• Authors:
    • Hernandez, R. M.
    • Bravo, C.
    • Rivero, C.
    • Lozano P.,Z.
  • Source: REVISTA DE LA FACULTAD DE AGRONOMIA DE LA UNIVERSIDAD DEL ZULIA
  • Volume: 28
  • Issue: 1
  • Year: 2011
  • Summary: Some researchers suggest the use of different SOM organic matter (SOM) fractions or compartiments like indicators of the agricultural systems sustainability. In order to evaluate the amount, composition and distribution in the profile of different SOM fractions from the soil on conservation agriculture systems, evaluations in an Ustoxic Quartzipsament soil located at Venezuelan savannahs, were carried out. Three cover crop treatments were evaluated, as improved land fallows for the establishing of maize no-tillage system and grazing with ovine cattle: Brachiaria dictyoneura (BD), Centrosema macrocarpum (CM), and spontaneous vegetation (SV), and its comparison with the natural savannah ecosystem (NS). Samples to three depths (0-5, 5-15 and 15-30 cm), and were taken at three times: initial, 286 days after the establishment (dae), and 1463 dae. At all depths and to 1463 dae were evaluated: total organic carbon (TOC), hidrosoluble carbon (HSC), and particulate organic matter carbon (POMC). At all times and in the the 0 to 5 cm layer physical and chemical fractions of the SOM, were evaluated. The results show statistical differences between cover crops types in some SOM fractions, mainly in the light fractions (HSC, and fulvic acid carbon), with the greater values in BD and the minors in SV. The cover crops introduction produced the diminution in some fractions; but after three continuous cycles under the proposed management, these fractions reached similar values or superior to those initials. The humification indexes, and the relations between the different fractions and the TOC, were the most sensible indicators.
  • Authors:
    • Aibar, J.
    • Cirujeda, A.
    • Zaragoza, C.
  • Source: Agronomy for Sustainable Development
  • Volume: 31
  • Issue: 4
  • Year: 2011
  • Summary: Management practices, geographical gradients and climatic factors are factors explaining weed species composition and richness in cereal fields from Northern and Central Europe. In the Mediterranean area, the precise factors responsible for weed distribution are less known due to the lack of data and surveys. The existence of weed survey data of year 1976 in the Zaragoza province of the Aragon region, Spain, offered us the opportunity to compare present weed species with weed species growing 30 years ago. No detailed comparison of changes in weed species composition in cereal fields in that period of time has been conducted in the Mediterranean area. Here a survey was conducted in the Aragon region from 2005 to 2007. Weeds were surveyed in 138 winter cereal fields in ten survey areas where winter cereals are the main crops, using the same methodology applied 30 years ago. In the Zaragoza province, 36 fields were chosen in the same municipalities than in the previous survey. Several management, geographic and climatic variables of each field were recorded and related to weed species with multivariate analysis. Diversity index were calculated and related to survey area and altitude. Our results show that out of the 175 species only 26 species were found in more than 10% of the surveyed fields. The main species were Papaver rhoeas, Lolium rigidum, Avena sterilis and Convolvulus arvensis found in more than half of the surveyed fields. L. rigidum was related to dryland, while the other species were found overall. Furthermore, we found that management, geographical and climatic factors were significantly related to weed species distribution. In particular altitude, survey areas, irrigation and herbicide use in post-emergence were the most driving factors explaining weed species distribution. Species richness was higher in survey areas with extensive management practices and increased with altitude excepting a very productive area with intensive management practices at high altitude where richness was as low as in the irrigated lowlands. The main differences found between the 1976 and the 2005-2007 surveys were (1) the striking increase of grass weeds, (2) the high decrease of mean weed species number found in each field declining from 9 to 3 and (3) the frequency decrease of many weed species probably caused by agriculture intensification in that period of time. The growing importance of other weed species is probably related to their adaptation to minimum tillage, which is a widespread technique nowadays.
  • Authors:
    • Risaliti, R.
    • Antichi, D.
    • Barberi, P.
    • Sapkota, T. B.
    • Mazzoncini, M.
  • Source: Soil & Tillage Research
  • Volume: 114
  • Issue: 2
  • Year: 2011
  • Summary: No-tillage, N fertilization and cover crops are known to play an important role in conserving or increasing SOC and STN but the effects of their interactions are less known. In order to evaluate the single and combined effects of these techniques on SOC and STN content under Mediterranean climate, a long term experiment started in 1993 on a loam soil (Typic Xerofluvent) in Central Italy. The experimental variants are: conventional tillage (CT) and no-tillage (NT), four N fertilization rates (N0, N1, N2 and N3) and four soil cover crop (CC) types (C - no cover crop; NL - non-legume CC; LNL - low nitrogen supply legume CC, and HNL - high nitrogen supply legume CC). The nitrogen fertilization rates (N0, N1, N2 and N3) were: 0, 100, 200, 300 kg N ha(-1) for maize (Zea mays, L); 0, 60, 120,180 kg N a(-1) for durum wheat (Triticum durum Desf.); 0, 50, 100, 150 kg N ha(-1) for sunflower (Helianthus annuus L.). From 1993 to 2008, under the NT system the SOC and STN content in the top 30 cm soil depth increased by 0.61 and 0.04 Mg ha(-1) year(-1) respectively. In the same period, the SOC and STN content under the CT system decreased by a rate of 0.06 and 0.04 Mg ha(-1) year(-1) respectively. During the experimental period, N1, N2 and N3 increased the SOC content in the 0-30 cm soil layer at a rate of 0.14, 0.45 and 0.49 Mg ha(-1) year(-1). Only the higher N fertilization levels (N2 and N3) increased STN content, at a rate of 0.03 and 0.05 Mg ha(-1) year(-1). NL, LNL and HNL cover crops increased SOC content by 0.17, 0.41 and 0.43 Mg C ha(-1) year(-1) and -0.01, +0.01 and +0.02 Mg N ha(-1) year(-1). Significant interactions among treatments were evident only in the case of the N fertilization by tillage system interaction on SOC and STN concentration in the 0-10 cm soil depth in 2008. The observed SOC and STN variations were correlated to C returned to the soil as crop residues, aboveground cover crop biomass and weeds (C input). We conclude that, under our Mediterranean climate, it is easier to conserve or increase SOC and STN by adopting NT than CT. To reach this objective, the CT system requires higher N fertilization rates and introduction of highly productive cover crops. (C) 2011 Elsevier B.V. All rights reserved.
  • Authors:
    • Moreno, F.
    • Muñoz-Romero, V.
    • López-Bellido, L.
    • López-Bellido, R. J.
    • Melero,S.
    • Murillo, J. M.
  • Source: Soil & Tillage Research
  • Volume: 114
  • Issue: 2
  • Year: 2011
  • Summary: Studies of the impacts of the interactions of soil agricultural practices on soil quality could assist with assessment of better management to establish sustainable crop production system. The main objective was to determine the long-term effects of tillage system, crop rotation and N fertilisation on soil total N and organic C (SOC), labile fractions of organic matter (water soluble carbon, WSC, and active carbon, AC), nitrate content, and soil enzymatic activities (dehydrogenase (DHA), beta-glucosidase (Glu) and alkaline phosphatase (AP)) at four different soil depths (0-5, 5-10, 10-30 and 30-50 cm), in a Mediterranean dryland Vertisol in SW Spain. Tillage systems were conventional tillage (CT) and no tillage (NT). Crop rotations were wheat-sunflower (WS), wheat-chickpea (WC), wheat-faba bean (WFb), wheat-fallow (WF) and continuous wheat (WW). Nitrogen fertiliser rates were 0, 50 and 150 kg N ha(-1). The different crop rotation systems had a great influence in soil C and N fractions and enzymatic activities. In general, the SOC. total N. WSC, and beta-glucosidase contents were higher in the no tillage system than in conventional tillage system in the wheat-wheat and in the wheat-faba bean rotations at upper layer (0-5 cm), while the lowest ones were obtained in the wheat-fallow rotation in both tillage systems. Carbon and N fractions, calculated by volumetric soil, showed an increase with depth in both tillage systems and in all crop rotations, which could be related to the increase of soil bulk density and soil mass with depth. The highest N fertiliser rate increased most of soil variables, especially nitrate content at deeper layers, thereby precautions should be taken with long-term N fertilisation to avoid leaching of nitrates below the tillage layer. With the exception of wheat-fallow rotation, slightly greater grain and above-ground biomass yields were obtained for wheat in NT, especially at 150 kg N ha(-1). Combination of NT with any biannual rotation except fallow could be an adequate sustainable management in order to improve soil quality of Vertisols, under our conditions. (C) 2011 Elsevier B.V. All rights reserved.
  • Authors:
    • Nichols, K. A.
    • Toro, M.
  • Source: Soil & Tillage Research
  • Volume: 111
  • Issue: 2
  • Year: 2011
  • Summary: Soil aggregate stability is a frequently used indicator of soil quality, but there is no standard methodology for assessing this indicator. Current methods generally measure only a portion of the soil or use either dry-sieved or wet-sieved aggregates. Our objective was to develop a whole soil stability index (WSSI) by combining data from dry aggregate size distribution and water-stable aggregation along with a 'quality' constant for each aggregate size class. The quality constant was based on the impact of aggregate size on soil quality indicators. Soil quality indicators can be loosely defined as those soil properties and processes that have the greatest sensitivity to changes in soil function. The WSSI was hypothesized to have a better relationship to the impacts of aboveground management than other soil aggregation indices such as a mean weight diameter (MWD), geometric mean diameter (GIVID), and the normalized stability index (NSI). Soil samples used in this study were collected from sites established on the same or similar soil types at the Northern Great Plains Research Laboratory in Mandan, ND. By utilizing dry aggregate size distribution, water-stable aggregation, and the quality constant, the WSSI detected differences in soil quality due to management (such as amount of disturbance, plant cover, and crop rotation) with the highest values occurring for the undisturbed, native range and the lowest values for conventional tillage, fallow treatments. The WSSI had the best relationship with management and is recommended as a standard measurement for soil aggregation. Published by Elsevier B.V.
  • Authors:
    • Rosolem, C. A.
    • dos Santos, G. P.
    • Castoldi, G.
    • Pivetta, L. A.
  • Source: Pesquisa Agropecuária Brasileira
  • Volume: 46
  • Issue: 11
  • Year: 2011
  • Summary: The objective of this work was to assess winter and spring crop effects on soybean root system growth, and on yield, and to compare a direct method (soil core sampling) with an indirect method (with rubidium) in evaluating the root system. The experimental design was a randomized complete block design, in a split-plot arrangement, with four replicates. Plots consisted of the winter crops, triticale (X Triticosecale) and sunflower (Helianthus annuus), and subplots of the spring crops, pearl millet (Pennisetum glaucum), forage sorghum (Sorghum bicolor) and sunn hemp (Crotalaria juncea), besides chisel tillage in 2003 and 2009. Soybean (Glycine max) was grown in the summer, and its root system was evaluated by physical sampling of the roots and by root activity assessment using rubidium. Changes in the architecture or in the activity of soybean roots did not affect yield. The distribution and activity of soybean roots were not significantly affected by the winter cover crops, but root growth was favored after millet and sorghum were grown in the spring. The direct measurement of the soybean root system with an auger has low correlation with root activity.
  • Authors:
    • Nonnecke, G. R.
    • Portz, D. N.
  • Source: HortScience
  • Volume: 46
  • Issue: 10
  • Year: 2011
  • Summary: Yield of strawberry grown continuously on the same site often declines over time as a result of proliferation of weed seeds and pathogenic organisms in the soil. Plots were established and maintained in seven different cover crops and as continuous strawberry or continuous tillage for 10 years (1996 to 2005) in a site that was previously in strawberry production for 10 years (1986 to 1995). Cover crops included blackeyed Susan (Rudbeckia hirta L.), sorghum Sudangrass [Sorghum bicolor (L.) Moench], marigold (Tagetes credo L.), big bluestem (Andropogon gerardii Vitman), perennial ryegrass (Lolium permute L.), switchgrass (Panicum virgatum L.), and Indiangrass [Sorghastrum nutans (L.) Nash]. Treatments were ended in 2005 and plots were planted with 'Honeoye' strawberry in a matted row. Effectiveness of soil pretreatments in reducing weed populations and enhancing strawberry production was evaluated for four growing seasons by quantifying weed growth by type and biomass and strawberry plant density and yield. The results indicate that matted-row strawberry production plots that were either in continuous tillage or established in S. bicolor, P. virgatum, or A. gerardii before planting strawberry had lower weed biomass and greater strawberry plant establishment and yield than plots established in L. permute or R. hirta or that had supported continuous strawberry production.
  • Authors:
    • Nichols, R. L.
    • Kelton, J. A.
    • Culpepper, S. A.
    • Balkcom, K. S.
    • Price, A. J.
    • Schomberg, H.
  • Source: Journal of Soil and Water Conservation
  • Volume: 66
  • Issue: 4
  • Year: 2011
  • Summary: Conservation tillage reduces the physical movement of soil to the minimum required for crop establishment and production. When consistently practiced as a soil and crop management system, it greatly reduces soil erosion and is recognized for the potential to improve soil quality and water conservation and plant available water. Adoption of conservation tillage increased dramatically with the advent of transgenic, glyphosate-resistant crops that permitted in-season, over-the-top use of glyphosate (N-[phosphonomethyl] glycine), a broad-spectrum herbicide with very low mammalian toxicity and minimal potential for off-site movement in soil or water. Glyphosate-resistant crops are currently grown on approximately 70 million ha (173 million ac) worldwide. The United States has the most hectares (45 million ha [99 million ac]) of transgenic, glyphosate-resistant cultivars and the greatest number of hectares (46 million ha [114 million ac]) in conservation tillage. The practice of conservation tillage is now threatened by the emergence and rapid spread of glyphosate-resistant Palmer amaranth (Amaranthus palmeri [S.]Wats.), one of several amaranths commonly called pigweeds. First identified in Georgia, it now has been reported in Alabama, Arkansas, Florida, Georgia, Louisiana, Mississippi, North Carolina, South Carolina, and Tennessee. Another closely related dioecious amaranth, or pigweed, common waterhemp (Amaranthus rudis Sauer), has also developed resistance to glyphosate in Illinois, Iowa, Minnesota, and. Missouri. Hundreds of thousands of conservation tillage hectares, some currently under USDA Natural Resources Conservation Service conservation program contracts, are at risk of being converted to higher-intensity tillage systems due to the inability to control these glyphosate-resistant Amaranthus species in conservation tillage systems using traditional technologies. The decline of conservation tillage is inevitable without the development and rapid adoption of integrated, effective weed control strategies. Traditional and alternative weed control strategies, such as the utilization of crop and herbicide rotation and integration of high residue cereal cover crops, are necessary in order to sustain conservation tillage practices.
  • Authors:
    • Passos, A. M. A. dos
    • Albuquerque, A. de
    • Resende, P. M. de
    • Baliza, D. P.
    • Reis, W. P.
    • Botrel, E. P.
  • Source: Revista de Agricultura
  • Volume: 86
  • Issue: 1
  • Year: 2011
  • Summary: The objective of this work was to compare the potential of the irrigated wheat under no tillage and conventional cropping systems, as well as to evaluate the performance of fifteen wheat cultivars in the two cropping systems, in succession to soybean crop, in the South of Minas Gerais. The experiment was carried out in the Federal University of Lavras (UFLA), in Lavras, MG, in the years of 2006/07 and 2007/08, in a split-block-designed scheme in a randomized complete block design, with three replications. The cropping systems (conventional and no-tillage) were installed in the rows and, in the columns, the fifteen wheat cultivars were distributed. The wheat yield and others agronomic characteristics were evaluated. The no-tillage provided an average increase of 25% in the organic matter levels in the topsoil layer in relation to previous levels and to conventional cropping system. The cultivars tested, independent of the agricultural year, significantly altered the grain yields and the agronomic characteristics. The high yield presented by the cultivars evaluated in this study indicates the high potential of the irrigated wheat cropped in succession to soybean crops, under similar climatic and soil conditions used in this study.
  • Authors:
    • Isla, R.
    • Salmeron, M.
    • Cavero, J.
  • Source: Field Crops Research
  • Volume: 123
  • Issue: 2
  • Year: 2011
  • Summary: Under semiarid Mediterranean conditions irrigated maize has been associated to diffuse nitrate pollution of surface and groundwater. Cover crops grown during winter combined with reduced N fertilization to maize could reduce N leaching risks while maintaining maize productivity. A field experiment was conducted testing two different cover crop planting methods (direct seeding versus seeding after conventional tillage operations) and four different cover crops species (barley, oilseed rape, winter rape, and common vetch), and a control (bare soil). The experiment started in November 2006 after a maize crop fertilized with 300 kg N ha(-1) and included two complete cover crop-maize rotations. Maize was fertilized with 300 kg N ha(-1) at the control treatment, and this amount was reduced to 250 kg N ha(-1) in maize after a cover crop. Direct seeding of the cover crops allowed earlier planting dates than seeding after conventional tillage, producing greater cover crop biomass and N uptake of all species in the first year. In the following year, direct seeding did not increase cover crop biomass due to a poorer plant establishment. Barley produced more biomass than the other species but its N concentration was much lower than in the other cover crops, resulting in higher C:N ratio (> 26). Cover crops reduced the N leaching risks as soil N content in spring and at maize harvest was reduced compared to the control treatment. Maize yield was reduced by 4 Mg ha(-1) after barley in 2007 and by 1 Mg ha(-1) after barley and oilseed rape in 2008. The maize yield reduction was due to an N deficiency caused by insufficient N mineralization from the cover crops due to a high C:N ratio (barley) or low biomass N content (oilseed rape) and/or lack of synchronization with maize N uptake. Indirect chlorophyll measurements in maize leaves were useful to detect N deficiency in maize after cover crops. The use of vetch, winter rape and oilseed rape cover crops combined with a reduced N fertilization to maize was efficient for reducing N leaching risks while maintaining maize productivity. However, the reduction of maize yield after barley makes difficult its use as cover crop. (C) 2011 Elsevier B.V. All rights reserved.