Renato Lara de Assis

Ciclagem de nutrientes por plantas de cobertura na entressafra em um solo de cerrado

The objective of this work was to evaluate the accumulation and the liberation of nutrients (N, P, K, Ca, Mg and S) of cultural residues by three species of cover crops, in off-season. Tested cover crops were amaranthus (Amaranthus cruentus L.), pearl millet (Pennisetum glaucum L.) and finger millet (Eleusine coracana (L.) Gaertn.). The experiment was carried out in a Typic Haplorthox clay texture soil. A randomized block desing in a split-plot array in time, with four replications, was used. At the flowering of the species, the production of dry matter and the accumulation of nutrients were evaluated. Proportional samples of dry matter of each cover crop species were placed in litter bags, which were distributed on the field plots surface, collected and weighed every 30 days, until 240 days after installation of the bags. The largest amounts of accumulated nutrients in the dry matter of the cover crops were observed with the pearl millet and the finger millet. The potassium was the nutrient accumulated in larger amount, reaching 416.9 kg ha -1 , in pearl millet. The largest rates of nutrient liberation were observed in the cultural residues of the amaranthus.

Crescimento de plantas de cobertura sob diferentes níveis de compactação em um Latossolo Vermelho

With the objective of evaluating the growth of cover crops under different levels of soil compaction an experiment was installed under greenhouse conditions. A completely randomized block design was used with four replications, in which the treatments consisted of a factorial with four vegetal species of cover crops: Cajanus cajan, Sesamum indicum L., Pennisetum glaucum L. cultivar ADR 300 and Chenopodium quinoa Willd., in four levels of subsurface compaction (soil bulk density: 1.18; 1.34; 1.51 and 1.60 Mg m-3) in a Typic distropheric Red Latosol. The compaction of the subsurface soil was restrictive to the root growth of the studied species, concentrating them in the upper layer. The Pennisetum glaucum cultivar ADR 300 excelled in the production of dry matter and was able to develop in the compacted layers and below them. The increase of soil density in the compacted layer did not influence the root length density of the Cajanus cajan, Sesamum indicum and Chenopodium quinoa, however these species had inferior performance when compared with the Pennisetum glaucum (L.) cultivar ADR 300, which presented greater root length density in all layers and densities.

Efeito de doses e da época de aplicação de nitrogênio nos caracteres agronômicos da cultura do milho sob plantio direto

Maize is an important crop for grain production in the Center-West region of Brazil. An experiment was installed in Rio Verde (GO) in the 2002/03 growing season to evaluate the effect of doses and timing of nitrogen application on the agronomic traits of no-tillage maize. The experiment was evaluated as a 6 x 4 + 1 factorial in a randomized complete block design with 4 repetitions. The factors consisted of six nitrogen applications (before sowing; at sowing; top dressed 30 days after sowing; at sowing and top dressed 30 days after sowing; at sowing and top dressed 30 and 45 days after sowing; pre-sowing and at sowing and top dressed 30 days after sowing) and four nitrogen levels (25, 50, 100 and 150 kg ha-1), plus one control treatment without nitrogen application. The corn hybrid P30K75 and urea fertilizer were used. The dose of 150 kg ha-1 led to the highest grain yield, nitrogen leaf concentration, grain weight per ear and plant height. The nitrogen leaf concentration was higher for applications in top dressing, at sowing and top dressed 30 days after sowing and at sowing and after top dressed 30 and 45 days after sowing. The nitrogen applications as top dressing (30 days) and split application (pre-sowing plus at sowing and top dressed 30 days after sowing ) led to the highest kernel weight per ear and per 1.000 grains. The effect of dose or date of nitrogen application on protein yield and disease severity was not significant. The highest net profit was obtained with the application of 25 kg ha-1 nitrogen at sowing.

Sistema radicular de plantas de cobertura sob compactação do solo

With the objective of evaluate the root growth capacity in the compacted soil layer, four vegetal species of the cover crops (amaranth, pearl millet ADR500, finger millet and kenaf) were cultivated in columns of PVC with increasing levels of subsurface compaction (soil bulk densities: 1.18; 1.34; 1.51 and 1.60 Mg m-3). The experiment was carried out in a greenhouse conditions, using a Dusky Red Latosol. The subsurface compacted layer was restrictive to the roots growth of the studied species, causing the root concentrating to the surface. Pearl millet ADR500 and the amaranth were the species that had detached in the production of dry matter weight and developed itself in the compacted layers and below of them. Pearl of millet ADR500 presented the biggest root length density in all layers. Finger millet and the amaranth had similar behavior in relation to the shoot length root. Finger millet and kenaf had presented minor dry matter weight of root in relation to the other species. The kenaf presented minors values of dry matter, but it was not affected by the presence of compacted layers.

Produção e ciclagem de nutrientes por plantas de cobertura nas culturas de arroz de terras altas e de soja

The cover crops in no-till system can contribute to the formation of mulch and nutrient cycling to annual crops in succession. The objective of this study was to evaluate biomass production and nutrient cycling of cover crops sown in the second growing season, in crop rotation after upland rice and soybean, in no-tillage and conventional tillage systems, on a Red Latassol of Rio Verde, state of Goias, from April 2008 to April 2010. The experiment was evaluated in randomized strips, in a 5 x 6 factorial design, with four replications. In the horizontal strips two soil management systems (after three years of no-tillage and conventional systems) were evaluated and the cover crops in the vertical strips. Biomass and ground cover and nutrient cycling rates were only evaluated in the no-till treatments, in a 5 x 6 factorial arrangement, where the plots were subdivided, corresponding to six harvest dates of dried biomass 0, 15, 30, 60, 90 and 120 days after cutting of the cover crops. The following cover crops were sown in the second growing season: Brachiaria ruziziensis, Pennisetum glaucum and B. ruziziensis + Cajanus cajan and a fallow treatment as reference. Biomass production and the rates of soil cover and nutrient accumulation and release by cover crops as well as rice and soybean yield were evaluated. B. ruziziensis and B. ruziziensis + C. cajan performed best in biomass production, ground cover and nutrient accumulation at the end of the cover crops. The nutrients N and K had the highest concentration in the biomass, and the highest nutrient release to the soil was observed for K and P. The highest rice yield was observed when grown in no-tillage on crop residues of P. glaucum and B. ruziziensis, while soybean yields did not differ in the treatments.

Avaliação da resistência do solo à penetração em diferentes solos com a variação do teor de água

As human population and demand for food grow, new technologies have emerged to increase productivity and reduce production costs. If these technologies on the one hand have increased production and reduced costs, on the other hand the intense traffic of machinery and tractors have modified the soil structure, causing compaction and compromising agricultural productivity. In this study we relate soil moisture to soil resistance to penetration in four soil types under four moisture conditions, using a hydraulic-electronic penetrometer containing a DGPS navigation system. The results showed there were changes in the friction conditions between the cone and the soil as moisture increased, facilitating rod penetration and making the soil more plastic due to the lubricating action among its particles. The highest values of soil resistance to penetration were detected around the soil shrinkage limit. There was a negative correlation between cone index and moisture. The best fit for all soils was provided by a decreasing linear function, with high coefficients of determination. Under higher soil moisture conditions, soil resistance to penetration values can be considered not to prevent root growth. Soil type also had a significant impact on cone index results.

Atividade residual de herbicidas pré-emergentes aplicados na cultura da soja sobre o milheto cultivado em sucessão

-1 ), diclosulam (0,035 kg ha-1), sulfentrazone (0,600 kg ha-1) e flumioxazin (0,050 kg ha-1) e uma testemunha, aplicados logo apos a semeadura do cultivar de soja Msoy-6101. Nas subparcelas, realizou-se a semeadura do milheto, cultivar ADR-7010, em quatro periodos, correspondendo a 0, 40, 80 e 120 dias apos a aplicacao dos herbicidas (DAA). Durante a conducao do ensaio, foram determinados os niveis de intoxicacao, estande, altura e massa seca da parte aerea das plantas de milheto. No final do ciclo foi avaliado o rendimento de graos da cultura. O hibrido de milheto ADR-7010 apresentou elevada sensibilidade com relacao a atividade residual dos herbicidas sulfentrazone, diclosulam e imazaquin quando cultivado logo apos a aplicacao destes. A bioatividade dos herbicidas imazaquin, diclosulam e flumioxazin nao foi suficiente para alterar o rendimento de graos do milheto cultivado em sucessao a soja (120 DAA), mostrando que esse intervalo de tempo e suficiente para dissipacao desses herbicidas. Dos herbicidas pre-emergentes avaliados, o sulfentrazone apresentou maior atividade residual, influenciado negativamente o rendimento da cultura durante o intervalo de tempo estudado. Palavras-chave: carryover, sulfentrazone, diclosulam, imazaquin, flumioxazin, Pennisetum glaucum. ABSTRACT - The objective of this study was to evaluate the persistence of herbicides applied in pre-emergence in soybean crop and the effects of these herbicides on pearl millet grown in succession. The herbicides imazaquin (0.160 kg ha-1), diclosulam (0.035 kg ha-1), sulfentrazone (0.600 kg ha-1), and fumioxazin (0.050 kg ha-1) were used immediately after sowing of soybean Msoy-6101, in plots of 80 m2, divided into sub-plots of 20 m2 (5 x 4 m). A randomized block design with four replications was used in a split-plot scheme 5 x 4. In the sub-plots, pearl millet hybrid ADR-7010 was sown in four periods after herbicide application, corresponding to 0, 40, 80 and 120 days after herbicide application (DAA). Pear millet injury, stand, height and dry biomass of the plant were evaluated at 7, 15, and 28 days after emergence; crop grain yield was evaluated at the end of the cycle. Pearl millet hybrid ADR-7010 showed high sensitivity to the residual activity of sulfentrazone, imazaquin, and diclosulam when grown immediately after herbicide application. The bioactivity of imazaquin, diclosulam, and flumioxazin was not sufficient to affect grain yield of millet grown after soybean (120 DAA), suggesting that this interval is sufficiently long for dissipation of these herbicides. Among the pre-emergent herbicides, sulfentrazone showed longer residual activity, negatively influencing the crops yield during the time interval studied.

Liberação de nutrientes pela palhada de milheto em diferentes estádios fenológicos

This study was carried out in an experimental area of the Faculdade de Agronomia of the Universidade de Rio Verde, from October 2004 to May 2005, in a clayey dystroferric Red Latosol (Oxisol). The purpose of the experiment was to evaluate nutrient release from Pennisetum glaucum straw, cv. ADR300, in three different phenological stages (pre-booting, pre-flowering and early flowering). Pennisetum glaucum was used as cover crop in a no tillage system, in a randomized block design, and split plots in time, with four replications, totalizing 9 m2. To evaluate nutrient release, a decomposition bag system was used. After Pennisetum glaucum management, decomposition was evaluated during 150 days, at intervals of 30 days. Nutrient accumulation was highest at the early flowering stage. Nutrient release dynamics differed in all phenological stages, with exception of K, which was the nutrient of easiest release, regardless of the phenological stage.

Ciclagem de nutrientes por plantas de cobertura e produtividade de soja e arroz em plantio direto

The objective of this work was to evaluate nutrient cycling by cover crops and its influence on the performance of the rotation between upland rice and soybean. The crops were sown under no-tillage, in a Rhodic Haplustox, in the Cerrado region of the state of Goias, Brazil. The cover crops were sown mechanically, also under no-tillage, after the harvest of soybean (3/25/2008) and rice (4/7/2009). A randomized complete block design was used, split-plotted in time, with four replicates. The treatments consisted of the following cover crop species, besides fallow: Urochloa ruziziensis, U. brizantha, Pennisetum glaucum and U. ruziziensis + Cajanus cajan. The evaluation of the remaining nutrient in straw was performed at 0, 15, 30, 60, 90, and 120 days from the desiccation date of the cover crops. Urochloa ruziziensis and U. brizantha were the most efficient in the accumulation and release of nutrients, especially potassium. Urochloa ruziziensis is the most suited species for use as a cover crop previous to upland rice cultivation under no-tillage. However, none of the cover crop species significantly affect soybean grain yield.

Cultivo do milho e disponibilidade de P sob adubação com cama-de-frango

The aim of this study was to evaluate the effect of rates and incubation periods of poultry manure in the initial development of corn and the availability of phosphorus in the soil. The experiment was carried out in greenhouse, at FESURV - Rio Verde University, from November/2007 to January/2008. The experimental design was set as completely randomized-block design in a factorial with one additional treatment, 5 x 4 + 1 with four replications, consisted of five rates of poultry manure (4; 7; 14; 21 and 28 Mg ha-1), incubation periods of the residue in soil (0, 7, 15 and 30 days before the seedling) and one additional treatment (mineral fertilizer). Before and 45 days after the planting the soil of all plots were sampled and the content of phosphorus availability (Mehlich-1) was determine and at 45 days after the planting, the height of the plants, yields of leaves and dry matter of stalks were evaluated. The doses of poultry manure were superior than mineral fertilizer in all evaluated characteristics. The greatest height of the plants, yields of leaves and dry matter of stalks and contents of P in the soil were obtained using 21 Mg ha-1of poultry manure and 30 days of incubation.