Jefferson Schick

Propriedades físicas de um cambissolo húmico álico afetadas pelo manejo do solo

A degradacao fisica do solo e um dos principais processos responsaveis pelo aumento da erosao hidrica. Os preparos convencionais normalmente sao aceleradores desse processo, pois a sua execucao exige um intenso revolvimento mecânico do solo. Assim, a semeadura direta apresenta-se como um manejo conservacionista, pois a ausencia de preparo preserva os residuos culturais e aumenta a materia orgânica, apesar de aumentar a densidade e diminuir a porosidade superficial do solo. O trabalho foi desenvolvido num cambissolo humico alico, no Centro de Ciencias Agroveterinarias de Lages - SC, no periodo de maio de 1995 a novembro de 1997. Os tratamentos de preparo do solo, preparo convencional executado com uma aracao+duas gradagens, e semeadura direta sem revolvimento do solo, foram instalados em quatro repeticoes. Na semeadura direta, foram cultivadas aveia, milho, aveia, milho e aveia e, no preparo convencional, aveia, milho, pousio, milho e pousio, em sequencia. Foram avaliadas a densidade do solo, carbono orgânico, macroporosidade, microporosidade, porosidade total e relacao macroporos/porosidade total, nas camadas 0-2,5, 2,5- 5,0, 5,0-10,0 e 10,0-15,0cm de profundidade. Nas camadas de 0- 2,5 e 2,5 a 5,0cm, a semeadura direta apresentou maior densidade do solo e consequente menores macroporosidade e relacao macroporos/porosidade total do que o preparo convencional. Na semeadura direta, a densidade do solo diminuiu com a profundidade, com consequente aumento na macroporosidade e na relacao macroporos/porosidade total, enquanto no preparo convencional este comportamento foi inverso.

ERODIBILIDADE DE UM CAMBISSOLO HÚMICO ALUMÍNICO LÉPTICO, DETERMINADA SOB CHUVA NATURAL ENTRE 1989 E 1998 EM LAGES (SC)

The soil erodibility factor (K factor) of the Universal Soil Loss Equation (USLE) refers to the natural soil susceptibility to erosion and represents the quantity of lost soil per rain erosivity unit (R factor), a factor, which is of great importance in conservation management. Using data of soil loss, measured under natural rainfall conditions in collector ponds of superficial runoff, and of natural rainfall erosivity (EI30) in the period from 1989 to 1998 in Lages (SC), the soil erodibility factor for a Inceptisol was calculated with an average incline/gradient of 0.102 m m-1 by the quotient and simple linear regression between these variables. With this objective, erosivity values (EI30) of 437 rainfalls and soil loss were used, measured in 3.5 x 22.1 m plots, without vegetation or superficial covering. Soil preparation, carried out twice a year parallel to the incline/gradient, consisted in ploughing/tillage and two discings. Annual average erodibility values, estimated by the quotient and by simple linear regression between soil loss and erosivity, were 0.0115 and 0.0151 Mg ha h ha-1 MJ-1 mm-1, respectively. The estimated average seasonal erodibility values were 0.0105 and 0.0121 Mg ha h ha-1 MJ-1 mm-1 for spring/summer and 0.0132 and 0.0220 Mg ha h ha-1 MJ-1 mm-1 for fall/winter, according to the respective ways of measurement.

EROSIVIDADE DAS CHUVAS DE LAGES, SANTA CATARINA

The erosive capacity of rainfall can be expressed by an index and knowing it allows recommendation of soil management and conservation practices to reduce water erosion. The objective of this study was to calculate various indices of rainfall erosivity in Lages, Santa Catarina, Brazil, identify the best one, and discover its temporal distribution. The study was conducted at the Center of Agricultural and Veterinary Sciences, Lages, Santa Catarina, using daily rainfall charts from 1989 to 2012. Using the computer program Chuveros , 107 erosivity indices were obtained, which were based on maximum intensity in 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 70, 80, 90, 100, 110, 120, 135, 150, 165, 180, 210, and 240 min of duration and on the combination of these intensities with the kinetic energy obtained by the equations of Brown & Foster, Wagner & Massambani, and Wischmeier & Smith. The indices of the time period from 1993 to 2012 were correlated with the respective soil losses from the standard plot of the Universal Soil Loss Equation (USLE) in order to select the erosivity index for the region. Erosive rainfall accounted for 83 % of the mean annual total volume of 1,533 mm. The erosivity index (R factor) of rainfall recommended for Lages is the EI30, whose mean annual value is 5,033 MJ mm ha-1 h-1, and of this value, 66 % occurs from September to February. Mean annual erosivity has a return period estimated at two years with a 50 % probability of occurrence.

Razão de perdas de solo e fator C para milho e aveia em rotação com outras culturas em três tipos de preparo de solo

Soil and water loss data under natural rainfall in Lages, Santa Catarina State (Brazil), from November 1992 to October 1998, were utilized to calculate the soil loss ratio (SLR) and C factor for the Universal Soil Loss Equation (USLE) under three soil tillage systems for corn and oat in rotation with other crops. The studied treatments were: plowing followed by disking twice (P + D), chiseling plus disking (C + D) and no-tillage (NT)/direct sowing, cultivated with corn (Zea mays) and oat (Avena sativa) in rotation with other crops and compared to a check plot: plowing followed by double disking without crops (PDW), on an Inceptisol with an average slope of 0.102 m m-1. The culture cycle was divided in five crop stages with equal time intervals. The SLR and C factors varied remarkably among the soil tillage systems, crop cycle stages, cycle stages for same crops, and between crops, indicating a strong effect of soil management, season, crop and rainfall on these variables. The SLR values for corn were 0.1189, 0.0888 and 0.0611 (Mg ha-1) (Mg ha-1)-1 for the P + D, C + D and NT soil tillage systems, respectively, while for oat the SLR values for the same tillage systems were 0.0783, 0.0655 and 0.0760 (Mg ha-1) (Mg ha-1)-1. For the above mentioned soil tillage systems, the C factors were 0.1097, 0.0809 and 0.0610 (Mg ha-1) (Mg ha-1)-1 for corn and 0.0671, 0.0409 and 0.0372 (Mg ha-1) (Mg ha-1)-1 for oat.

Erodibilidade de um Cambissolo Húmico sob chuva natural

Estimation of soil loss is critical to conservation planning. To make that estimation, use of the Universal Soil Loss Equation (USLE) is prominent in Brazil. For use of the USLE, there is a shortage of data obtained according to the standard method of this model. Among the factors that compose the USLE, soil erodibility (K factor) is difficult to obtain due to the need to conduct experiments in the field for a long time under natural rainfall. Aiming to quantify soil erodibility in a Humic Inceptisol in Lages, Santa Catarina, Brazil, with the use of the standard method of USLE, we quantified the erosivity (EI30) of natural rainfall and respective soil loss for the period 1993-2012. Erodibility was determined by the ratio between these variables and by simple linear regression of the same variables. Annual erodibility values, estimated by the ratio and by simple linear regression between soil loss and erosivity, were 0.0175 and 0.0172 Mg ha h ha-1 MJ-1 mm-1, respectively. The erodibility in spring-summer and autumn-winter showed small variations in relation to the annual average. The monthly erodibility ranged from 0.0083 Mg ha h ha-1 MJ-1 mm-1 in December to 0.0241 Mg ha h ha-1 MJ-1 mm-1 in April. Throughout the time period evaluated, annual erodibility exhibited a greater increase in the initial years and a smaller increase in the final years.