Ildegardis Bertol

Propriedades físicas do solo sob preparo convencional e semeadura direta em rotação e sucessão de culturas, comparadas às do campo nativo

In soils with naturally favorable characteristics for cultivation, conventional tillage degrades the physical soil properties, since this management system causes the rupture of aggregates, soil compaction, and eliminates soil cover. No-tillage, on the other hand, maintains soil cover and improves physical properties, but consolidates the surface layer. Our study was conducted on a Haplumbrept soil, from May 1995 to April 2001. Five soil tillage treatments were used: conventional tillage crop rotation (CTR), conventional tillage crop succession (CTS), no-tillage crop rotation (NTR), no-tillage crop succession (NTS), and natural pasture (NP), in four replications each. The crop sequences were bean/fallow/maize/fallow/soybean/fallow in CTR, maize/fallow/maize/fallow/maize/fallow in CTS, bean/oat/maize/turnip/soybean/vetch in NTR and maize/vetch/maize/vetch/maize/vetch in NTS. Soil density, macroporosity, microporosity, total porosity, organic carbon, and water aggregate stability (MWD) were evaluated in April 2001 for the soil layers 0-2.5, 2.5-5, 5-10, 10-15, 15-20, and 20-30 cm. In the 0-10 cm layer, soil density was higher in no-tillage than conventional tillage and natural pasture, while macroporosity, total porosity, and the macroporosity/total porosity relation was higher in conventional tillage in the mean for cropping systems, in this layer. Organic carbon, MWD, and sensibility index for MWD means of layers and tillage systems were higher in no-tillage and natural pasture than in conventional tillage.

Características químicas de um cambissolo húmico afetadas por sistemas de preparo, com ênfase à matéria orgânica

Organic matter is considered the soil attribute most sensitive to the changes triggered by the management systems. The objective of this study was to evaluate the effect of nine years using three soil tillage systems -conventional tillage, reduced tillage and no tillage- on soil chemical characteristics of a Humic Cambisol in southern Brazil. Soil samples were collected in September 1996 at depths of 0-2, 2-5, 5-10, 10-15, and 15-20 cm, and analysed for C and N contents in total organic matter and its coarse fraction and for other soil chemical characteristics. Soil management with no tillage and reduced tillage increased C and N at the soil layer of 0-20 cm in comparison to the conventional tillage. With reduced tillage, the increases of C and N in the total organic matter were of 12% (6.3 t ha-1) and 17% (593 kg ha-1), respectively, in relation to conventional tillage. With no tillage, the increases of C and N in total organic matter were of 17% (8.5 t ha-1) and 24% (808 kg ha-1), respectively, in relation to conventional tillage. The increases of C and N in coarse organic matter (> 53 ∝m) with reduced tillage were of 85% and 45%, respectively, in relation to conventional tillage. With no tillage, the increases of C and N in coarse organic matter were of 275 and 230%, respectively, in relation to conventional tillage. A close relationship was observed between effective CEC and soil pH and C content [CEC = -13.53 + 3.58 pH + 3.51 C(%); R2 = 0.76], confirming the dependence of CEC on soil organic matter. No tillage resulted in a stratification of Ca, P and K along soil depth, as compared with reduced tillage and conventional tillage, while pH and Al were not affected by the soil tillage treatments. None of the treatments resulted in any chemical limitation for crop development and productivity.

Erosão hídrica em cambissolo húmico alumínico submetido a diferentes sistemas de preparo e cultivo do solo: I. perdas de solo e água

Raindrop impact and runoff are the active agents of water erosion, which is influenced by soil roughness and cover, crop type and tillage system. Conservation tillage reduces water erosion in relation to conventional tillage by means of surface roughness and cover. This work was conducted in Centro de Ciencia Agroveterinarias, in Lages, Santa Catarina, Brazil, from January 1993, to October 1998 to quantify soil and runoff losses under natural rainfall in the following soil tillage downslope systems: no-tillage, chisel plow plus disking and plowing plus disking, both on crop rotation and succession, and one bare soil tillage treatment with plowing plus disking. Soybean, oat, bean, vetch, corn, vetch, soybean, wheat, bean, fodder radish, corn and oat were cropped in rotation and wheat and soybean in crop succession. The soil was a clayey Inceptisol (Haplumbrept) with a slope of 0.102 m m-1. The no-tillage system reduced soil losses in 52, 68 and 98% in relation to chisel plus disking, and plowing plus disking and bare soil, respectively. Soil losses were 63% lower in the spring-summer than in the autumn-winter period. Soil losses were reduced by 37% with crop rotation in relation to crop succession, on the average of the soil tillage systems used in the trial. Water losses were similar to soil losses, differing in their magnitude.

Erosão hídrica em cambissolo húmico alumínico submetido a diferentes sistemas de preparo e cultivo do solo: II. perdas de nutrientes e carbono orgânico

Erosion is one of the main causes of soil degradation because of the transport of nutrients. The nutrients are transported by water either dissolved or adsorbed on the soil particles, and the erosion rate may vary according to the tillage system. This work was conducted at the Centro de Ciencias Agroveterinarias in Lages, Santa Catarina, Brazil, from January 1993 to October 1998, to quantify the losses of phosphorus, potassium, calcium, magnesium and organic carbon due to erosion caused by natural rainfall in the following soil tillage systems: no-tillage, chisel plow plus disking, and plowing plus disking. Both, crop rotation and succession, were used for these three soil preparation systems. An additional treatment consisted of bare soil tillage + plowing plus disking. Soybean, oat, bean, vetch, corn, vetch, soybean, wheat, bean, fodder radish, corn, and oat were cropped in rotation and wheat and soybean in crop succession. The soil was a clayey Inceptisol (Haplumbrept) with a slope of 0.102 m m-1. The soil concentration of phosphorus, potassium, calcium, magnesium and organic carbon was higher under conservation tillage than conventional tillage. Total loss of the elements, however, was little influenced by the tillage systems, but were related with soil and water losses. The concentration of those elements in the erosion sediment was correlated with their concentration in 0-0.025 m soil layer, with presenting an enrichment rate close to one.

Perdas de solo e de água e infiltração de água em latossolo vermelho sob sistemas de manejo

Os sistemas de manejo do solo alteram o microrrelevo e a cobertura por residuos vegetais, influenciando a perda de solo e de agua. Assim, os objetivos deste estudo foram avaliar as perdas de solo e de agua e estimar a taxa de infiltracao estavel de agua no solo (TIE) em diferentes sistemas de manejo, sob chuva simulada. As avaliacoes de campo foram conduzidas sobre residuos vegetais, apos a colheita da cultura da soja (Glycine max L. Merril). Estudaram-se tres sistemas de manejo do solo: semeadura direta, preparo com grade aradora e com escarificador associados a tres niveis de cobertura do solo com residuo vegetal: 0,0; 2,0; e 4,0 Mg ha-1. Para caracterizar a area experimental foram feitas analises de densidade do solo, macroporosidade, estabilidade de agregados, umidade inicial do solo, percentual de cobertura e rugosidade superficial do solo. Por meio do uso do simulador de chuvas portatil, as parcelas receberam aplicacao de precipitacoes de 60 mm h-1. Os tratamentos foram dispostos segundo o delineamento inteiramente casualizado, arranjados em esquema fatorial 3 x 3, com tres repeticoes. As perdas de solo variaram de 1,40 a 116,30 x 10-3 Mg ha-1 h-1, enquanto as de agua, de 1,60 a 106,94 m3 ha-1 h-1. Os valores da TIE apresentaram variacao entre 23 e 52 mm h-1. Os tratamentos sob semeadura direta sem cobertura do solo e sob preparo com grade aradora apresentaram maiores perdas de solo e de agua e valores mais baixos de TIE.

Nutrient losses by water erosion

Water erosion causes soil degradation, which is closely related to nutrient losses either in, the soluble form or adsorbed to soil particles, depending mainly on the adopted soil management system. This study was carried out in Sao Jose do Cerrito, SC, Brazil, between March 2000 and June 2001. The objective was to quantify available nitrogen, phosphorus, potassium, calcium and magnesium losses in water erosion obtained with simulated rainfall in the following soil management systems: conventional tillage with no-crop (bare soil) (BS), conventional tillage with soybean (CT), reduced tillage with soybean (RT), no tillage with soybean on a desiccated and burned natural pasture (DBNP), and no tillage with soybean on a desiccated natural pasture (DNP). A rotating boom rainfall simulator was used to perform three rainfall tests with constant intensity of 64 mm h-1 and sufficient duration to reach constant runoff rate, on a clayey-loam, well-structured Typic Hapludox, with an average slope of 0.18 m m-1. The first test was carried out five days before soybean emergence and the second and third at 30 and 60 days, respectively. The nutrient concentration in water and total losses of nitrogen, phosphorus, potassium, calcium and magnesium were higher under CT than in the other soil management systems.

Physical properties of an Haplumbrept as affected by soil management

Physical degradation of soils favors water erosion. Because of its intensity, conventional tillage usually acellerates the soil erosion process. Therefore, no-tillage is considered a soil conservation management system, because it preserves crop residues on soil surface. However, no-tillage may also increase bulk density and decrease surface soil total porosity. This study investigates the effects of soil management on a Haplumbrept, from May 1995 to November 1999, in the region of Lages, SC, Brazil. Three soil tillage treatments were used: conventional tillage (plowing plus disking), no-tillage and natural pasture. The crop sequences used were maize and vetch in the no-tillage system, and maize and fallow in the conventional tillage system. Soil strength and mean weight diameter of soil aggregates (MWD) were evaluated for soil layers of 0-2.5 cm, 2.5-5.0 cm, 5.0-10.0 cm and 10.0-15.0 cm. Soil water intake rate was also evaluated. The MWD did not differ betwen treatments for the 0-2.5 cm layer; in the other layers the soil presented higher values for the natural pasture and no-tillage treatments. Soil strength was higher for the no-tillage treatment in the 0-2.5 cm layer. The water intake rate was higher in the soil of the conventional tillage as compared to other management treatments.

Tolerância de perda de solo por erosão para os principais solos do estado de Santa Catarina

Soil loss tolerance refers to the maximum rate of annual soil loss that will permit crop productivity to be obtained economically and indefinitely. Besides the usual form, it can also be used in the Universal Soil Loss Equation as a criteria to better define terrace spacing on croplands. This research work was developed during 1998, at the Agroveterinary Center/UDESC, in Lages, Santa Catarina, Brazil, to establish soil loss tolerance values by water erosion for 73 soil profiles of Santa Catarina, grouped within 19 taxonomic classes, and using three methods: (a) Method I, based on both rooting depth and textural ratio between B and A horizons; (b) Method II, similar to Method I, plus the clay content in the A horizon; and (c) Method III, similar to Method II, plus the organic matter content in the 0-20 cm soil depth and the soil permeability of the soil profile. Tolerance values for the studied soils varied from 0.15 to 1.16 mm year-1, depending on both soil type and estimation method. Latosols (except for the brown/reddish), Podzolic soils, brown structured earth, Cambisols, and Quartz sands showed lower values of soil loss tolerance by method III - which is suggested for estimating T-values for these soils - than methods I and II. Litolic soils, brunizens, red and brown/reddish structured earth, and brown/reddish Latosols showed similar soil loss tolerance values, regardless of the method used. Therefore, for these soils, any of the three methods studied can be used for estimating soil loss tolerance values.

Erosão hídrica em diferentes preparos do solo logo após as colheitas de milho e trigo, na presença e na ausência dos resíduos culturais

A rotating-boom rainfall simulator, operating at a constant rainfall intensity of 64 mm h-1 for sufficient time to runoff reaches steady-rate, was used to investigate water erosion and other related parameters in three tillage systems. The experiments were carried out immediately following corn and wheat harvesting, in a sandy loam Red-Yellow Podzolic soil (Paleudult) with a 0.066 m m-1 average slope, in Eldorado do Sul, State of Rio Grande do Sul, Brazil, from 1992 to 1994. No-tillage, chiselling and disk-plowing followed by disking, were studied in the presence and absence of fresh crop residues. Results showed that no-tillage and disk plowing followed by disking, combined with residues maintained on the surface, reduced soil losses more efficiently than when the residues were removed. No-tillage, with residues maintained, was the most efficient system to control erosion, while disk plowing followed by disking, without residues, was the least efficient. Water losses followed the same tendency of soil losses, although being less affected by the treatments.

Propriedades físicas do solo relacionadas a diferentes níveis de oferta de forragem de capim-elefante-anão cv. Mott

O excesso de carga animal ocasionado por diferentes lotacoes sobre as pastagens pode afetar algumas propriedades do solo, aumentar a suscetibilidade a erosao hidrica e diminuir sua capacidade produtiva. A pesquisa, realizada em 1996, na Estacao Experimental da EPAGRI, Ituporanga, SC, objetivou avaliar as alteracoes na densidade do solo, porosidade, diâmetro medio ponderado dos agregados e taxa de infiltracao de agua no solo submetido a diferentes niveis de oferta de forragem numa pastagem de capim-elefante-anao (Pennisetum purpureum Schum.) cv. Mott. Foram estudados os niveis de oferta de forragem: 4,0, 8,0, 12,0 e 16,0%, alem de uma area de campo natural sem pastejo e uma area de mata nativa (testemunha), em Cambissolo alico. Os resultados indicaram uma diminuicao da densidade, com consequente aumento da porosidade e do diâmetro medio dos agregados com o aumento da oferta de forragem equivalente a diminuicao da pressao de pastejo. A taxa inicial de infiltracao de agua no solo tendeu a diminuir com o aumento da oferta de forragem. Abaixo do nivel critico de 12,0% de oferta de forragem, as propriedades fisicas do solo foram fortemente afetadas pelas altas pressoes de pastejo.