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Search Results: 1 - 10 of 410735 matches for " BACCHI O.O.S. "
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Efeitos da aplica??o de vinha?a sobre a popula??o e controle químico de plantas daninhas na cultura da cana-de-a?ucar (Saccharum SPP.)
Christoffoleti, P.J.;Bacchi, O.O.S.;
Planta Daninha , 1985, DOI: 10.1590/S0100-83581985000100008
Abstract: to evaluate the chemical control and the influence of weed population occurring in the sugarcane culture (3rd ratoon), variety na56-79, with different vinasse dosages, an experiment was installed at santa lúcia sugar and alcohol mill, in araras-sp. the soil was distrophic red yellow latossol, loam texture, haplorthox. no rainfall level occurred during the 10 days following herbicide application . the experiment was installed in 10/08/83, being the soil dry at the moment of vinasse application, which was through tank truck, with pump discharge without pressure. herbicides were applied with knapsac at constant pressure co2 , using teejet 110.04 nozzle, at an outflow of 370 1/ha. experimental design was constituted by randomized blocks with split plots and 3 replications. treatments were 0, 50, 100 and 150 m3/ha vinasse and mineral fertilization. subtreatments were constituted by the herbicides alachlor at 2.40 kg a.i/ha; diuron at 1.60 kg a.i/ha; ametrin at 2.40 a.i/ha and tebuthiuron at 0.96 kg a.i/ha. infestation of crabgrass (digitaria horizontalis willd) was highter in the areas which received only mineral fertilization, however, in the treatments receiving increasing vinasse dosages, crabgrass population was higher with the increase of doses. the most efficient control was provided by tebuthiuron, having alachlor caused a marked control when applied with 150 m3 /ha of vinasse. this was also observed with diuron and less markedly with ametrin. the purple nutsedge (cyperus rotundus l.) had a less intense infestation in the treatments receiving 100 m3 /ha vinasse, increasing its population with lower doses. the best control was achieved was with alchlor and less satisfactory with tebuthiuron. purslane (portulaca oleracea l.) wire weed (sida rhombifolia l.) and red tassel flower (emilia sonchifolia d.c.) had their populations altered by the interaction of vinasse and the herbicide dosages. therefore, by this assay it was concluded that the different vinasse dosages i
Geometria fractal em física do solo
Bacchi, O.O.S.;Reichardt, K.;
Scientia Agricola , 1993, DOI: 10.1590/S0103-90161993000200021
Abstract: fractal geometry has been applied on different branches of science, showing high potential in describing complex structures. its applications in soil science have received large attention and have been intensified in the last few years. inspite of the large number of internationally published papers, the subject seems not having received the same attention by brazilian soil scientists, as verified by the absence of the subject in our scientific journals. this paper presents the basic concepts of this new tool and some of its applications in soil physics.
On simple methods for unsaturated soil hydraulic conductivity determination
Bacchi, O.O.S.;Reichardt, K.;
Scientia Agricola , 1993, DOI: 10.1590/S0103-90161993000200022
Abstract: the simple methods of libardi et al. (1980) and sisson et al. (1980) for k(q) estimation, although developed on completely different theoretical basis, are rigorously identical for the exponential hydraulic conductivity model. the unit gradient approximation used in these methods seems valid for practical purposes but is theoretically in valid.
Heterogeneidade dos pontos experimentais de curvas de reten??o da água no solo
Moraes, S.O.;Libardi, P.L.;Reichardt, K.;Bacchi, O.O.S.;
Scientia Agricola , 1993, DOI: 10.1590/S0103-90161993000300011
Abstract: in an area of "terra roxa estruturada latossólica" (rhodic kanhapludalf), in piracicaba, sp, brazil (20° 42' 30" s, 47° 38' 00" w, 576 m), 250 undisturbed soil samples were collected at 25 cm soil depth, according to a regular grid of spacing of 5 m, resulting a network of 25 unes and 10 columns. these samples were used to determine 250 soil water retention curves each one with eigth experimental points, using haines funnels (tensions of 5xl02, 1x103, 6x103 and 1x104 pa) and richards pressure chambers (pressures of 3x104, 8x104,3x105 and 1x106 pa), totalizing two thousand values. position measurements (mode, median and arithmetic mean), variability (total amplitude, interquartil amplitude, standard deviation, coefficient of variation, assimetry, kurtosis and confident limits around the mean) and number of samples to estimate the mean of the soil water content at a specific probability level, were used with the following objectives: a) to verify how close to the normal distribution are the values of soil water content for the different considered tensions and hence, to investigate what is the best position measurement; b) to quantify the variability in each considered tension, identifying the most problematic in the study of soil-water retention and also to analyse the measurement sensibility through the calculation of the necessary number of samples to estimate the mean (assuming a spatial independence of the samples). from the analysis of the obtained results, it could be concluded that the soil-water content values corresponding to tensions of 5x102 and 1x103 pa showed very skewed distributions, so that care should be taken in using the arithmetic mean as a position measurement. the neglection of problem-samples, based on the physical analyses of results, allowed a better aproximation to the normal distributions for these tensions, indicating that a complete soil-water retention curve should always be prefered in the place of only two or three points of restricted
BALAN?O HíDRICO EM CULTURA DE AVEIA FORRAGEIRA DE INVERNO NA REGI?O DE S?O CARLOS-SP
BACCHI, O.O.S;GODOY, R;FANTE Jr, L;REICHARDT, K;
Scientia Agricola , 1996, DOI: 10.1590/S0103-90161996000100025
Abstract: the aim of this experiment was to perform a water balance for a forrage oat winter crop (variety s?o carlos) cultivated under sprinkler irrigation condition. the main objectives were to obtain basic information about the crop behavior under irrigation and the crop water requirement for the region of s?o carlos, sp, brazil. crop yield and water balance results under two soil water availability levels gave indications that the lower level of soil water availability, indicated by a minimum matric potential of -20kpa at the 20cm depth, is sufficient to provide conditions for highest yield under these soil and climate conditions.
Field determined variation of the unsaturated hydraulic conductivity functions using simplified analysis of internal drainage experiments
Villagra, M. M.;Michiels, P.;Hartmann, R.;Bacchi, O.O.S.;Reichardt, K.;
Scientia Agricola , 1994, DOI: 10.1590/S0103-90161994000100018
Abstract: experimentally determined values of unsaturated soil hydraulic conductivity are presented for an alfisol of the county of piracicaba, s.p., brazil. simultaneous measurements of soil water content and pressure head are made along a 125 m transect within an irrigated field during the internal drainage process. calculations of the soil hydraulic conductivity were made using the instantaneous profile method (watson, 1966) and the unit gradient method (libardi et al., 1980). the spatial variability of the soil hydraulic conductivity manifested along the transect indicates the need to develop a field method to measure k(q) within prescribed fiducial limits, taking into account quantitative evaluation of spatial and temporal variances associated with the mathematical model, instrument calibration and soil properties.
Efeito de épocas de deficiência hídrica na evapotranspira??o atual da cultura do feij?o cv. imbabello
CALVACHE, A.M.;REICHARDT, K.;BACCHI, O.O.S.;
Scientia Agricola , 1998, DOI: 10.1590/S0103-90161998000300018
Abstract: the objective of this paper was to identify specific growth stages of the common bean crop at which the plant is less sensitive to water stress, in which irrigation could be omitted without significant decrease in evapotranspiration, in order to better define irrigation management practices for farmers. the field experiment was conducted at "la tola" university experiment station, tumbaco, pichincha, ecuador, on a sandy loam soil (typic haplustoll), the climate being tempered and dry (mean air temperatura 16oc and mean relative humidity, 74%) and 123 mm of rain-fall were recorded during the cropping period (july to november, 1994). seven irrigation regimes were used, including normal watering, full stress, tradicional practice, single stress at vegetation, at flowering, at yield formation and at ripening. irrigation treatments were started after uniform germination and crop establishment. soil moisture was monitored with neutron probes down to the 0.50 m depth, 24 hours before and after each irrigation. the actual evapotranspiration (eta) of the crop was estimated by the water-balance technique. the yield formation stage was the most sensitive to moisture stress, in wich crop water use efficiency (0.46 kg/m3) was the lowest.
EFEITO DA DEFICIêNCIA HíDRICA E DA ADUBA??O NITROGENADA NA PRODUTIVIDADE E NA EFICIêNCIA DO USO DE áGUA EM UMA CULTURA DO FEIJ?O
CALVACHE, A.M.;REICHARDT, K.;MALAVOLTA, E.;BACCHI, O.O.S.;
Scientia Agricola , 1997, DOI: 10.1590/S0103-90161997000200019
Abstract: a field experiment was conducted at "la tola" university experimental station, tumbaco, pichincha, ecuador, on a sandy loam soil (typic haplustoll) to identify specific growth stages of the common bean crop at which the plant is less sensitive to water stress, in which irrigation could be omitted without significant decrease in final yield. the climate of the area is temperate and dry (mean air temperature 16°c and mean relative humidity 74%) during the cropping season, and 123 mm of rainfall were recorded from july to november, 1994. to achieve the proposed goal seven irrigation regimes were used, including normal watering, full stress, traditional irrigation practice, single stress at vegetation, at flowering, at yield formation and at ripening and, two levels of applied n (20 and 80 kg/ha). plot sizes were 33.6 m2 (8 rows, 7 m long) with a population of 120,000 plants/ha arranged in a split-plot design with four replicates. the irrigation treatments started after uniform germination and crop establishment. soil moisture was monitored with neutron probe down to the 0.50 m depth, 24 hours before and after each irrigation. the actual evapotranspiration (eta) of the crop was estimated by the water-balance technique. field water efficiency and crop water use efficiency were calculated dividing the actual grain yield (10% seed water content) by irrigation and by eta, respectively. yield data show that treatments with irrigation deficit had lower yield than those with supplementary irrigation (1% prob.). the pod formation stage was the most sensitive to moisture stress, in wich crop water use efficiency (0.46 kg/m3) was the lowest and the yield response factor (ky = 2.2) was the highest. nitrogen fertilization significantly increased the number of pods and grain yield.
Deficit irrigation at different growth stages of the common bean (Phaseolus vulgaris L., cv. Imbabello)
Calvache, M.;Reichardt, K;Bacchi, O.O.S.;Dourado-Neto, D.;
Scientia Agricola , 1997, DOI: 10.1590/S0103-90161997000300002
Abstract: to identify specific growth stages of the common bean crop at which the plant is less sensitive to water stress, in which irrigation could be omitted without significant decrease hi final yield, two field experiments were conducted at "la tola" university experimental station, tumbaco, pichincha, ecuador, on a sandy loam soil (typic haplustoll). the climate is tempered and dry (mean air temperature 16°c and mean relative humidity 74%, during the cropping season) 123 and 109 mm of rainfall were recorded during the experimental cropping periods (july to october), of 1992 and 1994, respectively. the treatments consisted of combinations of 7 irrigation regimes including normal watering; full stress; (traditional management practice); single stress at vegetative stage; flowering; seed formation and ripening, and of 2 levels of applied n (20 and 80 kg/ha). these 14 treatment combinations were arranged and analysed in a split-plot design with 4 replications. the plot size was 33.6 m2 (8 rows, 7 m long) with a plant population of 120,000 pl/ha. irrigation treatments were started after uniform germination and crop establishment soil water content was monitored with a neutron probe down to 0.50 m depth, before and 24 h after each irrigation. the actual evapotranspiration of the crop was estimated by the water-balance technique. field water efficiency and crop water use efficiency were calculated. yield data showed that the treatments which had irrigation deficit had lower yield than those that had supplementary irrigation. the flowering stage was the most sensitive to water stress. nitrogen fertilization significantly increased the number of pods and gram yield. crop water use efficiency (kg/m3) was the lowest with stress at the flowering period, and the yield response factor (ky) was higher hi treatments of full stress and stress at flowering. in relation to the traditional management practice adopted by farmers, only treatments of normal watering and stress at maturation ha
Daily rainfall variability at a local scale (1,000 ha), in Piracicaba, SP, Brazil, and its implications on soil water recharge
Reichardt, K.;Angelocci, L.R.;Bacchi, O.O.S.;Pilotto, J.E.;
Scientia Agricola , 1995, DOI: 10.1590/S0103-90161995000100008
Abstract: daily rainfall variability at a local scale (1,000 ha) was studied at piracicaba, sp, brazil, for the period of one year (1993-1994), in order to better understand the process of soil water recharge. coefficients of variation of daily data for ten observation points varied from 2.2 to 169.3% and the variability was independent of rain type, i.e. whether convective, frontal or of other origin. data were not related to separation distances between observation points and it is concluded that one observation point does not represent areas as far as 1,000 to 2,500 m apart, for daily, monthly or even quarterly averages. yearly totals for the ten observation points presented a coefficient of variation as low as 3.06%, indicating that all points can replace each other in annual terms.
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