Resumen La curva de retención de agua del suelo (SWRC) relaciona la humedad con la energía de retención de agua (potencial de matriz). En suelos retráctiles, este volumen varía de acuerdo con el secado o la humectación del suelo, lo que puede provocar errores en la humedad calculada. El objetivo de este estudio es cuantificar la variación de volumen en los suelos retráctiles y elaborar el SWRC a través del método tradicional, que no considera la retracción del suelo, y un segundo método, que considera la retracción. Se han recolectado muestras de suelo en los horizontes A y B de seis perfiles de suelo. Por lo tanto, para suelos retráctiles, se recomienda que el ajuste del SWRC se lleve a cabo considerando el volumen real del suelo (retraído), que varía para cada potencial de matriz aplicado. Este ajuste reduce los errores, principalmente al determinar el punto de marchitez permanente y el agua disponible.

Abstract The soil water retention curve (SWRC) relates moisture to soil water retention energy (matrix potential). The calculation of the volumetric humidity considers the sample volume. In retractable soils, this volume varies according to the drying or wetting of the soil, which can result in errors in the calculated moisture. The objective of this study is to quantify the volume variation in retractable soils and to elaborate the SWRC via the traditional method, which does not consider soil retraction, and a second method, called adjusted, that considers the phenomenon of soil retraction. Soil samples have been collected in horizons A and B from six soil profiles Thus, for retractable soils, it is recommended that the adjustment of the SWRC be carried out considering the actual volume of the soil (retracted), which varies for each matrix potential applied. This adjustment reduces errors, mainly in determining the permanent wilt point and available water.

Resumo: O objetivo deste trabalho foi avaliar as aplicações superficial e injetada de dejeto líquido de suínos e ureia ao solo, quanto aos seus efeitos sobre as propriedades físicas de um Nitossolo Vermelho distroférrico, em um sistema de semeadura direta. Os tratamentos foram: dejeto injetado no sulco, com injetor de dejeto líquido de suínos (IDLS); dejeto em superfície, aplicado às linhas com o IDLS erguido; ureia injetada, por meio de abertura do sulco com o IDLS, e distribuída manualmente; e milho, em semeadura direta, como controle. A semeadura e a injeção de dejeto líquido ou de ureia não modificam o teor de carbono orgânico, o pH e a agregação, mas alteram a densidade e a porosidade do solo na linha mobilizada, e aumentam os macroporos.

Abstract: The objective of this work was to evaluate the superficial and injected applications of swine slurry and urea to the soil, regarding their effects on the physical properties of a Nitossolo Vermelho distroférrico under a no-tillage system. The treatments were: injected slurry into the groove with a liquid swine slurry injector (LSSI); slurry on surface, applied on the lines by the LSSI kept raised; urea injected by opening the groove with the LSSI and distributed manually; and corn, under no-tillage, as a control. Sowing and the injection of liquid slurry or urea do not modify the organic carbon content, pH, and aggregation, but alter the soil bulk density and porosity in the mobilized line, and increase the macropores.

ABSTRACT: Soil water retention and availability are important properties for agricultural production, which can be measured directly or estimated by pedotransfer functions. Some studies on this topic were carried out in Santa Catarina, Brazil. To improve the estimates, it is necessary to evaluate other properties, to analyze more soil types, as well as to use other analysis techniques such as artificial neural networks and regression trees. Thus, the objective of the study was to estimate the field capacity (FC), permanent wilting point (PWP), and available water (AW) in soils of Santa Catarina (SC), through multiple linear regressions (MLR), artificial neural networks (ANN), and regression trees (RT), more efficiently than the current pedotransfer functions. For this, samples of the horizons A and B of 70 profiles were collected to determine the texture, plasticity limit, FC, PWP, AW, specific surface (SS), organic carbon (OC) content, and microporosity. Pedotransfer functions were generated through MRL, ANN, and RT, considering as dependent variables the FC, PWP, and AW, and as independent variables the content of clay, silt, OC, plasticity limit, SS, and microporosity, through the test of four models, for surface and subsurface horizons. The RT estimated FC, PWP, and AW better than ANN and MRL. The best models to estimate water retention were those that used microporosity. When the database has few input variables, the model with clay, silt, and OC content is an alternative to estimate FC, PWP, and AW.

ABSTRACT Brown Nitossolos (Nitisols) and Latossolos (Ferralsols), according to the Brazilian System of Soil Classification (SiBCS), have a “caráter retrátil” as their distinctive property. Because this is a new topic, it is necessary to propose methods for evaluation. The objectives of this study were to evaluate methodologies for quantifying the shrinkage of soil using the Syringe Method and the Metallic Mercury Method, and to propose a new one, the “Ring with Sand Method”. Soil samples from eight pedons were used, with six Nitossolos and Latossolos with shrinkage, a Latossolo without shrinkage, and a Vertissolo (Vertissol) with admittedly high shrinkage and expansion. The methods were effective in identifying the greater degree of shrinkage of the Vertissolo . However, the Ring with Sand Method was the only one to indicate significant differences between the Vertissolo and the Latossolo without shrinkage, and this method differentiated the shrinkable soils as to the intensity of the characteristic. The proposed method was effective and can serve as a standard to quantify shrinkage.

No sul do Brasil, há ocorrência espontânea de papuã (Urochloa plantaginea (Link) R.D. Webster), nas lavouras, no período de verão, sendo que essa planta possui grande potencial forrageiro. Neste trabalho, objetivou-se avaliar as alterações ocorridas nas características físicas e na matéria orgânica do solo, em pasto de papuã, com diferentes alturas de manejo, na presença e na ausência de pisoteio animal. O trabalho foi realizado na Estação Experimental do IAPAR, no município de Pato Branco, Paraná. O delineamento experimental utilizado foi o de blocos casualizados com três repetições. Os tratamentos foram arranjados em esquema bifatorial, com parcelas subdivididas, durante o período de pastejo. As parcelas receberam os níveis do fator altura de manejo de pasto de papuã (0,1; 0,2; 0,3 e 0,4 m), enquanto as subparcelas foram constituídas de áreas com (pastejadas por cabras) e sem pisoteio animal (corte manual). Foram avaliados, após o período de pastejo, os teores de matéria orgânica, a densidade, a porosidade total, a macro e a microporosidades do solo. De maneira geral, a altura de manejo do papuã, na presença, ou não, de pisoteio animal, não alterou significativamente as características físicas e a matéria orgânica do solo, avaliadas após o primeiro ciclo de aplicação dos tratamentos. O pisoteio animal não causou compactação adicional e, mesmo com pastejo animal, os teores de matéria orgânica no solo mantiveram-se altos.

In southern Brazil there is spontaneous occurrence of alexandergrass (Urochloa plantaginea (Link) R.D. Webster) in crops during summer, and this plant has great potential forage production. The objective of this study was to evaluate the changes in physical characteristics and soil organic matter in pastures of Alexandergrass with different sward heights, in the presence and absence of animal trampling. The experiment was conducted at the Experimental Station IAPAR, in Pato Branco. The experimental design was randomized blocks with three replications. The treatments were arranged in a split-plot factorial model during the grazing period. The plots consisted of levels of the factor height of pasture management (0.1, 0.2, 0.3 and 0.4 m), while the subplots consisted of areas with (grazed by goats) and without animal trampling (manual cutting). After the grazing period, the variables organic matter levels, bulk density, total porosity, macro and micro porosities of the soil were evaluated. Generally, the management height of alexandergrass, in the presence or absence of trampling, did not significantly affect the physical characteristics and soil organic matter after the first cycle of treatment application. Animal trampling caused no additional compression and even with animal grazing, the organic matter levels in the soil remained high.