Cássio Antonio Tormena

Caracterização do intervalo hídrico ótimo de um latossolo roxo sob plantio direto

Soil physical attributes, i. e., soil water potential, soil oxygen, and soil strength, directly affect plant growth. The least limiting water range (LLWR) is the range of soil water content within which plant growth is least limited by water potential, aeration and mechanical resistance and has not been evaluated in tropical soils. The objective of this research was to characterize the LLWR of a Typic Hapludox cropped to corn under no-tillage. Seventy-two undisturbed soil samples were collected at the crop row and interrow. The soil water retention curve and the soil resistance curve were evaluated in order to compute the LLWR. The results indicated that the LLWR varied positively with bulk density up to 1.1 Mg m-3 and negatively for higher densities. The LLWR ranged from 0.0073 to 0.1252 m3 m-3. Soil resistance to penetration was the limiting factor at the dry end of the LLWR in 85% of the samples while field capacity was the limiting factor at the wet end in 97%. Further studies on the LLWR in tropical soils would be relevant under a wide range in texture and management.

Propriedades físicas de um Latossolo Vermelho distrófico cultivado e sob mata nativa

The understanding and quantification of the impact caused by soil use and management on the physical soil quality are fundamental for the development of sustainable agricultural systems. The objective of this research was to quantify some physical soil properties to evaluate the physical quality of a dystrophic Red Latosol (Rhodic Ferralsol) in the northwest of the State of Parana, Brazil. Undisturbed soil samples were collected from two contiguous areas on an Experimental Farm of the State University of Maringa. One area was cultivated with annual crops under conventional tillage (disk plow and harrowing) and the other under native forest (semidecidual seasonal forest). The evaluated physical soil attributes were soil porosity and bulk density, soil water retention curve, soil resistance curve, and the least limiting water range. Results indicated significantly higher values of bulk density and lower values of soil porosity in the cultivated area. The soil water retention curve was not influenced by the soil use system, but was negatively influenced by bulk density. The soil resistance curve was influenced by the soil use system, evidenced by high values of soil resistance to root penetration under increasing drought in the cultivated soil. The least limiting water range was significantly smaller in the cultivated soil owing to the soil resistance to root penetration and air-filled porosity, which determined the lower and upper limits of soil water availability with bulk density increase. In the soil under native forest, the least limiting water range was equal to the water availability determined by the field capacity and the permanent wilting point. Soil compaction in the cultivated soil induced changes in the soil porous system, which were described by lower values of the least limiting water range than in virgin soil.

Variação temporal do intervalo hídrico ótimo de um latossolo vermelho distroférrico sob sistemas de plantio direto

O plantio direto e eficiente no controle das perdas de solo e agua, mas o trafego de maquinas e a ausencia de revolvimento podem induzir a compactacao superficial dos solos de textura argilosa. O intervalo hidrico otimo (IHO) traduz os efeitos de sistemas de manejo na melhoria ou na degradacao da qualidade fisica do solo. O objetivo deste estudo foi quantificar o IHO para discriminar os efeitos de sistemas de manejo em plantio direto na qualidade fisica do solo. Os tratamentos utilizados foram: plantio direto com sucessao de culturas, plantio direto com rotacao de culturas e plantio direto com rotacao de culturas e escarificacao do solo. Em duas epocas distintas - em outubro de 2002, apos a cultura de inverno (trigo), e em abril de 2003, apos a cultura de verao (soja) - foram retiradas 44 amostras indeformadas em cada tratamento. Essas amostras foram utilizadas para determinar a curva de retencao de agua, a curva de resistencia do solo a penetracao, a densidade do solo, o IHO e a densidade critica do solo. A resistencia do solo a penetracao determinou o limite inferior do IHO em todos os tratamentos e reduziu os seus valores com o aumento da densidade do solo. A densidade critica do solo nao dependeu do sistema de manejo em plantio direto. A variacao temporal do IHO nos tratamentos foi dependente da variacao da densidade do solo. No plantio direto com rotacao, a maior retencao de agua em elevados potenciais proporcionou, temporalmente, maiores valores do IHO.

Propriedades físicas do solo sob plantio direto influenciadas por calagem, preparo inicial e tráfego

In the no-tillage system, the absence of soil revolving, combined with the traffic of machines, promotes excessive soil surface compaction. An experiment was conducted in the county of Ponta Grossa, State of Parana, Brazil, during the agricultural years of 1989/1990 and 1990/1991, with the objective of studying several factors that intervene in this process. This research compared the effects of three previous soil tillage methods and two liming levels on several physical properties of a clayey Dark Red Latosol under a no-tillage system and controlled traffic. Soil bulk density, soil porosity, and water retention between the potentials of -0.006 and -0.5 MPa were evaluated. Results showed significant effects of traffic increasing soil density and reducing soil porosity and water content retained between the above mentioned potentials. There was no significant effect of liming on the studied properties. The in-depth distribution of the load applied by the traffic of machines, mainly harvesters, seemed to be influenced by the soil volume revolved by the different soil initial tillage systems. Soil structure was modified by the traffic of machines, altering soil quality and reducing soybean yield, when compared to areas with absence of traffic.

Efeitos de sistemas de preparo nas propriedades físicas de um Latossolo Vermelho distrófico

Soil tillage systems and the crop residue management are essential for the sustainability of cassava production in sandy and sandy loam soils of Northwestern Parana State, Southern Brazil. The objective of this study was to evaluate the effects of different tillage systems used for planting cassava: no-tillage (NT), minimum tillage using chiseling (MT) and conventional tillage with moldboard plow and disking (CT) on some physical properties of a dystrophic Red Latosol. The following soil physical properties were evaluated in the 0-0.15 m and 0.15-0.30 m soil layers: soil bulk density (BD), soil water retention curve, soil resistance to penetration curve and least limiting water range (LLWR). Higher values of BD and soil resistance to penetration were verified in the NT and MT treatments. The soil water retention curve was only influenced by BD, which incorporated the effects of the soil tillage systems independent of sampled layers. The soil resistance curve to penetration was influenced by tillage systems and layers, indicating that the soil resistance to root penetration was higher in NT > MT > CT, and was accentuated at the 0.15-0.30 m depth. The increase in the BD led to a reduction in the LLWR due to the effects of soil resistance to penetration and air-filled porosity, which in turn determined the range of soil available water. Results indicated that LLWR value followed the sequence: PC = PM > PSR in the 0-0.15 m soil layer, and was not influenced by tillage systems in the 0.15-0.30 soil layer The critical bulk density value (BDc), the BD value at which LLWR = 0, was lower in NT and MT tillage systems compared with CT, therefore resulting in a smaller frequency of higher BD values than BDc in the soil under CT.

Soil bulk density, porosity and resistance to root penetration in an Oxisol managed by different soil tillage systems

Os sistemas de preparo e manejo do solo determinam as condicoes fisicas para o crescimento das plantas e produtividade das culturas. O objetivo deste estudo e o de avaliar algumas propriedades fisicas de um Latossolo Vermelho distrofico, cultivado com mandioca, apos dois anos de implantacao em diferentes sistemas de preparo do solo. Os tratamentos utilizados foram: Plantio Direto (mobilizacao do solo somente ao longo das linhas de plantio); Preparo Minimo (escarificacao a 0,30 m, seguido de gradagem niveladora) e Preparo Convencional (aracao, com arado de aiveca a uma profundidade de 0,25 m, seguido de gradagem niveladora). Avaliaram-se, nas camadas de 0-0,10 m e 0,10-0,20 m, as seguintes propriedades fisicas do solo: densidade, volume de macroporos, microporos, a porosidade e a resistencia do solo a penetracao das raizes, a cada 0,05 m, ate a profundidade de 0,40 m, em tres diferentes epocas. Constataram-se maiores valores de densidade do solo e menores valores de macroporosidade na camada de 0-0,10 m no plantio direto e preparo minimo do solo. Resultados similares foram obtidos na avaliacao da resistencia do solo a penetracao, independente da epoca de avaliacao e da umidade do solo. Os sistemas de preparo minimo e preparo convencional do solo proporcionam condicoes fisicas menos restritivas ao crescimento das plantas, quando comparado com o plantio direto. Avaliacoes de medio-longo prazo sao necessarias face as mudancas dinâmicas na qualidade fisica do solo, impostas pelos sistemas de preparo e manejo do solo e da cultura.

Quantification of the soil physical quality of a tropical oxisol using the S index

Soil physical quality is fundamental for the sustainability of agro ecosystems. Soil physical quality assessment must be developed using parameters that describe physical behavior. S, a new soil physical parameter has recently been introduced for assessing the soil physical quality. A good soil physical quality has been associated with values of S > 0.035 in soils from temperate climates. However, S has not been evaluated in tropical soils yet. Therefore we tested the hypothesis that S is a reliable soil physical quality indicator of a Typic Hapludox cropped with maize under no-tillage (NT) and conventional tillage (CT). Undisturbed samples were collected from each tillage system in the row and interrow positions. Soil bulk density was determined in the samples and the S parameter was calculated using a pedotransfer function from the same samples. The parameter S was able to differentiate tillage and position with SNT < SCT independent of the row and interrow sampling positions. Higher S values were verified in row position than in the interrow in both tillage systems. With the use of a pedotransfer function it was also possible to establish a negative relationship between S and soil compaction. The results confirmed our hypothesis and suggest that further studies should be carried out to evaluate S in other tropical soils and management systems.

Critérios para avaliação do potencial de lixiviação dos herbicidas comercializados no Estado do Paraná

A survey was carried out on the commercialization of herbicides in Parana, to verify their total input in the environment. Based on the chemical properties of these herbicides, theoretical criteria ranking them according to their leaching potential were evaluated. The highest volume of commercialization was found to occur from October to November, probably related to the increased demand caused by the summer crop cycle. The mechanisms of action whose consumption is most expressive are the aminoacid synthesis inhibitors (36.9% of the total volume), followed by the photosynthesis inhibitors (31.3%), synthetic auxins (11%) and mitosis inhibitors (8.8%). The herbicides glyphosate (4526.28 t), atrazine (3075.91), 2,4-D (1659.33) and sulfosate (631.60 t) account together for around 65% of the total volume commercialized in the state. Ranking herbicides according to their leaching potential showed that acifluorfen-sodium, alachlor, atrazine, chlorimuron-ethyl, fomesafen, hexazinone, imazamox, imazapyr, imazaquin, imazethapyr, metolachlor, metribuzin, metsulfuron-methyl, nicosulfuron, picloram, sulfentrazone and tebuthiuron are potential leachers according to the three theoretical criteria adopted (GUS, CDFA and Cohen).

Sorption-Desorption of Atrazine and Diuron in Soils from Southern Brazil

The objective of this study was to investigate the behavior of sorption and desorption of the herbicides atrazine (6-chloro-N 2-ethyl-N 4-isopropyl-1,3,5-triazine-2,4-diamine) and diuron [3-(3,4-dichlorophenyl)-1,1-dimethyleurea] in soil samples from a typical lithosequence located in the municipality of Mamborê (PR), southern Brazil. Five concentrations of 14C-atrazine and 14C-diuron were used for both herbicides (0.48, 0.96, 1.92, 3.84, and 7.69 mg L−1). Sorption of both herbicides correlated positively with the organic carbon and clay content of the soil samples. Sorption isotherms were well described by the Freundlich model. The slope values of the isotherm (N) ranged from 0.84 to 0.90 (atrazine) and from 0.75 to 0.79 (diuron) for the lithosequence samples. Sorption of diuron was high regardless of the soil texture or the concentration added. The desorption isotherms for atrazine and diuron showed good fit to the Freundlich equation (R 2 ≥ 0,87). Atrazine slope values for the desorption isotherms were similar for the different concentrations and were much lower than those observed for the sorption isotherms. Significant hysteresis was observed in the herbicide desorption. When the two herbicides were compared, it was found that diuron (N = 0.06–0.22) presented more pronounced hysteresis than atrazine. The results showed that, quantitatively, a greater atrazine fraction applied to these soils remains available to be leached in the soil profile, as compared to diuron.

Variabilidade e correlação espacial de propriedades físicas de solo sob plantio direto e preparo convencional

Soil management systems modify the spatial distribution of soil physical properties. The objectives of this study were to verify the spatial dependency and co-relationship of some soil physical properties by data fitting to individual and cross-semivariograms in an Oxisol (Typic Haplorthox) under no-till and conventional tillage, in Campo Mourao, state of Parana, Brazil. In April 2004, 128 undisturbed soil samples were collected in a 3 x 5 m grid, in the middle of the 5-0.15 m layer. The following soil physical properties were measured: soil bulk density, macroporosity, microporosity, total soil porosity and soil water content at a tension of 100 hPa (field capacity). The spatial variability in the single semivariogram of these soil physical properties was higher and the range in no-tillage was smaller than in conventional tillage. On the other hand, the cross-semivariogram of soil bulk density and total porosity or field capacity indicated spatial co-relationships with lower spatial variability and higher ranges in no-tillage than conventionally tilled soils. The cross-semivariogram suggested that soil bulk density showed a spatial co-relationships with the other soil physical properties in both soil management systems studied.