José A. A. Moreira

Compactação do solo na cultura do feijoeiro. I: efeitos nas propriedades físico-hídricas do solo

O problema de compactacao do solo vem aparecendo sistematicamente na regiao do Cerrado, onde os sistemas convencionais de manejo do solo tem causado desagregacao excessiva da camada aravel, o encrostamento superficial e a formacao de camadas coesas ou compactadas (pe-de-grade ou pe-de-arado). Como alternativa, os agricultores adotaram o Sistema Plantio Direto; entretanto, em varias situacoes vem sendo relatadas ocorrencias de aumento da densidade do solo e diminuicao da macroporosidade, o que tem sido diagnosticado como compactacao, fazendo com que o agricultor seja obrigado a movimentar o solo. Este trabalho teve por objetivo verificar como a compactacao do solo afeta as suas propriedades fisicas e de transmissao de agua. Para isto, utilizaram-se colunas de solo compactadas artificialmente, para produzir densidades do solo de 1,0; 1,2; 1,4 e 1,6 kg dm-3. As propriedades de transmissao de agua foram determinadas com infiltrometros de tensao, para as cargas de pressao de -0,5; -2,0 e -6,0 cm de agua. O aumento da densidade do solo aumentou sua resistencia a penetracao e reduziu linearmente a porosidade total e a macroporosidade. Houve ainda, reducao no tamanho dos poros para o fluxo de agua, reduzindo a condutividade hidraulica do solo. Esta reducao foi mais acentuada na maior carga de pressao testada. Com a carga de pressao de -2,0 cm de agua, a reducao no tamanho dos poros foi parcialmente compensada com aumento do seu numero. O metodo do infiltrometro de tensao mostrou-se adequado em distinguir diferencas nas propriedades de transmissao de agua de um solo submetido a diferentes niveis de compactacao.

Compactação do solo na cultura do feijoeiro. II: efeito sobre o desenvolvimento radicular e da parte aérea

This study was conducted with the objective of verifying how soil compaction affects root and shoot development of a bean crop. The experiment was carried out in a greenhouse of Embrapa Rice & Beans, in Santo Antonio de Goias, GO, Brazil, in soil columns packed in PVC tubes 40 cm high and 25 cm of internal diameter. The soil columns were artificially compacted to provide soil bulk densities of 1.0, 1.2, 1.4 and 1.6 kg dm-3 in the 0 - 20 cm soil layer. Bean varieties Perola and BAT 477 were grown in the soil columns. The soil water potential was maintained between -35 and -10 kPa. The evaluations were made at 15, 30, 45, 60, and 72 days after emergence. The root dry matter, root length density, root thickness, leaf area, shoot dry matter, and specific leaf weight were evaluated. The increase in soil compaction negatively affected root and shoot development of bean, the effect being more expressive at bulk density values higher than 1.2 kg dm-3. Perola variety showed more root and shoot development than BAT 477 when there was no physical restriction in the soil for root development. BAT 477, however, was more rustic being less affected by soil compaction and showing higher leaf area and shoot dry matter under this situation.

Nitrogênio e água como fatores de produtividade do trigo no cerrado

Two experiments were carried out at Embrapa Rice and Beans, located at the municipality of Santo Antonio de Goias, Goias state, Brazil, under no-tillage in the soybean straw, to evaluate the effects of irrigation management and nitrogen doses on the grain yield and its components of two wheat cultivars. In the first experiment, the irrigation was started at soil-water tension of 40 kPa, and in the second one, at soil-water tension of 60 kPa. For both experiments, a randomized block design with subdivided plots, with four replications, was used. In the plots were established five doses of nitrogen (0, 50, 100, 150, and 200 kg ha-1) and, in the subplots, the cultivars EMBRAPA 22 and EMBRAPA 42. Soil-water tension of 60 kPa was more adequate for management of irrigation in wheat, since it did not affect its grain yield and quality and used less water. The dose of nitrogen that promoted maximum technical efficiency was 73 kg ha-1. The crude protein content increased as nitrogen increased. The increase of irrigation frequency and nitrogen decreased the hectoliter-grain weight.

Correlação entre leituras de clorofila e níveis de nitrogênio aplicados em feijoeiro

Two experiments were carried out at greenhouse conditions in nutrient solution and soil, using six nitrogen levels (28, 56, 84, 112, 140 and 168 mg/L of N) to adjust the chlorophyll meter readings (Minolta SPAD-501) to the nitrogen levels in the bean leaves. Chlorophyll content, leaf area, fresh and dry matter of leaves, N, Ca, Mg and S leaf concentration, and grain yield were evaluated. Good correlations were obtained between chlorophyll meter readings and nitrogen application rates (R = 0.86) and leaf nitrogen concentration (R = 0.75). These results indicate that the chlorophyll meter is a useful device to detect nitrogen deficiency in bean plants.

Eficiência de uso da radiação solar na produtividade do trigo decorrente da adubação nitrogenada

An experiment was carried out at Embrapa Rice and Beans, Santo Antonio de Goias, Goias State, Brazil, under no-tillage in the soybean mulch to evaluate the effects of nitrogen doses on the solar radiation use efficiency, leaf area index in the anthesis, biomass in the anthesis, in the physiological maturation and grain yield of two wheat cultivars. A randomized block design in subdivided plots, with four replications was used. In the plots five nitrogen topdressing doses, 0, 50, 100, 150, and 200 kg ha-1 were established and in the subplots, the cultivars Embrapa 22 and Embrapa 42. The cultivars differed only in relation to biomass in anthesis. The analyzed variables showed a quadratic response to nitrogen doses. Wheat grain yield response to nitrogen was due to the effect of this nutrient in the leaf area index, that affected solar radiation use efficiency and biomass, which showed a positive correlation with grain yield. Under low nitrogen availability, grain yield showed higher correlation to biomass accumulated in the anthesis than to that accumulated in the physiological maturation.

Consumo relativo de água do feijoeiro no plantio direto em função da porcentagem de cobertura morta do solo

In Brazilian Savannas, large part of irrigated common bean is cultivated under no-tillage system. The ground mulch reduces water requirement of common bean, which affects the management of irrigation. The present study was conducted to determine relative crop coefficients (Kr) under no-tillage system, related to the percentage of soil covered by mulch. The experiment was conducted at Embrapa - Rice & Bean Experimental Station, located in the municipality of Santo Antonio de Goias, GO, in an Oxisol, in a randomized block design, with four replications. The treatments were five different percentages of soil cover with sorghum mulch: 0, 25, 50, 75, and 100%. Crop evapotranspiration (ETc) was determined using field water balance approach. Kr was determined by the relationship between ETc and reference evapotranspiration (ETo). ETo was determined based on Class A pan evaporation. The ETc decreased as the percentage of soil cover increased. The maximum Kr values were 1.25, 1.24, 1.15, 1.12 and 1.01 for the percentages of soil cover of 0, 25, 50, 75 and 100%, respectively.

Atributos químicos de solo sob produção orgânica influenciados pelo preparo e por plantas de cobertura

This study aimed to determine the influence of the cover crops sunhemp (Crotalariajuncea), pigeon pea (Cajanus cajan (L.) Millsp), velvet bean (Mucuna aterrima), sorghum (Sorgum technicum), and fallow on chemical attributes of soil cultivated with organic common bean and corn, under no-tillage (NT) and conventional tillage (CT) systems. The work was conducted in Santo Antonio de Goias-GO, in Oxisol, in a randomized block design, with four replications. In November 2003 four experiments were installed, two of them under NT and the other two in CT. In each soil management system, an experiment was carried out with common bean crop and another with corn. Samples were taken from soil layers of 0-0.10 and 0.10-0.20 m in September 2003 and in November 2007. The soil pH and the contents of P, K+, Ca2+, Mg2+, Cu2+, Zn2+, Fe3+, Mn2+, H+ + Al3+, and soil organic matter were analyzed, and cation exchange capacity and base saturation were calculated. After four years, cover crops did not differ in their effects on soil chemical attributes, however, they increased the content of organic matter in relation to initial condition, under NT or in CT. In general, the nutrient recycling by cover crops was not sufficient to maintain the P, K+, Fe3+ and Mn2+ contents in the soil.

Soil physical attributes under different tillage systems and cover crops, as influenced by pore distribution

This study aimed to evaluate the influence of pore distribution on some physical attributes of soil under no-tillage (NT) and conventional tillage (CT) systems, cultivated with different cover crops, in organic production of common bean and corn. The work was carried out in Santo Antonio de Goias, GO, on an Oxisol. In November 2003 four experiments were installed, two of them under NT and the other two under CT. In each soil tillage system, an experiment was conducted with corn and another with common bean. Sunn hemp, pigeon pea, velvet bean, sorghum, and fallow were compared in a randomized block design, with four replications. Samples were taken from soil layers of 0-0.10 and 0.10-0.20 m in November 2007, in the plots and in a near by native forest (Cerrado), for determination of soil organic matter (OM) content and physical attributes. Cerrado soil use for agricultural production, regardless of tillage system, resulted in decrease of soil total porosity (TP), macroporosity (Mp), and soil air capacity (SAC). Soil physical attributes were favorably affected by OM. Variations in TP, Mp, SAC, and available soil water capacity can be explained by variation in soil pore size distribution, mainly by those with ∅ > 0.075 mm.

Risco climático do feijão da seca no Estado de Goiás, sob preparo de solo convencional e plantio direto

In the Cerrado Region, farmers have been adopting the no-till system, to protect the soil and give sustainability to agriculture. In that system, soil covered by crop residues can minimize climatic risks by reducing water deficit of crops sowed in late season. The objective of this study was to compare the climatic risk of dry season common beans grown in the State of Goias, under conventional and no-till systems. The BIPZON model was used to calculate the water balance. Geographic Information System was used for the characterization of the results in time and space. Areas of low, medium and high climatic risks were identified for the no-till system, with 50 and 100% of soil coverage by crop residues, as well as for the conventional till system. It was verified that the use of no-till system increased the areas with lower risks and extended the period of sowing for the bean crop in relation to conventional till system. The effect was higher with 100% soil covered with crop residues.