Gerd Sparovek

Physiological and Biochemical Effects of Rare Earth Elements on Plants and Their Agricultural Significance: A Review

Abstract The rare earths include the elements scandium [Sc, atomic number (Z) = 21], yttrium (Y, Z = 39), and the lanthanides from lanthanum (La, Z = 57) to lutetium (Lu, Z = 71). Crop responses to application of rare earth elements (REEs) have only been documented in a few countries. The reasons for promoting growth or yield increases are still not sufficiently understood. Recently, physiological interaction of REEs with calcium (Ca), effects on structure and function of cytoplasm membranes, photosynthesis, hormone metabolism, enzyme activity, and water use efficiency have been discussed. This review covers the significance of REEs for agricultural plant production, beginning with a description of the history of their application. The recorded physiological and biochemical effects and responses of selected crops to REEs were also reviewed. Agricultural research needs on REEs are also suggested.

Bacterial functional redundancy along a soil reclamation gradient

ABSTRACT A strategy to measure bacterial functional redundancy was developed and tested with soils collected along a soil reclamation gradient by determining the richness and diversity of bacterial groups capable of in situ growth on selected carbon substrates. Soil cores were collected from four sites along a transect from the Jamari tin mine site in the Jamari National Forest, Rondonia, RO, Brazil: denuded mine spoil, soil from below the canopy of invading pioneer trees, revegetated soil under new growth on the forest edge, and the forest floor of an adjacent preserved forest. Bacterial population responses were analyzed by amending these soil samples with individual carbon substrates in the presence of bromodeoxyuridine (BrdU). BrdU-labeled DNA was then subjected to a 16S-23S rRNA intergenic analysis to depict the actively growing bacteria from each site. The number and diversity of bacterial groups responding to four carbon substrates (l-serine, l-threonine, sodium citrate, and α-lactose hydrate) increased along the reclamation-vegetation gradient such that the preserved forest soil samples contained the highest functional redundancy for each substrate. These data suggest that bacterial functional redundancy increases in relation to the regrowth of plant communities and may therefore represent an important aspect of the restoration of soil biological functionality to reclaimed mine spoils. They also suggest that bacterial functional redundancy may be a useful indicator of soil quality and ecosystem functioning.

Tropical agriculture and global warming: impacts and mitigation options

O uso intensivo da terra invariavelmente causa efeitos negativos ao ambiente e producao agricola se praticas conservativas nao forem adotadas. Reducao na quantidade de materia orgânica do solo significa emissao de gases (principalmente CO2, CH4, N2O) para a atmosfera e aumento do aquecimento global. A sustentabilidade do solo e tambem afetada, uma vez que a qualidade da materia orgânica remanescente muda. Alteracoes podem ser verificadas, por exemplo, pela desagregacao do solo e mudanca na sua estrutura. As consequencias sao erosao, reducao na disponibilidade de nutrientes para as plantas e baixa capacidade de retencao de agua no solo. Estes e outros fatores refletem negativamente na produtivade das culturas e sustentabilidade do sistema solo-planta-atmosfera. Ao contrario, a adocao de boas praticas de manejo, tal como o sistema plantio direto, pode parcialmente reverter o processo, uma vez que objetiva o aumento das entradas de material orgânico no solo e/ou diminuicao das taxas de decomposicao da materia orgânica do solo.

Rare Earth Elements in Soils

Abstract Rare earth elements (REEs) comprise a group of 17 elements with very similar chemical and physical properties, which include scandium (Sc, Z=21), yttrium (Y, Z=39), and the lanthanides with successive atomic numbers (Z from 57 to 71). Lanthanides are the elements lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). REEs are required in modern industry, and their use in agriculture yielded positive effects in terms of crop yield and body weight of poultry. However, the question of whether the use of REEs in agriculture yields an enrichment of these elements in the environment remains open. It was the aim of this review to summarize the data about REEs in soils with view to their content, fractions, availability, chemical behavior, and translocation in soils and to elucidate further research needs.

Brazilian Agriculture and Environmental Legislation: Status and Future Challenges

Brazilian agriculture covers about one-third of the land area and is expected to expand further. We assessed the compliance of present Brazilian agriculture with environmental legislation and identified challenges for agricultural development connected to this legislation. We found (i) minor illegal land use in protected areas under public administration, (ii) a large deficit in legal reserves and protected riparian zones on private farmland, and (iii) large areas of unprotected natural vegetation in regions experiencing agriculture expansion. Achieving full compliance with the environmental laws as they presently stand would require drastic changes in agricultural land use, where large agricultural areas are taken out of production and converted back to natural vegetation. The outcome of a full compliance with environmental legislation might not be satisfactory due to leakage, where pristine unprotected areas become converted to compensate for lost production as current agricultural areas are reconverted to protected natural vegetation. Realizing the desired protection of biodiversity and natural vegetation, while expanding agriculture to meet food and biofuel demand, may require a new approach to environmental protection. New legal and regulatory instruments and the establishment of alternative development models should be considered.

Agricultural intensification in Brazil and its effects on land-use patterns: an analysis of the 1975–2006 period

Does agricultural intensification reduce the area used for agricultural production in Brazil? Census and other data for time periods 1975-1996 and 1996-2006 were processed and analyzed using Geographic Information System and statistical tools to investigate whether and if so, how, changes in yield and stocking rate coincide with changes in cropland and pasture area. Complementary medium-resolution data on total farmland area changes were used in a spatially explicit assessment of the land-use transitions that occurred in Brazil during 1960-2006. The analyses show that in agriculturally consolidated areas (mainly southern and southeastern Brazil), land-use intensification (both on cropland and pastures) coincided with either contraction of both cropland and pasture areas, or cropland expansion at the expense of pastures, both cases resulting in farmland stability or contraction. In contrast, in agricultural frontier areas (i.e., the deforestation zones in central and northern Brazil), land-use intensification coincided with expansion of agricultural lands. These observations provide support for the thesis that (i) technological improvements create incentives for expansion in agricultural frontier areas; and (ii) farmers are likely to reduce their managed acreage only if land becomes a scarce resource. The spatially explicit examination of land-use transitions since 1960 reveals an expansion and gradual movement of the agricultural frontier toward the interior (center-western Cerrado) of Brazil. It also indicates a possible initiation of a reversed trend in line with the forest transition theory, i.e., agricultural contraction and recurring forests in marginally suitable areas in southeastern Brazil, mainly within the Atlantic Forest biome. The significant reduction in deforestation that has taken place in recent years, despite rising food commodity prices, indicates that policies put in place to curb conversion of native vegetation to agriculture land might be effective. This can improve the prospects for protecting native vegetation by investing in agricultural intensification.

Variabilidade espacial de atributos de solo e de Crotalaria juncea L. em área severamente erodida

A field experiment, located on a private farm close to Piracicaba, State of Sao Paulo, Brazil, was conducted on a severely eroded soil (Ultisol-Entisol association), which has been planted with sugar cane for the last 30 years. The objective was to characterize the spatial variability of soil and plant attributes. An area of 50 by 70 m was divided into 10 columns and 14 rows in a grid of 5 m, resulting in 140 sampling points. Soil samples were collected from each of the sampling points at 0.00-0.20 m (topsoil) and 0.20-0.40 m (subsoil) depths. The field was planted with Crotalaria juncea, a green manure frequently used in association with sugar cane production, after tillage and lime application. At flowering, the above ground part of the plants were harvested in 2 by 2.5 m plots, from which the dry matter was calculated. Soil depth was measured as the depth down to the C horizon by augering. Values lying outside the plus or minus four standard deviation were rejected, which represented less than 1.5% of the data set. Spatial dependence was evaluated by the analysis of scaled semivariograms and their adjusted parameters. Except for P at 0.00-0.20 m, K at both depths, all attributes showed spatial dependence, which can be classified by the ranges of the semivariograms, separating the soil fertility (12 a 32 m) < plant components (25 a 32 m) < particle size fractions (32 a 42 m). The attributes which best explained crop yield were H + Al, cations exchange capacity and base saturation.

A revisão do Código Florestal brasileiro

The article offers information and analysis that intend to demonstrate the importance of the Brazilian Forest Act for the protection of the remaining preserved natural vegetation in Brazil, as well as the reasons and guidelines for its revision, in order to reach the possible and desired balance between respect to the natural environment and improved agricultural development.

A falsa dicotomia entre a preservação da vegetação natural e a produção agropecuária

Through the analysis of census data on land use in Brazil this article shows that the dichotomy between food production and preservation of natural vegetation used as the main driver to change the Forest Code is false. We showed here that Brazil has already cleared an area large enough that support the production of food, fiber and bioenergy to meet the requirements of the country and global markets. We also showed the area of export-oriented crops like soybean and sugar cane have been expanded significantly in the last decades, while staple crops like rice and bean have decreased and the area planted with cassava has been stable for the last four decades. At the same time we show that the productivity of export-oriented crops has increased in a much more significant rate than staple crops or cattle stocking rate, which in average is extremely low in Brazil. We concluded by stating that the real constraint for food production in Brazil does not rely on the Forest Code environmental restrictions but instead in inequalities in land distribution and income, coupled with lack of credit to small producers and investment in research and development in the staples crops of the country.

Soil tillage and precision agriculture: A theoretical case study for soil erosion control in Brazilian sugar cane production

The variability of most soil properties is expressed at small scales. Agronomic practices and treatments are usually designed to be extremely uniform at this scale. The contradiction of applying uniform treatments to variable conditions is the key issue of precision agriculture. Traditionally, precision agriculture means variable application of material inputs such as fertilizers, pesticides and amendments. Although the practical results expressed in terms of economic feasibility or advantages for crop production are controversial, the basic concepts of precision agriculture applied to other inputs, such as time and labor, have theoretical advantages and may have a greater possibility to develop into profitable technology. This paper describes a theoretical example based on sugar cane production in a 77 ha watershed located in the southeastern part of Brazil. Precision agriculture concepts focusing on P-fertilizer inputs were compared with optimization of mechanical operations such as planting and harvesting. Measurable advantages for precision agriculture compared with traditional treatments were observed for mechanical operation efficiency but not for P-fertilizer. Recent practical experiences in Brazilian sugar cane production of treating soil conservation as spatially variable to gain efficiency in mechanical operations is a clear example of the economic feasibility of implementing precision agriculture by increasing efficiency instead of decreasing materials or increasing yields.