Intervalo hídrico ótimo e grau de compactação de um latossolo vermelho após 30 anos sob plantio direto

A qualidade física do solo é um dos fatores determinantes da sustentabilidade agronômica, econômica e ambiental no sistema plantio direto (SPD). A compactação do solo tem sido apontada como um dos fatores de redução da qualidade física em solos sob SPD. Contudo, com a utilização do SPD, pode haver o incremento de matéria orgânica do solo e o desenvolvimento de um sistema poroso contínuo e estável, que atenuam os impactos negativos da compactação. O objetivo deste trabalho foi avaliar a qualidade física de um Latossolo Vermelho distroférrico sob SPD durante 30 anos, utilizando o intervalo hídrico ótimo (IHO) e o grau de compactação do solo (GC). Em uma área comercial com histórico de altas produtividades sob SPD, foram coletadas amostras de solo com estrutura preservada e deformada, para determinação da densidade do solo (Ds), do IHO e do GC. As amostras com estrutura preservada foram obtidas em três posições, relativas às linhas (L), entrelinhas (E) e posição intermediária entre as linhas e entrelinhas (PI) da cultura do milho. Foram determinadas as curvas de retenção de água e resistência do solo à penetração, bem como a Ds. A amostra de solo com estrutura deformada foi usada para obter a curva de compactação, utilizando o teste de Proctor. A Dmax foi obtida a partir da curva de compactação, e o GC foi determinado pela razão entre a Ds e a Dmax. Independentemente dos limites críticos de resistência à penetração (RP), verifica-se redução do IHO com o aumento da Ds. Os maiores valores do IHO foram verificados na posição de amostragem L, e a utilização de RP crítica maior que 2,0 MPa resultou em IHO condizente com a qualidade física desse solo sob SPD de longo tempo. A Dmax foi de 1,52 kg dm-3, e o GC variou de 64 a 87 %, sendo os maiores valores obtidos nas posições E e PI. Os valores de IHO e GC obtidos neste estudo indicam que a qualidade física desse solo não é limitante à produção das culturas após 30 anos de utilização do SPD.

Abundant and Stable Char Residues in Soils: Implications for Soil Fertility and Carbon Sequestration

Large-scale soil application of biochar may enhance soil fertility, increasing crop production for the growing human population, while also sequestering atmospheric carbon. But reaching these beneficial outcomes requires an understanding of the relationships among biochar's structure, stability, and contribution to soil fertility. Using quantitative C-13 nuclear magnetic resonance (NMR) spectroscopy, we show that Terra Preta soils (fertile anthropogenic dark earths in Amazonia that were enriched with char >800 years ago) consist predominantly of char residues composed of similar to 6 fused aromatic rings substituted by COO- groups that significantly increase the soils' cation-exchange capacity and thus the retention of plant nutrients. We also show that highly productive, grassland-derived soils in the U.S, (Mollisols) contain char (generated by presettlement fires) that is structurally comparable to char in the Terra Preta soils and much more abundant than previously thought (similar to 40-50% of organic C). Our findings indicate that these oxidized char residues represent a particularly stable, abundant, and fertility-enhancing form of soil organic matter.

Biochemical Analysis of a Castor Bean Leaf Extract and its Insecticidal Effects Against Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae)

Plant extracts represent a great source of molecules, with insecticidal activity, which are used for pest control in several crop production systems. This work aimed to evaluate the toxicity of an aqueous extract of leaves of castor bean against larvae of Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae) in search for different classes of molecules with insecticidal activities by using in vitro assays. The effects of the castor bean leaf extract on the food utilization, development, and survival of S. frugiperda larvae was evaluated by feeding the larvae an artificial diet supplemented with different concentrations of the extract (0%, 1%, 2.5%, 5%, and 10% w/v). The effects observed were dose-dependent, and the highest concentration evaluated (10% w/v) was the one the most affected food utilization by altering the nutritional indices, as well as larval weight gain, development time, and survivorship. In vitro assays to detect saponins, lectins, and trypsin inhibitors in the castor bean leaf extract were performed, but only trypsin inhibitors were detected. No preference for the diet source was detected in S. frugiperda by feeding the larvae in choice experiments with diets containing different concentrations of the castor bean extract tested. The data obtained indicate the existence of a potential molecule in the tested extract of castor bean to be used as an alternative insecticide to be integrated in the management of S. frugiperda.

PRODUÇÃO DE BIOMASSA E COMPOSIÇÃO QUÍMICA DE ADUBOS VERDES CULTIVADOS NO VALE DO RIBEIRA

A contribuição da adubação verde com leguminosas para melhoria do solo e produção agrícola depende em primeiro lugar da produção de biomassa e da sua composição química, que variam em função da espécie, região e estação de cultivo. Objetivo do presente trabalho foi avaliar a composição química da biomassa produzida por adubos verdes no Vale do Ribeira, São Paulo, Brasil. Para tal, foi conduzido um experimento em Pariquera-Açu-SP, no ano agrícola 2006/2007, em blocos casualizados, com quatro tratamentos (três adubos verdes e vegetação espontânea) e cinco repetições. Aos 30, 60, 90 e 120 dias após a semeadura, foram coletadas amostras em 1 m² da parte aérea das plantas e determinada a matéria fresca e seca, bem como a composição da biomassa. Crotalária, guandu e mucuna produziram, em ordem decrescente, as maiores quantidades de biomassa e foram mais eficientes do que a vegetação espontânea. A biomassa produzida pelos adubos verdes apresentou qualidade superior à produzida pela vegetação espontânea. Crotalária e guandu apresentam maior proporção de matéria seca acumulada no caule que possui baixo teor de N, alta relação C/N e L/N, variáveis que tornam a decomposição dos resíduos mais lenta. A análise particionada da matéria seca permite indicação mais precisa da composição química dos resíduos e a previsão da disponibilidade dos nutrientes no solo.

Maize and soybeans production in integrated system under no-tillage with different pasture combinations and animal categories

The adoption of no-till system (NTS) combined with crop-livestock integration (CLI) has been a strategy promoted in Brazil, aiming to maximize areas yield and increase agribusiness profitability. This study aimed to evaluate grains yield and phytotechnical attributes from maize and soybean culture by CLI system under NTS after winter annual pure and diversified pastures with the absence or presence of grazing animals. The experiment was installed in Castro (Parana State, Brazil) on in a dystrophic Humic Rhodic Hapludox with a clay texture, using experimental design of randomized complete blocks in 4 x 2 factorial scheme with three replications. Treatments included four pasture combinations (diversified or pure) and animal categories (light and heavy) subjected or not to grazing animals during the winter. During 2008/09 and 2009/10 summers, the area was cultivated with soybeans and maize, respectively, with yield assessment of grains and phytotechnical attributes. Treatments did not alter the yield and weight of a thousand seeds (WTS) of soybeans. In maize culture, the grazing animal during the winter increased the plant population and grains yield, but gave slight decrease in WTS. Pasture combinations (diversified or pure) and animal categories (light and heavy) did not interfere in soybean culture, but benefited the maize crop.

Active crop sensor to detect variability of nitrogen supply and biomass on sugarcane fields

Nitrogen management has been intensively studied on several crops and recently associated with variable rate on-the-go application based on crop sensors. Such studies are scarce for sugarcane and as a biofuel crop the energy input matters, seeking high positive energy balance production and low carbon emission on the whole production system. This article presents the procedure and shows the first results obtained using a nitrogen and biomass sensor (N-Sensor (TM) ALS, Yara International ASA) to indicate the nitrogen application demands of commercial sugarcane fields. Eight commercial fields from one sugar mill in the state of Sao Paulo, Brazil, varying from 15 to 25 ha in size, were monitored. Conditions varied from sandy to heavy soils and the previous harvesting occurred in May and October 2009, including first, second, and third ratoon stages. Each field was scanned with the sensor three times during the season (at 0.2, 0.4, and 0.6 m stem height), followed by tissue sampling for biomass and nitrogen uptake at ten spots inside the area, guided by the different values shown by the sensor. The results showed a high correlation between sensor values and sugarcane biomass and nitrogen uptake, thereby supporting the potential use of this technology to develop algorithms to manage variable rate application of nitrogen for sugarcane.

Seasons of desiccant application in the soybean crop: water content and productivity

The herbicides glyphosate and paraquat have been used by Brazilian soybean producers to obtain crop desiccation and to anticipate and uniformity at harvest. However, improper use of herbicides can to occasion problems in agronomic and physiologic characteristics of crop. This study aimed to evaluate the use of the glyphosate and paraquat herbicides as a desiccant for growing soybeans. The experiment was conducted in 2005/06 crop year, in an experimental design of randomized blocks with four replications. Treatments were arranged in two factorial design, 3x3x5x2 and 3x2x5x2: two desiccants (glyphosate and paraquat) and control (without drying), three and two growth stages (R6, R7 and R8) and (R7 and R8) for varieties MSOY 6101 of superprecocious cycle, and MG / BR 46 (Conquista) of precocious cycle, respectively, five sampling times (2, 4, 6, 8 and 10 days after application) and two positions in the plants on the ground assessment (apex and base). Was evaluated for seed Production, mass and water content of 100 seeds. Desiccants tested were effective in reducing the water content of seeds, without affecting productivity and mass of 100 seeds.

Material embodiment and energy flows as efficiency indicators of soybean (Glycine max) production in Brazil

As the requirement for agriculture to be environmentally suitable there is a necessity to adopt indicators and methodologies approaching sustainability. In Brazil, biodiesel addition into diesel is mandatory and soybean oil is its main source. The material embodiment determines the convergence of inputs into the crop. Moreover, the material flows are necessary for any environmental analysis. This study evaluated distinct production scenarios, and also conventional versus GMO crops, through the material embodiment and energy analysis. GMO crops demanded less indirectly applied inputs. The energy balance showed linearity with yield, whereas for EROI, the increases in input and yield were not affected.

Ontology for Data Representation in the Production of Cotton Fiber in Brazil

An important feature in computer systems developed for the agricultural sector is to satisfy the heterogeneity of data generated in different processes. Most problems related with this heterogeneity arise from the lack of standard for different computing solutions proposed. An efficient solution for that is to create a single standard for data exchange. The study on the actual process involved in cotton production was based on a research developed by the Brazilian Agricultural Research Corporation (EMBRAPA) that reports all phases as a result of the compilation of several theoretical and practical researches related to cotton crop. The proposition of a standard starts with the identification of the most important classes of data involved in the process, and includes an ontology that is the systematization of concepts related to the production of cotton fiber and results in a set of classes, relations, functions and instances. The results are used as a reference for the development of computational tools, transforming implicit knowledge into applications that support the knowledge described. This research is based on data from the Midwest of Brazil. The choice of the cotton process as a study case comes from the fact that Brazil is one of the major players and there are several improvements required for system integration in this segment.