Eduardo Fávero Caires

ALTERAÇÕES QUÍMICAS DO SOLO E RESPOSTA DA SOJA AO CALCÁRIO E GESSO APLICADOS NA IMPLANTAÇÃO DO SISTEMA PLANTIO DIRETO

There has been an increasing interest to search alternatives for the establishment of crops under no-tillage systems in the southern region of Brazil, opening up new areas without soil disturbance. A field trial was carried out on a dystrophic Clay Rhodic Hapludox in Ponta Grossa, Parana State, Brazil, from 1998 to 2001, with the aim to evaluate changes in chemical soil characteristics, as well as the soybean response to lime and gypsum applications in a no-tillage system. A completely randomized block design with three replications in a split-plot experiment was used. The main plots received dolomitic limestone treatments (no lime, total rate of 4.5xa0txa0ha-1 of lime, 1/3 of this dosage during three years, as surface application and incorporated into the soil) and the subplots, the gypsum rates (0, 3, 6, and 9xa0txa0ha-1). Liming, whether surface applied or incorporated into the soil, provided a more accentuated soil acidity correction in the superficial layer (0-5xa0cm), but there was a stronger reaction in the 5-10 and 10-20xa0cm layers when lime was incorporated into the soil. The beneficial effects of lime for subsoil acidity correction were not very pronounced and more evident where lime was incorporated. Gypsum improved the subsoil, increasing the pH (CaCl2 0.01xa0molxa0L-1), Ca, and S-SO42- concentrations, P concentrations in the superficial soil layer (0-5xa0cm) and in soybean leaves, and decreased Mg concentrations in the soil and soybean leaves. Results showed no soybean response, in three years, to lime and gypsum treatments. It was concluded that gypsum, whether applied as superficial or incorporated liming, did not present an interesting strategy for the installation of soybean crop in a no-tillage system, since no improvement in grain yields could be observed.

Alterações químicas do solo e resposta do milho à calagem e aplicação de gesso

Root growth and crop yield can be affected by chemical modifications of the soil profile owing to lime and gypsum applications. A field trial was carried out on a dystrophic Clay Rhodic Hapludox in Ponta Grossa, Parana State, Brazil, aiming to evaluate the changes in the chemical soil properties and corn response to lime and gypsum applications at the installation of a no-tillage system. A randomized complete block design was used, with three replications, in a split-plot experiment. The main plots received dolomitic limestone treatments (no lime; 4.5 t ha-1 of lime applied on the surface supplying the total demand; 1/3 of the total demand applied on the surface during three years; total demand incorporated into the soil) and the subplots received gypsum rates (0, 3, 6, and 9 t ha-1). The treatments with lime were applied in July 1998 and the rates of gypsum in October 1998. Corn was evaluated in the agricultural year of 2001/02. The applied surface liming, at full or split rates, provided a more accentuated soil acidity correction in the superficial layer (0-0.05 m), and there was a stronger reaction in the 0.05-0.10 and 0.10-0.20 m layers, when lime was incorporated into the soil. Gypsum improved the subsoil, increasing the concentrations of Ca and S-SO42-, raised N, K, and Ca concentrations in the corn leaves, while it reduced the Mg concentration in soil and corn leaves. Liming and gypsum treatments did not affect the corn root growth. Liming (whether surface applied, at full or split rates, or incorporated into the soil) and gypsum increased the corn yield, due to an increase in the Ca soil saturation of the superficial layers. The application of gypsum associated to liming was an effective strategy to maximize grain yields.

Correção da acidez do solo, crescimento radicular e nutrição do milho de acordo com a calagem na superfície em sistema plantio direto

Os efeitos das alteracoes quimicas do solo, decorrentes da calagem na superficie, em sistema plantio direto, no crescimento radicular e na nutricao do milho nao sao muito conhecidos. Com o objetivo de estudar a correcao da acidez do solo, o crescimento de raizes de milho (hibrido AG 9090), a nutricao da planta e seus reflexos sobre a producao de graos, considerando a aplicacao superficial de calcario no sistema plantio direto, foi realizado um experimento em um Latossolo Vermelho distrofico textura media, em Ponta Grossa (PR). O delineamento experimental empregado foi o de blocos ao acaso em parcelas subdivididas, com tres repeticoes. As parcelas receberam quatro doses de calcario dolomitico na superficie (0, 2, 4 e 6 t ha-1), em julho de 1993, e, nas subparcelas, foram reaplicadas duas doses de calcario dolomitico na superficie (0 e 3 t ha-1), em junho de 2000. A calagem, apos 92 meses, aumentou o pH, o Ca trocavel e a saturacao por bases e reduziu o Al trocavel do solo, ate a profundidade de 0,60 m. A reaplicacao de calcario, apos nove meses, proporcionou aumento no pH, Ca trocavel e saturacao por bases e reducao no Al trocavel do solo, ate a profundidade de 0,20 m. A reacao do calcario reaplicado na superficie foi mais rapida em condicoes de maior acidez do solo. Nao houve limitacao do crescimento radicular e da producao de milho para concentracao de 10 mmolc dm-3 de Al trocavel, na ausencia de deficit hidrico em solo com alto teor de materia orgânica, mas a calagem na superficie melhorou a distribuicao relativa de raizes na presenca de solo compactado. O calcario dolomitico aplicado na superficie em plantio direto proporcionou reducao no teor de K no tecido foliar do milho, sem alterar a producao de graos.

Structural quality of a no-tillage red latosol 50 months after gypsum aplication

Gypsum application may enhance the soil quality for plants in terms of soil chemical and physical properties. The objective of this study was to evaluate the effects of gypsum application on the structural quality of a no-tillage Red Latosol. The experiment was initiated in September 2005 in Guarapuava-PR, with gypsum applications of 0; 4; 8; and 12xa0Mgxa0ha-1 on the soil surface. In November 2009, two soil blocks were sampled from the 0-0.3xa0m layer for visual evaluation of the soil structure quality (Sq) and to determine the aggregate-tensile strength (ATS). Soil penetration resistance (PR) and gravimetric moisture (H%) of the 0-0.300xa0m layer were evaluated, and soil cores were collected (layers 0.000-0.075 and 0.075-0.150xa0m), to determine soil bulk density (BD), total soil porosity (TP), microporosity (Mi), and macroporosity (Ma). Data were subjected to analysis of regression at 5xa0%. No significant effects of gypsum application on ATS and Hxa0% of aggregates were observed, but for Sq, a quadratic effect (0.000-0.075xa0m) and linear increase (0.075-0.150 and 0.150-0.300xa0m) were stated, indicating soil quality decrease, although Sq remained mostly below 3.0, with good to intermediate soil quality. Soil PR increased with gypsum, but also remained below critical levels. No effect was observed for soil Hxa0% at the moment of PR determination on the field. The gypsum applications decreased BD in the 0.075-0.150xa0m layer, and increased PT and Ma, while in 0.000-0.075xa0m some Ma was converted to Mi, without affecting PT and BD. These last results indicate a gain in soil structural quality by gypsum applications, but the higher scores of soil structure and values of soil penetration resistance, though still below thresholds, should be monitored to prevent limitations to soil use in the future.

Soil Chemical Attributes and Grape Yield as Affected by Gypsum Application in Southern Brazil

Yields of many crops are limited to subsoil acidity. Crop positive responses to gypsum have been shown, however, information regarding the use of gypsum in vine is scarce. A field trial was performed in Paraná State, Brazil, on a clayey Rhodic Hapludox to evaluate the effects of gypsum application (0, 3, 6, 9, and 12 Mg ha−1) on soil chemical attributes and grape (cv. ‘Niagara Rosada’) yield. Gypsum was surface applied in July 2005 and the soil and plant evaluations were realized during the years of 2006 and 2007. Gypsum decreased the subsoil exchangeable aluminum (Al) level, increased the calcium (Ca) and sulfate (SO4) contents in the soil profile, and caused leaching of magnesium (Mg) from the topsoil. The leached Mg resulted in decreases of leaf Mg concentrations and fruit production. The researchers estimated a critical level of Ca/Mg ratio in soil as well as in leaves of 1.9 for vine.

Surface Application of Lime and Cover Black Oat and Corn Residues for No‐Till Soybean Production

Abstract: Crop residues that are left on the soil surface to serve as mulch can diminish the soybean response to surface application of lime under no‐till management by ameliorating soil chemical and physical attributes and the plant nutrition. A field experiment was performed in the period from 2000 through 2003 in Paraná State, Brazil, on a clayey‐sandy Rhodic Hapludox. Soil chemical attributes and soybean [Glycine max (L.) Merrill] nutrition, grain yield, and quality were evaluated after surface application of lime and covering with crop residues of black oat (Avena strigosa Schreb) and corn (Zea mays L.) under a no‐till system. Dolomitic lime was surface applied at the rates of 0, 2.5, 5.0, and 7.5 t ha−1 on the main plots, and three treatments with vegetable covering were applied on the subplots: (i) without covering, (ii) with covering of corn straw, and (iii) with covering of corn straw and black oat residue (oat–corn–oat). After 30 months, surface‐applied lime increased soil pH and the exchangeable calcium (Ca2+) and magnesium (Mg2+) levels down to a 10‐cm depth, independent of the vegetable covering treatments. The black oat and corn residues on the soil surface increased the soil exchangeable K+ level at the 5‐ to 10‐cm depth. Liming increased leaf potassium (K) content and phosphorus (P) content in the soybean grain and reduced leaf zinc (Zn) content and manganese (Mn) content in the soybean leaf and grain. There was no effect of liming on soybean grain, oil, or protein yields, independent of the vegetable residues kept on the soil surface. The treatment with black oat covering and corn straw increased leaf N content, P content in the leaf and grain, and the contents of K, Mg, copper (Cu), and Zn in the soybean grain. It also increased soybean grain and protein yields. The corn straw left at the surface after harvesting was very important to the performance of the no‐till soybean.

Estimating gypsum equirement under no-till based on machine learning technique

Chemical stratification occurs under no-till systems, including pH, considering that higher levels are formed from the soil surface towards the deeper layers. The subsoil acidity is a limiting factor of the yield. Gypsum has been suggested when subsoil acidity limits the crops root growth, i.e., when the calcium (Ca) level is low and/or the aluminum (Al) level is toxic in the subsoil layers. However, there are doubts about the more efficient methods to estimate the gypsum requirement. This study was carried out to develop numerical models to estimate the gypsum requirement in soils under no-till system by the use of Machine Learning techniques. Computational analyses of the dataset were made applying the M5Rules algorithm, based on regression models. The dataset comprised of soil chemical properties collected from experiments under no-till that received gypsum rates on the soil surface, throughout eight years after the application, in Southern Brazil. The results showed that the numerical models generated by rule induction M5Rules algorithm were positively useful contributing for estimate the gypsum requirements under no-till. The models showed that Ca saturation in the effective cation exchange capacity (ECEC) was a more important attribute than Al saturation to estimate gypsum requirement in no-till soils.

Chemical and physical soil attributes in integrated crop-livestock system under no-tillage

Although integrated crop-livestock system (ICLS) under no-tillage (NT) is an attractive practice for intensify agricultural production, little regional information is available on the effects of animal grazing and trampling, particularly dairy heifers, on the soil chemical and physical attributes. The objective of this study was to evaluate the effects of animal grazing on the chemical and physical attributes of the soil after 21 months of ICLS under NT in a succession of annual winter pastures (2008), soybeans (2008/2009), annual winter pastures (2009), and maize (2009/10). The experiment was performed in the municipality of Castro (PR) in a dystrophic Humic Rhodic Hapludox with a clay texture. The treatments included a combination of two pasture (annual ryegrass monoculture and multicropping - annual ryegrass, black oat, white clover and red clover) with animal grazing during the fall-winter period with two animal weight categories (light and heavy), in a completely randomized block experimental design with 12 replications. After the maize harvest (21 months after beginning), soil samples were collected at 0-10 and 10-20 cm layers to measure soil chemical and physical attributes. The different combinations of pasture and animal weight did not alter the total organic carbon and nitrogen in the soil, but they influence the attributes of soil acidity and exchangeable cations. The monoculture pasture of ryegrass showed greater soil acidification process compared to the multicropping pasture. When using heavier animals, the multicropping pasture showed lesser increase in soil bulk density and greater macroporosity.

Surface Liming and Zinc Availability in a Long‐Term Experiment under No‐Till System

No‐till (NT) system with crop rotation is one of the most effective strategies to improve agricultural sustainability in tropical and subtropical regions. To control soil acidity in NT, lime is broadcast on the surface without incorporation. The increase in soil pH due to surface liming may decrease zinc (Zn) availability and its uptake by crops. A field experiment was performed in Paraná State, Brazil, on a loamy, kaolinitic, thermic Typic Hapludox to evaluate Zn bioavailability in a NT system after surface liming and re‐liming. Dolomitic lime was surface applied on the main plots in July 1993 at the rates of 0, 2, 4, and 6 Mg ha−1. In June 2000, the main plots were divided in two subplots to study of the effect of surface re‐liming at the rates of 0 and 3 Mg ha−1. The cropping sequence was soybean [Glycine max (L.) Merrill] (2001–2 and 2002–3), wheat (Triticum aestivum L.) (2003), soybean (2003–4), corn (Zea mays L.) (2004–5), and soybean (2005–6). Soil samples were collected at the following depths: 0–0.05, 0.05–0.10, and 0.10–0.20 m, 10 years after surface liming and 3 years after surface re‐liming. Soil Zn levels were extracted by four extractants: (i) 0.005 mol L−1 diethylenetriaminepentaacetic acid (DTPA) + 0.1 mol L−1 triethanolamine (TEA) + 0.01 mol L−1 calcium chloride (CaCl2) solution at pH 7.3 (DTPA–TEA), (ii) 0.1 mol L−1 hydrochloric acid (HCl) solution, (iii) Mehlich 1 solution, and (iv) Mehlich 3 solution. Zinc concentrations in leaves and grains of soybean, wheat, and corn were also determined. Soil pH (0.01 mol L−1 CaCl2 suspension) varied from 4.4 to 6.1, at the 0‐ to 0.05‐m depth, from 4.2 to 5.3 at the 0.05‐ to 0.10‐m depth, and from 4.2 to 4.8 at the 0.10‐ to 0.20‐m depth, after liming and re‐liming. Zinc concentrations evaluated by DTPA–TEA, 0.1 mol L−1 HCl, Mehlich 1, and Mehlich 3 solutions were not changed as a result of lime rate application. Re‐liming increased Zn concentrations extracted by 0.1 mol L−1 HCl at 0–0.05 m deep and by DTPA–TEA at 0.05–0.10 m deep. Surface‐applied lime promoted a decrease in Zn concentrations of the crops, mainly in grains, because of increased soil pH at the surface layers. Regardless of the liming treatments, levels of Zn were sufficient to soybean, wheat, and corn nutrition under NT.