• Authors:
    • Benez, S.
    • Silva, P.
  • Source: Energia na Agricultura
  • Volume: 23
  • Issue: 1
  • Year: 2008
  • Summary: This work had as objective evaluate the penetration depth of cut disks (flat, corrugated and wavy) of seeder in different vegetable coverings (corn, sorghum, black oats, triticale and grass) and applied vertical loads (750, 1500, 2250 and 3000 N). The work was developed at University of Agronomic Sciences - UNESP of Botucatu in a soil classified like NITOSSOLO VERMELHO distroferrico. The experimental design used was in blocks at random with factorial outline (3 coulter disks and 4 vertical loads) and 4 repetitions. The results showed that for all vegetable covering, as larger is the vertical load applied adult as larger is the penetration depth of the coulter disks. The wavy disk cut obtained the smallest values of penetration depth in relation to the others. This happened due to smaller cut pressure in the straw. The largest values of penetration depth of the cut disks were obtained for the covering with straw of nabica following by the triticale, black oats, corn and sorghum. The seeder should be regulated with minimum load of seed and fertilizer so that happen the cash cuts of the straw during the sowing process.
  • Authors:
    • Pereira, M.
    • Torres, J.
  • Source: REVISTA BRASILEIRA DE CIENCIA DO SOLO
  • Volume: 32
  • Issue: 4
  • Year: 2008
  • Summary: A study with eight cover crops types was developed: pearl millet ( Pennisetum americanum [ Pennisetum glaucum] syn. tiphoydes), brachiaria grass ( Brachiaria brizantha [ Urochloa brizantha]), sorghum ( Sorghum bicolor), pigeonpea ( Cajanus cajan), sunn hemp ( Crotalarea juncea) and black oat ( Avena strigosa [ Avena nuda]), fallow land and conventional culture (control) in the experimental area of CEFET-Uberaba-MG, in a cerrado area to evaluate K accumulation and release. The dry mass production, crop residue decomposition in litter bags and K release were evaluated. A mathematical model was used to describe residue decomposition and K release, which calculates the decomposition constant (k) and half-time life. Pearl millet, sorghum and the sunn hemp were the cover crops that produced most dry matter while K accumulation was highest in the grasses. K release was highest in pearl millet, oats, brachiaria grass and sunn hemp in the first 42 days after handling. Brachiaria grass had the shortest half-time life and the highest K release rate.
  • Authors:
    • Fabian, A.
    • Pereira, M.
    • Torres, J.
  • Source: PESQUISA AGROPECUARIA BRASILEIRA
  • Volume: 43
  • Issue: 3
  • Year: 2008
  • Summary: This study investigated dry biomass production, decomposition rate and macronutrients release (N, P, Ca, Mg and S) of cover crops cultural residues, in a no-till savanna soil in Minas Gerais, Brazil. The cover crops tested were: pearl millet ( Pennisetum americanum syn. typhoides), brachiaria grass ( Brachiaria brizantha [Urochloa brizantha] cv. Marandu), sorghum ( Sorghum bicolor), pigeon pea ( Cajanus cajan), sunn hemp ( Crotalaria juncea) and black oat ( Avena nuda), compared to a fallow plot (control). The experiment was carried out in an Oxisol, medium texture. A randomized block design, in a split-plot array in time, with four replications, was used. Dry biomass production was evaluated 110 days after sowing. Decomposition rate was evaluated by litter bags containing cultural residues. Millet and sunn hemp were the cover crops (grass and legume) with the highest dry biomass production and N accumulation, in the two evaluation periods. The highest decomposition rate and nutrient release occurred at 42 days after desiccation. The highest values of half life were observed in dry period.
  • Authors:
    • Castoldi, G.
    • Gobbi, F.
    • Pivetta, L.
    • Costa, L.
    • Steiner, F.
    • Costa, M.
    • Tremea, A.
  • Source: Central theme, technology for all: sharing the knowledge for development. Proceedings of the International Conference of Agricultural Engineering, XXXVII Brazilian Congress of Agricultural Engineering, International Livestock Environment Symposium - ILES V
  • Year: 2008
  • Summary: The objective of this work was to evaluate the effect of two soil tillage systems (rotation and succession crops) and three fertilizations (mineral, organic and organomineral) in the wheat yield, under no-tillage system. The assay was conducted in the Experimental Station Prof. Dr. Antonio Carlos dos Santos Pessoa, located at the Nucleo of Experimental Station belonging to West Parana State University - Marechal Candido Rondon. In the winter of the 2006 was cropping the wheat in the plots in succession crops and black oat+radish+hairy vetch in the plots in rotation crops. The wheat received the mineral, organic and organomineral fertilization, while the cover crops weren't fertilized. In the summer was cropping corn in all the plots, receiving the three kind of fertilization. In the winter of the 2007 was cropping wheat in all the plots, receiving again the three kind of fertilization. The plant high and the weight of 100 grains weren't affected by the management systems and fertilizations. The succession system (wheat/corn/wheat) showed superior yield than the rotation system (green manure/corn/wheat). The organic manure showed superior hectoliter weight than mineral fertilization.
  • Authors:
    • Finger, J.
    • Gobbi, F.
    • Souza, J.
    • Conti, C.
    • Fey, E.
    • Vanin, J.
  • Source: Central theme, technology for all: sharing the knowledge for development. Proceedings of the International Conference of Agricultural Engineering, XXXVII Brazilian Congress of Agricultural Engineering, International Livestock Environment Symposium - ILES V
  • Year: 2008
  • Summary: The soil tillage is one of the most important agricultural operations, when used crops which the root depends system directly from the physical conditions of the soil. Aiming higher soil conservation, the use of plants of covering becomes an alternative to the maintenance of soil moisture and aggregates, improving too, characteristics such as resistance to penetration. The objective of the present work was evaluate properties of the soil and cultivation of cassava on different tillages and plants of covering. The experiment was conducted in the western region of Parana in Latosol red eutrophic. The experimental design was completely randomized in split plot, and 6 main plots of soil management systems: disk plow, chisel plow and offset disk harrow (followed by an offset leveling) in the months of April and August. The sub-plots were formed by plants of covering oat, Forage turnip and Without crop. The tillages with disk plow and chisel plow in August showed greater depth of furrow and seed cuttings of cassavas. Behavior similar happened to the soil moisture of 10 to 20 cm for the disk plow and the chisel plow in August. The tillages did not influence the final population of plants, number of stems per plant and percentage of plants fall. For plants of covering, the oats presented biggest difference in the soil moisture from 0 to 10 cm.
  • Authors:
    • Yu, T. -H.
    • Hayes, D.
    • Tokgoz, S.
    • Fabiosa, J.
    • Elobeid, A.
    • Dong, F.
    • Houghton, R. A.
    • Heimlich, R.
    • Searchinger, T. D.
  • Source: Science
  • Volume: 319
  • Issue: 5867
  • Year: 2008
  • Summary: Most prior studies have found that substituting biofuels for gasoline will reduce greenhouse gases because biofuels sequester carbon through the growth of the feedstock. These analyses have failed to count the carbon emissions that occur as farmers worldwide respond to higher prices and convert forest and grassland to new cropland to replace the grain (or cropland) diverted to biofuels. By using a worldwide agricultural model to estimate emissions from land-use change, we found that corn-based ethanol, instead of producing a 20% savings, nearly doubles greenhouse emissions over 30 years and increases greenhouse gases for 167 years. Biofuels from switchgrass, if grown on U.S. corn lands, increase emissions by 50%. This result raises concerns about large biofuel mandates and highlights the value of using waste products.
  • Authors:
    • Fargione,Joseph
    • Hill,Jason
    • Tilman,David
    • Polasky,Stephen
    • Hawthorne,Peter
  • Source: Science
  • Volume: 319
  • Issue: 5867
  • Year: 2008
  • Summary: Increasing energy use, climate change, and carbon dioxide (CO2) emissions from fossil fuels make switching to low-carbon fuels a high priority. Biofuels are a potential low-carbon energy source, but whether biofuels offer carbon savings depends on how they are produced. Converting rainforests, peatlands, savannas, or grasslands to produce food crop-based biofuels in Brazil, Southeast Asia, and the United States creates a "biofuel carbon debt" by releasing 17 to 420 times more CO2 than the annual greenhouse gas (GHG) reductions that these biofuels would provide by displacing fossil fuels. In contrast, biofuels made from waste biomass or from biomass grown on degraded and abandoned agricultural lands planted with perennials incur little or no carbon debt and can offer immediate and sustained GHG advantages.
  • Authors:
    • Barfoot, P.
    • Brookes, G.
  • Year: 2008
  • Authors:
    • Eriksen-Hamel, N. S.
    • Angers, D. A.
  • Source: Soil Science Society of America Journal
  • Volume: 72
  • Issue: 5
  • Year: 2008
  • Summary: While the adoption of no-till (NT) usually leads to the accumulation of soil organic C (SOC) in the surface soil layers, a number of studies have shown that this effect is sometimes partly or completely offset by greater SOC content near the bottom of the plow layer under full-inversion tillage (FIT). Our purpose was to review the literature in which SOC profiles have been measured under paired NT and FIT situations. Only replicated and randomized studies directly comparing NT and FIT for >5 yr were considered. Profiles of SOC had to be measured to at least 30 cm. As expected, in most studies SOC content was significantly greater (P < 0.05) under NT than FIT in the surface soil layers. At the 21- to 25-cm soil depth, however, which corresponds to the mean plowing depth for the data set (23 cm), the average SOC content was significantly greater under FIT than NT. Moreover, under FIT, greater SOC content was observed just below the average depth of plowing (26-35 cm). On average, there was 4.9 Mg ha(-1) more SOC under NT than FIT (P = 0.03). Overall, this difference in favor of NT increased significantly but weakly with the duration of the experiment (R-2 = 0.15, P = 0.05). The relative accumulation of SOC at depth under FIT could not be related to soil or climatic variables. Furthermore, the organic matter accumulating at depth under FIT appeared to be present in relatively stable form, but this hypothesis and the mechanisms involved require further investigation.
  • Authors:
    • Fabian, E.
    • Pegoraro, R.
    • Bertol, I.
    • Zoldan Junior, W.
    • Zavaschi, E.
    • Vazquez, E.
  • Source: REVISTA BRASILEIRA DE CIENCIA DO SOLO
  • Volume: 32
  • Issue: 1
  • Year: 2008
  • Summary: Surface soil roughness is affected by many factors, such as the residual effect of the soil management, tillage and rainfall erosivity and, together with the soil cover of crop residues, influences water erosion. The objective of this study was to determine the effects of a chiselling operation, together with rainfall erosivity, on soil surface roughness, from June 2005 to March 2006, in an aluminic Typical Hapludox, under the following soil management systems: bare soil under conventional tillage (BCT), cultivated soil under conventional tillage (CCT), no-tillage in a never-tilled soil with burnt plant residues (BNT), and traditional no-tillage (TNT). The crop sequence in the treatments CCT, BNT and TNT was black oat, soyabean, common vetch, maize, black oat, common bean, fodder radish, soyabean, common vetch, maize and black oat. Five simulated rain tests were applied, with a constant intensity of 64 mm h -1 and durations of 20, 30, 40, 50, and 60 min each. Natural rains during the experimental period accounted for 57 mm, between the 2nd and 3rd rainfall test; 21 mm, between the 3rd and 4th test; and, 30 mm, between the 4th and 5th test. The surface roughness was determined immediately before and immediately after the chiseling tillage, and immediately after each test of rain simulation. The original and linear soil surface roughness was not influenced by the management, unlike random roughness, at the end of a six-month fallow period. The original, linear and random roughness in different soil management systems was affected by a six-month fallow period, when the soil was subjected to chiselling. Random roughness was less influenced by soil slope than by tillage marks, which decreased with the increasing rainfall erosivity. The coefficient of decay of this kind of soil roughness was similar in the studied soil management systems under no tillage and conventional tillage.