19602015
  • Authors:
    • Hao,X.
    • Kravchenko,A. N.
  • Source: Agronomy Journal
  • Volume: 99
  • Issue: 1
  • Year: 2007
  • Summary: Management practice and soil texture are known to affect soil C. Relatively little information exists, however, on interactions between textural and management effects. The objective of this study was to evaluate management effects on soil total C along a textural gradient in well-drained Typic Hapludalfs in southwest Michigan. Three management practices considered in this study were conventional tillage (CT) and no-till (NT) both with conventional chemical inputs, and conventional tillage with leguminous cover crops and no chemical inputs (CT-cover). Four replicate plots were sampled for each practice, with approximately 100 soil samples taken at the 0- to 5-cm depth in each plot. In all management practices, the relationships of total C and N with clay + silt varied depending on the range of clay + silt values, with regression slopes at clay + silt 570 g kg-1. Total C in the CT-cover and NT treatments was higher than that in the CT treatment across the whole range of studied textures; however, a greater difference in total C between NT and CT occurred at greater clay + silt contents. Total C in the CT-cover and NT treatments were not different when clay + silt was 600 g kg-1. The results indicate that the potential for C accumulation in surface soils via NT treatment depends on soil texture.
  • Authors:
    • Tourdonnet, S. D.
    • Carof, M.
    • Coquet, Y.
    • Hallaire, V.
    • Roger-Estrade, J.
  • Source: Soil Use and Management
  • Volume: 23
  • Issue: 3
  • Year: 2007
  • Summary: We studied soil hydraulic conductivity (K) and porosity in five combinations of soil tillage and cover crop management systems. Treatments were winter wheat (Triticum aestivum L.) grown on a conventionally tilled soil (CT), on a no-till soil (NT), and on an NT with three different cover crops: red fescue (Festuca rubra L.; Fr), bird's-foot-trefoil (Lotus corniculatus L.; Lc) and alfalfa (Medicago sativa L.; Ms). Measurements were made on a loamy soil in Grignon, France, in November 2004, May 2005 and October 2005. K and mean size of hydraulically active pores were measured in situ at three water potentials (22120.6, 22120.2 and 22120.05 kPa) at the soil surface and at 10 cm depth. In November 2004 and May 2005, pore space was described using 2D image analysis of pores on undisturbed soil samples in the 0201310 cm layer and in the 10201320 cm layer. The major differences were caused by soil tillage that created two heterogeneous soil layers and increased K in the 0201310 cm layer relative to NT. The effects of cover crop on K and porosity were not affected by the root type: there were no major differences between the grass cover crop (fibrous-root type) and the leguminous ones (tap-root type). However, we recorded larger functional pores and more tubules in the no-till treatments with a cover crop, compared with the no-till treatment without cover crop; this was probably the result of root activity. Although these changes generally did not result in larger values of K, they participated in the maintenance of soil structure and K over time.
  • Authors:
    • Chicago Climate Exchange
  • Year: 2007
  • Summary: Chicago Climate Exchange (CCX) is the world's first and North America's only active voluntary, legally binding integrated trading system to reduce emissions of all six greenhouse gases (GHGs), with Offset Projects worldwide. CCX employs independent verification and has been trading GHG emission reductions since 2003. CCX Members that cannot reduce their own emissions can purchase credits from those who make extra emission cuts or from verified Offset Projects. CCX issues tradable Carbon Financial Instrument (CFI) contracts to owners or aggregators of eligible projects on the basis of sequestration, destruction or displacement of GHG emissions. Eligible projects include: agricultural methane, landfill methane, coal mine methane, agricultural and rangeland soil carbon, forestry and renewable energy.
  • Authors:
    • King, A. J.
    • Cooper, J. E.
    • Strong, W. M.
    • Dalal, R. C.
  • Source: Australian Journal of Experimental Agriculture
  • Volume: 47
  • Issue: 7
  • Year: 2007
  • Summary: No-tillage (NT) practice, where straw is retained on the soil surface, is increasingly being used in cereal cropping systems in Australia and elsewhere. Compared to conventional tillage (CT), where straw is mixed with the ploughed soil, NT practice may reduce straw decomposition, increase nitrogen immobilisation and increase organic carbon in the soil. This study examined N-15-labelled wheat straw ( stubble) decomposition in four treatments (NT v. CT, with N rates of 0 and 75 kg/ha. year) and assessed the tillage and fertiliser N effects on mineral N and organic C and N levels over a 10-year period in a field experiment. NT practice decreased the rate of straw decomposition while fertiliser N application increased it. However, there was no tillage practice x N interaction. The mean residence time of the straw N in soil was more than twice as long under the NT (1.2 years) as compared to the CT practice (0.5 years). In comparison, differences in mean residence time due to N fertiliser treatment were small. However, tillage had generally very little effect on either the amounts of mineral N at sowing or soil organic C (and N) over the study period. While application of N fertiliser increased mineral N, it had very little effect on organic C over a 10-year period. Relatively rapid decomposition of straw and short mean residence time of straw N in a Vertisol is likely to have very little long-term effect on N immobilisation and organic C level in an annual cereal cropping system in a subtropical, semiarid environment. Thus, changing the tillage practice from CT to NT may not necessitate additional N requirement unless use is made of additional stored water in the soil or mineral N loss due to increased leaching is compensated for in N supply to crops.
  • Authors:
    • Surek, D.
    • Karacam, M.
    • Meyvec, K.
    • Akar, T.
    • Avc, M.
  • Source: Wheat production in stressed environments. Proceedings of the 7th International Wheat Conference, Mar del Plata, Argentina, 27 November - 2 December, 2005
  • Year: 2007
  • Summary: Because most of the dryland cereal varieties were improved under fallow/cereal rotation system, their performances in other cropping systems were questionable and reported unsatisfactory by some farmers. Therefore, the objective of this study was to investigate the performances and adaptation of newly registered varieties in different two course rotations for targeted recommendations. 12 cereal varieties were tried on 9 different 23-year-crop rotations plots for three consecutive years, 1999/2000, 2000/2001, 2001/2002. The varieties were 4 barley (malting two rowed Aydanhanm, and feeding Tarm and six rowed Cetin and Avci), 4 durum wheat (Altn, Ankara, Altntas, and Ylmaz), and 4 bread (Dagdas, Gun, Krgz and Mzrak) wheat. The cereal varieties were rotated with fallow, wheat, winter vetch, winter lentil, sunflower, safflower, lentil, chickpea and barley/vetch mixture. Grain and biomass yields, plant height, harvest index, kernel per spike, kernel weight and spike number per square meter were traits determined. Biplot analysis showed that responses of cereal varieties varied in dry (2001), wet and cold (2000) and normal (2003) seasons. Overall evaluations of responses indicated that some varieties adapted more to certain rotations than other varieties such as Aydanhanm for Safflower/cereal rotation. There was a general tendency that Tarm and Gun varieties performed well in winter cold and dry seasons in all rotations. Dagdas yielded pretty well following winter legumes and winter legume/cereal mixture except dry season. Six rowed barleys, Altntas and Ylmaz, were better in mild winter season in all rotations. Traits correlations indicated that spike number per square meter was always positively correlated with grain yields for all experimental seasons. While all yield components had positive contribution to the grain yields in wet season, kernel weight and kernel per spike had negative contribution to grain yields in the dry season. General evaluation showed that cereals succeeding chickpea and spring lentil crops were leading in terms of height, biomass, harvest index and grain yields, except cereals following fallow which were exceptionally superior in dry season. They also had higher kernel weight in dry and normal seasons.
  • Authors:
    • Hons, F.
    • Wright, A.
    • Dou, F.
  • Source: Soil & Tillage Research
  • Volume: 94
  • Issue: 2
  • Year: 2007
  • Summary: Crop management practices have potential to enhance subsoil C and N sequestration in the southern U.S., but effects may vary with tillage regime and cropping sequence. The objective of this study was to determine the impacts of tillage and soyabean cropping sequence on the depth distribution of soil organic C (SOC), dissolved organic C (DOC), and total N after 20 years of treatment imposition for a silty clay loam soil in central Texas. A continuous soyabean monoculture, a wheat-soybean doublecrop, and a sorghum-wheat-soybean rotation were established under both conventional (CT) and no tillage (NT). Soil was sampled after soyabean harvest and sectioned into 0-5, 5-15, 15-30, 30-55, 55-80, and 80-105 cm depth intervals. Both tillage and cropping intensity influenced C and N dynamics in surface and subsurface soils. No tillage increased SOC, DOC, and total N compared to CT to a 30 cm depth for continuous soyabean, but to 55 cm depths for the more intensive sorghum-wheat-soybean rotation and wheat-soybean doublecrop. Averaged from 0 to 105 cm, NT increased SOC, DOC, and total N by 32, 22, and 34%, respectively, compared to CT. Intensive cropping increased SOC and total N at depths to 55 cm compared to continuous soyabean, regardless of tillage regime. Continuous soyabean had significantly lower SOC (5.3 g kg -1) than sorghum-wheat-soybean (6.4 g kg -1) and wheat-soybean (6.1 g kg -1), and 19% lower total N than other cropping sequences. Dissolved organic C was also significantly higher for sorghum-wheat-soybean (139 mg C kg -1) than wheat-soybean (92 mg C kg -1) and continuous soyabean (100 mg C kg -1). The depth distribution of SOC, DOC, and total N indicated treatment effects below the maximum tillage depth (25 cm), suggesting that roots, or translocation of dissolved organic matter from surface soils, contributed to higher soil organic matter levels under NT than CT in subsurface soils. High-intensity cropping sequences, coupled with NT, resulted in the highest soil organic matter levels, demonstrating potential for C and N sequestration for subsurface soils in the southern U.S.
  • Authors:
    • Sweeney, D.W.
    • Kelley, K.
  • Source: Agronomy Journal
  • Volume: 99
  • Issue: 4
  • Year: 2007
  • Summary: Because of improved equipment technology, many producers in the eastern Great Plains are planting winter wheat ( Triticum aestivum L.) no-till (NT) into previous crop residues, but management of fertilizer N and P remains critical. This field study was conducted from 1998 through 2003 in southeastern Kansas on a Parsons silt loam soil (fine, mixed, thermic, Mollic Albaqualf). The objectives were to determine effects and interactions of previous crop [corn, Zea mays L.; grain sorghum, Sorghum bicolor (L.); and soybean, Glycine max (L.) Merr.], preplant placement method of liquid N-P fertilizer [subsurface-knife (KN), surface-band (SB), and surface-broadcast (BC)], and fertilizer N rate (22, 45, 90, and 134 kg N ha -1) on NT winter wheat yield, yield components, and nutrient uptake in a 2-yr cropping rotation. Wheat yields averaged 3.73, 3.56, and 2.97 Mg ha -1 following soybean, corn, and grain sorghum, respectively. However, as fertilizer N rate increased, yield differences between previous crops decreased. Grain yields also were influenced by placement of N-P fertilizer, averaging 3.68 Mg ha -1 for KN, 3.40 Mg ha -1 for SB, and 3.19 Mg ha -1 for BC. Plant and grain N responses indicated that grain yield differences were primarily related to greater immobilization of both fertilizer and soil N following grain sorghum, compared with soybean and corn, and to better utilization of KN N-P than surface-applied. Fertilizing with greater N rates applied as a subsurface band, especially if following grain sorghum, may be necessary to maximize NT wheat yield potential in the eastern Great Plains.
  • Authors:
    • Schumacher, R.
    • Schroeder, K.
    • Li, C.
    • Okubara, P.
    • Lawrence, N.
  • Source: Canadian Journal of Plant Pathology
  • Volume: 29
  • Issue: 3
  • Year: 2007
  • Summary: Soilborne pathogens are important biotic factors in yield reduction in the dryland cereal production region of the Pacific Northwest. Rhizoctonia solani AG-8, Rhizoctonia oryzae, and Pythium spp. are causal agents of root rot, bare patch, and damping-off of wheat ( Triticum aestivum) and barley ( Hordeum vulgare). Although these pathogens can be rapidly and specifically quantified using quantitative real-time PCR, the extraction of Rhizoctonia DNA from agricultural samples is often inconsistent, especially at low pathogen population densities. Using a novel extraction system that uses pressure cycling technology (PCT), we improved the extraction of R. solani AG-8 DNA up to 16-fold and of P. abappressorium DNA up to 2-fold from three types of agricultural soils compared with a bead beating extraction method. PCT also yielded quantifiable amounts of R. solani AG-8 and R. oryzae DNA from lyophilized wheat roots that were otherwise recalcitrant to homogenization. Furthermore, the extractions were so consistent that pathogen quantification generally could be derived from two rather than three or four replicated extracts. Because PCT is performed in a closed system and minimizes sample shearing and heating, it confers a substantial advantage over conventional extraction systems. Here, we report for the first time the application of PCT in a laboratory setting for the improved extraction and quantification of three types of soilborne pathogens in soil samples. The effectiveness of PCT for three soils suggests that it will be beneficial for other hard-to-extract pathogen samples.
  • Authors:
    • Salagean, D.
    • Oprea, G.
    • Pacurar, I.
  • Source: Analele Institutului National de Cercetare-Dezvoltare Agricola Fundulea
  • Volume: 75
  • Year: 2007
  • Summary: During 50 years (1957-2007), as part of NARDI Fundulea, Romania, studies and research on producing high quality seed, in small grains were performed. These investigations had as aim to improve the methodology and technology used in winter wheat and barley seed multiplication. Research regarding the variability of some traits in winter wheat and barley varieties during different periods, allowed their morphological and physiological characterization useful to maintain initial biological value of varieties during seed multiplication. Based on these studies, the seed multiplication schedule in small grains was established. Study regarding the influence of different seed biological categories on yielding capacity emphasized the fact that, during their multiplication, there is a slightly descendant tendency of this ability, but the yield diminutions became significant starting with the fourth multiplication of basic seed. The wheat crop fertilization under dryland and irrigation, with different nitrogen and phosphorus fertilizers demonstrated that, under both conditions, the application of some optimum rates favourably influenced the obtainment of seeds which lead to the yield increasing in the first year vs. fertilization with reduced rates. Harvesting of wheat and barley seed trials in three different stages (wax ripeness, full maturity and overmaturation) emphasized the fact that, the harvesting in optimum time (about 15% seed moisture) ensures the highest seed yields with superior quality indices. Study regarding the increasing of seed multiplication coefficient of new wheat and barley varieties to rapidly extend them into production emphasized the fact that, by using some reduced seed rates at sowing (about 25% of optimum seed rate), in the first two years after their registration, the seed multiplication coefficient increases from 1:20 to 1:80, four times respectively. Thus, the time for their extension into production could be reduced with two years minimum, with favourable economical effects.
  • Authors:
    • Azarnivand, H.
    • Jafari, M.
    • Sharifani, F.
    • Abbasi, H.
    • Sori, M.
  • Source: Iranian Journal of Range and Desert Research
  • Volume: 13
  • Issue: 4
  • Year: 2007
  • Summary: The effects of plant growth on soil quality in the Sagzi plain of Isfahan (Iran) were determined to evaluate the influence of agriculture on the desertification processes in dry lands. Inappropriate crop management significantly affected soil and water salinization which is one of the important processes of desertification. To determine if agriculture is a positive or negative factor for the reclamation of saline soils, improved and degraded factors of desertification in Sagzi plain of Isfahan were considered. Medicago, wheat and barley were evaluated to determine which crop is more effective for soil reclamation. Wheat and barley were selected and compared with derelict land, which was and independent variable in this study. The soils considered were cultivated with these products successively for at least 5 years. Soil samples were then obtained at different depths (0-3, 30-60, 60-90, 90-120, 120-150 cm) and were analysed for CaCO 3, electrical conductivity, organic matter, K +, Mg +, Ca 2+, Na +, CaSO 4, Cl -, sodium adsorption ratio, HCO 3- and SO 4-. Variance analysis showed significant difference between treatments at different depths and that among the three crops, wheat cropping is the best for soil reclamation.