Cut Intervals Research Articles

Características morfogênicas e estruturais e produção de forragem do capim-marandu submetido a intensidades e freqüências de desfolhação

Este trabalho foi realizado com o objetivo de avaliar a influência de intensidades (10 e 20 cm) e freqüências de desfolhação (três intervalos de cortes, definidos pelo aparecimento de 5, 7 e 9 folhas/perfilho após cada evento de desfolhação) nas características morfogênicas e estruturais, no perfilhamento e na produção de forragem de Brachiaria brizantha (A. Rich.) Stapf cv. Marandu. Foi utilizado um arranjo fatorial 2 x 3 seguindo um delineamento inteiramente casualizado, com três repetições, totalizando 18 unidades experimentais. Foram realizados dois cortes no tratamento com maior freqüência de desfolhação e um corte nos demais. A maior intensidade de desfolhação proporcionou maior renovação de tecidos foliares, que, aliada a maiores freqüências de desfolhação, condicionou ao dossel perfilhos mais jovens, que se desenvolveram em ambiente com menos competição por luz. A menor intensidade de desfolhação favoreceu a passagem dos perfilhos da fase vegetativa para a reprodutiva, promovendo maior contribuição de pseudocolmo e material morto para a forragem produzida. Em situações em que são utilizadas maiores freqüências de desfolhação, recomenda-se a utilização da intensidade de corte de 10 cm. Quando utilizadas menores freqüências de desfolhação, o corte a 10 cm pode promover a redução na quantidade de forragem produzida, principalmente na freqüência de sete folhas. As maiores freqüências de desfolhação foram as que apresentaram a maior renovação do dossel, com maiores taxas de alongamento e aparecimento de folhas, maior comprimento de lâmina foliar e menor acúmulo e alongamento de pseudocolmo. Apesar da elevada quantidade de forragem produzida no corte a 20 cm e com a freqüência de sete folhas, considerando-se as características morfogênicas e estruturais, o perfilhamento e o acúmulo de forragem, os cortes mais freqüentes ocasionam, além de alta renovação de tecidos, elevada produção de forragem com grande quantidade de folhas e menor quantidade de pseudocolmo e material morto, condicionando melhor eficiência na produção de forragem.

Parametric representation of fuzzy numbers and application to fuzzy calculus

We present several models to obtain simple parametric representations of the fuzzy numbers or intervals, based on the use of piecewise monotonic functions of different forms. The representations have the advantage of allowing flexible and easy to control shapes of the fuzzy numbers (we use the standard α - cuts setting, but also the membership functions are obtained immediately) and can be used directly to obtain error-controlled-approximations of the fuzzy calculus in terms of a finite set of parameters. The general setting is the Hermite-type interpolation, where the values and the slopes of the monotonic interpolators are given by appropriate parameters and the overall errors of the fuzzy computations can be controlled within a prefixed tolerance by eventually augmenting the total number of pieces (and of the parameters) by which the results are obtained. The representations are designed to model the lower and the upper extremal values of each α - cut (compact) intervals of the fuzzy numbers and are able to produce almost any possible configuration (differentiable, continuous or with a finite number of discontinuity points) by using parametric monotonic functions of different types. We show applications in the standard fuzzy calculus and we stress the generality and the applicability of the proposed representation to a large class of problems, including the numerical solution of fuzzy differential equations, the fuzzy linear regression and the stochastic extensions of the fuzzy mathematics. The proposed model is called the Lower–Upper representation and we denote the associated fuzzy numbers or intervals as LU-fuzzy.

Within-season grass herbage crude-protein- and nitrate-N concentrations as affected by rates and seasonal distribution of fertilizer nitrogen in a high yearly rainfall climate

An orchardgrass study in which three rates of N (100, 200 and 400 kg ha−1) each distributed in 1/0/0/0, 0.75/0.25/0/0, 0.50/0.25/0.25/0 and 0.25/0.25/0.25/0.25 proportions prior to four cut intervals examined crude-protein-N and nitrate-N concentrations in grass herbage at each cut in three trials. Crude-protein-N concentration frequently increased to a greater degree and in a different pattern (based on cut) than yield as the rate of N application increased. This showed that crude-protein-N by itself cannot be used as a method for determining the N sufficiency status of grass. Both rate and distribution of fertilizer N strongly influenced plant nitrate-N concentration; the degree of change varied considerably among cuts and trials. Plant nitrate-N concentration in the control did not correspond to yield responsiveness to N application, making it a poor indicator of the plant's need for fertilizer applications. Residual effects of N applications on plant nitrate-N were noted into the last cut of the season from a single spring application. The effect of N rate and distribution, then, was a function of immediate and residual effects of the applications. There was some evidence that N present in the soil in nitrate-N form enhanced the potential for high nitrate-N in the plant. Plant nitrate-N concentrations accounted for up to 29% of the total N in the plant with concentrations greater than 4000 mg N kg−1 at the highest N application rates. Plant nitrate-N did not exceed 1000 mg N kg−1, a concentration considered safe for ruminants, when 75 kg N ha−1 or less ammonium nitrate was applied as a single application prior to a growth interval for all cuts. Since grass protein- and nitrate-N concentrations respond differently than yield to N applications, a specific combination of rate and distribution of fertilizer will not necessarily produce maximum herbage quantity and quality simultaneously. Key words: Crude-protein-N, plant nitrate-N, residual effect, split applications

Freqüências de corte e intensidades de desfolha em duas cultivares de alfafa (Medicago sativa, L). 1. peso, número, produção estacional e dinâmica de aparecimento das brotações basilares

O experimento foi realizado em Piracicaba, SP, durante um ano, com duas cultivares de alfafa (Crioula e CUF-101), plantadas em vasos a céu aberto. O peso e o número de brotos basilares foram mensurados. Foram avaliados a dinâmica de sua rebrota após o corte e a estacionalidade de produção, por intermédio de três freqüências de corte, 28, 35 e 42 dias, e três intensidades de desfolha, e os cortes a 7 cm de altura com e sem preservação da área foliar remanescente e corte rente ao solo. Foi usado delineamento inteiramente casualizado em arranjo fatorial 2 x 3 x 3 (cultivar, freqüência de corte e intensidade de desfolha), com três repetições. Para a avaliação da produção estacional, nas três freqüências isoladamente, o delineamento experimental em parcelas subdivididas no tempo foi usado, em que as parcelas foram representadas pelos tratamentos (cultivar vs intensidade de desfolha) e as subparcelas, pelos cortes. A freqüência de corte de 28 dias foi a melhor para ambos as cultivares quanto à produção de matéria seca de brotos/vaso, principalmente no verão. Quanto ao número de brotações, as freqüências de corte de 28 e 35 dias foram superiores à freqüência de corte de 42 dias. A intensidade de desfolha a 7 cm, com preservação da área foliar remanescente, foi superior às demais, quanto ao peso e número de brotos. O período de verão mostrou-se bastante favorável à produção destas cultivares de alfafa. Quanto ao aparecimento das brotações, mais de 2/3 dos brotos surgiram nas duas primeiras semanas após o corte, independente da freqüência do corte e da intensidade de desfolha. Em condições tropicais, existe possibilidade de obtenção de altos níveis de produção em plantas de alfafa, desde que seja adotado intervalo de cortes por volta de 28 dias. Além disso, cortes de aproximadamente 7 cm do solo são favoráveis, por explorarem a capacidade fotossintética da área foliar remanescente e das brotações já presentes no momento do corte.

Determining the probability of detecting cervical spine fractures with computed tomographic scans using the visible human database

Cross-table lateral radiography alone is frequently unreliable for clearing of the cervical spine in cases of acute trauma. Computerized tomography (CT) is a standard procedure for detecting occult cervical spine fractures when cervical spine radiographs are equivocal or inadequate. There is evidence, however, that a significant number of fractures may still be missed by CT scans if too large a distance is used between scanning cuts in the axial plane. The purpose of this study was to determine the probability of detecting hidden fractures of the cervical spine over a wide range of fracture sizes and CT axial cut intervals. Digitized anatomic data of the cervical spine from the Visible Human ProjectTM of the National Library of Medicine were used as a model template for the study. From a series analysis, it was determined that use of the standard 5-mm cut intervals missed 25–75% of fractures, depending on the size of the lesion. The 4-mm cuts were able to detect all of the 3-mm lesions but still missed a significant number of the smaller fractures. The probability of finding occult fractures at the 3-mm axial interval was 100% for all except the smallest fracture sizes. This mathematical analysis suggests that computerized tomography is a less than optimal method for detecting occult fractures of the cervical spine unless the cut interval is 3 mm or less. The addition of sagittal plane reconstruction of these images would further enhance the ability to detect subtle subluxations or fractures.

Growth rates of ‘Grasslands Puna’ chicory (Cichorium intybusL.) at various cutting intervals and heights and rates of nitrogen

Abstract Cutting intervals were 1, 2, 4, and 8 weeks, nitrogen (N) fertiliser levels 0, 50, and 200 kg N/ha, and cutting heights 0 and 10 cm above groundlevel. The experiment went from 26 October to 21 December 1988 with residual effects measured on 7 February 1989. Total dry matter (DM) yields were 2187, 3262,4869, and 6402 kg/ha for cutting intervals of 1, 2, 4, and 8 weeks, and 3029, 3910, and 5684 kg DM/ha for N rates of 0, 50, and 200 kg N ha. N had a greater effect on total yield at 4- and 8-weekly cutting intervals than at shorter intervals. A cutting height of 10 cm gave increased yields at 1-, 2-, and 4-week intervals but less at 8 weeks. Maximum leaf yield was predicted to occur at a cutting interval of 4.9 weeks with yields of 2460, 2667, and 3286 kg DM/ha for 0, 50, and 200 kg N ha. Stem yield was still increasing at 8 weeks. The average N response was 4.1 kg leaf DM/kg N and 6.5 kg stem DM/kg N. Residual regrowth and plant density was decreased on treatments that received 200 kg N/ha on plots...

Título en español

Un experimento en un suelo Ultisol de la región húmeda montañosa de Puerto Rico se realizó para evaluar el potencial de producción de forraje y proteína bruta de cinco selecciones de la leguminosa Stylosanthes guianensis, una de Stylosanthes gracilis y la gramínea Digitaria milanjiana USDA PI 299699. En el primer período experimental, las forrajeras se cortaron nueve y seis veces cada 45 y 65 días, respectivamente. Durante el segundo período, se cortaron 5 y 4 veces cada 65 y 79 días respectivamente. Las parcelas de leguminosas recibieron 112 kg por ha y año de fósforo y potasio en una sola aplicación. Las de la gramínea recibieron 3,360 kg por ha y año de un abono 15-5-10; se aplicó la cantidad indicada después de cada corte, según el intervalo asignado. Las parcelas no se regaron en ninguno de los períodos experimentales. La gramínea D. milanjiana sobrepasó significativamente en producción de forraje verde y seco las seis selecciones de Stylo a los 3 intervalos de 45, 65 y 79 días. La gramínea produjo 29,574 y 29,920 kg/ha en 13.5 meses cuando se cortó cada 45 y 65 días, respectivamente. A intervalos de 79 días, produjo 25,046 kg por ha en un período de 10.5 meses. Las leguminosas más productivas de forraje seco fueron la cultivar Fine Stem (IRFL-1416), S. guianensis USDA PI 361877 y las cultivares comerciales Endeavour y Schofield. La cultivar Fine Stem produjo rendimientos de 18,522 y 18,936 kg/ha en 13.5 meses, que pueden considerarse altos para una leguminosa tropical. Cuatro de las cultivares produjeron casi tanta proteína bruta como la D. milanjiana al cortarse cada 45 días, mientras que a intervalos de corte de 65 y 79 días todos se acercaron a la gramínea en este criterio. En la época lluviosa surgió un brote de antracnosis que redujo el crecimiento de las seis leguminosas, pero en menor grado a las cultivares Endeavour y Fine Stem. Se sugiere cortar la leguminosa cada 65 días. Al cortarse cada 45 días, los yerbajos tienden a invadirla despues del año. A intervalos de 79 días, la leguminosa tiende a producir menos forraje y proteína bruta que cuando se corta cada 65 días. Se presenta el contenido en nitrógeno, fósforo, potasio, calcio y magnesio de las leguminosas y la gramínea para los tres intervalos de corte estudiados. En general, las cultivares arrojaron marcadamente mayores contenidos en nitrógeno, calcio y magnesio que la gramínea D. milanjiana.

Production and Quality of Limpograss for Use in the Subtropics1

Abstract‘Greenalta’, ‘Redalta’, and particularly ‘Bigalta’ limpograsses [Hemarthria altissima (Pior.) Stapf and Hubbard] have been commercially planted in south Florida during the past decade. Since little information is available on agronomic attributes of limpograss during the cool‐season when tropical grass growth is markedly reduced, cool‐season productivity and in vitro organic matter digestibility (IVOMD) were compared with other commercial tropical grasses adapted to south Florida.Effects of nitrogen rates, cutting interval, and fall fertilization dates also were determined for Bigalta to provide information on productivity and IVOMD. The soil used was an Oldsmar fs, a spodosol.The three limpograss cultivars, ‘Transvala’ digitgrass (Digitaria decumbens Stent.), and ‘Coastcross‐1’ bermudagrass (Cynodon sp.) were equally productive during the cool season and more productive than ‘Pangola’ digitgrass (Digitaria decumbens Stent.), Bigalta IVOMD generally was greater than that of Greenalta and particularly Redalta, equal to that of Transvala and Pangola, and higher than that of Coastcross‐1. Dry matter yields of Bigalta, Coastcross‐1‐ and Transvala were similar at 3 or 4‐week cutting intervals (CI), but Bigalta produced less at a 2‐week CI. During a 24‐week period as CI increased from 4 to 12 weeks (total of 336 kg N/ha applied), Bigalta total yields increased, forage IVOMD and N contents decreased, and yield of digestible organic matter increased. Delaying fall fertilization from 17 September or 1 October until 29 October resulted in greatly reduced forage production when harvested on 17 December. The IVOMD and N contents increased as fertilization was delayed. Many of the N contents from the fertilization date and CI studies were below the acceptable level for maximum voluntary intake of forage by ruminants.Productivity of the limpograsses and Bigalta response to N during the cool season indicate that they offer alternatives to other commercially available tropical grasses. The high digestibility of Bigalta can provide reserve coolseason pasture with quality equal to or better than that from other grasses, however, low N contents may limit intake without proper grass management and N fertilization.