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Resumen en: The aim of this study was a survey of the estimated costs of soil erosion, an issue of fundamental importance in view of the current worldwide discussion...

http://www.redalyc.org/pdf/1802/Resumenes/Abstract_180218547001_2.pdf

Revista Brasileira de Ciência do Solo

Environmental factors affecting n2 fixation in grain legumes in the tropics, with an emphasis on brazil

Biochar is increasingly being recognized by scientists and policy makers for its potential role in carbon sequestration, reducing greenhouse gas emissions, renewable energy, waste mitigation, and as a soil amendment. The published reviews on biochar application to soil have so far focused mainly on the agronomic benefits, and have paid little attention to the potential unintended effects. The purpose of this chapter is to provide a balanced perspective on the agronomic and environmental impacts of biochar amendment to soil. The chapter highlights the physical and chemical characteristics of biochar, which can impact on the sorption, hence efficacy and biodegradation, of pesticides. As a consequence, weed control in biochar-amended soils may prove more difficult as preemergent herbicides may be less effective. Since biochars are often prepared from a variety of feedstocks (including waste materials), the potential introduction of contaminants needs to be considered before land application. Metal contaminants, in particular, have been shown to impact on plant growth, and soil microbial and faunal communities. Biochar has also been shown to influence a range of soil chemical properties, and rapid changes to nutrient availability, pH, and electrical conductivity need to be carefully considered to avoid unintended consequences for productivity. This chapter highlights some key areas of research which need to be completed to ensure a safe and sustainable use of biochar. In particular, understanding characteristics of biochars to avoid ecotoxicological impacts, understanding the effects of biochar on nutrient and contaminant behavior and transport, the effects of aging and the influence of feedstock and pyrolysis conditions on key properties are some of the areas that require attention.

Biochar Application to Soil: Agronomic and Environmental Benefits and Unintended Consequences

“ No other single chemical soil characteristic is more important in determining the chemical environment of higher plants and soil microbes than the pH There are few reactions involving any component of the soil or of its biological inhabitants that are not sensitive to soil pH This sensitivity must be recognized in any soil-management system” “ Lime is truly a foundation for much of modern humid-region agriculture Knowing how pH is controlled, how it influences the supply and availability of essential plant nutrients as well as toxic elements, how it affects higher plants and human beings, and how it can be ameliorated is essential for the conservation and sustainable management of soils throughout the world” (Brady and Weil, 1999) Under areas where rainfall exceeds evapotranspiration, soil acidification is an ongoing natural process, which can either be accelerated by the activity of plants, animals and humans or can be impeded by careful management practices In areas affected by industrial activities, soil acidification is caused by acid drainage from pyrite oxidation and also from acid precipitation In areas that remain unaffected by industrial pollution, soil acidification in managed ecosystems is mainly caused by the release of protons (H + ) during the transformation and cycling of carbon (C), nitrogen (N) and sulfur (S) Just like in managed ecosystems, soil acidification in natural ecosystems caused by acid drainage and acid precipitation can have adverse impacts where soils have low pH buffering capacity Liming is the most common management practice aimed at neutralizing the acid produced, thereby overcoming the adverse impacts of soil acidification This review brings together fundamental aspects of soil acidification and recent developments on the implications of liming in relation to soil processes, particularly nutrient and heavy metal transformation and bioavailability in soils The article first outlines the various soil, plant and microbial processes that generate acid (protons; H + ions) both under natural and managed ecosystems It then discusses the effects of soil acidity on soil chemical and biological properties The effect of liming to overcome the problems associated with soil acidity is examined in relation to the transformation of nutrient ions and heavy metals The practical implications of liming to overcome heavy metal toxicity have been discussed in relation to the adsorption, leaching and phytoavailability of these metal ions Future research should aim to focus on the development of methods to quantify lime-enhanced (im)mobilization of nutrient ions and heavy metals in soils and to explore further the role of liming in remediating contaminated soils

Soil acidification and liming interactions with nutrientand heavy metal transformationand bioavailability

It is generally accepted that liming ameliorates soil acidity. However, the method of lime application is thought by many to influence its effectiveness in acid soils. In this study, we wanted to assess the degree of effectiveness of surface-applied lime and lime incorporated into the soil on soil structural attributes and water retention of a Dystrudept soil in the SE region of the State of Paran a, Brazil. Lime was added at the rate of 15 t/ha to soil through: (i) surface broadcasting, (ii) incorporation via ploughing and harrowing, (iii) incorporation via subsoiling and harrowing. A control treatment with zero lime application was included in the experiment. The addition of lime by surface broadcasting resulted in significant reductions in soil bulk density (BD) and macroporosity (Ma) and increases in total porosity (TP) and microporosity (Mi) of the top soil layer (0–0.10 m). The reverse was the case in the 0.10to 0.20-m soil layer; where lime was incorporated via ploughing and harrowing, increases in BD and reductions in TP and Ma were observed. Addition of lime also significantly increased soil water retention, with maximum retention recorded from soil amended with surface broadcast lime. Changes in soil chemical attributes (increases in pH, Ca and Mg contents; reductions in potential acidity and Al content) were responsible for the changes observed in structural and physical attributes, and water retention. Bearing in mind the lower application costs, improvement in the soil chemical attributes for plant development and soil physical quality, surface broadcast lime can be considered a promising alternative for no-till farmers.

Effects of surface-applied and soil-incorporated lime on some physical attributes of a Dystrudept soil.

A correcao da acidez do solo no sistema plantio direto (SPD) e feita por meio da aplicacao de calcario na superficie sem incorporacao. Com a hipotese de que a fonte e granulometria dos corretivos interferem na velocidade de reacao no solo em curto prazo e na resposta das culturas a calagem na superficie em SPD, foram realizados dois experimentos, sendo um em Latossolo Vermelho Distrofico textura muito argilosa e outro em Neossolo Litolico Humico textura franco-arenosa, no periodo de 2010 a 2012. O delineamento empregado, em cada experimento, foi em blocos completos ao acaso, no esquema fatorial 2 × 2 × 4, com tres repeticoes. Os tratamentos foram constituidos de duas fontes de calcario, calcitico (25-50 g kg-1 MgO) e dolomitico (160-180 g kg-1 MgO), duas faixas de poder relativo de neutralizacao total (PRNT), faixa B (PRNT de 60 a 75 %) e faixa D (PRNT>90 %), e quatro doses de calcario na superficie, sendo um tratamento-controle sem calagem e tres doses estimadas para elevar a saturacao por bases do solo (0,00-0,20 m), a 50, 70 e 90 %. Nos dois experimentos, o calcario foi aplicado a lanco sobre a superficie do solo, em agosto de 2010. Realizaram-se dois cultivos em 2010/11 e 2011/12, com milho e soja, no Latossolo Vermelho Distrofico, e soja e milho, no Neossolo Litolico Humico, respectivamente. A aplicacao superficial de calcario nos dois solos, apos 12 meses, proporcionou reducao da acidez na camada de 0,00-0,05 m e, em menor grau, na de 0,05-0,10 m. A amenizacao da acidez nas camadas da superficie foi mais acentuada com o emprego de doses mais elevadas de calcario calcitico e de corretivo com granulometria mais fina. A calagem superficial aumentou as concentracoes de Ca-foliar com a utilizacao de calcario calcitico e de Mg-foliar com o uso de calcario dolomitico, e reduziu os teores foliares de Mn e Zn, independentemente da fonte de calcario, nas culturas de milho e soja. As produtividades de graos de milho e soja no Latossolo Vermelho Distrofico e Neossolo Litolico Humico aumentaram com as doses de calcario, mas nao foram influenciadas pelas fontes e faixas de PRNT dos corretivos. A calagem superficial e uma pratica efetiva e importante para maximizar a produtividade de graos das culturas em SPD, independentemente do teor de Mg e da granulometria dos corretivos.

/pdf/aplicacao-superficial-de-calcario-com-diferentes-teores-de-3pwocyz2vq.pdf

Aplicação superficial de calcário com diferentes teores de magnésio e granulometrias em sistema plantio direto

The effects of superficial lime application on chemical soil attributes under no-tillage systems and its influence on root growth and mineral nutrition in maize crops have not been thoroughly investigated yet. To evaluate these effects on maize and its reflexes on grain yield performance, a field trial was carried out on a dystrophic clayey Rhodic Hapludox, previously managed under no-tillage for six years, at Tibagi, State of Parana, Brazil. The experimental design was a randomized complete block with four replications, using 44.8 m2 plots. The treatments consisted of four liming rates (0, 1, 2 and 3 t.ha-1, pure CaCO3 equivalents) which represented 1/3, 2/3 and the total amount calculated for the soil to reach a base saturation of 70%, in the 0-20 cm layer. Dolomitic limestone (27% of CaO, 20% of MgO and 85% of ECCE) was broadcast-applied to the soil surface without incorporation. After 22 months, lime application increased soil pH in CaCl2 0.01 mol.L-1, exchangeable Ca and Mg, and base saturation, and reduced H + Al and exchangeable Al at the superficial layer (0-10 cm). It also increased exchangeable Ca and decreased exchangeable Al at the subsoil (20-40 cm). Liming did not significantly affect length and relative distribution of corn root at the 40 cm depth, reduced average root radius and increased plant uptake of P, Ca, Mg, and S, with no significant effects on grain yields. Surface lime application did not affect Cu, Fe, Mn and Zn concentrations in the soil and leaves or plant uptake of these micronutrients.

/pdf/efeitos-da-calagem-em-semedura-direta-de-milho-1vwq471pfq.pdf

Efeitos da calagem em semedura direta de milho

Yields of many crops are limited to subsoil acidity. Crop positive responses to gypsum have been shown, however, information regarding the use of gypsum in vine is scarce. A field trial was performed in Parana State, Brazil, on a clayey Rhodic Hapludox to evaluate the effects of gypsum application (0, 3, 6, 9, and 12 Mg ha−1) on soil chemical attributes and grape (cv. ‘Niagara Rosada’) yield. Gypsum was surface applied in July 2005 and the soil and plant evaluations were realized during the years of 2006 and 2007. Gypsum decreased the subsoil exchangeable aluminum (Al) level, increased the calcium (Ca) and sulfate (SO4) contents in the soil profile, and caused leaching of magnesium (Mg) from the topsoil. The leached Mg resulted in decreases of leaf Mg concentrations and fruit production. The researchers estimated a critical level of Ca/Mg ratio in soil as well as in leaves of 1.9 for vine.

Soil Chemical Attributes and Grape Yield as Affected by Gypsum Application in Southern Brazil

Peanut response to lime has been associated to calcium (Ca) nutrition, but a higher nitrogen (N) Uptake has been observed in limed plots probably due to an increase in molybdenum (Mo) availability. A two‐year experiment was conducted to study the effects of Mo, cobalt (Co), and liming on peanut yields and N nutrition. Peanut seeds were treated with Mo and/or Co and grown in soil with base saturation about 13, 41, 57, and 71%. There was no effect of seed treatment with Co on peanut yields or N nutrition. Liming and Mo application increased N contents in the leaves. Nitrogen uptake was increased by Mo and liming in cv. Tatu and only by liming in cv. Tupa. Manganese (Mn) contents in the leaves were decreased by liming. The higher yields were observed when the Ca/Mn ratio in the leaves was above 25. In acid soils, low availability of Mo and Mn toxicity can impair N acquisition by peanut plants and decrease grain yields.

Eduardo Fávero Caires

Papers

Effects of surface-applied and soil-incorporated lime on some physical attributes of a Dystrudept soil.

Aplicação superficial de calcário com diferentes teores de magnésio e granulometrias em sistema plantio direto

Efeitos da calagem em semedura direta de milho

Soil Chemical Attributes and Grape Yield as Affected by Gypsum Application in Southern Brazil

Yield and nitrogen uptake of peanuts as affected by lime, cobalt, and molybdenum