RZWQM2. The CC scenarios for CO 2, temperature and precipitation were based on a synthesis of Intergovernmental Panel on Climate Change (IPCC 2007) projections for Colorado. The CC for years 2025, 2050, 2075, and 2100 (CC projection years) were super-imposed on measured baseline climate data for 15-17 years collected during the long-term WF and WCF (1992-2008), and WCM (1994-2008) experiments at the location to provide inter-annual variability. For all the CC projection years, a decline in simulated wheat yield and an increase in actual transpiration were observed, but compared to the baseline these changes were not significant ( p>0.05) in all cases but one. However, corn and proso millet yields in all rotations and projection years declined significantly ( p<0.05), which resulted in decreased transpiration. Overall, the projected negative effects of rising temperatures on crop production dominated over any positive impacts of atmospheric CO 2 increases in these dryland cropping systems. Simulated adaptation via changes in planting dates did not mitigate the yield losses of the crops significantly. However, the no-tillage maintained higher wheat yields than the conventional tillage in the WF rotation to year 2075. Possible effects of historical CO 2 increases during the past century (from 300 to 380 ppm) on crop yields were also simulated using 96 years of measured climate data (1912-2008) at the location. On average the CO 2 increase enhanced wheat yields by about 30%, and millet yields by about 17%, with no significant changes in corn yields.