Laércio Augusto Pivetta

Crescimento e atividade de raízes de soja em função do sistema de produção

The objective of this work was to assess winter and spring crop effects on soybean root system growth, and on yield, and to compare a direct method (soil core sampling) with an indirect method (with rubidium) in evaluating the root system. The experimental design was a randomized complete block design, in a split-plot arrangement, with four replicates. Plots consisted of the winter crops, triticale (X Triticosecale) and sunflower (Helianthus annuus), and subplots of the spring crops, pearl millet (Pennisetum glaucum), forage sorghum (Sorghum bicolor) and sunn hemp (Crotalaria juncea), besides chisel tillage in 2003 and 2009. Soybean (Glycine max) was grown in the summer, and its root system was evaluated by physical sampling of the roots and by root activity assessment using rubidium. Changes in the architecture or in the activity of soybean roots did not affect yield. The distribution and activity of soybean roots were not significantly affected by the winter cover crops, but root growth was favored after millet and sorghum were grown in the spring. The direct measurement of the soybean root system with an auger has low correlation with root activity.

Nitrogen budget in a soil-plant system after brachiaria grass desiccation

Abstract Brachiaria spp. have been grown in a variety of cropping systems and are often terminated with herbicides, which may cause nitrogen (N) loss from the soil-plant system. In this study ammonia (NH3-N) loss by shoots and N balance in a soil-plant system were determined after desiccation of palisade grass (Brachiaria brizantha (Hochst. ex A. Rich) Stapf, cv. Marandu), signalgrass (Brachiaria decumbens Stapf), humidicola (Brachiaria humidicola (Rendle) Schweick) and Congo grass (Brachiaria ruziziensis Germain et Evrard). The grasses were grown in pots filled with an Oxisol in a greenhouse. Sixty days after planting, the plants were desiccated with glyphosate. Analyses were performed on plant and soil at desiccation and then at 7, 14, 21 and 28 days after desiccation in order to assess NH3-N losses by shoots and to estimate the N balance in the system. Total nitrogen (Total-N) concentration in shoots and roots of brachiarias decreased after desiccation, thereby reducing the amount of N in plants of the four brachiaria species. However, as most of the N lost by plants was released into the soil, N losses from the soil-plant system were small compared with the total N in the system: 1.2, 0.5, 0.4 and 1.4% for palisade grass, signalgrass, humidicola and Congo grass, respectively. N losses as NH3 from the soil-plant system after desiccation with glyphosate varied among brachiaria species, ranging from 0.8 to 2.0 g m−2 kg−1, and accounted for 30–80% of total loss.

Alternative substrates in the production of lettuce seedlings and their productivity in the field

Based on the hypothesis that alternative substrates should improve the yield of lettuce crops by producing better quality seedlings, the objective of this work was to evaluate the effect of different substrates on the production of seedlings of this species, and their growth in the field. The study was in two stages. The first consisted of the production of lettuce seedlings, and the second assessed their development in the field. Four alternative substrates were tested, obtained by mixing together a sieved vermicompost from which all clumps had been removed, sterilized sand, charred rice husks and basalt powder. The commercial substrate, Plantmax HA®, was also tested. In the first phase, which was conducted in a completely randomised design with four replications, the height, root length, number of leaves, leaf area and dry weight of the seedlings were all evaluated 28 days after sowing. In the second phase, which was carried out in the field in a randomised block design with four replications, the plants were harvested 50 days after transplanting and the head diameter, fresh weight, number of leaves and leaf and stem dry weight were evaluated. The alternative substrates produced larger seedlings in less time than the commercial substrate, resulting in a reduction of 10 days in the total crop cycle. The reduction in the time between sowing and harvesting, together with those aspects relating to sustainability, are the main advantages of the use of alternative substrates, since in the field crop production did not differ between treatments.

Avaliação de híbridos de girassol e relação entre parâmetros produtivos e qualitativos

O presente estudo teve o objetivo de determinar genotipos superiores de girassol, bem como realizar estudos de correlacao entre suas caracteristicas. Avaliou-se seis hibridos de girassol em condicoes de safrinha no municipio de Palotina - PR. O estudo avaliou quinze variaveis: massa seca de folhas, massa seca de caule e peciolos, massa seca total, area foliar, altura de planta, diâmetro de colmo, massa de graos por capitulo, diâmetro de capitulo, percentagem de graos normais, massa de mil graos, numero de graos por capitulo, produtividade, teor de proteina bruta, teor de oleo e rendimento de oleo. Os dados direcionam os hibridos H360 e MG2 com boa produtividade e maior teor de oleo para a producao de oleo e os hibridos M734 e Aguara 3 para a alimentacao animal, com boa produtividade e menor teor de oleo. As correlacoes entre produtividade e os componentes de producao foram de 0,62; 0,47; 0,60; 0,49 e 0,47 para massa de graos por capitulo, diâmetro de capitulo, percentagem de graos normais, massa de mil graos e numero de graos por capitulo, respectivamente, concluindo que a selecao de materiais a partir desses componentes ocasionara a selecao de materiais promissores em produtividade.

Atributos físicos do solo e produtividade do milho sob sistemas de manejo e adubações

No-tillage system is an efficient technique in control of soil erosion, when compared with conventional tillage, however, some studies indicate higher compaction under no-tillage, mainly in the surface layer. Strategies that increase the organic matter content, as crop rotation and organic fertilization, can be used to solve the soil compaction. The aim of this study was to evaluate the effect of soil managements (crop succession and crop rotation) and fertilization (organic, mineral and organic-mineral) in the physical properties of the soil, under no-tillage system, from 2006 to 2008. The evaluations were carried out in February 2007, after the summer corn harvest, and in September 2008, after the winter corn harvest. Crop rotation decreased the soil density and soil resistance to penetration and increased the macroporosity and total porosity. The use of organic sources of fertilization did not affect any of the physical attributes of soil. The yield of summer corn was highest in succession crop and mineral fertilization, however, in the winter, there was no difference between the soil managements and among the fertilizations.

Nutrição e produtividade da cultura do milho em sistemas de culturas e fontes de adubação

The use of animal wastes in agriculture coupled with the growing of cover crops can provide sustainability to the agricultural system. Aiming to evaluate the effect of two systems of crops and sources of fertilizer on the corn crop, was conducted an experiment on Oxisol in the municipality of Marechal Candido Rondon (PR). The experimental design used was of randomized block with four replications and treatments in factorial scheme 2 x 3, consisting of two culture systems (succession wheat/corn and oat+vetch+turnip/corn) and three nutrient sources (mineral, organic and organic mineral). In June 2006, was deployed to the wheat crop and intercropping of cover crops. In October 2006 was sowed corn on the two systems. The fertilizations organic and organic mineral consisted of application of pig manure alone and combined with mineral fertilizer, respectively. The consortium of oats, hairy vetch, wild radish has shown itself capable of providing good amount of biomass, showing its viability for the production of plant cover the soil during winter. Corn grown in rotation with wheat yielded the highest uptake of N and K and higher yield. Mineral fertilization gave higher N uptake and corn yield compared with the organic fertilizer and organic-mineral fertilizer based on pig manure

Soil nitrogen dynamics after Brachiaria desiccation

Especies do genero Brachiaria, particularmente a B. humidicola, podem sintetizar e liberar de suas raizes compostos que inibem o processo de nitrificacao, o que pode provocar alteracoes na dinâmica do nitrogenio (N) no solo, principalmente em solos com baixa disponibilidade de N. Isso pode ser importante em sistemas com integracao lavoura-pecuaria, em que a forrageira e cultivada junto ou em rotacao com culturas graniferas. Neste estudo, objetivou-se determinar se isso ocorre tambem em ambiente mais rico em N e se outras especies de Brachiaria tem o mesmo efeito. Para tal, avaliou-se a dinâmica do N no solo apos a dessecacao de B. brizantha, B. decumbens, B. humidicola e B. ruziziensis, especies amplamente cultivadas no Brasil. As plantas foram cultivadas em vasos com um Latossolo Vermelho distroferrico, em casa de vegetacao. Sessenta dias apos a semeadura, as plantas foram dessecadas com aplicacao do herbicida glifosato. Foram realizadas analises de planta e solo, na data da dessecacao e aos 7, 14, 21 e 28 dias apos a dessecacao. Os maiores teores de materia orgânica, N-total e amonio foram encontrados no solo rizosferico das plantas. A rizosfera da B. humidicola apresentou ainda o menor valor de pH, o que poderia estar associado ao efeito supressivo dessa especie no processo de nitrificacao. Entretanto, as variacoes encontradas nos teores de amonio e nitrato nao foram suficientes para confirmar o efeito supressivo da B. humidicola. Essa observacao se repetiu para B. brizantha, B. decumbens e B. ruziziensis, demonstrando que, em condicoes de boa disponibilidade de N, nenhuma das brachiarias avaliadas influencia significativamente o processo de nitrificacao no solo.

Potentials of biogas production from young bulls manure fed with different diets

Physical and chemical characteristics of manure are modified by different animal production systems. In cattle feeding system for young bulls there is an inversion of the proportion between forage and concentrate. In other words, the animals receive a smaller amount of forage compared to the traditional system. These changes in the manure characteristics involve changes in the treatment systems. The aim of this study was to determine the potential production of biogas of batch digesters fed with manure from young bulls that received two diets containing different proportions between forage and concentrate, with or without inoculums and submitted to three levels of temperature (25, 35 and 400C). The evaluated parameters were total solids (TS) and volatile solids (VS) reduction and biogas potentials production. The digesters fed with manure from animals that received the diet 2 (80%C + 20% R) showed the largest reductions of TS and VS. About the potentials of biogas production there was interaction between the factors diet and inoculums, but no effects of temperatures. The treatment content manure from animals fed with diet 2 without inoculums presented the greatest potential of biogas production per kg of TS added (0.2123 m3).

Nitrate leaching in soybean rotations without nitrogen fertilizer

BackgroundNitrate leaching is a primary pathway of nitrogen loss from agricultural systems, and is affected by both tillage and cropped species. However, there is little information on conservation systems without nitrogen fertilization.MethodsNitrate leaching was assessed in soybean (Glycine max) cropped in rotation with the following cover crops under no-till and chiseling: ruzigrass (Brachiaria ruziziensis), grain sorghum (Sorghum bicolor), pearl millet (Pennisetum glaucum), forage sorghum (Sorghum bicolor), Sunn hemp (Crotalaria juncea), triticale (X Triticosecale) and sunflower (Helianthus annuus).ResultsRuzigrass and grain sorghum cropped in the fall/winter resulted in similar NO3− leaching, which was greater under sunflower than under triticale, likely due to high N uptake and immobilization in plant residues. Sunn hemp as a spring crop resulted in higher NO3− leaching than pearl millet at two locations and forage sorghum at one location likely due to a higher N input by biological fixation. Millet resulted in the lowest N leaching by depleting the soil solution. Chiseling/fallow resulted in higher nitrogen leaching as compared with non-fixing N cover crops.ConclusionsEven when N is not applied, it is important to intensify cropping systems in tropical environments using cover crops with vigorous root systems and high N demand, which prevent N leaching, as well as provides N to the following crop as the straw is mineralized.