The numbers of sample design for evaluation of the soil fertility

The determination of the amount of sample units that will compose the sample express the optimization of the workforce, and reduce errors inherent in the report of recommendation and evaluation of soil fertility. This study aimed to determine in three systems use and soil management, the numbers of units samples design, needed to form the composed sample, for evaluation of soil fertility. It was concluded that the number of sample units needed to compose the composed sample to determination the attributes of organic matter, pH, P, K, Ca, Mg, Al and H+Al and base saturation of soil vary by use and soil management and error acceptable to the mean estimate. For the same depth of collected, increasing the number of sample units, reduced the percentage error in estimating the average, allowing the recommendation of 14, 14 and 11 sample in management with native vegetation, pasture cultivation and corn, respectively, for a error 20% on the mean estimate.

Income composition, endogenous fertility and schooling investments in children

This paper studies how the eomposition of ineome between mothers and fathers affeets fertility and sehooling investments in ehildren, using data from the 1976 and 1996 PNAD, a Brazilian household survey. Ineome composition affeets the time eost of fertility because mothers and fathers alloeate different amounts of time to child-rearing. These effects are in turn transmitted to investments in ehildren through a tradeoffbetween quantity and quality of ehildren. The main contribution of this paper is twofold. First, it derives new implications about the relationship between household ineome composition and schooling investments in ehildren. Seeond, this paper devises and implements an empirieal approaeh to assess these implieations, using two eross-seetions of fertility and schooling data from Brazil. The main empirical findings of the paper ean be summarized as follows. First, the empirical analysis shows that a larger negative effect of the mother's labor in come on fertility in 1996 is associated with a larger positive effect on the adult child's schooling, refleeting the interaction between quantity and quality of children. Second, the larger negative effect of the mother's labor income on fertility in 1996 is associated with a reduction in the effect of other determinants of number of children. This suggests that an increase in the relative importanee of time costs of fertility may be an important determinant of variations in fertility over time in Brazil and other developing countries .

A competitive growth model with endogenous fertility

This paper investigates the interaction between endogenous fertility behavior and the distribution of income and wealth arnong farnilies in a competitive market economy. We construct a growth model in which altruistic dynasties are heterogeneous in their initial stocks of physical capital. Dynasties make choices of farnily size along with decisions about consumption and intergenerational transfers. We show that if the rate of time preference is increasing in the number of children and preferences over nurnber of children satisfy a norrnality assumption, all steady states are characterized by equality of capital stocks and consumption arnong families. We also provide sufficient conditions for uniqueness of the steady state. In order to illustrate these results, we present an example in which preferences over number of children are logarithrnic and the technology is Cobb-Douglas. For this combination of preferences and technology, there exists a unique egalitarian steady state. Moreover, the economy converges to this steady state in only one generation .

Life expectancy, educational attainment, and fertility choice

This paper explores the role of mortality as a determinant of educational attainment and fertility, both during the demographic transition and after its completion. Two main points distinguish our analysis from the previous ones. Together with the investments of parents in the human capital of children, traditional in the fertility literature, we introduce investments of adult individuals (parents) in their own education, which ultimately determines productivity in both the goods and household sectors. Second, we let adult longevity affect the way parents value each individual child. Increases in adult longevity or reductions in child mortality eventually raise the investments in adult education. Together with the higher utility derived from each child, this tilts the quality-quantity trade off towards less and better educated children, and increases the growth rate of the economy. This setup can explain both the demographic transition and the recent behavior of fertility in “post-transition” countries. Evidence from historical experiences of demographic transition, and from the recent behavior of fertility, education, and growth generally supports the predictions of the model.

Fertility and the value of Life

The value of life methodology has been recently applied to a wide range of contexts as a means to evaluate welfare gains attributable to mortality reductions and health improvements. Yet, it suffers from an important methodological drawback: it does not incorporate into the analysis child mortality, individuals’ decisions regarding fertility, and their altruism towards offspring. Two interrelated dimensions of fertility choice are potentially essential in evaluating life expectancy and health related gains. First, child mortality rates can be very important in determining welfare in a context where individuals choose the number of children they have. Second, if altruism motivates fertility, life expectancy gains at any point in life have a twofold effect: they directly increase utility via increased survival probabilities, and they increase utility via increased welfare of the offspring. We develop a manageable way to deal with value of life valuations when fertility choices are endogenous and individuals are altruistic towards their offspring. We use the methodology developed in the paper to value the reductions in mortality rates experienced by the US between 1965 and 1995. The calculations show that, with a very conservative set of parameters, altruism and fertility can easily double the value of mortality reductions for a young adult, when compared to results obtained using the traditional value of life methodology.

Wealth composition, endogenous fertility and the dynamics of income inequality

This paper analyzes how differences in the composition of wealth between human and physical capital among families affect fertility choices. These in tum influence the dynamics of wealth and income inequality across generations through a tradeoffbetween quantity and quality of children. Wealth composition affects fertility because physical capital has only a wealth effect on number of children, whereas human capital increases the time cost of child-rearing in addition to the wealth effect. I construct a model combining endogenous fertility with borrowing constraints in human capital investments, in which weaIth composition is determined endogenously. The model is calibrated to the PNAD, a Brazilian household survey, and the main findings of the paper can be summarized as follows. First, the model implies that the crosssection relationship between fertility and wealth typically displays a U-shaped pattem, reflecting differences in wealth composition between poor and rich families. Also, the quantity-quality tradeoff implies a concave cross-section relationship between investments per child and wealth. Second, as the economy develops and families overcome their bOlTowing constraints, the negative effect of weaIth on fertility becomes smaller, and persistence of inequality declines accordingly. The empirical evidence presented in this paper is consistent with both implications .

Artificial fertilization of oocytes and sperm activation in pacu: effects of the spermatozoa:oocyte ratio, water volume, and in natura semen preservation

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Organic matter fractions and soil fertility under the influence of liming, vermicompost and cattle manure

Os efeitos do vermicomposto de esterco de curral associado à calagem em atributos da fertilidade do solo foram avaliados através de experimento em vasos empregando um Latossolo Vermelho, distrófico, textura média. Cinco doses do vermicomposto (equivalentes a 0; 28; 42; 56 e 70 t ha-1, peso seco) e cinco doses de calcário (visando elevar a saturação por bases a: 20; 30; 40; 50 e 60%) foram combinadas em esquema fatorial, sendo as amostras de solo incubadas por 180 dias. Para comparação entre o vermicomposto e o esterco de curral, amostras do mesmo solo receberam o equivalente a 70 t ha-1 do esterco de curral que originou o vermicomposto e as cinco doses de calcário listadas anteriormente. Através do cálculo do Índice de Eficiência Agronômica, foi verificado que o potencial de fornecimento de K e de Mg pelo esterco é maior do que o do vermicomposto, e que o de P, é semelhante. O vermicomposto aumentou os teores de Ca2+ e de matéria orgânica (MO), os valores de pH em CaCl2 e a CTC a pH 7. Com o aumento das doses de vermicomposto houve diminuição do C-ácidos húmicos e aumento do C-humina e com a calagem o C-total não aumentou mas houve diminuição do C-ácidos húmicos.

Effect of crude protein levels and organic selenium supplementation in the diets fed during the breeding season on reproductive parameters of red-winged tinamous (Rhynchotus rufescens)

There is little information on the nutrition of red-winged tinamous (Rhynchotus rufescens) reared in captivity, and their nutritional requirements still need to be determined. This study aimed at determining dietary crude protein requirements and testing four organic selenium supplementation levels in the diet of red-winged tinamous during the breeding season. Birds were housed in a conventional broiler house divided in 16 boxes with one male and three females each. Iso-energy (2800kcal ME/kg) pelleted feeds, based on corn and soybean meal, were supplied in tube feeders. In the first experiment, treatments consisted of four different diets containing different crude protein (CP) contents (15, 18, 21, or 24%) and in the second experiment, the four diets contained equal protein level (22.5%) and four different organic selenium levels (0, 0.2, 0.4, or 0.8ppm). Data were analyzed by the least square method. The best egg weight and eggshell thickness were obtained with 22.5% dietary CP. Organic selenium did not influence the studied reproductive traits of red-winged tinamous (Rhynchotus rufescens) males or females.

Fertility life table of Trichogramma pretiosum and Trichogramma acacioi (Hymenoptera : Trichogrammatidae) on Sitotroga cerealella (Lepidoptera : Gelechiidae) eggs at different constant temperatures

Fertility life tables were developed for both Trichogramma pretiosum and Trichogramma acacioi reared on Sitotroga cerealella eggs as an alternative host at five different temperatures. The egg parasitoids were first collected from Nipteria panacea eggs, a lepidopterous pest of avocado. Egg parasitoid females were individualized in small glass vials along with 40 eggs of the host during 24 h for parasitization. For evaluation of the parasitism capacity, a similar procedure was adopted, but cardboards with eggs were replaced every day. The net reproductive rate (Ro), intrinsic rate of increase (rm), finite rate of increase (lambda), and mean generation time (T) were estimated. Temperature affected all parameters for both Trichogramma species. The highest fecundity for both species was observed at 25degreesC. Extreme temperatures such as 15degreesC or 35degreesC negatively affect the development rate of both species.

Biology and fertility life table of the South American fruit fly Anastrepha fraterculus on grape

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Induction of the acrosome reaction test to in vitro estimate embryo production in Nelore cattle

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Uso do diluente água de coco em pó (ACP-103®) na conservação prolongada do sêmen do varrão: avaliação in vitro e in vivo

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)