The combined effects of cover design parameters on tomato production of a passive greenhouse

The objective of this paper is to demonstrate the need of a multiple design parameter approach to greenhouse design. To illustrate this need, we determined the combined effects of cover design parameters on tomato production of a passive greenhouse, that is a greenhouse with only natural ventilation and seasonal whitewash for climate management. The design parameters investigated in this research were the transmission of the cover for photosynthetically active radiation (PAR) and near infrared (NIR) radiation, the emission coefficient for long wave radiation of the cover and the ventilation area. First, we developed a model to link the tomato yield to the cover design parameters, through their effects on greenhouse climate. The model was validated by comparing the simulated greenhouse climate and yield with data obtained from field studies conducted in Almería, Spain. Thereafter, the sensitivity of the yield to the cover design parameters was analysed for three greenhouse configurations. This analysis gave insight into the effects of the cover design parameters on crop yield. Results showed that the sensitivity of the yield to a single design parameter depended on the absolute values of the other ones. For example, the yield in a greenhouse with a high ventilation capacity was the most sensitive to PAR transmission (0.45 % more yield for each 1% increase of PAR transmission) while in a greenhouse with a low ventilation capacity the crop yield is most sensitive to the ventilation area (0.63 %) and NIR transmission (-0.56 %). In addition, the yield sensitivity to the design parameters also varied over time because of changing outdoor climate conditions. In conclusion, a significant improvement of greenhouse design can be attained only through a multifactorial approach that accounts for the joint effect of design parameters, local climate and desired production period upon crop yield

Determining Optimal Levels of Nitrogen Fertilizer Using Random Parameter Models

The parameters of yield response functions can vary by year. Past studies usually assume yield functions are nstochastic ‘‘limited’’ stochastic. In this study, we estimate rye– ryegrass yield functions in which all parameters are random. The three functional forms considered are the linear response plateau, the quadratic, and the Spillman-Mitscherlich. Nonstochastic yield models are rejected in favor of stochastic parameter models. Quadratic functional forms fit the data poorly. Optimal nitrogen application recommendations are calculated for the linear response plateau and Spillman-Mitscherlich. The stochastic models lead to smaller recommended levels of nitrogen, but the economic benefits of using fully stochastic crop yield functions are small because expected profit functions are relatively flat for the stochastic yield functions. Stochastic crop yield functions provide a way of incorporating production, uncertainty into input decisions.cereal rye–ryegrass, Monte Carlo, nitrogen, random parameters, stochastic plateau, Production Economics, Q10, C12, D24,

Sensitivity analysis of the add-on price estimate for the edge-defined film-fed growth process

The analysis is in terms of cost parameters and production parameters. The cost parameters include equipment, space, direct labor, materials, and utilities. The production parameters include growth rate, process yield, and duty cycle. A computer program was developed specifically to do the sensitivity analysis

Phenomenological description of the states 0+0^+ and 2+2^+ in some even-even nuclei

A sixth-order quadrupole boson Hamiltonian is used to describe the states $0^+$ and $2^+$ identified in several nuclei by various types of experiments. Two alternative descriptions of energy levels are proposed. One corresponds to a semi-classical approach of the model Hamiltonian while the other one provides the exact eigenvalues. Both procedures yield close formulas for energies. The first procedure involves four parameters, while the second involves a compact formula with five parameters. In each case the parameters are fixed by a least-square fit procedure. Applications are performed for eight even-even nuclei. Both methods yield results which are in a surprisingly good agreement with the experimental data. We give also our predicted reduced transition probabilities within the two approaches, although the corresponding experimental data are not yet available.Comment: 27pages, 18 figure

Influence of ethephon stimulation on latex physiological parameters and consequences on latex diagnosis implementation in rubber agro-industry

Latex Diagnosis (LD) is currently considered by Cirad and most of its rubber agro-industry partners as a routine physiological tool to optimise, at block level, the rubber yield production of the rubber plantations. Without using LD, a general stimulation recommendation per clone and per tapping year is generally applied at plantation scale, as a function of tapping cut position and direction, whatever the local and actual yield potential is. Even though this general recommendation is based on clonal physiological latex characteristics, such a global approach does not permit to consider the local specificities of the yield potential, as it avoids considering factors like soil heterogeneity, microclimate variations in larger estates and differential expression of diseases (leaf diseases, root diseases...). In this case, plantations are almost "blind" regarding suitability of the applied stimulation intensities, and uniform application of the same rate of stimulant in all homogenous cultural units may sometimes lead to optimised exploitation but may also lead locally to under exploitation in higher yield potential areas or to over exploitation in lower yield potential areas. Using LD permits to optimize the stimulation at local level (decrease of stimulation when an over exploitation is detected, increase of stimulation intensity when an under exploitation is detected) and therefore permits the yield optimisation block per block, taking into account the plantations heterogeneities and therefore the actual local yield potential. Of course, LD interpretation depends on former set up LD parameters reference values. These ones are clonal and established for the 4 parameters used in LD: latex sucrose content, latex inorganic phosphorus content, latex reduced thiols content and DRC/TSC. These LD reference values are established for 5 limit levels (very low, low, normal, high and very high), for each LD parameter (Suc, Pi, RSH and DRC/TSC), either at regional scale or, in case of large estates and companies, at plantation scale when local LD parameters database is large enough. To set up correctly these LD reference values, it is required to know what can be the general evolution of the 4 LD parameters depending on exploitation intensity. These evolutions are detailed in the document. (Résumé d'auteur

Genotype and environment interaction on yield and quality parameters of organically grown winter wheat – Triticum aestivum L. genotypes

The interaction of genotype and environment upon yield and quality parameters of eight winter wheat (Triticum aestivum L.) genotypes was studied under organic conditions in Austria over two growing periods, 2001/2002 and 2002/2003, respectively. Two sites that have significantly different climatic conditions, Innviertel and Marchfeld, were chosen for the field experiment. Study site weather and soil conditions are important yield-affecting factors. Although the yield of Marchfeld-grown genotypes were lower, they had shown higher quality parameter values. Soil moisture conditions increase the grain yield but decrease its quality. To obtain seed with higher quality, a production site with favourable climate conditions should be chosen

The nonlinear viscoelastic behavior of polypropylene

A series of tensile relaxation tests is performed on isotactic polypropylene in the sub-yield and post-yield regions at room temperature. Constitutive equations are derived for the time-dependent response of a semicrystalline polymer at isothermal loading with small strains. Adjustable parameters in the stress-strain relations are found by fitting experimental data. It is demonstrated that the growth of the longitudinal strain results in an increase in the relaxation rate in a small interval of strains in the sub-yield domain. When the strain exceeds some critical value which is substantially less than the apparent yield strain, the relaxation process becomes strain-independent.Comment: 20 pages, 6 figure