Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

A mathematical model was developed to foretell yield by mean of regression calculation using as independent variables the final hight of the plant, lenght and weight of panicle, effective bud and percentage of empty grains. The regression model where all variables under study were included was the one with greater adjustement nevertheless, in some cases it can be used only for effective bud and lenght of panicle, with a high probability of finding good predictions. 

For two years, the effect of three periods of cuttings (21, 42 and 63 days) on the production of dry matter and chemical composition of the grasses Brachiaria radicans, Napper; Hemarthria altissima, cv. 299995 (Poir) Stapf et Hubbard; Cynodon plectostachyus (K. Schum) Pilg; Setaria sphacelata (Schumach, Stapf and Hubbard); Cynodon sp.; Digitaria sp.; Panicum maximum Jacq.; Brachiaria ruziziensis, Germain et Everard, was studied. Fertilization was uniform (300-100-100 kg of N, P2O5 and K2O ha/year, respectively). Cuttings were made at 10 cm of height for C. plectostachyus, Cynodon sp. and Digitaria sp. and at 15 cm for the other species. The grasses P. maximum, S. sphacelata and B. ruziziensis produced the higher yields of dry matter (9.41, 8.85 and 8.46 t/ha/year, respectively), but it didn't differ from that of the grasses B. radicans, C. plectostachyus, Cynodon sp. and Digitaria sp. The production of H. altissima (2.73 t/ha/year) was significantly lower (P<.01) than the production of S. sphacelata, P. maximum and B. ruziziensis but it didn't differed from the productions reached by the grasses B. radicans, C. plectostachyus, Cynodon sp. and Digitaria sp. The production of dry matter didn't differ between the periods of cutting of 42 and 63 days; but both of them overcame significantly (P<.01) the period of 21 days. The studied chemical compounds (dry matter, rough protein, phosphorus, calcium and magnesium) showed diferences (P<.01) between species, time and period of cuttings. To conclude, the species S. sphacelata, B. ruziziensis and P. maximum produced the higher yields of dry matter; Cynodon sp., B. radicans and Digitaria sp. produced half yields, while C. plectostachyus and H. altissima produced the lowest yields. Most of the species produced more of the 90% of their yields in dry matter during the raining season. The best period of cutting for the species was 42 years, nevertheless, when the period of cutting was extended from 21 to 42 years, the content of dry matter and calcium had the tendency to increase, while the contents of rough protein, phosphorus and magnesium tended to decrease.   

Dry matter productions from Faragua grass (Hyparrhenia rufa Nees Stapf) alone and in association with leguminous (Centrosema pubescens, Benth) and Tropical Kudzu (Pueraria phaseoloides, Roxb Bet), was sudied at Gualaca Research Station. The sowing of leguminous in parcels of land with previously established Faragua was done by means of gamic seed. Fertilization was uniform. Ninety days after sowing, the first cut was made with subsequent cuts under a 60 days interval system. Cuts hights were 0.15 m above ground level. Significant differences in regards to dry matter production were found (P<.01) between years and fields. During year one, dry matter average production fo the 3 prairies was 28.43 ton/hectare compared 25.49 ton/hectare during year two. On Faragua prairie, the average production over a two year period was 29.40 ton/hectare showing no significant difference over a Faragua + Kudzu prairie (26.47 ton/hectare), but both averages were higher than that of a prairie of Faragua + Centrosema (20.61 ton/hectare). For areas similar to that of this study, Faragua + Kudzu association is recommended not only because of forrage production, but also because of its resistance to insects, disease, and a better growth distribution during the dry season. 

Over a two year period, the effect of fertilization on the growth of native leguminouses under grazing was studied. Treatment were 0, 30, 60 and 90 kg of P2O5/hectare/year in combination with KCL (75 kg of K2O/hectare/year) and without KCL, with and without agricultural lime (2.5 ton/hectare/year). Treatments were applied on previously established Faragua pastures. Leguminous counts were done at 6, 12, 18, 24 and 30 months, taking note on each occasion of the population per square meter per treatment. Significative differences were found (P<.05) between treatments. Using K2O and lime, the average leguminous production of the three phosphatised treatments did not differ from the average of the witness treatment, while in presence of K2O without agricultural lime, without K2O with agricultural lime, and without K2O and agricultural lime, the average of the phosphatised treatments were significantly greater (P<.05) than the average of witnesses treatments. Higher population of leguminouses were obtained by the use of phosphatised treatments + agricultural lime without K2O; while smaller production was show using phosphatised treatments + K2O without agricultural lime, without K2O and agricultural lime. Levels of 60 and 90 kg of P2O5/hectare/year + agricultural lime with no K2O, gave higher leguminous production.   

In the distric of Bugaba, Province of Chiriqui, Republic of Panama, 5% of the total cattle farming activity (27 farms) were sampled under five animals per farm. Most of the soils are sandy loam; predominant grass, Panicum maximun, Jacq and mineral supplementation is scarce. All farms were sampled during 1981, in order to measure the relationship between minerals soil, plant and animal. Samples of soil, grass and blood were collected at the farm, while liver and bone were taken at the slaughterhouse. Levels of P, Ca, Mg, Mn, K, Al, Zn and Cu were determined in soil and grass; Zn and Cu in blood; Zn, Cu and Mn in liver and P in bone. Insufficiency of P in soil and grass, as well as in bone was the most ousttanding. Low levels of Zn and Cu in hematic and hepatic tissues, were also found. 

Four fungicides for the control of pathogenic fungi which infect the seed of rice, were tested. Three groups of seed with low, half and high germination were treated with Arasan (381 g), Dithane M-45 (381 g), Vitavax-300 (150 g) and Sisthane (176 cc) for ecah of the 100 g seed. For the measurements of these products, tests of pathology and germination were conducted, simultaneously at 0, 30, 60, 90 and 120 days after the treatments had been made. With the sistemic fungicides Vitavax-300 and Sisthane there were obtained the higher percentages of germination, increasing it to 26 and 38%, respectively for the group with half germination. The increase in the group with low germination was increased in an 11 and 18% by using the fungicides Dithane M-45 and Arasan, in the group with half germination. In the low one, the increase was of 36 and 18%. On the other hand, the lowest percentages of incidence of pathogenic fungi in seeds were obtained when treated with Arasan and Dithane M-45. None of the fungicides afected the germination 120 days after the treatment. 

The study was carried out at Gualaca Research Station with Zebu cattle grazing on unfertilized Faragua (hyparrhenia rufa) grass, with no mineral salt suplemented. Two mating periods of 3 months each during the year were studied; the first from April 15 to July 15, the second from August 15 to November 15. The same were repeated for 8 and 6 years respectively. Hards were made up of calving and noncalving cows, and heifers ready for service. The cow bult relation was 26:1. Results showed that under the first mating period, there was a greater percentage (57.2%) of pregnant cows than that of the second period (42.9%). 

The productive and reproductive performance of 1/2 and 3/4 Holstein x Zebu in first and fourth suckling period were studied. Cows were placed under equal management with a daily milk production of 6.0 liter, 254 days of lactation. There were 15.10 months between calving. The productive performance of cows 1/2 Holstein x Zebu was greater than that of 3/4 Holstein x Zebu cows. 

En una investigación previa efectuada por los autores se estudió, en forma paramétrica, la respuesta sísmica de edificios irregulares en elevación con comportamiento elástico. El fin de generalizar el método de análisis ahí propuesto, en este trabajo se estudia la influencia del comportamiento elastoplástico definido en términos de los espectros de diseño reducidos por ductilidad.Se muestra que el procedimiento conduce a mejores resultados que los del método estático establecido en el Reglamento de Construcciónes para el Distrito Federal, tomando como base de comparación de los resultado del método dinámico del mismo Reglamento.El método ha sido denominado causidinámico y se puede emplear para analizar edificios regulares e irregulares en elevación; es de aplicación sencilla y útil para ingenieros de la práctica profesional que se dedican al diseño sísmico de edificios.  

Se presenta un procedimiento basado en el método de los elementos finitos, para analizar muros de mampostería confinados por marcos de concreto, sujetos a cargas elásticas en su plano. Se considera la posible aparición de grietas en la zona de contacto entre muro y marco y a lo largo de la diagonal del muro.El procedimiento se emplea para estudiar varios muros confinados de un piso ante cargas laterales, haciendo variar la características geométricas del muro y del marco confinante. Con base a los resultados, se proponen métodos sencillos para evaluar la rigidez lateral de un conjunto marco-muro, y los esfuerzos que generan el muro y las columnas del marco, para diferentes estados de agrietamiento.