• Authors:
    • Angelocci, L. R.
    • Marin, F. R.
  • Source: Agricultural Water Management
  • Volume: 98
  • Issue: 6
  • Year: 2011
  • Summary: Crop evapotranspiration (ETc) was measured as evaporative heat flux from an irrigated acid lime orchard ( Citrus latifolia Tanaka) using the aerodynamic method. Crop transpiration (T) was determined by a stem heat balance method. The irrigation requirements were determined by comparing the orchard evapotranspiration (ETc) and T with the reference evapotranspiration (ETo) derived from the Penman-Monteith equation, and the irrigation requirements were expressed as ETc/ETo (Kc) and T/ETo (Kcb) ratios. The influence of inter-row vegetation on the ETc was analyzed because the measurements were taken during the summer and winter, which are periods with different regional soil water content. In this study, the average Kc values obtained were 0.65 and 0.24 for the summer and winter, respectively. The strong coupling of citrus trees to the atmosphere and the sensitivity of citrus plants to large vapor pressure deficits and air/leaf temperatures caused variations in the Kcb in relation to the ETo ranges. During the summer, the Kcb value ranged from 0.34 when the ETo exceeded 5 mm d -1 to 0.46 when the ETo was less than 3 mm d -1.
  • Authors:
    • Altieri, M. A.
    • Lana, M. A.
    • Bittencourt, H. V.
    • Kieling, A. S.
    • Comin, J. J.
    • Lovato, P. E.
  • Source: Journal of Sustainable Agriculture
  • Volume: 35
  • Issue: 8
  • Year: 2011
  • Summary: In Santa Catarina, southern Brazil, family farmers modified the conventional no-till system by flattening cover crop mixtures on the soil surface as a strategy to reduce soil erosion and lower fluctuations in soil moisture and temperature, improve soil quality, and enhance weed suppression and crop performance. During 2007 and 2008, we conducted three experiments aimed at understanding the processes and mechanisms at play in successful organic conservation tillage systems (OCT), especially the underpinnings of ecological weed suppression, a key advantage of OCT systems over conventional no-till systems. Our results, as well as farmers observations, suggest that cover crops can enhance weed suppression and hence crop productivity through physical interference and allelopathy and also a host of effects on soil quality, fertility, and soil moisture that we did not measure. Results from the three trials indicate that the best cover crop mixture should include a significant proportion of rye, vetch, and fodder radish as these mixtures produce large biomass, and are readily killed by rolling forming a thick mulch sufficient to provide effective weed control in the subsequent vegetable crop.
  • Authors:
    • Basso, F. C.
    • Andreotti, M.
    • P. e Carvalho, M. de
    • Lodo, B. N.
    • Montanari, R.
  • Source: Revista Brasileira de Ciências Agrárias
  • Volume: 6
  • Issue: 3
  • Year: 2011
  • Summary: With the use of no-till farming, the soil physical and chemical properties are constantly changed, directly reflecting on plant yield and composition. In 2006, in the municipality of Selviria, Mato Grosso do Sul, Brazil, the linear and spatial correlations between the plant attributes and the attributes of a Rhodic Hapludox were analyzed. The objective of this work was to select among the analyzed soil attributes the one that best explained the variability of agricultural yield. For this, the geostatistical grid was installed for the soil and plant collection in 124 sampling points in a 4,000 m2 area. In the soil samples, collected at three depths (0-0.10 m, 0.20-0.30 m and 0.10-0.20 m), the microporosity, macroporosity, total porosity, bulk density and organic matter content were determined. In the plant, the yield (fresh and dry matter) and the crude protein content were determined. From the spatial viewpoint, there was a direct correlation between the dry matter yield and the soil organic matter content, as well as an inverse correlation between the crude protein content and the macroporosity and total porosity of soil. Therefore, the surface organic matter content behaved as a soil chemical quality indicator to estimate the dry matter yield of Cajanus cajan L. under the conditions of this research.
  • Authors:
    • Caires, E. F.
    • Garbuio, F. J.
    • Churka, S.
    • Joris, H. A. W.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 6
  • Year: 2011
  • Summary: Gypsum has been used in tropical and subtropical agriculture when subsoil acidity is an important yield-limiting factor. However, the conditions that promote increased crop yield as a result of gypsum addition in no-till (NT) systems still remain unclear. A field trial examined the effects of newly and previously surface-applied gypsum in a long-term NT system on the soil chemical properties and nutrition and yield of corn ( Zea mays L.), wheat ( Triticum aestivum L.), and soybean [ Glycine max (L.) Merr.] on a clayey Rhodic Hapludox in Parana State, Brazil. Gypsum was surface-applied at 0 and 6 Mg ha -1 in 2004 on plots that had received gypsum previously at 0, 3, 6, and 9 Mg ha -1 in 1998. Surface-applied gypsum newly and previously improved exchangeable Ca and SO 4-S availability throughout the soil profile, and increased the cumulative grain yield of the crops. Exchangeable K losses through leaching caused by gypsum application were low, and a larger mobility of exchangeable Mg as compared with exchangeable K in soil was found as a result of gypsum addition. An increase in Ca content in the corn, wheat, and soybean leaves, and in S content in the corn and wheat leaves occurred following the gypsum application. The use of gypsum showed economic viability to maximize crop grain production in a long-term NT soil with a sufficient level of exchangeable Ca (≥8 mmol c dm -3) and low levels of exchangeable Al (≤4 mmol c dm -3) and Al saturation (≤15%) in the subsoil layers (20-60 cm).
  • Authors:
    • Calonego, J. C.
    • Rosolem, C. A.
  • Source: Revista Brasileira de Ciência do Solo
  • Volume: 35
  • Issue: 3
  • Year: 2011
  • Summary: Soil water availability to plants is affected by soil compaction and other variables. The Least Limiting Water Range (LLWR) comprises soil physical variables affecting root growth and soil water availability, and can be managed by either mechanical or biological methods. There is evidence that effects of crop rotations could last longer than chiseling, so the objective of this study was to assess the effect of soil chiseling or growing cover crops under no-till (NT) on the LLWR. Crop rotations involving triticale (X Triticosecale) and sunflower (Helianthus annuus) in the fall-winter associated with millet (Pennisetum glaucum), sorghum (Sorghum bicolor) and sunn hemp (Crotalariajuncea) as cover crops preceding soybean (Glycine max) were repeated for three consecutive years. In the treatment with chiseling (performed. only in the first year), the area was left fallow between the fall-winter and summer crops. The experiment was carried out in Botucatu, Sao Paulo State, Brazil, from 2003 to 2006 on a Typic Rhodudalf. The LLWR was determined in soil samples taken from the layers 0-20 cm and 20-40 cm, after chemical desiccation of the cover crops in December of the first and third year of the experiment. Chiseling decreases soil bulk density in the 0-20 cm soil layer, increasing the LLWR magnitude by lowering the soil water content at which penetration resistance reaches 2.0 MPa; this effect is present up to the third year after chiseling and can reach to a depth of 0.40 in. Crop rotations involving sunflower + sunn hemp, triticale + millet and triticale + sunn hemp for three years prevented soil bulk density from exceeding the critical soil bulk density in the 0-0.20 in layer. This effect was observed to a depth of 0.40 m after three years of chiseling under crop rotations involving forage sorghum. Hence, chiseling and some crop rotations under no tillage are effective in increasing soil quality assessed by the LLWR.
  • Authors:
    • Campos, L. P.
    • Leite, L. F. C.
    • Maciel, G. A.
    • Iwata, B. de F.
    • Nobrega, J. C. A.
  • Source: Pesquisa Agropecuária Brasileira
  • Volume: 46
  • Issue: 12
  • Year: 2011
  • Summary: The objective of this work was to evaluate the chemical attributes in a Xanthic Ferralsol under different tillage systems in the cerrado of Piaui State, Brazil. Four tillage systems were evaluated: three-year-old conventional tillage; no-tillage with three (NT3) and five years old (NT5), using millet as cover crop; and no-tillage with nine years old (NT9), of which seven years used millet as cover crop and two used forage. A native cerrado area was taken as reference. Soil samples were collected in wet and dry seasons at soil depths, 0.00-0.05, 0.05-0.10, 0.10-0.20 and 0.20-0.40 m, and analyzed for pH, Al 3+, H+Al, Ca 2+, Mg 2+, K +, sum of bases (SB), effective (t) and potential (T) cation exchangeable capacity, base (BS) and Al 3+ saturation (m%), available P and total organic carbon (TOC). The system NT9 showed the highest values of pH and lowest of Al 3+, H+Al, and m%. The highest values for Ca 2+, K, SB, t, T, V% and P, were observed under NT5 and NT9, until 0.20 m depth. The highest TOC contents were verified also under NT5 and NT9, except for 0.00-0.05 m soil depth. Organic matter accumulation associated with pasture under no-till increases TOC content at deeper soil layers in the dry period.
  • Authors:
    • Costa, M. S. S. de M.
    • Pivetta, L. A.
    • Steiner, F.
    • Costa, L. A. de M.
    • Castoldi, G.
    • Gobbi, F. C.
  • Source: Revista Brasileira de Ciencias Agrarias
  • Volume: 6
  • Issue: 4
  • Year: 2011
  • Summary: Crop systems and fertilization sources can affect the chemical properties of the soil and, consequently, its fertility. With the aim of evaluating the effect of such management practices, soil samples collected at 0.0-0.10; 0.10-0.20; and 0.20-0.40 m in depth were collected and analyzed in the second year of an experiment installed in 2006 in a Rhodic Hapludox under no-till farming, located in the Agronomic Experimental Station of UNIOESTE, in the city of Marechal Candido Rondon, Parana, Brazil. The experiment consisted of two crop systems (with and without rotation of cover crops) and three fertilization sources (mineral, organic and mineral+organic). The organic and mineral+organic fertilizations consisted of the application of animal manure alone and animal manure mixed with mineral fertilizer, respectively. The values of pH, exchangeable potassium (K +) and cation exchange capacity (CEC) were not affected by the different crop systems, related to the application of different fertilization sources. However, they did influence the organic matter contents (OM), potential acidity (H ++Al 3+), exchangeable aluminum (Al 3+), phosphorus (P), calcium (Ca 2+), magnesium (Mg 2+), and the bases sum and saturation (V%). The organic and mineral+organic fertilizations, with animal manure promoted the highest increase in soil Ca and Mg.
  • Authors:
    • Crusciol, C. A. C.
    • Garcia, . A.
    • Castro, G. S. A.
    • Rosolem, C. A.
  • Source: Revista Brasileira de Ciência do Solo
  • Volume: 35
  • Issue: 6
  • Year: 2011
  • Summary: Especially under no-tillage, subsuface soil acidity has been a problem, because it depends on base leaching, which has been associated with the presence of low molecular weigth organic acids and companion anions. The objective of this study was to evaluate exchangeable base cation leaching as affected by surface liming along with annual urea side-dressing of maize and upland rice. Treatments consisted of four lime rates (0, 1500, 3000, and 6000 kg ha -1) combined with four nitrogen rates (0, 50, 100, and 150 kg ha -1) applied to maize ( Zea mays) and upland rice ( Oryza sativa), in two consecutive years. Maize was planted in December, three months after liming. In September of the following year, pearl millet ( Pennisetum glaucum) was planted without fertilization and desiccated 86 days after plant emergence. Afterwards, upland rice was grown. Immediately after upland rice harvest, 18 months after surface liming, pH and N-NO 3-, N-NH 4+, K, Ca, and Mg levels were evaluated in soil samples taken from the layers 0-5, 5-10, 10-20 and 20-40 cm. Higher maize yields were obtained at higher N rates and 3000 kg ha -1lime. Better results for upland rice and pearl millet yields were also obtained with this lime rate, irrespective of N levels. The vertical mobility of K, Ca and Mg was higher in the soil profiles with N fertilization. Surface liming increased pH in the upper soil layers causing intense nitrate production, which was leached along with the base cations.
  • Authors:
    • Bustamante, M. M. da C.
    • Cruvinel, E. B. F.
    • Kozovits, A. R.
    • Zepp, R. G.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 144
  • Issue: 1
  • Year: 2011
  • Summary: In the last 40 years, a large area of savanna vegetation in Central Brazil (Cerrado) has been converted to agriculture, with intensive use of fertilizers, irrigation and management practices. Currently, the Cerrado is the main region for beef and grain production in Brazil. However, the consequences of these agricultural practices on NO, N 2O and CO 2 emissions from soil to atmosphere are still poorly investigated. The objectives of this study were to quantify soil emissions of NO-N, N 2O-N and CO 2-C in different no-till cultivation systems in comparison with native savanna vegetation. The agricultural areas included: (a) the maize and Brachiaria ruzizienses intercropping system followed by irrigated bean in rotation; (b) soybean followed by natural fallow; and (c) cotton planting over B. ruzizienses straw. The study was performed from August 2003 to October 2005 and fluxes were measured before and after planting, after fertilizations, during the growing season, before and after harvesting. NO-N fluxes in the soybean field were similar to those measured in the native vegetation. In the cornfield, higher NO-N fluxes were measured before planting than after planting and pulses were observed after broadcast fertilizations. During Brachiaria cultivation NO-N fluxes were lower than in native vegetation. In the irrigated area (bean cultivation), NO-N fluxes were also significantly higher after broadcast fertilizations. Most of the soil N 2O-N fluxes measured under cultivated and native vegetation were very low (<0.6 ng N 2O-N cm -2 h -1) except during bean cultivation when N 2O-N fluxes increased after the first and second broadcast fertilization with irrigation and during nodule senescence in the soybean field. Soil respiration values from the soybean field were similar to those in native vegetation. The CO 2-C fluxes during cultivation of maize and irrigated bean were twice as high as in the native vegetation. During bean cultivation with irrigation, an increase in CO 2-C fluxes was observed after broadcast fertilization followed by a decrease after the harvest. Significantly lower soil C stocks (0-30 cm depth) were determined under no-tillage agricultural systems in comparison with the stocks under savanna vegetation. Fertilizer-induced emission factors of N oxides calculated from the data were lower than those indicated by the IPCC as default.
  • Authors:
    • da Silva, D. A.
    • Ferreira de Souza, L. C.
    • Tadeu Vitorino, A. C.
    • Goncalves, M. C.
  • Source: Bragantia
  • Volume: 70
  • Issue: 1
  • Year: 2011
  • Summary: Soil physical degradation, like compaction, reduces water movement and root development. Soil structure is considered one of most importance to agriculture and closely related to it are other fundamental properties in soil-plant relationship. The objective of this study was to evaluate the effect of crop sequences on physical attributes. The research was realized in 2004/05 and 2005/06 growing seasons, in a Typic Clayey Rhodic Hopludox, under eight years of no-tillage system, at Dourados (MS). The experiment was a randomized complete block design, with three replications. Treatments were constituted by cover crops: sunflower (Helianthus annuus L.), sunnhemp (Crotalaria juncea L.), hairy vetch (Vicia villosa Roth), mixture of sunnhemp + black oat (Avena strigosa Schreb), and mixture of black oat + hairy vetch + oilseed radish (Raphanus sativus L. Var. oliferus Metzg). Differences were not observed in soil density, porosity and aggregation rate when it was cultivated with sunflower, hairy vetch, sunnhemp, or the mixtures. Differences were observed in soil physical properties between 0-5 cm layer and 5-10cm 10-20 cm layers, but no differences between 5-10 cm and 10-20cm layers. Soil carbon trend to higher contents in crops with high production of surface residues, although differences in carbon contents were insufficient to modify aggregation.