Hamilton Seron Pereira

ATRIBUTOS FÍSICOS, QUÍMICOS E BIOLÓGICOS DE SOLO DE CERRADO SOB DIFERENTES SISTEMAS DE USO E MANEJO

As knowledge on no-till system expands, it has become quite clear that separate chemical indicators cannot provide a detailed soil characterization. The objective of this study was to evaluate the effects of tillage systems and soil use in the physical, chemical and biological properties of a clayey dystrophic Red Latosol - Oxisol and a sandy Neosol - Entisol. The treatments for the Oxisol consisted of: native savanna, pasture, conventional tillage, no-tillage with turnip and with forage sorghum as cover crop. For the Entisol: native savanna, native pasture, integrated crop-livestock, cultivated pasture, no-tillage with soybean and corn in the summer. Soil samples were collected from a depth of 0-10 cm, in a clayey dystrophic Red Latosol - Oxisol and a sandy Neosol - Entisol in a savanna ecosystem, near the Parque Nacional das Emas. Treatments were arranged in a completely randomized design, in 5 plots of 150m2, where 10 sub-samples were collected randomly. Chemical, physical and biological analyses were carried out at a soil laboratory. In the Entisol, tillage influenced the soil density, total pore volume, macroporosity and penetration resistance. In the Oxisol, tillage induced variations in soil bulk density, macroporosity and penetration resistance. Small variations in chemical properties were observed in both soils, with higher potential acidity and lower exchangeable cation and phosphorus concentrations. The soil biological properties were influenced by tillage, and were most affected in systems with more anthropic action. In the canonical data analysis the greater weighting coefficient of the physical properties in the canonic variables demonstrated that these were the least important. The contribution of the separate soil properties to evaluate soil quality was minor, but the most sustainable management systems could be defined by multivariate analysis.

Silicon sources for rice crop

Although silicon is not an essential nutrient, its application is beneficial for plant growth and development. To evaluate silicon sources in relation to agronomic efficiency and economic viability in rice crops (Oryza sativa L.), a greenhouse experiment was conducted, Quartzipsamment soil, in a completely randomized experimental design (n = 4). Treatments were 12 silicon sources and a control. Silicon was applied at the rate of 125 kg Si ha-1. Data were compared to a standard response curve for Si using the standard source Wollastonite at rates of 0, 125, 250, 375, and 500 kg Si ha-1. All treatments received CaCO3 and MgCO3 to balance pH, Ca and Mg. One hundred and fifty days after sowing, evaluations on dry matter yield in the above-ground part of plants, grain yield, and Si contents in the soil and plant tissues were performed. Wollastonite had linear response, increasing silicon in the soil and plants with increasing application rates. Differences between silicon sources in relation to Si uptake were observed. Phosphate slag provided the highest Si uptake, followed by Wollastonite and electric furnace silicates which however, did not show differed among themselves. The highest Si accumulation in grain was observed for stainless steel, which significantly differed from the control, silicate clay, Wollastonite, and AF2 (blast furnace of the company 2) slag. Silicate clay showed the lowest Si accumulation in grain and did not differ from the control, AF2 slag, AF1 slag, schist ash, schist, and LD4 (furnace steel type LD of the company 4) slag.

Ammonia volatilization of urea in the out-of-season corn

The aim of this study was to evaluate the N losses due to volatilization at different rates of common urea, polymer coated urea and urease inhibitor-treated urea in the out-of-season corn, using semi-open static collectors. The treatments consisted of N levels on side-dressing fertilization with urea in different treatments: (a) control (without N), (b) urea 40 kg ha-1 N, (c) urea 80 kg ha-1 N, (d) polymer coated urea 40 kg ha-1 N, (e) polymer coated urea 80 kg ha-1 N and (f) urea with the urease inhibitor (UI) N 80 kg ha-1 N. The results showed that the treatments with polymer coated urea and with urease inhibitor-treated urea reduced the volatilization of N around 50 % compared to common urea, either in the first and the second N side-dressing fertilizations. Thus, they demonstrate that the polymer coat and the urease inhibitors were effective in reducing the volatilization of urea N applied in coverage, which resulted in higher productivity. There was also increasing urease activity in the treatments with application of common urea.

Produção de fitomassa de diferentes espécies de cobertura e suas alterações na atividade microbiana de solo de cerrado

The objective of this study was to evaluate the phytomass yield of nine species of cover crops of the soil and to verify the alterations in the activity and microbial biomass of Cerrado soil, in the State of Goias, Brazil. The work was developed from March to December, 2004, being sowed the following covering species: Avena strigosa, Cajanus cajan, Crotalaria juncea, Lablab purpureum, Pennicetum americanum, Raphanus sativus, Guizotia abyssinica, Canavalia ensiformis, Crotalatia spectabilis and an area in fallow considered with reference. In the occasion of the flower phytomass yield was determined and starting from August it leaves of this was conditioned in sacks of polyethylene to evaluate the decomposition tax, being in the soil for 120 days. During this period, in every month, they were evaluating the carbon of the microbial biomass and the microbial respiration of the soil. The Cajanus cajan, Pennicetum americanum, Canavalia ensiformis and Guizotia abyssinica are shown as the most promising species for phytomass yield, while the Avena strigosa, Crotalaria juncea and the Raphanus sativus present the smallest phytomass yield. The areas under Pennicetum americanum residues, Raphanus sativus, Crotalatia spectabilis and the fallow affect the carbon of the microbial biomass negatively. Area under resting provided to smallest phytomass yield, reduction in the carbon of the microbial biomass and larger loss of carbon, being this practice no suitable for the Cerrado region.

SOIL REACTION AND ABSORPTION OF SILICON BY RICE

A solubilidade e disponibilidade de silicio podem ser influenciadas pela reacao do solo. Com o objetivo de estudar o efeito da reacao do solo sobre a disponibilidade de silicio para a cultura do arroz, foi conduzido experimento em Latossolo Vermelho alico textura argilosa em casa-de-vegetacao. O experimento foi conduzido em fatorial 4 x 4, delineamento em blocos inteiramente casualizados e quatro repeticoes. Quatro materiais (calcario, silicato de calcio e magnesio, acido silicico purissimo e wollastonita) foram aplicados em doses equivalentes a 0, 2500, 5000, 7500 mg por vaso de 5 kg. Apos 60 dias, foram avaliadas producao de materia seca, absorcao de silicio da parte aerea do arroz, pHCaCl2, silicio extraido em acido acetico (0,5 mol L-1) e CaCl2 (0,01 mol L-1) no solo. Os materiais aumentaram o pH do solo com as doses, exceto o acido silicico. O silicio soluvel em acido acetico foi crescente com as doses dos materiais. Para o CaCl2, apenas houve aumento de silicio soluvel no solo com as doses de wollastonita e silicato de calcio e magnesio, concordando com seu teor total. A absorcao de silicio pela parte aerea do arroz foi linearmente crescente com as doses da wollastonita, seguida do silicato de calcio e magnesio, acido silicico e calcario. O aumento do pH do solo com calcario nao foi suficiente para fornecer silicio ao arroz. O silicio extraido com CaCl2 0,01 mol L-1 apresentou maior correlacao com a absorcao de silicio pelas plantas. Mais estudos sao necessarios em condicoes de campo e outros solos para corroborar os resultados apresentados.

Avaliação de fontes e de extratores de silício no solo

The objective of this work was to evaluate silicon extractors and sources in the culture of the rice in a Quartzipsamment soil in a greenhouse. The experiment was completely randomized as a factorial design (26x7), comprising 25 silicon sources with 250 kg ha -1 of Si applied, and the control, as well as 7 silicon extractors in the soil. Additional treatments with 125, 375 and 500 kg ha -1 of Si were applied with wollastonite. Ninety days after sowing, the yielded dry matter of aerial parts and the soil and plant tissue Si content were determined. The source that provided higher Si absorption to the plants of rice was gel silicon, and the source that provided lower absorption was the MB-4. The extractors presented increased linear content of Si in the soil with the increment of doses of wollastonite. Among treatments, the high Si extraction ocurred with the acetic acid, and the calcium chloride went the extractor with better correlation. Ammonium carbonate and ammonium acetate presented near correlations to calcium chloride and had a larger distribution of the points, which better discriminated variations among the Si sources.

Solubility of silicon in soils: effect of lime and silicic acid applied

Silicon has been utilized in brazilian agriculture, specially after its inclusion in regulations concerning fertilizers. However, there are few studies on Si solubility in tropical soils, which is important for silicate fertilization. Soluble silicon was evaluated in clayey (LVd, LVAd, NVef), loamy (PVAe, LVd, LVAd) and sandy soils (RQo) treated with lime (0, 2, 4 e 6 Mg ha-1) and silicic acid (0 e 400 mg kg-1), with 4 replications. The soil samples were dried and passed through sieve (50 mesh), placed in pots (250 g) with the treatments and incubated during 90 days (80 % of holding moisture capacity). The 0.5 mol L-1 acetic acid (AA) extracted more silicon than water (A) and 0.01 mol L-1 CaCl2 (CC). Si contents were higher in clayey than in loamy and sandy soils and B horizon had more silicon than A horizon in latosols. There was effect of lime decreasing potencial acidity and increasing pH(CaCl2), Ca, and AA extractable silicon contents in all soils. CC and A extractable Si increased in loamy and sandy soils and decreased clayey soils. Studies with plants to determinate suitable extractants for available Si are needed, especially in oxidic soils, where increasing pH decreases Si solubility.

Aplicações de fertilizantes foliares na nutrição e na produção do pimentão e do tomateiro

The efficiency of foliar fertilizers was evaluated on nutrition and yield of sweet pepper cv. Mayata and tomato cv. Carmem, cultivated in plastic greenhouse. For the two experiments the experimental design consisted of randomized blocks with three and four replications for tomato and sweet pepper, respectively, and six treatments (schist retortage water 0.1; 0.25; 0.5 and 1%; boric acid 0.15% plus clorate calcium 0.15% and quelate Ca 0.1% plus organic B 0.15%). The foliar application of schist retortage water 0.5% increased 27.4% the sweet pepper fruit yield and foliar concentrations of Mg and S compared to this fertilizer 0.1%. For tomato, the application of schist retortage water 0.5 and 1% increased 60.5 and 93.8% the fruit yield as compared to this fertilizer 0.1%. The higher levels of boron in sweet pepper leaves and in tomato leaves were obtained with salt applications and resulted in visual symptoms of boron toxicity on initial development of cultures.

Effect of the use of schist on chemical characteristics of soil and on tomato nutrition

Among the main environmental problems due to the use of schist is a massive production of highly alkaline schist processing waste. This residue, when deposited in great amounts liberates toxic elements in the atmosphere, polluting the soil, the surface water and the atmospheric air. The effect of the use of schist in agriculture was evaluated on the soil chemical attributes and tomato crop nutrition. Two experiments were performed on Typic Eutrustults under greenhouse conditions. Schist rates of 0; 3; 6; 9 and 12 t ha-1 were applied and incorporated in the soil. A randomized block design with four replications was used. Schist use promoted a significant sulfur and silicon content increase in the soil as well as in the tomato leaves; no soil pH alteration was verified neither the exchangeable cations capacity, but an increase in the phosphorous availability was observed. No environmental damage was verified, such as chemical contamination by heavy metals, nor decrease of the tomato yield. The use of schist as a fertilizer in the evaluated doses is viable in agriculture.

Fontes, doses e modos de aplicação de fósforo na recuperação de pastagem com brachiaria

Objetivando-se avaliar diferentes fontes, doses e metodos de aplicacao de fosforo na recuperacao da Brachiaria decumbens, um experimento foi conduzido na Fazenda Caminho das Pedras, municipio de Uberlândia-MG, em Latossolo Vermelho distrofico, textura media, entre novembro de 2003 e abril de 2004. Os tratamentos constaram de tres fontes de fosforo (Superfosfato Triplo, Termofosfato magnesiano e hiperfosfato de Gafsa) nas dosagens de 0; 50; 100 e 150 kg ha-1 de P2O5, com manejo incorporado e nao incorporado, em tres repeticoes, no delineamento de blocos casualizados. Foram utilizadas parcelas de 2,0 x 5,0 m, as quais foram adubadas uniformemente com 330 kg ha-1 de N e 220 kg ha-1 K2O, na forma de ureia + sulfato de amonio e cloreto de potassio, respectivamente. Foi avaliada a produtividade da Brachiaria em tres cortes da parte aerea, em um intervalo de 30 dias entre os cortes. A aplicacao de fosforo com diferentes fontes e doses promoveu incremento na produtividade da Brachiaria, porem nao houve diferenca comparando-se os metodos de aplicacao. A maior resposta foi obtida com 150 kg ha-1 de P2O5, na forma de superfosfato triplo com produtividade media de 2997 kg ha-1 de MS por corte, e a menor produtividade ocorreu no tratamento com 50 kg ha-1 de P2O5 na forma de hiperfosfato de Gafsa. Houve aumento na porcentagem do fosforo foliar e do fosforo no solo, com aumento da dose em todas as fontes, em ambos extratores. Na avaliacao dos extratores, o Mehlich-1 apresentou maior extracao na fonte hiperfosfato de Gafsa, contrariando os resultados de producao.