Physical attributes and organic material in pastures of Brachiaria brizantha at degradation levels

Pastures cover, in Brazil, around 165 million ha, most of them are at some degradation level. Recovering these pastures is essential. The objective of this study was to evaluate the sensibility of soil organic matter (SOM) and its physical attributes in pasture soil at different degradation levels (1 to 4), Capoeiras (1 and 2) and secondary Forest (Control). Samples were collected at four depths (0.00-0.05, 0.05-0.10, 0.10-0.20 and 0.20-0.40 m). We verified higher values for SOM and hydraulic conductivity (Ko) in Forest, especially in the most superficial layer (0.00-0.05). We noted low values for macroporosity in this area. In all areas under Pastures lower values for Ko were observed in the superficial layer (0.00-0.05 m) when compared to layers 0.05-0.10 and 0.10-0.20 m, which indicates that the pasture management and cattle trampling negatively affect the physical quality of the pastures. For field capacity and wilting point the average values were observed in Pasture 4 (more degraded), which caused higher values for water availability. According to the principal components analysis, except for SOM at 0.20-0.40 m, all variables studied presented correlation above 0.6. From grouping analysis, we separated 3 groups: Forest; Capoeiras 1 and Capoeira 2 and Pastures 1 to 4.

Effects of Mulching on Soil Water Content, Maize Performance and Weed Growth in Dry Land Area of Bangladesh

Aims: The objectives of the research work were to evaluate the effects of mulching on soil water content, maize performance and weed growth in dry land area of Bangladesh Study Design: The experiment was laid out in a randomized complete block design (RCBD) with three replications Place and Duration of Study: Central research field of Sher-e-Bangla Agricultural University, Dhaka-1207 during November 2019 to April 2020. Methodology: The experimental field is divided into 3 blocks to represent 3 replications. There are 6 unit plots (each unit plot consists of 3m � 2m area) in the experimental farm. Distances of 1 m and 0.5 m are maintained between replication to replication and plots to plots, respectively. Plant to plant and row to row distances are considered to be 0.25 m and 0.75 m, respectively. The treatments are assigned in random plots. The land is ploughed four times followed by laddering to have fine tilth of the soil. The maize cultivars Shuvra and KS-510 are used as plant materials. Fig. 1 represents the six mulch treatments are imposed on the plants: Control (without mulch, CK), water hyacinth dry (10 t/ha, WH), rice straw dry (10 t/ha, RS), black polythene (4m � 3m, BP), white polythene (4m � 3m, WP), and transparent polythene (4m � 3m, TP) (S2). The mulches are applied as per treatment in each plot just after sowing to maintaining an equal thickness throughout the plot. Dried and cleaned mulches are used before applying to the experiment. The significance of the difference among the treatment means were estimated by the MSTAT-C package programme at 5% level of probability. Results: It is found in the experimental results that the soil water content of the no-mulching treatment is lower as compared to that of the other treatments from 0-10 cm, 10-20 cm and 20-30 cm soil depths. It is also observed that the RS mulching provides the highest soil water content, leaf area index (LAI), chlorophyll contents, and total biomass. Significant enhancement of maize yield (20.55 ton/ha) is recorded for the rice straw mulching. In contrast, the weed dry weight of 7.45g/m2 is observed in the RS mulching, which is lower than the other treatments. Conclusions: Therefore, it can be concluded that the RS mulching, compared to other mulching, would be more efficient for maximum utilization of limited water resources, weed suppression as well as to increase the maize yield. The present research approach would be applicable to manage the soil water for enhancing the maize production in dry land area.

Efeitos do uso de lodo de estações de tratamento de esgoto sobre a disponibilidade de água em um substrato minerado no Cerrado / Effects of the use of wastewater sludge on water availability of a mine substrate in the Brazilian Savanna

RESUMO A mineração expõe à superfície material genericamente denominado de substrato, que possui atributos físicos, químicos e biológicos diferentes do solo natural. O lodo de estações de tratamento de esgoto (ETE) é a principal fonte de matéria orgânica utilizada na recuperação de áreas mineradas no Distrito Federal. Apesar de as tecnologias de recuperação afetarem positivamente o substrato minerado, seus efeitos sobre a disponibilidade de água para a vegetação foram pouco estudados. Diante disso, este estudo objetivou verificar se a disponibilidade de água em um substrato de mineração de cascalho foi alterada pela aplicação de lodo de ETE. Três materiais foram investigados: substrato minerado sem aplicação de lodo, substrato minerado com aplicação de lodo e solo sob Cerrado original. Esses materiais foram caracterizados por meio da granulometria, densidade aparente, porosidade total, microporosidade, macroporosidade, condutividade hidráulica saturada, teor volumétrico de água à capacidade de campo e ponto de murcha permanente. Posteriormente, monitorou-se, nesses materiais, o teor volumétrico de água e de ar durante 22 semanas. Os resultados indicaram que o substrato minerado armazenou água acima da capacidade de campo durante 86% do período investigado e o teor de ar permaneceu em níveis críticos durante 55% do mesmo período. A incorporação de lodo de ETE e a colonização de plantas aumentaram os valores de condutividade hidráulica na saturação (Ksat) e reduziu o período em que a água se manteve armazenada à capacidade de campo. Todavia, o regime de umidade do substrato tratado com lodo de ETE se manteve dissimilar ao do solo original usado como referência.

ABSTRACT Mining exposes to surface a material generically called substrate, which has different physical, chemical and biological attributes compared to natural soils. The wastewater sludge (WWS) is the main source of organic matter used in reclamation works of mines in the Federal District of Brazil. Reclamation works positively affect mine substrate but their effects on water availability (AW) have been little studied. This work aimed to evaluate the effects of WWS into a mine substrate on its hydraulic conductivity (Ksat) and AW. Samples of a mine substrate exposed to surface, the same material treated with wastewater sludge and soil under natural Savanna vegetation were collected and analyzed for bulk density, granulometry, total porosity, microporosity, macroporosity, saturated Ksat, volumetric water content at field capacity (FC) and at permanent wilt point (PWP). Subsequently, volumetric water and air content were monitored on the field for 22 weeks. Results showed that the substrate exposed by mining presented water content above FC during 86% of the investigation period and air content at critic levels during 55% of the same period. The incorporation of WWS and subsequent plant colonization increased Ksat values and shortened the period in which water was store at FC. However, the moisture regime in the substrate treaded with WWS remained dissimilar to that of the original soil used as reference.

Kriging Versus Cokriging and Collokated Cokriging for Soil Physical-Hydraulic Attributes and their Influence on Soybean Growth

Abstract in Brazil, management agricultural practices not currently consider the soil spatial variability as a result, crop growth can be non-uniform and yields often is low. This research aims to compare Kriging, Cokriging and Collocated cokriging using soil physical and hydraulic properties and their influences on soybean development. We hypothesized that spatial variability of physical and hydraulic properties has influence on soybean development and this variability can be better represented by Collocated Cokriging method. To test these hypotheses, we accessed the soil physical and hydraulic attributes in a field experiment under no-till system, cultivated with soybean. Geostatistical interpolators were applied to generate maps from which spatial dependence of the variables was evaluated. The experiment was conducted on a sandy clay loam Oxisol, on an experimental station located in Ponta Grossa, Paraná, Brazil. Evaluation of the soil attributes was performed: bulk density (BD), particle size distribution, saturated soil hydraulic conductivity (K fs ), total porosity (TP), macroporosity and microporosity. The plant was plant height and stand. Data analysis were performed by geostatistical methods; the spatial dependence was established using experimental univariate and cross semivariograms with datasets. Modeling semivariograms led to the generation of attribute maps by Kriging, Cokriging and Collocated cokriging. The estimation by Cokriging and Collocated cokriging was similar from Kriging. From the semivariogram, it was possible to identify that soil and plant attributes were spatially related with each other. The soya growth was mainly changed by slope of the area and little changed by saturated hydraulic conductivity.

Allelopathic Effect of Water Extracts from Rhizosphere Soil of Three Medicinal Plants on Polygala tenuifolia Seeds and Their Seedlings / 中国实验方剂学杂志

Objective:To investigate the allelopathic effects of water extracts from rhizosphere soil of three medicinal plants Rehmannia glutinosa，Pinellia ternata and Isatis indigotica on seed germination and seedling growth of Polygala tenuifolia， screen the stubble varieties suitable for crop rotation with P. tenuifolia， and provide some scientific basis for continuous cropping obstacles of P. tenuifolia. Method:The bioassay method was used to study the effects of rhizosphere soil water extracts from three medicinal plants Rehmannia glutinosa，Pinellia ternata and Isatis indigotica at concentrations of 0.3，0.6，0.9 g·mL-1 on the germination of P. tenuifolia seed and seedling growth. Result:The rhizosphere soil water extracts of Rehmannia glutinosa and Pinellia ternata showed basically low-promotion and high-inhibition concentration effects on the final germination rate，germination potential，and germination index of P. tenuifolia seeds，while the water extract of Isatis indigotica showed significant allelopathic inhibition effect. All three rhizosphere soil water extracts showed significant allelopathic inhibition effects on the growth index of P. tenuifolia seedlings. Among them，the rhizosphere soil water extract of Rehmannia glutinosa showed lower inhibitory effect on the plant height and root length of P. tenuifolia seedlings than the other two water extracts. The photosynthetic pigment content，proline（Pro） content，and soluble sugar content of P. tenuifolia chinensis seedlings were the highest under 0.3 g·mL-1 soil water extract of Rehmannia glutinosa， with relatively higher content of soluble protein， and relatively lower content of hydrogen oxide（H2O2）. Under the treatment of 0.9 g·mL-1 soil water extract of Rehmannia glutinosa，P. tenuifolia seedlings had the highest peroxidase（POD） and superoxide dismutase（SOD） activities，low catalase（CAT） activity，and lowest content of malondialdehyde（MDA）. Conclusion:Based on the comprehensive analysis of the above experimental data and allelopathic effects，the water extract of rhizosphere of Rehmannia glutinosa can promote the germination of P. tenuifolia seeds to a certain extent，and lay the foundation for seedling resistance to biochemical stress. Therefore， Rehmannia glutinosa is more suitable for crop rotation with P. tenuifolia.

Comparison of soil hydraulic properties in wild and cultivated areas of Notopterygium incisum / 中国中药杂志

To clarify the difference of soil moisture characteristics between mixed broad leaf-conifer forest soil and artificial cultivation of Notopterygium incisum, the HYPROP system and the dew point potential meter were used to determine soil water retention curves(SWRC) for samples of two horizons(i.e. 2-7 cm, 10-15 cm). The basic physical and chemical properties of soil and its water characteristic parameters were also determined. The result showed as fllows:①The bulk density of mixed coniferous-broad leaf forest soil was between 0.33 and 0.52 g·cm~(-3), significantly lower than the corresponding value of field soil(1.01-1.18 g·cm~(-3))(P<0.05), While the organic matter content was significantly higher than the corresponding value of field soil(P<0.05). ②The saturated water content(θ_s), field water holding capacity(θ_(FC)) and Water that can be effectively utilized by plants(θ_(PAC)) of mixed coniferous-broadleaved forest soil were significantly higher than the corresponding value of field soil(P<0.05), while the retained water content(θ_r) value that cannot be effectively utilized by plants was significantly lower than that of field soil(P<0.05). ③The values of structural porosity(0.13-0.24 cm~3·cm~(-3)) and Matrix porosity(0.34-0.44 cm~3·cm~(-3)) of mixed coniferous-broadleaved forest soil were higher than the corresponding values of field soil. Therefore, with low bulk density and high content of organic matter, mixed coniferous-broadleaved forest soil can store more water in soil in the form of effective water to meet the needs of plants for water, thus possibly forming high quality medicinal materials of Notopterygii Rhizoma et Radix. In conclusion, the results of this study can provide theoretical basis guidance for soil structure improvement and water management to form high quality medicinal materials in the artificial cultivation of N. incisum.

Assessing pedotransfer functions to estimate the soil water retention / Validação de funções de pedotransferência para estimativa da retenção de água no solo

Considering the importance of soil water retention for agricultural and environmental purposes, the objective of this study was to assess three pedotransfer functions (PTFs) used to estimate the soil moisture at field capacity (FC) based on soil attributes easily determined. A collection of 17 soils from the Cerrado and Pantanal biomes, including surface and subsurface horizons, was used. PTF-1 considers clay, organic matter, coarse sand, and microporosity; PTF-2 clay, total sand, and organic matter; and PTF-3 only microporosity. The estimated FC values were correlated to soil moisture values measured at different soil water potentials (0, 6, 10, 33, 100, 300, and 1500 kPa) to verify which potential corresponded to estimated FC. The data were subjected to regression analysis and Mann-Whitney rank-sum test to compare predicted and measured values and to principal component analysis (PCA). The analysis of the full dataset indicated that there was a strong correlation (R 0.84­0.91; R2 0.71­0.82; RMSE 0.07­0.09) between estimated FC and soil water retention measured at potentials of 10 kPa and 33 kPa. FC estimated by PTF-3 correlated better with water holding capacity at 6 kPa. When the PTFs were reapplied to homogeneous soil groups (identified by PCA analysis), the correlation between predicted and measured FC was decreased.

Considerando a importância da retenção de água no solo para fins agronômicos e ambientais, objetivou-se com este trabalho avaliar três funções de pedotransferência (FP) para estimativa da capacidade de campo (CC) com base em atributos de solo facilmente determinados. Uma coleção de 17 solos dos biomas Cerrado e Pantanal, incluindo amostras superficiais e subsuperficiais, foram utilizadas. FP 1 considera o conteúdo de argila, matéria orgânica, areia grossa e microporosidade. FP 2 considera argila, areia total e matéria orgânica. A FP 3 leva em consideração apenas microporosidade. Os valores estimados de CC foram correlacionados aos valores de umidade obtidos em diferentes potenciais (0, 6, 10, 33, 100, 300, and 1500 kPa) com o intuito de verificar qual potencial corresponde à CC estimada. Os dados foram submetidos à análise de regressão, ao teste Mann-Whitney rank-sum para comparar valores medidos e estimados e realizada análise de componentes principais (PCA). Considerando todo o conjunto de dados, foi obtida uma forte correlação (R 0.84­0.91; R2 0.71­0.82; RMSE 0.07­0.09) entre CC estimada e a umidade do solo obtida nos potenciais de 10 kPa e 33 kPa. A CC estimada pela FP 3 correlacionou melhor com a retenção de água no potencial de 6 kPa. Quando as FP's foram reaplicadas em grupos de solos homogêneos (identificados pela PCA), a correlação entre valores estimados e medidos diminuiu.

Effects of soil water content on growth and accumulation of active ingredients of Notopterygium incisum / 中国中药杂志

To investigate the adaptive mechanism of Notopterygium incisum to water changes, one-year-old seedlings were used as test materials. The characteristics of growth, physiology, and active ingredients of N. incisum were studied at different soil water content by pot experiments. The result showed that: ①The water content at 100% field capacity is conducive to the growth and accumulation of biomass of N. incisum. The leaf length, petiole length, petiole diameter, root diameter, root length and biomass of underground dry of N. incisum were all significantly increased at the 100% field capacity, and they slightly declined at 70% field capacity. 20% field capacity could not provide the necessary water to growth of N. incisum, all N. incisum withered and died. ②With the extension of moisture treatment time, the relative content of chlorophyll (SPAD) in leaves and the activity of peroxidase (POD) in rhizome showed a trend of increasing firstly, decreasing then; the tendency of activity of superoxide dismutase (SOD) in rhizome increased; the content of malondialdehyde (MDA) in rhizome decreased firstly and increased then;. For the late test, the SPAD value, the activity of POD and SOD in N. incisum at the 40% field capacity were lower than 70% field capacity and 100 field capacity, while the content of MDA in rhizome were higher than 70% field capacity and 100% field capacity. ③ At 70% field capacity, the active ingredients accumulated most in the N. incisum. At the 70% field capacity, the notopterol and isoimperatorinwerehigher than100 field capacity and 40 field capacity. In summary, the soil water content at 70%-100% field capacity would contribute to the growth and accumulation of active ingredients of N. incisum.

Drought-induced alterations in the uptake of nitrogen, phosphorus and potassium, and the relation with drought tolerance in sugar cane / Alterações induzidas pela seca na absorção de nitrogênio, fósforo e potássio, e as relações com a tolerância da cana-de-açúcar ao deficit hídrico

ABSTRACT Although there are evidences that the proper supply of mineral nutrients to plants relieves water stress, little is known on the approach of how the drought affects the absorption and accumulation of nutrients by distinct sugar cane genotypes, or in different parts of a same plant. Thus, the objective of this study was to determine the content and accumulation of N, P and K in the aerial part of plant from three genotypes of sugar cane, submitted to three water potentials in the soil, and check the relationship of these variables with the tolerance of plants to prolonged drought. In order to access this objective, an experiment under greenhouse conditions, comprised by a fatorial 3 × 3, in a randomized block design, and four replicates was carried out. After 90 days from treatment imposition, the plant transpiration rate, plant dry mass, concentration of N, P and K were determined in leaves and culms, as well as in total plant shoot were measured. It was found that tolerance to drought in sugar cane is related to higher levels of N and K in the leaves and stems, and larger accumulations of K and P in the plant shoot. There is high positive correlations among accumulation of N, P and K in the plant shoot and dry matter production by plants submitted to drought. There are intermediate correlations among plant transpiration and nutrient uptake by plants under drought. Plants of the genotype SP81-3250 are more tolerante to prolonged drought, than the RB855453 and IACSP95-5000 plants.

RESUMO Embora existam evidências de que o adequado fornecimento de nutrientes minerais para plantas alivia o estresse hídrico, pouco se sabe sobre a abordagem de como a seca afeta a absorção e acumulação de nutrientes por distintos genótipos de cana-de-açúcar, ou por diferentes partes de uma mesma planta. Assim, o objetivo deste estudo foi determinar o teor e acúmulo de N, P e K na parte aérea da planta de três genótipos de cana-de-açúcar, submetidos a três potenciais hídricos do solo e verificar se existe relação dessas variáveis ​​com a tolerância das plantas ao déficit hídrico prolongado. Para isso, foi realizado um experimento em casa de vegetação, em um esquema fatorial 3×3, em delineamento de blocos casualizados, com quatro repetições. Após 90 dias da imposição dos tratamentos, foi determinada a massa seca e a taxa de transpiração das plantas, a concentração de N, P e K nas folhas e colmos, além do acúmulo desses nutrientes na parte aérea das plantas. Verificou-se que a tolerância à seca em cana está relacionada com níveis mais altos de N e K nas folhas e caules e maiores acumulações de K e P na parte aérea das plantas. Existem fortes correlações positivas entre acúmulo de N, P e K na parte aérea das plantas e produção de matéria seca. Existem correlações intermediárias entre a transpiração da planta e absorção de nutrientes pelas plantas sob seca. Plantas do genótipo SP81-3250 são mais tolerantes à seca prolongada, que as plantas RB855453 e IACSP95-5000.

Yield, water use efficiency, and yield response factor in carrot crop under different irrigation depths / Produtividade, eficiência no uso da água e fator de resposta em produção de cenoura sob diferentes lâminas de irrigação

ABSTRACT: The aim of the present study was to evaluate the effect of different irrigation depths on the yield, water use efficiency (WUE), and yield response factor (Ky) of carrot (cv. 'Brasília') in the edaphoclimatic conditions of Baixada Fluminense, RJ, Brazil. Field trials were conducted in a Red-Yellow Argisol in the 2010-2011period. A randomized block design was used, with 5 treatments (depths) and 4 replicates. Depths were applied by drippers with different flow rates, and the irrigation was managed by time domain reflectometry (TDR) technique. The reference (ETo) and crop (ETc) evapotranspiration depths reached 286.3 and 264.1mm in 2010, and 336.0 and 329.9mm in 2011, respectively. The root yield varied from 30.4 to 68.9t ha-1 as a response to treatments without irrigation and 100% replacement of the soil water depth, respectively. Values for WUE in the carrot crop varied from 15 to 31kg m-3 and the mean Ky value was 0.82. The mean values for Kc were obtained in the initial (0.76), intermediate (1.02), and final (0.96) stages. Carrot crop was influenced by different water depths (treatments) applied, and the highest value for WUE was obtained for 63.4% of soil water replacement.

RESUMO: O objetivo deste estudo foi avaliar o efeito de diferentes lâminas de irrigação na produtividade, na eficiência de uso da água (EUA) e no coeficiente de resposta de produção (Ky) da cenoura (cv. 'Brasília') ao déficit hídrico do solo, nas condições edafoclimáticas da Baixada Fluminense-RJ. Ensaios de campo foram conduzidos em 2010 e 2011, em um Argissolo Vermelho-Amarelo, usando um delineamento em blocos casualizados, com 5 tratamentos (lâminas) e 4 repetições. As lâminas foram aplicadas por gotejadores com diferentes vazões e o manejo da irrigação foi realizado com a técnica da TDR. As lâminas de evapotranspiração de referência (ETo) e da cultura (ETc) totalizaram 286,3 e 264,1mm, em 2010, e 336,0 e 329,9mm, em 2011, respectivamente. A produtividade de raízes variou de 30,4 a 68,9t ha-1 como resposta aos tratamentos sem irrigação e com 100% de reposição da lâmina de água no solo, respectivamente. Os valores de EUA no cultivo da cenoura variaram de 15 a 31kg m-3 e o Ky médio foi de 0,82. Foram obtidos os valores médios de Kc nas fases inicial (0,76), intermediária (1,02) e final (0,96). A cultura da cenoura foi influenciada pelas diferentes lâminas aplicadas (tratamentos) e a maior EUA foi obtida para o tratamento com reposição de 63,4% da água do solo.

Effects of Different Soil Water Content on the Yield and Quality of Rehmannia Glutinosa / 世界科学技术-中医药现代化

This study aimed to elucidate the effects of different soil water contents on the yield and quality of R.glutinosa.Different soil water contents were adjusted in different periods of growth of R.glutinosa.The yield,content of water extract,catalpol,verbascoside and polysaccharide were determined and analysed by the grey pattern recognition after harvests.The impacts of soil water content from the most important to the least important were medium moisture content (M2),high moisture content (M3),low moisture content (M1) and blank (M4).In the cultivation of R.glutinosa,the soil water content should be remained in the range of 40％-50％ at seedling stage,while 50％-60％ at the stage of root formation and tuber enlargement,and 20％-30％ during harvesting,which can significantly improve the yield and quality of R.glutinosa.

Condição de contorno para calibração de reflectômetro usado para medição de água no solo / Boundary conditions for calibration of reflectometer used to measure soil water

A reflectometria no domínio do tempo (TDR, na sigla em inglês) é uma técnica indireta usada para estimar o conteúdo de água do solo (θ) em função de sua constante dielétrica aparente (Ka). Neste estudo, o objetivo principal foi investigar as consequências de se incluir ou não medidas de Ka em água, na elaboração da curva de calibração do TDR. Foram avaliados horizontes de solo com 0,13kg kg-1, 0,23kg kg-1 e 0,64kg kg-1de argila. Para cada horizonte, a Ka foi medida em amostras desde solo seco até solo saturado. Adicionalmente, a Ka foi medida apenas em água. As medições foram feitas usando-se cabos coaxiais RGC58, 50 Ohm e sensor dupla haste metálica de 19cm. Para cada horizonte, foram formados dois conjuntos de dados com θ e Ka, um com e outro sem as medidas de Ka em água. Em cada conjunto, foi ajustada uma equação polinomial de terceiro grau, estimando θ em função de Ka. Com a inclusão das medidas de Ka em água, o polinômio de terceiro grau se ajustou melhor ao extremo saturado e preveniu erros na estimativa de θ. Como não há garantia de que as medidas de Ka de campo não serão maiores que as medidas de Ka das amostras saturadas em laboratório, recomenda-se a inclusão de medidas de Ka em água para obtenção da curva de calibração. Sem esse procedimento e sem verificação de campo das medidas de Ka, erros na estimativa de θ da ordem de 0,1m3 m-3 podem ocorrer facilmente.

The time domain reflectometry is a technique used to estimate soil water content (θ) as a function of its apparent dielectric constant (Ka). In this study the main objective was to investigate the consequences of including or not measures of Ka in water on the TDR calibration curve. Three horizons with different clay content were used: 0.13kg kg-1, 0.23kg kg-1 and 0.64kg kg-1. In each horizon, Ka was measured from dry to saturated soil. Additionally, Ka was measured in water. Measurements were made ​​using coaxial cables RGC58, 50 ohms and double stainless rod of 19cm. For each soil two data sets with θ and Ka were formed, one with and another without the addition of Ka measured in water. In each set a cubic polynomial equation was adjusted, estimating θ as a function of Ka. With the inclusion of Ka measured in water the cubic polynomial adjusted better the extreme saturated and avoided errors in the estimated θ. Since there is no certainty that the measures of Ka on field will not be greater than the measures of Ka in the saturated samples in the laboratory, it's recommend to include measures of Ka in water to obtain the calibration curve. Without this procedure and no field verification of Ka measurements, errors in estimated θ of the order of 0.1m3 m-3 can easily occur.

Qualidade física de um latossolo vermelho sob sistema de semeadura direta e cultivo convencional / Physical quality of an oxisol under no-tillage and conventional tillage

Para garantir a sustentabilidade dos sistemas agrícolas, a compreensão e a quantificação do impacto do uso e manejo do solo na sua qualidade física são de fundamental importância. Nesse sentido, objetivou-se com este trabalho avaliar a qualidade de um Latossolo Vermelho sob cultivo convencional (CC) e sistema de semeadura direta (PD), por meio de diferentes indicadores físicos. Os sistemas de uso e manejo do solo foram: CC e PD por sete e oito anos consecutivos (solo de textura média) e CC e PD por nove e dez anos consecutivos (solo de textura argilosa). Foram determinadas, nas camadas de 0-0,10; 0,10-0,20 e 0,20-0,30 m, a resistência do solo à penetração, a porosidade total, a macroporosidade e a microporosidade, a retenção de água no solo, o índice S, a densidade, a densidade do solo máxima e também a densidade do solo relativa. Foi verificada grande variação da resistência do solo à penetração ao longo do ciclo das culturas da soja e do milho, sendo que seus maiores valores foram constatados nas camadas superficiais. Dentre os sistemas de manejo, o PD apresentou maior resistência do solo à penetração. Dentre os sistemas de manejo, o CC apresentou melhores resultados em relação aos indicadores de qualidade física do solo.

The understanding and quantification of the impact of tillage systems in their physical quality are fundamental in the development of sustainable agricultural systems. This study aimed to evaluate the quality of an Oxisol under conventional tillage (CT) and no-tillage system (NT), through different physical indicators. The management systems were: CT and NT for seven or eight consecutive years (medium textured soil) and CT and NT by nine and ten consecutive years (clay soil). Were determined, at the layers 0-0.10, 0.10-0.20; 0.20-0.30 m, soil resistance to penetration, total soil porosity, macroporosity and microporosity, soil water retention, S index, soil bulk density, maximum density and relative bulk density. Was observed great variation of soil resistance to penetration throughout the soybean and corn cycles, with its highest values were found in the surface layers. The NT showed greater resistance to penetration. Among the management systems, the results against indicators of soil physical quality were similar.

A Soil Water Extraction Method Using Accelerated Solvent Extraction Technique for Stable Isotope Analysis / 分析化学

Soil water is one of the most important components in hydrological cycle. The stable hydrogen and oxygen isotopes in soil water have been increasingly used in the ecological, environment and hydrological research. In view of different techniques for extracting soil water, there is significant difference in theδD andδ18 O composition. This paper presents a method for analyzing hydrogen and oxygen isotopes in soil water by using elemental analyzer and isotope ratio mass spectrometry with accelerated solvent extraction for sample pretreatment. The conditions are: extraction solvent: dichloromethane, temperature: 100 ℃, pressure of 10. 3 MPa, static time:10 min. The samples were extracted three times, and with cycle values of four, four and three, respectively. Comparing with the added water, the deuterium and oxygen isotope values in the extracted soil water enrich 2. 12‰-4. 58‰ and 0. 17‰-0. 93‰, respectively. The reproducibility of replicate extractions of soil water is around ±0. 89‰ for δD and ±0. 37‰ for δ18 O.

Hidrogel como substituto da irrigação complementar em viveiro telado de mudas de cafeeiro / Hydrogel as a substitute for irrigation in screened seed nursery coffee

O cafeeiro, em sua fase inicial de mudas, requer um adequado suprimento de água, pois o estresse hídrico pode causar reduções no crescimento e subsequentemente na produção em campo. A hipótese deste trabalho foi que o uso do hidrogel como substituto da irrigação de mudas de café cv. 'Iapar 59' proporciona mudas de qualidade igual ou superior àquelas irrigadas. O experimento foi conduzido em viveiro telado (50% sombrite) em Presidente Prudente - SP - de fevereiro a outubro de 2008. Utilizou-se o delineamento inteiramente casualizado, com cinco tratamentos (sem polímero e irrigado diariamente; 0,0; 1,0; 2,0 e 3,0g por saco de polietileno sem irrigação) e 20 repetições. Realizaram-se seis avaliações periódicas: número de folhas (NF), matéria seca da parte aérea (MSPA) e raízes (MSR); comprimento da parte aérea (CPA) e raízes (CR) e MSPA/MSR. Para as condições do ensaio, o uso do hidrogel na dose de 2g por saco de polietileno proporcionou mudas de mesma qualidade que aquelas irrigadas. A relação MSPA/MSR foi superior para o tratamento irrigado.

The coffee seedlings require an adequate water supply because the water stress can cause reductions in growth and subsequently in the production field. The hypothesis of this research was that the hydrogel used as a substitute for the irrigation of seedlings of 'Iapar 59' coffee provides quality equal or higher seedling irrigated. The experiment was conducted in a screened seed nursery (50 shading) in Presidente Prudente city, São Paulo State, Brazil, since February to October 2008. The statistical design was completely randomized, with 5 treatments (without polymer and without irrigation; 0.0; 1.0; 2.0 and 3.0g of hydrogel per polythene bag without irrigation) and 20 repetitions. We conducted six periodic evaluations: number of leaves (NF), dry matter of aerial part (MSPA) and roots (MSR); length of aerial part (CPA) and roots (CR) and the MSPA/MSR. Under test conditions, the use of hydrogel in the dose of 2g per polyethylene bag results in seedlings of same quality of seedlings irrigated. The MSPA/MSR relation was higher for the irrigated treatment.

The influence of physical soil properties on the water supply of irrigated orchards-some examples from Val Venosta (South Tyrol/Northern Italy).

In irrigated agriculture, irrigation water volume and duration of irrigation can be optimized utilizing soil water dynamics data. Val Venosta in South Tyrol (Northern Italy) is a region where irrigation represents a central factor of production in the Tyrolese fruit-growing areas. Intensive orchard production is practised within an area of about 18.000 ha. Although fruit cultivation experts believe that intensive fruit cultivation should be based on regular irrigation of the fruit trees to guarantee optimum results in both fruit quantity and quality; however, fruit growers in the region follow very subjective criteria in regard to irrigation. At many locations much more water is used than the fruit trees actually need. Therefore irrigation in this region is a very cost-intensive factor of production and is criticized by the public for both economic and ecological reasons. To optimize the irrigation practice in this region it is essential to provide an objective basis for the irrigation process. A system of “precision irrigation” proposed, which is therefore based on objective and quantitative criteria focusing primarily on soil properties and hydrologic balance. This contribution will provide an overview of the current situation of irrigation and present results from soil-physical and soil-hydrological studies performed in this region since 2003.

The effect of climate and soil conditions on tree species turnover in a Tropical Montane Cloud Forest in Costa Rica

On a global level, Tropical Montane Cloud Forests constitute important centers of vascular plant diversity. Tree species turnover along environmental gradients plays an important role in larger scale diversity patterns in tropical mountains. This study aims to estimate the magnitude of beta diversity across the Tilarán mountain range in North-Western Costa Rica, and to elucidate the impact of climate and soil conditions on tree species turnover at a local scale. Seven climate stations measuring rainfall, horizontal precipitation (clouds and wind-driven rain) and temperatures were installed along a 2.5km transect ranging from 1 200m.a.s.l. on the Atlantic to 1 200m.a.s.l. on the Pacific slope. The ridge top climate station was located at 1 500m.a.s.l. Climate data were recorded from March through December 2003. Additionally, seven 0.05ha plots were established. On all plots soil moisture was monitored for one year, furthermore soil type and soil chemistry were assessed. Woody plants with a diameter at breast height (dbh) ≥5cm were identified to species. Species’ distributions were explored by feeding pairwise Sørensen measures between plots into a Principal Component Analysis. Relationships between floristic similarity and environmental variables were analyzed using Mantel tests. Pronounced gradients in horizontal precipitation, temperatures and soil conditions were found across the transect. In total, 483 woody plants were identified, belonging to 132 species. Environmental gradients were paralleled by tree species turnover; the plots could be divided in three distinctive floristic units which reflected different topographic positions on the transect (lower slopes, mid slopes and ridge). Most notably there was a complete species turnover between the ridge and the lower Pacific slope. Floristic similarity was negatively correlated with differences in elevation, horizontal precipitation, temperatures and soil conditions between plots. It is suggested that beta-diversity in the study area is largely driven by species with narrow spatial ranges, due to the interactions between topography, climate and soil formation processes, especially around the wind-exposed and cloud covered ridge area. The findings emphasize the extraordinary conservation value of tropical montane cloud forests in environmentally heterogeneous areas at mid-elevations. Rev. Biol. Trop. 58 (4): 1489-1506. Epub 2010 December 01.

A nivel global, los bosques nubosos tropicales constituyen importantes centros de diversidad florística. El recambio de especies a través de gradientes ambientales juega un papel importante en los patrones de diversidad en las montañas tropicales. Este estudio tiene como objetivo estimar la diversidad beta de plantas leñosas a través de la Cordillera de Tilarán en el noroeste de Costa Rica y aclarar el impacto del clima y las condiciones del suelo en la distribución de especies a una escala local. Se instalaron siete estaciones meteorológicas, en las cuáles se midió lluvia, precipitación horizontal y temperatura, a lo largo de un transecto de 2.5km desde 1 200msnm de altitud en la vertiente Atlántica a 1 200msnm en la vertiente Pacífica. La estación de la cima se localizó a 1 500msnm. Los datos climáticos se registraron entre marzo y diciembre del 2003. Además, se establecieron siete parcelas de 0.05ha. En cada parcela se monitoreó la humedad del suelo por un año. Se determinaron los tipos de suelo y sus propiedades químicas. Las plantas leñosas con un diámetro ≥5cm fueron identificadas. La distribución de las especies fue explorada insertando las medidas Sørensen entre parcelas en un Análisis de Componentes Principales. Las relaciones entre la similitud florística y las variables ambientales se analizaron mediante pruebas de Mantel. Se encontraron gradientes pronunciados en la precipitación horizontal, temperaturas y condiciones del suelo a través del transecto. En total, se identificaron 483 plantas leñosas, pertenecientes a 132 especies. El recambio de especies leñosas se efectuó de forma paralela a los gradientes ambientales; según los análisis las parcelas se dividen en tres unidades distintivas florísticas que reflejan diferentes posiciones topográficas del transecto. Notablemente se produjo un recambio total de especies entre la cima y la vertiente Pacifica inferior. La similitud florística fue correlacionada negativamente con las diferencias de altitud, precipitación horizontal, temperaturas y condiciones del suelo entre las parcelas. Se sugiere que la diversidad beta en el área de estudio resulta en gran parte de la distribución de especies con rangos limitados, debido a las interacciones entre la topografía, el clima y los procesos de formación del suelo, especialmente alrededor de la cima que está expuesta a los vientos alisios y frecuentemente cubierta de nubes. Los resultados subrayan el valor de conservación extraordinaria que tienen los Bosques Nubosos Tropicales en áreas ambientalmente heterogéneas en alturas medianas.

Aplicação de modelos matemáticos na estimativa do volume de bulbo molhado por gotejamento superficial em diferentes tipos de solo / Application of mathematical models to estimate the wet soil volume in superficial drip irrigation in different types of soils

A informação do volume de solo molhado pela irrigação localizada é importante para o dimensionamento e manejo da irrigação por gotejamento superficial, bem como para a estimativa da quantidade de água disponível para as plantas. Com o objetivo de avaliar cinco modelos para estimar o volume molhado pela irrigação por gotejamento superficial, foram instalados experimentos em seis tipos de solos (Luvissolo Crômico, Argissolo Vermelho-Amarelo, Cambissolo Háplico, Neossolo Quartzarênico, Latossolo Vermelho e Neossolo Flúvico). A partir desses experimentos, constatou-se que, com exceção do modelo proposto por NARDA & CHAWLA, os demais modelos estimam satisfatoriamente o volume de solo molhado pela irrigação por gotejamento superficial. Além disso, concluiu-se que o volume médio molhado para as mesmas combinações entre a vazão do emissor e o tempo de aplicação de água foram maiores para o Argissolo e menores para o Neossolo Flúvico e que, com exceção do Argissolo e do Neossolo Flúvico, o volume molhado do solo pode ser estimado por uma única equação em função do volume de água aplicado e do tempo de aplicação de água.

The information of wetting soil volume under drip irrigation has great importance in design and management of surface drip irrigation for delivering required amount of water to the plant. This study aimed to describe the wetted soil volume for five mathematic models by water applied on soil surface from drip emitter. For that, six experiments were installed in different soils (Entisol, Ultisol, Inceptisol, Psamment, Oxisol, Fluvent) with the objective of evaluating models which can estimate wetted soil volume in function of emitter discharged and time of water application. It was concluded that except for the model proposed by NARDA & CHAWLA, the other models estimated satisfactorily the wetted soil volume for the superficial drip irrigation. The wetted soil volume for the same combinations of emitter discharged and water application time, were larger for Ultisol and smaller for Fluvent and excepting Ultisol and Fluvent, the wetted soil volume can be estimated for a single equation in function of emitter discharged and time of water application.

Textura do solo e a estimativa do teor de água no ponto de murcha permanente com psicrômetro / Soil texture and the estimation by Dewpoint Potential Meter of water retention at wilting point

A determinação do volume de água disponível às plantas é fundamental para o correto manejo da irrigação e definição quanto ao uso dos solos agrícolas. Os principais fatores que exercem influência na retenção e disponibilidade de água às plantas são a textura e a estrutura do solo. O objetivo deste trabalho foi quantificar a influência da textura na retenção da água, na condição de ponto de murcha permanente (PMP) das plantas (-1,5MPa), sendo utilizado um psicrômetro modelo WP4-T. Determinaram-se a textura de 100 amostras de solo e o teor de água no PMP. Os resultados indicaram que, em potenciais maiores que -1,0MPa, o psicrômetro mostrou-se pouco preciso, não se recomendando a sua utilização nessa condição. O PMP aumentou de 0,059 para 0,29g g-1, quando o teor de argila aumentou de 120 para 779g kg-1. Obteve-se um bom ajuste dos resultados do teor de água no PMP em função do teor de argila do solo, e 91 por cento da variação do teor de água no PMP puderam ser atribuídos à variação no teor de argila. Conclui-se que o psicrômetro é um equipamento que pode ser utilizado para determinar o PMP, e a equação PMP (g g-1)=0,0003*Argila (g kg-1)+0,0118 pode ser utilizada para estimar o PMP.

The determination of the available water to plants is essential to right irrigation management and definition regarding the use in agricultural soils. The main factors that exert influence on retention and availability of water to plants are texture and soil structure. The aim of this study was to quantify the influence of the texture on water retention in the condition of permanent wilting point (PWP) of plants (-1,5MPa) using a WP4-T Dewpoint Potentia Meter. The texture of 100 soil sample and soil moisture at PWP was determined. Results indicated that, in potentials higher than -1,0MPa, WP4-T seemed not very precise, therefore its use is not recommended in this condition. PWP increased from 0,059 to 0,29g g-1, while the clay content increased from 120 to 779g kg-1. It was obtained a good adjustment of the results of water content at PWP based on clay content of soil, being that 91 percent of variation in water content at PWP could be attributed to variation in clay content. It was concluded that WP4-T is an equipment that can be used to determine PWP and the equation PWP (g g-1)=0,0003 * Clay(g kg-1)+0,0118 can be used to estimate PWP.

Pore system changes of damaged Brazilian oxisols and nitosols induced by wet-dry cycles as seen in 2-D micromorphologic image analysis

Soil pore structure characterization using 2-D image analysis constitutes a simple method to obtain essential information related to soil porosity and pore size distribution (PSD). Such information is important to infer on soil quality, which is related to soil structure and transport processes inside the soil. Most of the time soils are submitted to wetting and drying cycles (W-D), which can cause important changes in soils with damaged structures. This report uses 2-D image analysis to evaluate possible modifications induced by W-D cycles on the structure of damaged soil samples. Samples of three tropical soils (Geric Ferralsol, GF; Eutric Nitosol, EN; and Rhodic Ferralsol, RF) were submitted to three treatments: 0WD, the control treatment in which samples were not submitted to any W-D cycle; 3WD and 9WD with samples submitted to 3 and 9 consecutive W-D cycles, respectively. It was observed that W-D cycles produced significant changes in large irregular pores of the GF and RF soils, and in rounded pores of the EN soil. Nevertheless, important changes in smaller pores (35, 75, and 150 µm) were also observed for all soils. As an overall consideration, it can be said that the use of image analysis helped to explain important changes in soil pore systems (shape, number, and size distribution) as consequence of W-D cycles.

A caracterização da estrutura do solo usando a análise de imagens bidimensionais (2-D) constitui um método simples na obtenção de informações essenciais relacionadas com a porosidade do solo e a distribuição do tamanho de poros. Tal informação é importante para obter dados sobre a qualidade do solo, a qual está diretamente ligada à sua estrutura e aos processos de transporte que ocorrem no seu interior. Na maior parte do tempo os solos são submetidos a vários ciclos de umedecimento ("wetting") e secamento ("drying") (W-D) que podem causar importantes mudanças em solos que possuem estruturas danificadas. Neste estudo foi usada a análise de imagens em 2-D na avaliação de possíveis modificações devido a vários ciclos de W-D na estrutura de amostras de solo danificadas.Três solos diferentes em textura (Latossolo vermelho-amarelo distrófico - LVAd; Nitossolo vermelho eutrófico - NVe, Latossolo vermelho distrófico - LVd) foram submetidos a três diferentes tratamentos: 0WD, amostras controle não submetidas a nenhum ciclo de W-D; 3WD e 9WD, amostras submetidas a 3 e 9 ciclos consecutivos de W-D, respectivamente. Foi observado que os ciclos de W-D produziram mudanças significativas nos poros grandes irregulares dos solos LVAd e LVd e nos poros arredondados do NVe. Importantes mudanças nos poros de 35 até 150 µm foram observadas para todos os solos estudados. A partir dos resultados obtidos pode ser dito que o uso da análise de imagens auxiliou com sucesso na explicação de variações no sistema poroso (formato, número e distribuição de tamanho dos poros) devido aos ciclos de W-D para todos os solos analisados.