• Authors:
    • Finlay, L. A.
    • Weaver, T. B.
    • Hulugalle, N. R.
    • Lonergan, P.
  • Source: Soil Research
  • Volume: 50
  • Issue: 4
  • Year: 2012
  • Summary: Comparative studies of soil quality and energy use in two- and three-crop rotations in irrigated cotton ( Gossypium hirsutum L.) based cropping systems under varying stubble management practices in Australian Vertosols are sparse. Our primary objective was to quantify selected soil quality indices (salinity, sodicity, exchangeable cations, nitrate-N, pH), crop yields, and greenhouse gas emissions in four irrigated cotton-based cropping systems sown on permanent beds in a Vertosol with subsoil sodicity near Narrabri in north-western New South Wales. A secondary objective was to evaluate the efficacy of sowing vetch in rotation with cotton over a long period on the incidence of black root-rot in cotton seedlings. Results: presented in this report pertain to the period June 2005-May 2011. The experimental treatments were: cotton-cotton; cotton-vetch ( Vicia benghalensis L.); cotton-wheat ( Triticum aestivum L.), where wheat stubble was incorporated; and cotton-wheat-vetch, where wheat stubble was retained as in-situ mulch. Vetch was terminated during or just before flowering by a combination of mowing and contact herbicides, and the residues were retained as in-situ mulch. Soil pH, electrical conductivity (EC 1:5), Cl -, NO 3--N, exchangeable cations, exchangeable sodium percentage (ESP), electrochemical stability index (=EC 1:5/ESP), and EC 1:5/ESC (exchangeable sodium concentration) were evaluated in samples taken from the 0-1.2 m depth before sowing cotton during late September or early October of each year. Incidence of black root-rot was assessed 6 weeks after sowing cotton. Compared with sowing cotton every year, including wheat in cotton-based cropping systems improved cotton yield and reduced soil quality decline, emissions of carbon dioxide equivalents (CO 2-e) per unit area, and CO 2-e emissions per unit of cotton yield. Including vetch in the rotation was of negligible benefit in terms of yield and CO2-e emissions per unit of yield. The rate of soil quality decline was unaffected by including vetch in a cotton-wheat rotation but was accelerated when included in a cotton-cotton sequence. Among all cropping systems, soil quality was best with cotton-wheat and cotton-wheat-vetch but poorest with cotton-vetch. Although CO2-e emissions associated with growing 1ha of cotton could be reduced by 9% by growing vetch because of substituting fixed atmospheric N for N fertiliser derived from fossil fuels, this advantage was partly negated by the emissions from farming operations associated with growing a vetch crop. Relative to a two-crop rotation (one cotton-one rotation crop), negligible benefits in terms of yield, soil quality, greenhouse gas emissions, and black root-rot control accrued from a three-crop rotation (one cotton-two rotation crops). Incidence of black root-rot increased as the number of cotton crops sown increased. In addition to the cropping systems, soil quality indices and yield were significantly influenced by irrigation water quality and climate.
  • Authors:
    • Singh, M.
    • Jhala, A. J.
  • Source: Weed Technology
  • Volume: 26
  • Issue: 3
  • Year: 2012
  • Summary: Soil-applied herbicides are commonly used for broad-spectrum residual weed control in Florida citrus. Groundwater contamination from some soil-applied herbicides has been reported in citrus growing areas in Florida. Indaziflam is a new soil-applied herbicide recently registered for broad-spectrum weed control in Florida citrus. There is no information available on leaching behavior of indaziflam in sandy soil. Experiments were conducted to compare leaching of indaziflam with five commercially used residual herbicides in a Florida Candler soil under simulated rainfall of 5 or 15 cm ha -1. Herbicide movement down soil columns was measured by visually evaluating injury and harvesting aboveground biomass of the bioassay species annual ryegrass. Ryegrass was not injured and plant biomass was not affected beyond 30 cm when indaziflam at a recommended rate of 73 g ai ha -1 was leached through the soil column. Leaching of indaziflam increased with increasing amounts of rainfall. For example, indaziflam leached up to 12.20.8 cm (values are expressedSD) and 27.22.6 cm at 5 and 15 cm ha -1 rainfall, respectively. The herbicide ranking from high to low mobility at 15 cm ha -1 of rainfall was bromacil=norflurazon>indaziflam>simazine=pendimethalin>diuron. Overall results suggested that indaziflam leaching was limited in Florida Candler soil in this study; however, field experiments are required to confirm the leaching of indaziflam under natural rainfall situation.
  • Authors:
    • Sanderlin, R. S.
    • Melanson, R. A.
    • McTaggart, A. R.
    • Ham, J. H.
  • Source: Plant Disease
  • Volume: 96
  • Issue: 8
  • Year: 2012
  • Summary: Xylella fastidiosa causes disease in a number of economically important crops, ornamental plants, and shade trees, including grapevine, citrus, oleander, and sycamore. In pecan, X. fastidiosa causes pecan bacterial leaf scorch (PBLS), which leads to defoliation and reduces nut yield. No economically effective treatments are available for PBLS. In order to improve PBLS management practices, it is necessary to determine the subspecies of X. fastidiosa strains that infect pecan so that potential sources of inoculum may be identified. Multiprimer polymerase chain reaction (PCR) and phylogenetic analyses using nucleotide sequence data from the 16S-23S rRNA intergenic transcribed spacer (ITS) region and pglA consistently identified strains of X. fastidiosa isolated from pecan as X. fastidiosa subsp. multiplex. Enterobacterial repetitive intergenic consensus PCR and repetitive extragenic palindromic (REP)-PCR analyses were congruent with phylogenetic analyses. REP-PCR analyses indicated genetic variation within strains of X. fastidiosa from pecan. From these same analyses, X. fastidiosa strains from sycamore, grapevine, and oleander from Louisiana were identified as subsp. multiplex, subsp. fastidiosa, and subsp. sandyi, respectively. This study provides additional information about the host ranges of X. fastidiosa subspecies.
  • Authors:
    • Jennings, K. M.
    • Meyers, S. L.
    • Monks, D. W.
  • Source: Weed Technology
  • Volume: 26
  • Issue: 3
  • Year: 2012
  • Summary: Studies were conducted in 2008 and 2009 to determine the effect of S-metolachlor rate and application time on sweetpotato cultivar injury and storage root shape under conditions of excessive moisture at the time of application. S-metolachlor at 1.1, 2.2, or 3.4 kg ai ha -1 was applied immediately after transplanting or 2 wk after transplanting (WATP) to 'Beauregard', 'Covington', 'DM02-180', 'Hatteras', and 'Murasaki-29' sweetpotato. One and three d after S-metolachlor application plots received 1.9 cm rainfall or irrigation. S-metolachlor applied immediately after transplanting resulted in increased sweetpotato stunting 4 and 12 WATP, decreased no. 1 and marketable sweetpotato yields, and decreased storage root length to width ratio compared with the nontreated check. Sweetpotato stunting, no. 1 and marketable yields, and storage root length to width ratio in treatments receiving S-metolachlor 2 WATP were similar to the nontreated check. In 2008, Covington and Hattaras stunting 12 WATP was greater at 2.2 and 3.4 kg ha -1 (11 to 16%) than 1.1 kg ha -1 (1 to 2%). In 2009, S-metolachlor at 3.4 kg ha -1 was more injurious 4 WATP than 2.2 kg ha -1 and 1.1 kg ha -1. While cultivar by treatment interactions did exist, injury, yield, and storage root length to width ratio trends were similar among all cultivars used in this study.
  • Authors:
    • Assis, C. P.
    • Jucksch, I.
    • Mendonça, E. S.
    • Neves, J. C. L.
    • Silva, L. H. M.
    • Wendling, B.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 43
  • Issue: 5
  • Year: 2012
  • Summary: The objective of this study was to evaluate changes in distribution and quality of organic matter in light and heavy fractions of a medium-texture Red Latosol under different uses and management practices in Capinopolis, Brazil. Soil samples were collected from different layers in the profile (0-5, 5-10, and 10-20 cm). The following treatments were evaluated: NTs, no till (no tillage) for 4 years with maize (silage)/soybean in succession; NTg, no till for 4 years with maize/maize/maize/soybean in succession; NTtf, no till for 3 years with tifton (hay) and soybeans in the last year; CS, about 30 years with conventional cultivation system (maize/soybean) with only soybean in the past 4 years; and NF, native forest. The heavy fraction contributed 75-98% of total carbon and 94-99% of total nitrogen, indicating that most carbon and nitrogen in the soil are associated with the mineral fraction, which is fundamental for the maintenance of their stocks. Tifton grass in no tillage was efficient in increasing the amounts of light fraction (free and occluded). Increases of occluded light fraction in no-till systems were greater than in conventional cultivation system. The light fraction was shown to be sensitive to soil cultivation and can be considered indicative of soil degradation. Light-fraction analysis by Fourier transform infrared spectroscopy (FTIR) allowed the study of changes in the chemical structure of these fractions under different uses and management practices. Occluded light fraction was shown to be more recalcitrant and condensed than the free light fraction. The surface layer in the conventional cultivation system has a more aromatic and condensed free light fraction than in no-tillage system. In general, the upper layers were less aromatic than the deepest ones.
  • Authors:
    • Antle, J. M.
    • Ogle, S. M.
  • Source: Climatic Change
  • Volume: 111
  • Issue: 3/4
  • Year: 2012
  • Summary: Previous research has demonstrated that soil carbon sequestration through adoption of conservation tillage can be economically profitable depending on the value of a carbon offset in a greenhouse gas (GHG) emissions market. However adoption of conservation tillage also influences two other potentially important factors, changes in soil N2O emissions and CO2 emissions attributed to changes in fuel use. In this article we evaluate the supply of GHG offsets associated with conservation tillage adoption for corn-soy-hay and wheat-pasture systems of the central United States, taking into account not only the amount of carbon sequestration but also the changes in soil N2O emission and CO2 emissions from fuel use in tillage operations. The changes in N2O emissions are derived from a meta-analysis of published studies, and changes in fuel use are based on USDA data. These are used to estimate changes in global warming potential (GWP) associated with adoption of no-till practices, and the changes in GWP are then used in an economic analysis of the potential supply of GHG offsets from the region. Simulation results demonstrate that taking N2O emissions into account could result in substantial underestimation of the potential for GHG mitigation in the central U.S. wheat pasture systems, and large over-estimation in the corn-soy-hay systems. Fuel use also has quantitatively important effects, although generally smaller than N2O. These findings suggest that it is important to incorporate these two effects in estimates of GHG offset potential from agricultural lands, as well as in the design of GHG offset contracts for more complete accounting of the effect that no-till adoption will have on greenhouse gas emissions.
  • Authors:
    • Grace, P. R.
    • Basso, B.
  • Source: Agricultural Systems
  • Volume: 105
  • Issue: 1
  • Year: 2012
  • Authors:
    • Blanco-Canqui, H.
    • Claassen, M. M.
    • Presley, D. R.
  • Source: Agronomy Journal
  • Volume: 104
  • Issue: 1
  • Year: 2012
  • Summary: Impact of cover crops (CCs) on winter wheat ( Triticum aestivum L.) and grain sorghum [ Sorghum bicolor (L.) Moench] yields is not well understood. We assessed crop yield and its relationships with CC-induced changes in soil properties for a 15-yr CC experiment in wheat-sorghum rotation at 0, 33, 66, and 100 kg ha -1 of N application in south central Kansas. Hairy vetch ( Vicia villosa Roth) was used as a winter CC from 1995 to 2000, while sunn hemp (SH; Crotalaria juncea L.) and late-maturing soybean [LMS; Glycine max (L.) Merr.] were used as summer CCs in no-till from 2002 to 2008. Summer CCs increased crop yields particularly at low rates of N application. At 0 kg N ha -1, SH increased sorghum yield by 1.18 to 1.54 times, while wheat yield increased by 1.60 times in the first year (2004) after CC establishment relative to non-CC plots. At 66 kg N ha -1, SH had no effects on sorghum yield, but it increased wheat yield in 2 of 3 yr. Cover crops increased soil total N pool by 270 kg ha -1 for the 0- to 7.5-cm depth. Crop yield increased with the CC-induced decrease in soil maximum compactibility (soil's susceptibility to compaction) and soil temperature, and increase in soil aggregate stability, soil organic carbon (SOC) and total N concentration, and soil water content, particularly at 0 kg N ha -1. Principal component analysis (PCA) selected soil compactibility and total N as the best yield predictors. Inclusion of summer legume CCs in no-till fixes N, increases crop yield, and improves soil-crop relationships.
  • Authors:
    • Briedis, C.
    • Sa, J. C. de M.
    • Caires, E. F.
    • Navarro, J. de F.
    • Inagaki, T. M.
    • Boer, A.
    • Ferreira, A. de O.
    • Quadros Neto, C.
    • Canalli, L. B.
    • Santos, J. B. dos
  • Source: Soil Science Society of America Journal
  • Volume: 76
  • Issue: 1
  • Year: 2012
  • Summary: In a no-till system (NTS) on naturally acidic soils, surface liming is essential to neutralize soil acidity and increases crop productivity. As a result, the soil organic matter (SOM) pools of the soil surface layers may change, reflecting increased C inputs by crop residues. The objective of this study was to quantify changes in SOM pools and the rate of C sequestration that occur in response to surface liming in a long-term NTS experiment. The experiment was conducted in an Oxisol in southern Brazil. The treatments consisted of the application of 0 or 6 Mg ha -1 of dolomitic lime on the soil surface in 1993 and a reapplication of 0 or 3 Mg ha -1 of dolomitic lime in 2000 to plots with or without the previous lime application. Liming caused total organic C (TOC) accumulation, especially in the 0- to 2.5-cm layer. The amount of TOC stored in the 20-cm layer was 49.9, 52.9, 52.7, and 57.5 Mg ha -1 in the control, 6+0, 0+3, and 6+3 Mg ha -1 treatments, respectively. The levels of particulate organic C (POC) and mineral-associated organic C (MAOC) in the SOM were also enhanced by liming. The increase in POC was directly related ( R2=0.99, P=0.002) to the accumulation of C from crop residues, which was greater in the plots receiving lime treatment. There were positive correlations between TOC and C extractable with hot water, total polysaccharides, and labile polysaccharides. The correlation analysis also demonstrated that TOC was more tightly correlated with POC than with MAOC, indicating a greater influence of the labile fraction on the increase in TOC with surface liming.
  • Authors:
    • Caires, E. F.
    • Joris, H. A. W.
    • Churka, S.
    • Zardo Filho, R.
  • Source: Brazilian Archives of Biology and Technology
  • Volume: 55
  • Issue: 2
  • Year: 2012
  • Summary: The aim of this work was to study the effects of organic and mineral fertilizers at sowing (without fertilizers, organic poultry litter fertilizer on the surface and mineral NK+reactive natural phosphate from Arad and NK+triple superphosphate in the furrow) and topdressing (without fertilizers, organic poultry litter fertilization and urea) on chemical attributes of a no-till Oxisol and nutrition and yield of maize landrace ( Zea mays L.), Carioca variety in a field experiment. Results revealed that P content (Mehlich 1 and resin) was increased in the soil surface layer with organic poultry litter fertilizer on the surface at sowing. Mineral fertilizer in the sowing furrow could be replaced by organic fertilizer with poultry litter on the surface, but topdressing fertilization with urea resulted better N nutrition for the plants and higher grains yield than the organic poultry litter fertilization.