• Authors:
    • Souza, L.
    • Silva, D.
  • Source: Revista Brasileira de Milho e Sorgo
  • Volume: 6
  • Issue: 2
  • Year: 2007
  • Summary: Brazil has been producing maize in almost all regions, although the costs of production increased in the last years. New techniques which provide economy without yield loss can motivate producers, as maize is an important culture used at crop rotation system. Green manure may reduce maize production costs, maily to the incorporation of nitrogen. Data from an experiment were used for these comparisons; treatments were conducted in Mato Grosso do Sul, Brazil in three precedent maize cultures (black oat, oilseed radish and hairy vetch) and six nitrogen fertilizers levels (zero, 50, 100, 150, 200 and 250 kg/ha). Maize after black oat showed damage when N 25 kg/ha was used, while increasing levels increased yield up to 150 kg/ha, wherein the maximum yield was 1233 kg/ha. Maize after oilseed radish showed under zero rate a yield of 1500 kg/ha, but MEE occurs at N 40 kg/ha. Maize after hairy vetch showed no response to N, so MEE occurs at zero N, where yield was 2100 kg/ha. Maize antecessor cultures that release more nitrogen could provide higher yield to the system with lower use of fertilizers.
  • Authors:
    • Mielniczuk, J.
    • Dieckow, J.
    • Zanatta, J.
    • Bayer, C.
    • Vieira, F.
    • He, Z.
  • Source: Soil & Tillage Research
  • Volume: 96
  • Issue: 1/2
  • Year: 2007
  • Summary: The carbon management index (CMI) is derived from the total soil organic C pool and C lability and is useful to evaluate the capacity of management systems to promote soil quality. However, the CMI has not been commonly used for this purpose, possible due to some limitations of the 333 mM KMnO 4-chemical oxidation method conventionally employed to determine the labile C fraction. We hypothesized, however, that physical fractionation of organic matter is an alternative approach to determine the labile C. The objectives of this study were (i) to assess the physical fractionation with density (NaI 1.8 Mg m -3) and particle-size separation (53 m mesh) as alternative methods to the KMnO 4-chemical oxidation (60 and 333 mM) in determining the labile C and thus the CMI, and (ii) to evaluate the capacity of long-term (19 years) no-till cropping systems (oat/maize: O/M, oat + vetch/maize: O + V/M, oat + vetch/maize + cowpea: O + V/M + C, and pigeon pea + maize: P + M) and N fertilization (0 and 180 kg N ha -1) to promote the soil quality of a Southern Brazilian Acrisol, using the CMI as the main assessment parameter. Soil samples were collected from 0 to 12.5 cm layer, and the soil of an adjacent native grassland was taken as reference. The mean annual C input of the cropping systems varied from 3.4 to 6.0 Mg ha -1 and the highest amounts occurred in legume-based cropping systems and N fertilized treatments. The C pool index was positively related to the annual C input ( r2=0.93, P
  • Authors:
    • Goncalves, P. de S. should be de Souza Gonçalves, Paulo Antonio
  • Volume: 20
  • Issue: 3
  • Year: 2007
  • Summary: Methods of controlling thrips in onion crops growing in Santa Catarina state, Brazil, which do not require or reduce the use of chemical insecticides are described, including (i) the cultivation of early cultivars which naturally escape the peak occurrence of the pest, (ii) adopting a system of direct (no-till) planting, (iii) growing cover crops such as mucuna ( Stizolobium [ Mucuna] spp.), Canavalia ensiformis, fodder rape ( Brassica napus), Avena strigosa [ A. nuda] and rye ( Secale cereale), and (iv) use of alternative substances as insecticides.
  • Authors:
    • Mielniczuk, J.
    • Vieira, F. C. B.
    • Dieckow, J.
    • Bayer, C.
    • Zanatta, J. A.
  • Source: Soil & Tillage Research
  • Volume: 94
  • Issue: 2
  • Year: 2007
  • Summary: Conservation management systems can improve soil organic matter stocks and contribute to atmospheric C mitigation. This study was carried out in a 18-year long-term experiment conducted on a subtropical Acrisol in Southern Brazil to assess the potential of tillage systems [conventional tillage (CT) and no-till (NT)], cropping systems [oat/maize (O/M), vetch/maize (V/M) and oat + vetch/maize + cowpea (OV/MC)] and N fertilization [0 kg N ha-1 year-1 (0 N) and 180 kg N ha-1 year-1 (180 N)] for mitigating atmospheric C. For that, the soil organic carbon (SOC) accumulation and the C equivalent (CE) costs of the investigated management systems were taken into account in comparison to the CT O/M 0 N used as reference system. No-till is known to produce a less oxidative environment than CT and resulted in SOC accumulation, mainly in the 0-5 cm soil layer, at rates related to the addition of crop residues, which were increased by legume cover crops and N fertilization. Considering the reference treatment, the SOC accumulation rates in the 0-20 cm layer varied from 0.09 to 0.34 Mg ha-1 year-1 in CT and from 0.19 to 0.65 Mg ha-1 year-1 in NT. However, the SOC accumulation rates peaked during the first years (5th to 9th) after the adoption of the management practices and decreased exponentially over time, indicating that conservation soil management was a short-term strategy for atmospheric C mitigation. On the other hand, when the CE costs of tillage operations were taken into account, the benefits of NT to C mitigation compared to CT were enhanced. When CE costs related to N-based fertilizers were taken into account, the increases in SOC accumulation due to N did not necessarily improve atmospheric C mitigation, although this does not diminish the agricultural and economic importance of inorganic N fertilization.
  • Authors:
    • Amado, T. J. C.
    • Pontelli, C. B.
    • Santi, A. L.
    • Viana, J. H. M.
    • Sulzbach, L. A. de S.
  • Source: Brazilian Journal of Agricultural Research (PAB)
  • Volume: 42
  • Issue: 8
  • Year: 2007
  • Summary: The objective of this work was to analyze the spatial and temporal yield variability of soybean, corn and wheat in a 57 ha cropland, without irrigation, under no-till for more than ten years in a Typic Hapludox, located in Palmeira das Missões, RS. Yield data of crops from 2000 to 2005 were collected using a combine equipped with yield monitor. Statistical and geostatistical analysis were performed to monitor the range of the spatial variability and its spatial dependence, as well as its behavior over the years. Soybean, corn and wheat yield present spatial variability, which is maintained over time. In dry years, yield variance coefficient increases compared to wet years. Corn was more efficient than soybean to identify spatial yield variability in the cropland.
  • Authors:
    • Klemick, H.
  • Year: 2007
  • Summary: With tropical deforestation a major contributor to greenhouse gas emissions and biodiversity loss, the land use decisions of small-scale farmers at the forest margins have important implications for the global environment. In some tropical forests, such as the Eastern Brazilian Amazon, farmers practice a shifting cultivation system that maintains large amounts of land under forest fallow. I examine whether local benefits of fallowing such as soil restoration, erosion mitigation and hydrological regulation are of sufficient value to farmers to stem the expansion of permanent cropland at the expense of forest. I quantify the value of ecosystem services provided by fallow to agriculture and test whether local forest externalities are economically significant, using farm survey and GIS data from the Eastern Amazon. I estimate a production function to determine the contribution of on-farm and upstream fallow to income, using an instrumental variables approach to address endogeneity. I find that on-farm and upstream fallow are both associated with higher farm income. This result both confirms the agronomic evidence that fallow boosts yields and suggests that fallow provides positive hydrological externalities to downstream farms. I also examine whether farmers respond strategically to their neighbors' land use, taking advantage of ecosystem services provided by upstream farms. I use a spatial econometric model to estimate the effect of upstream farms' fallow on downstream land allocation. I find no evidence that farmers alter their fallowing based on land use upstream. I then investigate whether market failures encourage fallowing. If farmers cannot purchase inputs used in cultivation due to liquidity constraints, they may keep more land under fallow than optimal. I use the estimated production function parameters to determine whether each farm's allocation of land between cropping and fallow is efficient from an individual perspective. I then estimate the effect liquidity indicators on land use efficiency. I find that over-fallowing is negatively associated with commercial credit use and off-farm income, suggesting that liquidity constraints do hinder agricultural intensification. Because I find evidence to support the existence of positive externalities to fallow, the loosening of liquidity constraints that encourage fallowing has ambiguous implications for community-level welfare.
  • Authors:
    • Mielniczuk, J.
    • Vieira, F.
    • Dieckow, J.
    • Bayer, C.
    • Zanatta, J.
  • Source: Soil & Tillage Research
  • Volume: 94
  • Issue: 2
  • Year: 2007
  • Summary: Conservation management systems can improve soil organic matter stocks and contribute to atmospheric C mitigation. This study was carried out in a 18-year long-term experiment conducted on a subtropical Acrisol in Southern Brazil to assess the potential of tillage systems [conventional tillage (CT) and no-till (NT)], cropping systems [oat/maize (O/M), vetch/maize (V/M) and oat+vetch/maize+cowpea (OV/MC)] and N fertilization [0 kg N ha -1 year -1 (0 N) and 180 kg N ha -1 year -1 (180 N)] for mitigating atmospheric C. For that, the soil organic carbon (SOC) accumulation and the C equivalent (CE) costs of the investigated management systems were taken into account in comparison to the CT O/M 0 N used as reference system. No-till is known to produce a less oxidative environment than CT and resulted in SOC accumulation, mainly in the 0-5 cm soil layer, at rates related to the addition of crop residues, which were increased by legume cover crops and N fertilization. Considering the reference treatment, the SOC accumulation rates in the 0-20 cm layer varied from 0.09 to 0.34 Mg ha -1 year -1 in CT and from 0.19 to 0.65 Mg ha -1 year-1 in NT. However, the SOC accumulation rates peaked during the first years (5th to 9th) after the adoption of the management practices and decreased exponentially over time, indicating that conservation soil management was a short-term strategy for atmospheric C mitigation. On the other hand, when the CE costs of tillage operations were taken into account, the benefits of NT to C mitigation compared to CT were enhanced. When CE costs related to N-based fertilizers were taken into account, the increases in SOC accumulation due to N did not necessarily improve atmospheric C mitigation, although this does not diminish the agricultural and economic importance of inorganic N fertilization.
  • Authors:
    • Silva, A. C.
    • Duarte, A. P.
    • Deuber, R.
  • Source: PLANTA DANINHA
  • Volume: 25
  • Issue: 2
  • Year: 2007
  • Summary: A weed infestation survey was performed in 20 second maize crop areas in 1997 and in 40 areas in 1998 and 1999 after soyabean planting in the Medio Paranapanema Region, Sao Paulo, Brazil. The survey was conducted in the counties of Assis, Campos Novos, Candido Mota, Cruzalia, Florinea, Maracai, Palmital, Pedrinhas Paulista and Platina. When the maize reached the grain filling stage, the crop weeds were evaluated by zigzag walking through the areas starting from different points to represent the whole area. The crops were classified in three types, according to the system applied: no-tillage, conventional system with disc plowing, and second maize crop in the soyabean straw only. Infestation level and occurring weed species were evaluated in each crop. The weed control systems adopted were also considered, according to the herbicides applied. The most important weed species occurring in the areas were: Cenchrus echinatus, Bidens pilosa, Euphorbia heterophylla, Raphanus sativus, Digitaria horizontalis, Commelina benghalensis, Amaranthus sp., Achyrocline satureioides, Sinapis arvensis, Sida sp., Glycine max, Avena strigosa [ Avena nuda], Eleusine indica and Sorghum halepense. The results showed a strong infestation increase of C. echinatus, which turned out to be the most important weed species in the area evaluated. R. sativus was also important and showed an expressive increase from 1997 to 1999. Weed infestations were higher in the conventional system areas, showing that this system is inferior to the others, concerning weed control. The chemical weed control most used was the mixture of (atrazine+oil) plus 2,4-D, followed by (atrazine+oil) and atrazine alone. No weed control was used in 22% of the crops, which were the most infested. The infestation level varied from year to year for the different weed control systems, depending on climate conditions.
  • Authors:
    • Borghi, E.
    • Crusciol, C.
    • Mateus, G.
  • Source: Acta Scientiarum Agronomy
  • Volume: 29
  • Issue: 4
  • Year: 2007
  • Summary: The effects of cover plants on the performance of annual crops under no-tillage systems are not well defined yet. A field trial was carried out on a Rhodic Kandiudalf soil in Botucatu, state of Sao Paulo, Brazil, aiming to evaluate the effect of the amount of Gigante guinea sorghum straw on soybean nutrient uptake and its consequent performance of grain yield in no-tillage area. The experimental design was developed in randomized blocks with four replications. The treatments consisted of 6.1, 7.1, 19.5, 26.7, 28.1 e 30.2 ton ha -1 of guinea sorghum straw. The increase of straw provided increment of N and P plant levels until the amount of 25.0 and 17.5 ton ha -1, respectively. Thus, the highest soybean grain yields reported in soils under no-tillage systems might be related to the proper water and nutrient uptakes due to higher soil moisture availability.
  • Authors:
    • Avila, A.
    • Spera, S.
    • Tomm, G.
    • Santos, H.
  • Source: Bragantia
  • Volume: 66
  • Issue: 2
  • Year: 2007
  • Summary: The effects of soil management systems and crop rotations were assessed from 1997 to 2003, in Passo Fundo, Rio Grande do Sul State, Brazil. Four soil management systems (no-tillage, minimum tillage, conventional tillage using disc plough, and conventional tillage using mouldboard plough) and three crop rotation systems (system I (wheat/soyabean), system II (wheat/soyabean and common vetch/maize or sorghum), and system III (wheat/soyabean, common vetch/maize or sorghum and white oats/soyabean)) were compared. The main plot consisted of soil management systems, while the split-plots consisted of crop rotation systems. Energy conversion (energy available/energy consumed) and balance (energy available-energy consumed) during the seven-year period is presented. No-tillage resulted in higher energy conversion and balance (72.44 and 190 766 MJ/ha) than minimum tillage (64.06 and 167 349 MJ/ha), conventional tillage using disc plough (54.35 and 134 982 MJ/ha), and conventional tillage using mouldboard (52.02 and 128 159 MJ/ha), respectively. Wheat in crop rotations presented higher energy efficiency than that in monoculture. Maize had the highest energy efficiency among the crops.