Seasonal and Rotational Influences on Corn Nitrogen Requirements

This project was designed to study the N fertilization needs in continuous corn (CC) and corn rotated with soybean (SC) as influenced by location and climate. Multiple rates of fertilizer N were spring applied, with the intent to measure yield response to N within each rotation on a yearly basis for multiple years at multiple sites across Iowa. This will allow the determination of N requirements for each rotation, differences that exist between the two rotations, responses to applied N across different soils and climatic conditions, and evaluation of tools used to adjust N application.

Actividad insecticida de Ricinus Communis L. sobre Plodia Interpunctella Hbn. (Lepidoptera: Phycitinae).

La aplicación de insecticidas sintéticos como principal sistema de control de plagas de granos y productos almacenados ha originado el desarrollo de poblaciones de insectos resistentes a dichos químicos, la contaminación del medio ambiente y la acumulación de sustancias tóxicas en los alimentos. En este trabajo se evaluaron los efectos de la aplicación de molido de hojas de ricino sobre larvas de la «polilla de las harinas» (Lepidoptera: Phycitinae). Los molidos vegetales se obtuvieron a partir de hojas de Ricinus communis L. secadas en estufa a 40 ± 2 °C durante 48 horas y posteriormente molidas hasta lograr un polvo de textura similar a la harina de maíz, material con el que se mezcló a fin de lograr concentraciones de 5, 10 y 15 % y un testigo sin ricino. Las unidades experimentales consistieron en cajas de Petri con seis larvas de primer y segundo estadio y se efectuaron cinco repeticiones por tratamiento (n=120). Se registró el número de larvas, pupas y adultos vivos, cada cuatro días, hasta que las larvas sobrevivientes llegaron al estado adulto. Se calcularon los porcentajes de eficacia mediante la fórmula de Abbott. Los resultados se evaluaron por ANVA y test de Tukey. Se determinaron el tiempo efectivo medio (TE50) y concentración efectiva media (CE50) por el método Probit. Los resultados de mortalidad indicaron que la concentración al 15 % superó significativamente al resto de los tratamientos y al testigo.

Evaluation of the attack rates and level of damages by the fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), affecting corn-crops in the northeast of Argentina

The fall armyworm (FAW) is the most important threat to corn crops in Argentina, and there exists very little up-to-date information on its actual pest status because the available literature was published more than 20 years ago. Therefore, field surveys were carried out in the northeast of Argentina, in order to establish the attack rates and injury levels of the pest in relation to the crop phenology. The study was carried out at two localities: Colonia Benítez, an agricultural region, and Tapenagá, a cattle-raising area. At each site two 1-ha plots were sown either with a Bt-corn expressing Cry 1F protein or with an untransformed corn germplasm. Optimal and late sowing was assayed and FAW larval abundance, relative age composition, attack rates and level of damage to corn were recorded. At the moment of the field experiments, Bt-corn was not affected by FAW larvae. However, untransformed germplasms were severely affected by FAW larvae, with an average of attacked plants of 18% or more. In contrast to data obtained 30 years ago, higher values of FAW density were registered. Levels of damage to corn plants were higher after the V4 stage. It was found that the sowing date affected the infestation levels and early seeding avoided high armyworm densities that develop later in the season; in northern Argentina, this was only relevant in agricultural areas.

Nutritive value of palm kernel meal in diets for growing rabbits

The aim of this work was to determine the nutritive value of palm kernel meal (PKM) in diets for growing rabbits. In Experiment 1, 20 New Zealand × Californian growing rabbits 50 d-old were used to determine energy, crude protein, fibre and fat digestibility of PKM. The nutritive value was estimated by the difference method using a basal diet and another diet made by substituting 200 g/kg of basal diet with PKM. Energy, crude protein, ether extract and neutral detergent fibre of PKM digestibilities were, respectively, 0.549 (±0.056, SE), 0.541 (±0.069), 0.850 (±0.048) and 0.430 (±0.101), and the digestible energy concentration was 10.9 MJ/kg (±1.03) DM. In Experiment 2, 412 rabbits were allocated at random to the two experimental diets to measure growing performance. Inclusion of 200 g PKM/kg in the diet did not affect feed or digestible energy intake but decreased slightly (by around 5%) average daily gain (P = 0.003) and feed efficiency (P < 0.001). Neither mortality nor Clostridium perfringens counts in soft faeces were affected by type of diet. Palm kernel meal can be considered a palatable source of fibre, protein and fat for rabbits and can substitute significant amounts of other fibrous ingredients in the diet without adverse effects on growth performance.

Determination of the mechanical properties of corn grains and olive fruits required in DEM simulations

Discrete element method (DEM) is a numerical technique widely used for simulating the mechanical behavior of granular materials involved in many food and agricultural industry processes. Additionally, this technique is also a powerful tool to understand many complex phenomena related to the mechanics of granular materials. However, to make use of the potential of this technique it is necessary to develop DEM models capable of representing accurately the reality. For that, among some other questions, it is essential that the values of the microscopic material properties used to define the numerical model are accurately determined.

Effect of wheat inclusion and xylanase supplementation of the diet on intestinal enzyme activity, nutrient retention and performance in laying hen from 25 to 47 wks of age

A trial was conducted to examine the effects of increasing levels of wheat in the diet and xylanase (ES) supplementation on nitrogen and ether extract retention, pH of the GIT, productive performance from 25 to 47 wks of age, and enzyme activity at the small intestine level. The basal diets (from 25 to 33 wks and from 33 to 47 wks) consisted of soybean meal and corn, and the wheat was introduced in the experimental diets at expenses of corn, primarily.