Gilberto Nicolella

Índice de qualidade de água em microbacia sob uso agrícola e urbano

An assessment of water quality in a watershed of 9600 ha in Guaira, SP - Brazil, submitted to different occupations (rural and urban), was carried out during the period Jun/95 to Jun/96, using multivariate statistical techniques. Water samples were collected every 21 days at five sampling sites to evaluate ten water quality parameters (total and dissolved P, pH, dissolved O2, NH4, nitrate, electrical conductivity, turbidity, total suspended solids, and chlorophyll). A water quality index (WQI) was determined by the factorial analysis and the Bartlett method. The results point out a significant difference of WQI between the three upstream and the two downstream (in relation to Guaira) sampling sites (mean values of - 1.76 and 2.35 respectively). The factorial analysis indicated that dissolved O2, total P, NH4, and electric conductivity were the most important parameters in determining the value of the WQI. The first three factors explained 71% of the variance of the data, whereas the first factor alone explained 47%. The influence of climate parameters was of little significance for the WQI, causing a minor water quality deterioration during the rainy season. The paper discusses the applicability of the factorial analysis as a means of assessing water quality alterations, as well as for the selection of appropriate indicators for the assessment of environmental impact in watersheds.

Controle biológico do ácaro rajado com ácaros predadores fitoseídeos (Acari: Tetranychidae, Phytoseiidae) em culturas de pepino e morango

The two-spotted spider mite, Tetranychus urticae Koch, is considered one of the main pests of horticultural and other crops in Brazil, in areas where a considerable volume of acaricides is annually used for its control. The objective of this work was to test the technical viability of using phytoseiids Amblyseius idaeus (Denmark & Muma) and Phytoseudus macropilis (Banks), commonly found in Brazil, to control T .urticae in cucumber and strawberry crops in Jaguariuna,SP. A randomized complete block design was used, with 4 replicates and 4 treatments for cucumber (T1-T4) and 5 treatments for strawberry crops (T1-T5): T1, control; T2, weekly sprays of malathion for exclusion of native predators; T3, periodical releases of A.idaeus; T4, periodical releases of P. macropilis; T5, weekly sprays of avermectin for exclusion of native phytophagous and predatory mites. Only A. idaeus was successfully established on cucumber, significantly reducing T. urticae population. Both released phytoseiid species were established on strawberry and reduced significantly the population of T. urticae.

Paclobutrazol effects on soil microorganisms

The side effects of paclobutrazol, a plant growth regulator, on soil microbial community and activity were assessed in soil samples from Petrolina (PE), Pernambuco State and from Lins (SP), Sao Paulo State, in Brazil. The first experiment was carried out with soils from mango orchards of Petrolina, subjected to frequent field applications of paclobutrazol. A second experiment was conducted with soils from Petrolina and Lins with application of paclobutrazol under greenhouse conditions. For orchard soils, plate counting of soil microorganisms was carried out, while for the greenhouse experiment the parameters evaluated were: microbial biomass C, living hyphal length, dehydrogenase activity, and paclobutrazol dissipation. The paclobutrazol addition to soils of mango orchards in Petrolina, affected negatively the soil microbial community. The average values for total number of bacteria, fungi and actinomycetes were reduced by 58, 28, and 28%, respectively, compared to the paclobutrazol unamended soil. For the greenhouse experiment, the paclobutrazol application in the soils from Petrolina influenced negatively the dehydrogenase activity and the living hyphal length, but not the microbial biomass C. The addition of this substance to the Lins soils had no effect on the microbial parameters evaluated.

Método para monitorar perdas na aplicação de agrotóxicos na cultura de tomate

The available methodology for pesticide residues analysis is very expensive to be used on spraying losses studies and occupational exposure assessment during pesticide application. So, the marking of spray liquids prior to dispersion with easily detectable tracers has become widely accepted practice. The objective of this research was to evaluate a method to assessment the pesticide deposition, characterised by the use of a tracer marked spray liquid and a special sampling technique. The tracer used in this work was the copper, in a fungicide formulation, with low cost and easy atomic absorption spectrophotometric analysis. Cards of blotter-like papers were used as artificial target to catch the droplets. Cards were clipped on cotton strings at constant distances and were disposed on plants possibiliting a height stratified sampling. Cards on Petri dishes are used upon the soil. Between 59 and 76% of the spray were lost according to plant height.

Influência da época de corte sobre o teor de açúcares de colmos de sorgo sacarino

High energy sorghum (Sorghum bicolor (L.) Moench) cultivars have been recently developed for grain and biomass production. Whole plant utilization is the target of this concept. The objective of this study was to identify the relationship between the harvest date and biomass yield. Experimental trials were conducted with the cultivar BR 505 in the years 1984/85, 1985/86 and 1986/87 to determine its performance as a high energy crop. High biomass and sugar yields were obtained at the physiological maturity stage of the plants. Sucrose and total sugars of the plant increased continually from the visible spikelet stage to the physiological maturity. However, reducing sugar level showed a fall over the same period. In the years 1984/85 and 1985/86 the total biomass yield was 38.9 and 52.0 t/ha respectively. Late sowing date which occurred in the year 1986/87 and the elimination of the supplementary N fertilization reduced significantly the biomass yield as well as the sugar level in the stalks. Grain production of the complementary N fertilization was not affected significantly.

Lime application methods, water and bottom soil acidity in fresh water fish ponds

Alguns metodos para determinar a quantidade de calcario necessaria para corrigir a acidez do fundo dos viveiros de piscicultura estao disponiveis e rotineiramente em uso, mas ainda nao existe um consenso se e mais eficiente fazer a aplicacao diretamente no fundo ou sobre a superficie da agua apos o abastecimento dos viveiros. Alem disso, existem poucas informacoes disponiveis sobre ate que profundidade o calcario reage com o sedimento do fundo ao longo do tempo, e se a profundidade na qual ocorrem as reacoes e diferente quando o calcario e aplicado sobre a superficie da agua ou sobre o solo. Dessa forma, tres tecnicas para calagem foram avaliadas em viveiros com solo argiloso em uma piscicultura comercial de acordo com os seguintes metodos: aplicacao direta sobre a superficie da agua do viveiro, distribuicao uniforme sobre o fundo do viveiro vazio, distribuicao uniforme sobre o fundo do viveiro vazio seguida da aragem. A eficacia da aplicacao do calcario agricola nao diferiu entre os metodos de tratamento. O calcario agricola reagiu rapidamente para aumentar a alcalinidade e a dureza total da agua dos viveiros para concentracoes aceitaveis apos duas semanas. O aumento do pH do sedimento se completou essencialmente apos um a dois meses, e o calcario agricola nao teve efeito sobre as camadas de sedimento abaixo de 8 cm. A aracao do fundo dos viveiros para incorporacao de materiais e desnecessaria, consome tempo e e dispendiosa; a calagem pode ser feita de forma eficaz em viveiros cheios.

Geoestatística como suporte ao modelo de simulação de agrotóxico CMLS com validação em colunas de solos

O uso de modelos de simulacao e provavelmente a maneira mais eficiente para predizer o comportamento de agrotoxicos no sistema solo/agua/planta. O modelo de simulacao de destino de agrotoxicos CMLS (Chemical Movement in Layered Soils), foi usado para estudar o comportamento do herbicida tebuthiuron, utilizado na cultura de cana-de-acucar, a partir de uma grade de amostragem composta de 111 pontos amostrais, equi-espacados de 200 m e englobando tres tipos de solo: Neossolo Quartzarenico (RQ), Latossolo Vermelho distroferrico (LVdf) e Latossolo Vermelho distrofico (LVd), texturas media e argilosa. Os 373 pontos avaliados pelo simulador, gerados das amostras da grade original e atraves dos metodos geoestatisticos da variografia e krigagem, produziram valores de profundidade atingida pelo herbicida, apos seis anos de simulacao (1989-1995). Para Neossolo Quartzarenico (RQ), o tebuthiuron, em quatro pontos simulados, apresentou valores de profundidade acima de 43 m e com maximo de 50 m, com uma quantidade de produto permanecendo ainda no solo, proximo a 10% do valor aplicado de 1,1 kg ha-1. Resultados provenientes do ensaio em coluna, usados para a validacao do modelo, mostraram que o mesmo superestimou em 6,66% a profundidade atingida pelo herbicida quando comparado ao valor produzido pela coluna, para o Neossolo Quartzarenico (RQ), e subestimou com valores de 4,5% e 20,0%, para o Latossolo Vermelho distrofico (LVd) e o Latossolo Vermelho-distroferrico (LVdf), respectivamente. Esses dados confirmam, para o Neossolo Quartzarenico(RQ) e o Latossolo Vermelho-distrofico (LVd) a adequacao do modelo, na avaliacao do destino do herbicida.