The concept of degree of compactness (DC), referred to as field bulk density (BD) as a percentage of a reference bulk density (BD ref ), was developed to characterize compactness of soil frequently disturbed, but for undisturbed soil such as under no-tillage critical degree of compactness values have not been tested. The objective of this study was to compare methods to determine BD ref and limits of DC and BD for plant growth under no-tillage in subtropical soils. Data from the literature and other databases were used to establish relationships between BD and clay or clay plus silt content, and between DC and macroporosity and yield of crops under no-tillage in subtropical Brazil. Data of BD ref reached by the soil Proctor test on disturbed soil samples, by uniaxial compression with loads of 200 kPa on disturbed and undisturbed soil samples, and 400, 800 and 1600 kPa on undisturbed soil samples, were used. Also, comparisons were made with critical bulk density based on the least limiting water range (BDc LLWR) and on observed root and/or yield restriction in the field (BDc Rest). Using vertical uniaxial compression with a load of 200 kPa on disturbed or undisturbed samples generates low BD ref and high DC-values. The standard Proctor test generates higher BD ref -values, which are similar to those in a uniaxial test with a load of 1600 kPa for soils with low clay content but lower for soils with high clay content. The BDc LLWR does not necessarily restrict root growth or crop yield under no-tillage, since field investigations led to higher BDc Rest-values. A uniaxial load greater than 800 kPa is promising to determine BD ref for no-tillage soils. The BD ref is highly correlated to the clay content and thus pedotransfer functions may be established to estimate the former based on the latter. Soil ecological properties are affected before compaction restricts plant growth and yield. The DC is an efficient parameter to identify soil compaction affecting crops. The effect of compaction on ecological properties must also be further considered.

Reference bulk density and critical degree-of-compactness for no-till crop production in subtropical highly weathered soils

A B S T R A C T Soil compaction influences all stages of crop growth, but in many low yield sugarcane fields critical levels and effects of soil compaction are ignored. Therefore, identifying localization and intensity of compaction are very relevant for descompactation of soil. In this context, this study aimed to apply three criteria for delineating zones for soil compaction management: soil layer where first appear values of soil penetration resistance considered critical for sugarcane growth; cone index for 0-40 cm layer, and depth of occurrence of maximum soil penetration resistance. Sampling was carried out in a grid with 113 points spaced at 100 m, georeferenced by means of a Global Positioning System receiver. Soil penetration resistance in eight layers of 5 cm depth, cone index and depth of occurrence of maximum penetration resistance were determined from data gathered by an automatic measuring penetrometer. Estimative of non-sampled values were obtained by means of kriging interpolation, which allowed drawing of contour maps and the definition of four regions in the field for site specific subsoiling . Palavras-chave: Saccharum ssp. resistencia do solo a penetracao geoestatistica penetrometro

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Revista Brasileira de Engenharia Agrícola e Ambiental

Several geopolitical factors, aggravated by worries of global warming, have been fueling the search for and production of renewable energy worldwide for the past few years. Such demand for renewable energy is likely to benefit the sugarcane ethanol industry in Brazil, not only because sugarcane ethanol has a positive energetic balance and relatively low production costs, but also because Brazilian ethanol has been successfully produced and used as biofuel in the country since the 1970s. However, environmental and social impacts associated with ethanol production in Brazil can become important obstacles to sustainable biofuel production worldwide. Atmospheric pollution from burning of sugarcane for harvesting, degradation of soils and aquatic systems, and the exploitation of cane cutters are among the issues that deserve immediate attention from the Brazilian government and international societies. The expansion of sugarcane crops to the areas presently cultivated for soybeans also represent an environmental threat, because it may increase deforestation pressure from soybean crops in the Amazon region. In this paper, we discuss environmental and social issues linked to the expansion of sugarcane in Brazil for ethanol production, and we provide recommendations to help policy makers and the Brazilian government establish new initiatives to produce a code for ethanol production that is environmentally sustainable and economically fair. Recommendations include proper planning and environmental risk assessments for the expansion of sugarcane to new regions such as Central Brazil, improvement of land use practices to reduce soil erosion and nitrogen pollution, proper protection of streams and riparian ecosystems, banning of sugarcane burning practices, and fair working conditions for sugarcane cutters. We also support the creation of a more constructive approach for international stakeholders and trade organizations to promote sustainable development for biofuel production in developing countries such as Brazil. Finally, we support the inclusion of environmental values in the price of biofuels in order to discourage excessive replacement of natural ecosystems such as forests, wetlands, and pasture by bioenergy crops.

Expansion of sugarcane ethanol production in Brazil: environmental and social challenges.

Biochar amendment improves crop production in problem soils: A review.

Soil Health refers to the ecological equilibrium and the functionality of a soil and its capacity to maintain a well balanced ecosystem with high biodiversity above and below surface, and productivity. To understand and use soil health as a tool for sustainability, physical, chemical, and biological properties must be employed to verify which respond to the soil use and management within a desired timescale. Attributes with a rapid response to natural or anthropogenic actions are considered good indicators of soil health. Among the physical indicators, soil texture, aggregation, moisture, porosity, and bulk density have been used, while among chemical indicators total C and N, mineral nutrients, organic matter, cation exchange capacity, among others are well established. However, most of them generally have a slow response, when compared to the biological ones, such as microbial biomass C and N, biodiversity, soil enzymes, soil respiration, etc., in addition to macro and mesofauna. Thus, a systemic approach based on different kinds of indicators (physical, chemical and biological) in assessing soil health would be safer than using only one kind of attribute. Many human activities have caused desertification, loss of biodiversity, disruption of aggregates, loss of organic matter and nutrients, among others. Today, it is imperious to maintain soil health and productivity with increasing emphasis on reforestation and recuperation of degraded areas through the use of organic amendments, reintroduction of plants, soil fauna and microorganisms. This review focused on an integrative view on indicators of soil health to be used as tools for prediction of sustainability in production systems.

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Soil health: looking for suitable indicators. What should be considered to assess the effects of use and management on soil health?

In compacted soils, changes in the distribution of plant root system occur in depth. The objective of this study was to evaluate the compaction effect in soybean root development and yield in an Oxisol. The treatments were 0, 1, 2, 4 and 6 passed of a 11 Mg tractor, side, by side, on soil surface. The experimental design was a completely randomized, with four replications. In December, 2002, soybean (Glycine max cv. Embrapa 48) was sown, and after that, the samples were collected in layers of 0.02-0.05, 0.07-0.10 and 0.15-0.18 m, for physical determinations. In R6 stadium, samples of 0.10 m in line x 0.20 m between lines, in layers of 0.0-0.05, 0.05-0.10, 0.10-0.15 and 0.15-0.20 m were collected. Soybean yield was evaluated in plots of 3.6 m2. The increase in compaction increased the root density and the root dry matter in layer of 0.0-0.05 m and caused linear decrease in the most compacted layers of 0.05-0.10 and 0.10-0.15 m. From the decrease of 18% of root density, in resistance to penetration of 0.85 MPa, in the depth of 0.05-0.15 m, there was reduction in soybean yield. Soil compaction promoted modifications in the distribution of the soybean root system.

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Compactação do solo no desenvolvimento radicular e na produtividade da soja

Balanco hidrico da regiao de ilha solteira

A curva de retencao de agua e especifica a cada solo e depende de varios atributos do solo. Assim, objetivou-se avaliar a influencia de atributos do solo na retencao de agua em Latossolo Vermelho distrofico (LVd) e Latossolo Vermelho eutroferrico (LVef) sob diferentes sistemas de uso e manejo. Os sistemas de uso e manejo foram: algodao, cana-de-acucar e mata. As amostras de solo foram coletadas nas profundidades de 0-10, 10-20, 20-30 e 30-40 cm, para determinar a composicao granulometrica, densidade do solo, materia orgânica, Fe2O3, Al2O3 e a curva de retencao de agua. A materia orgânica nao demonstrou participacao efetiva na retencao de agua, e a densidade do solo revelou maior correlacao positiva com a retencao de agua. O LVef apresentou maior retencao de agua em todas as tensoes e a mesma capacidade de agua disponivel (CAD) em relacao ao LVd.

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Retenção de água em dois tipos de latossolos sob diferentes usos

Na agricultura moderna, o trafego de maquinas sobre o solo e a principal causa da compactacao, que, muitas vezes, causa decrescimos da produtividade de soja. O objetivo deste estudo foi avaliar o desenvolvimento de cultivares de soja, considerando os niveis de compactacao do solo. Para tal, foi realizado um experimento em Jaboticabal, SP, em Latossolo Vermelho textura media. Os tratamentos de compactacao foram: T0 = 0; T1* = 1; T1 = 1; T2 = 2; T4 = 4 e T6 = seis passadas, no mesmo local, de um trator de 11 t, uma ao lado da outra, perfazendo toda a superficie do solo. No tratamento T1*, a compactacao ocorreu quando o solo estava mais seco para obter um menor nivel de compactacao. O delineamento experimental foi inteiramente casualizado em parcelas subdivididas (seis niveis de compactacao e quatro cultivares), com quatro repeticoes. Foram coletadas amostras indeformadas de solo nas camadas de 0,03-0,06; 0,08-0,11; 0,15-0,18 e 0,22-0,25 m, para determinacao dos atributos fisicos. Em dezembro de 2003, foram semeados os cultivares de soja (Glycine max) IAC Foscarin 31, MG/BR 46 (Conquista), BRS/MG 68 (Vencedora) e IAC 8-2. O cultivar de soja IAC Foscarim 31 foi o mais produtivo no Latossolo Vermelho, quando comparado aos cultivares MG/BR 46 (Conquista), BRS/MG 68 (Vencedora) e IAC 8-2. Os valores de resistencia do solo a penetracao a partir dos quais a produtividade dos cultivares de soja decresceu foram de 2,24 a 2,97 MPa, conforme os cultivares.

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Efeito da compactação na produtividade de cultivares de soja em latossolo vermelho

Universidade Estadual Paulista Faculdade de Ciencias Agrarias e Veterinarias Departamento de Tecnologia

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José Frederico Centurion

Papers

Compactação do solo no desenvolvimento radicular e na produtividade da soja

Balanco hidrico da regiao de ilha solteira

Retenção de água em dois tipos de latossolos sob diferentes usos

Efeito da compactação na produtividade de cultivares de soja em latossolo vermelho

Atributos físicos de Latossolos adubados durante cinco anos com biossólido