• Authors:
    • Belle, R. A.
    • Dutra, L. M. C.
    • Konig, O.
    • Kuss, R. C. R.
    • Roggia, S.
    • Sturmer, G. R.
  • Source: Ciência Rural
  • Volume: 38
  • Issue: 4
  • Year: 2008
  • Summary: The effects of irrigation (supplied throughout the crop growth period or during critical periods only) and plant density (250 000 or 400 000 plants/ha) on the grain yield of soyabean were studied from January to May 2005 in Santa Maria, Rio Grande do Sul, Brazil. The grain yield did not significantly vary between the plants irrigated throughout the growth period and plants irrigated during critical periods only. The grain yield of non-irrigated plants increased by 21% when the population was increased to 400 000 plants/ha.
  • Authors:
    • Reddy, K. N.
    • Zablotowicz, R. M.
    • Locke, M. A.
  • Source: Pest Management Science
  • Volume: 64
  • Issue: 4
  • Year: 2008
  • Summary: BACKGROUND: Conservation practices often associated with glyphosate-resistant crops, e.g. limited tillage and crop cover, improve soil conditions, but only limited research has evaluated their effects on soil in combination with glyphosate-resistant crops. It is assumed that conservation practices have similar benefits to soil whether or not glyphosate-resistant crops are used. This paper reviews the impact on soil of conservation practices and glyphosate-resistant crops, and presents data from a Mississippi field trial comparing glyphosate-resistant and non-glyphosate-resistant maize (Zea mays L.) and cotton (Gossypium hirsutum L.) under limited tillage management. RESULTS: Results from the reduced-tillage study indicate differences in soil biological and chemical properties owing to glyphosate-resistant crops. Under continuous glyphosate-resistant maize, soils maintained greater soil organic carbon and nitrogen as compared with continuous non-glyphosate-resistant maize, but no differences were measured in continuous cotton or in cotton rotated with maize. Soil microbial community structure based on total fatty acid methyl ester analysis indicated a significant effect of glyphosate-resistant crop following 5 years of continuous glyphosate-resistant crop as compared with the non-glyphosate-resistant crop system. Results from this study, as well as the literature review, indicate differences attributable to the interaction of conservation practices and glyphosate-resistant crop, but many are transient and benign for the soil ecosystem. CONCLUSIONS: Glyphosate use may result in minor effects on soil biological/chemical properties. However, enhanced organic carbon and plant residues in surface soils under conservation practices may buffer potential effects of glyphosate. Long-term field research established under various cropping systems and ecological regions is needed for critical assessment of glyphosate-resistant crop and conservation practice interactions. Published in 2008 by John Wiley & Sons, Ltd.
  • Authors:
    • Balkcom, K. S.
    • Delaney, D. P.
    • Mitchell, C. C.
  • Source: Agronomy Journal
  • Volume: 100
  • Issue: 5
  • Year: 2008
  • Summary: After more than 110 yr, the Old Rotation experiment on the campus of Auburn University in Alabama continues to document the long-term effects of crop rotation and winter legume cover crops on sustainable cotton (Gossypium hirsutum L.) production in the southeastern United States. Long-term yields indicate that winter legumes are as effective as fertilizer N in producing maximum cotton yields and increasing soil organic carbon (SOC). Higher SOC resulted in higher crop yields. However, rotating cotton with corn (Zea mays L.) in a 2-yr rotation or with corn, winter wheat (Triticum aestivum L.), and soybean [Glycine max. (L.) Merr.] in a 3-yr rotation produced little long-term cotton yield advantage beyond that associated with SOC. Cotton yields without winter legumes nor fertilizer N are only slightly higher than they were 110 yr ago. Nonirrigated corn grain yields in rotation with cotton are typically low for central Alabama and appear limited by N. Yields of all crops on the Old Rotation increased with increasing rates of P and K through the 1950s. Since adoption of in-row subsoiling, high-residue, conservation tillage, and genetically modified cultivars; in 1997, all crops have produced their highest, nonirrigated, recorded yields since the experiment began: 1910 kg cotton lint ha(-1) in 2006, 14.8 Mg corn grain ha(-1) in 1999, 6.34 Mg wheat ha-1 in 2001, and 4.50 Mg soybean ha(-1) in 2004.
  • Authors:
    • Nguyen, V. T.
    • Valentin, C.
    • Jouquet, P.
    • Orange, D.
    • Podwojewski, P.
    • Janeau, J. L.
    • Tran, D. T.
  • Source: CATENA
  • Volume: 74
  • Issue: 2
  • Year: 2008
  • Summary: Two consecutive years of investigation on soil surface features, surface runoff and soil detachment within 1-m(2) microplots on 40% slope highlighted the effects of land-use change, vegetation cover and biological activity on the water pathways in Northern Vietnam. Three replicate plots were setup on each of five land-uses: cassava (CAS), grass fodder of Bracharia ruziziensis (BRA), a 3-year old fallow (FAL), tree stands of Acacia mangium and Venicia montana (FOR), and a fallow with regrowth of Eucalyptus regularly cut (EUC). The second year, two of the microplots under FAL and EUC were treated with herbicide (FALh, EUCh), one of them was burnt (FALh+b, EUCh+b). The highest yearly surface runoff coefficient of 16%, and soil detachment rate of 700 g m(-2) yr(-1) in average with a maximum of 1305 g m(-2) yr(-1) have been recorded under CAS. On FALh and FALh+b, runoff ratios were 8.7 and 13.5%, respectively and detachment rates were 86 and 389 g m(-2). On FAL and BRA the yearly runoff ratio varied from 5.9 to 9.8% but the detachment rate was limited at 24 to 35 g m(-2). FOR and EUC annual runoff was
  • Authors:
    • Reddy, K. C.
    • Tazisong, I. A.
    • Nyakatawa, E. Z.
    • Senwo, Z. N.
    • Sainju, U. M.
  • Source: Journal of Environmental Quality
  • Volume: 37
  • Issue: 3
  • Year: 2008
  • Summary: Quantification of soil carbon (C) cycling as influenced by management practices is needed for C sequestration and soil quality improvement. We evaluated the 10-yr effects of tillage, cropping system, and N source on crop residue and soil C fractions at 0-to 20-cm depth in Decatur silt loam (clayey, kaolinitic, thermic, Typic Paleudults) in northern Alabama, USA. Treatments were incomplete factorial combinations of three tillage practices (no-till [NT], mulch till [MT], and conventional till [CT]), two cropping systems (cotton [Gossypium hirsutum L.]-cotton-corn [Zea mays L.] and rye [Secale cereale L.]/cotton-rye/cotton-corn), and two N fertilization sources and rates (0 and 100 kg N ha(-1) from NH4NO3 and 100 and 200 kg N ha(-1) from poultry litter). Carbon fractions weresoil organic C (SOC), particulate organic C (POC), microbial biomass C (MBC), and potential C mineralization (PCM). Crop residue varied among treatments and years and total residue from 1997 to 2005 was greater in rye/cottoil-rye/cotton-corn than in cotton-cotton-corn and greater with NH4NO3 than with poultry litter at 100 kg N ha(-1). The SOC content at 0 to 20 cm, after 10 yr was greater with poultry litter than with NH4NO3 in NT and CT, resulting in a C sequestration rate of 510 kg C ha(-1) yr(-1) with poultry litter compared with -120 to 147 kg C ha(-1) yr(-1) with NH4NO3. Poultry litter also increased PCM and MBC compared with NH4NO3. Cropping increased SOC, POC, and PCM compared with fallow in NT Long-term poultry litter application or continuous cropping increased soil C storage and microbial biomass and activity compared with inorganic N fertilization or fallow, indicating that these management practices can sequester C, offset atmospheric CO2 levels, and improve soil and environmental quality.
  • Authors:
    • Schlindwein, J. A.
    • Gianello, C.
  • Source: Revista Brasileira de Ciência do Solo
  • Volume: 32
  • Issue: 5
  • Year: 2008
  • Summary: The change of cultivation systems from conventional to no-tillage, the change in soil sampling depth and the higher crop yields over time can influence the critical P content, fertility ranges and fertilizer doses recommended for crops. This study calibrated the soil P tests, Mehlich-1, Mehlich-3 and anion-exchange (AER) resin for soyabean, wheat and maize plants cultivated under no-tillage system, and to estimate the P fertilizer amounts for a maximum economic yield. Soil samples and yield results from several experiments under no-till and different P doses, conducted by institutions of education, research and extension of the state of Rio Grande do Sul, Brazil, were used. The calibration curves were fitted using non-linear model functions, and the levels of soil fertility and fertilizer doses for a maximum economic yield were inferred. Results indicated that the average increases in maize, wheat and soyabean yields were 47.1, 12.4 and 7.2 kg/ha per kg of P 2O 5, respectively; the determination coefficients between the relative yield and soil P concentrations were higher when the soils were separated by texture classes and were highest in the 0-10 cm than the 0-20 cm layer; the critical values of P, based on Mehlich-1 were 7.5, 15.0 and 21.0 mg/kg in the 0-20 cm layer, and of 16.0, 28.0 and 40.0 mg/kg in the 0-10 cm layer in the clay classes 1, 2 and 3, respectively. Phosphorus fertility ranges were wider by Mehlich-3 and AER as compared to Mehlich-1. The quantities of P fertilizer were higher for soyabean and maize when compared to the currently recommended quantities. The critical P concentrations are higher in soils under no-tillage with soyabean, wheat and maize in the 0-20 as well as the 0-10 cm layer. The fertility ranges by resin and Mehlich-3 were wider than by Mehlich-1. The fertilizer P quantities are higher for soyabean and maize grown under no-tillage.
  • Authors:
    • Alves, M. C.
    • Arf, O.
    • Silva, M. G. da
    • Buzetti, S.
  • Source: Bragantia
  • Volume: 67
  • Issue: 2
  • Year: 2008
  • Summary: The soil physical properties are influenced by different soil tillage as well as by crop rotation. Field studies were conducted in Selviria, Mato Grosso do Sul, Brazil, in 2003/04, to evaluate the shoot dry matter production, soil covering percentage and the influence of crop rotation and tillage system on soil physical properties of a Rhodic Hapludox and to evaluate irrigated winter common bean yield. The treatments consisted of soil tillage systems (heavy harrow, chisel plough and no-tillage) and 6 rotations sown in the summer (maize, maize + black velvet bean, maize + brachiaria grass, soyabean, rice and sunn hemp). The crop rotations that presented larger soil coverage and shoot dry matter production were sunn hemp, maize + black velvet bean, maize + braquiaria grass and maize. No-tillage resulted in larger values of penetration resistance at 0.00-0.10 m layer. Except for macroporosity at the 0-0,1 m layer, the properties humidity, macroporosity, microporosity and total porosity of soil were not influenced by soil tillage systems. Despite differences in some yield components of common bean due to certain soil tillage or crop succession, the irrigated winter common bean crop yield was not affected.
  • Authors:
    • Follett, R. F.
    • Alley, M. M.
    • Spargo, J. T.
    • Wallace, J. V.
  • Source: Soil & Tillage Research
  • Volume: 100
  • Issue: 1/2
  • Year: 2008
  • Summary: Carbon sequestration in agroecosystems represents a significant opportunity to offset a portion of anthropogenic CO 2 emissions. Climatic conditions in the Virginia coastal plain and modern production practices make it possible for high annual photosynthetic CO 2 fixation. There is potential to sequester a substantial amount of C, and concomitantly improve soil quality, with the elimination of tillage for crop production in this region. The objectives of our research were to: (1) measure C sequestration rate with continuous no-till management of grain cropping systems of the Virginia middle coastal plain; (2) determine the influence of biosolids application history on C content and its interaction with tillage management; and (3) evaluate the impact of continuous no-till C stratification as an indicator of soil quality. Samples were collected from 63 sites in production fields using a rotation of corn ( Zea mays L.)-wheat ( Triticum aestivum L.) or barley ( Hordeum vulgare L.)/soybean double-crop ( Glysine max L.) across three soil series [Bojac (coarse-loamy, mixed, semiactive, thermic Typic Hapludults), Altavista (fine-loamy, mixed semiactive, thermic Aquic Hapludults), and Kempsville (fine-loamy, siliceous, subactive, thermic Typic Hapludults)] with a history of continuous no-till management ranging from 0 to 14 years. Thirty-two of the sites had a history of biosolids application. Five soil cores were collected at each site from 0-2.5, 2.5-7.5 and 7.5-15 cm and analyzed for bulk density and soil C. Bulk density in the 0-2.5 cm layer decreased and C stratification ratio (0-2.5 cm:7.5-15 cm) increased with increasing duration of continuous no-till due to the accumulation of organic matter at the soil surface. A history of biosolids application resulted in an increase of 4.191.93 Mg C ha -1 (0-15 cm). Continuous no-till resulted in the sequestration of 0.3080.280 Mg C ha -1 yr -1 (0-15 cm). Our results provide quantitative validation of the C sequestration rate and improved soil quality with continuous no-till management in the region using on-farm observations.
  • Authors:
    • Suzuki, L. G. A. S.
    • Alves, M. C.
    • Suzuki, L. E. A. S.
    • Rodrigues, R. A. F.
  • Source: Científica, Jaboticabal
  • Volume: 36
  • Issue: 2
  • Year: 2008
  • Summary: The objective of this study was to verify the biomass yield potential of different cover crops in a Cerrado region, in Selviria, Mato Grosso do Sul, Brazil. The work was conducted in the Experimental University Farm of the Paulista State University (UNESP). The experimental design was the randomized complete blocks in strips with splitsplit plot: the plots were the cover crops Mucuna aterrima, Pennisetum americanum, Crotalaria juncea, Cajanus cajan and a fallow area; the split plots were the no-tillage and the conventional tillage, and the splitsplit plots were corn ( Zea mays L.), soybean ( Glycine max (L.) Merrill), and cotton ( Gossypium hirsutum L.) crops. In the winter irrigated Phaseolus vulgaris L. was the crop. In the spring/summer season the cover crop with the greatest biomass yield was Pennisetum americanum. Crotalaria juncea and the fallow area showed medium results while Mucuna aterrima and Cajanus cajan were those with the least yields. Pennisetum americanum was the crop cover with the biggest production potential of dry biomass. The cultivation systems did not influence the dry biomass of the cover crops. Only Pennisetum americanum production was influenced by crop sequence.
  • Authors:
    • Egli, D. B.
  • Source: Field Crops Research
  • Volume: 106
  • Issue: 1
  • Year: 2008
  • Summary: The increases in crop yield that played an important role in maintaining adequate food supplies in the past may not continue in the future. Soybean ( Glycine max L. Merrill) county yield trends (1972-2003) were examined for evidence of plateaus using data (National Agricultural Statistics Service) for 162 counties (215 data sets) in six production systems [Iowa, Nebraska (irrigated and non-irrigated), Kentucky and Arkansas (irrigated and non-irrigated)] representing a range in yield potential. Average yield (1999-2003) was highest in irrigated production in Nebraska (3403 kg ha -1) and lowest in non-irrigated areas in Arkansas (1482 kg ha -1). Average yield in the highest yielding county in each system was 31-88% higher than the lowest. Linear regression of yield versus time was significant ( P=0.05) in 169 data sets and a linear-plateau model reached convergence (with the intersection point in the mid-1990s) in 35 of these data sets, but it was significantly ( P=0.10) better in only three data sets (