Techniques for using sprouts for potato production in the tropics
A series of experiments were conducted in Vietnam to develop a system whereby detached sprouts from physiologically old green sprouted seed tubers could be used to grow potatoes. Three node segments from the mid or basal portion of the detached sprout produced the greatest percentage of shoots and roots. Growth was best in a medium of equal parts of sub-soil, pig manure and brick kiln ash. Sprout cuttings produced plantlets ready for transplanting in 14–20 days with mean daily temperatures of 22 to 24°C. When transplanted in mid-November, yields from sprout cuttings in field experiments were 10 to 18 t/ha which were 33% lower than from healthy seed tubers but more than the national average yield using degenerated seed tubers. Tubers produced by plants grown from sprout stored well and gave good yields when replanted the following year.
Varying Nitrogen Concentrations to Optimize Basic Seed Potato Minitubers Production in a Three-Phase Hydroponic System
In hydroponics, nutrient management is the limiting factor to obtaining optimal production, and nitrogen (N) is the key component to consider when optimizing nutrient management in these types of systems. The objective of this study is to evaluate different combinations of N fertilizer concentrations in order to optimize the yield of basic seed potato minitubers in a three-phase hydroponic system. Treatments consisted of five combinations of N concentrations, applied before and after 21 days after plant transplant as follows, respectively: 1) 13 and 13, 2) 13 and 0, 3) 13 and 7.8, 4) 13 and 16, and 5) 13 and 26 mmol L−1. Propagation was performed by transplanting 3–4 cm potato plantlets cv. Agata from sprouts. There were significant effects of N treatments on all measured variables (root, leaf, stem, and plant dry weight and minituber number and weight). To obtain the maximum minituber number yield, 9.51 minitubers/plant, corresponding to 67 minitubers/m2, post 21-day adjusted N concentration was 18.4 mmol/L. Treatment 4 promoted higher basic seed potato minituber yield in a three-phase hydroponic system.ResumenEn hidroponía, el manejo de los nutrientes es el factor limitante para la obtención de producción óptima, y el nitrógeno (N) es el componente clave a considerar cuando se optimiza el manejo de nutrientes en estos tipos de sistemas. El objetivo de este estudio fue evaluar las diferentes combinaciones de concentraciones de fertilizante nitrogenado a fin de optimizar el rendimiento de minitubérculos de semilla básica de papa en un sistema hidropónico trifásico. Los tratamientos consistieron de cinco combinaciones de concentraciones de N, aplicados antes y después de 21 días del trasplante, de la siguiente manera, respectivamente: 1) 13 y 13, 2) 13 y 0, 3) 13 y 7.8, 4) 13 y 16, y 5) 13 y 26 mmol L-1. Se efectuó la propagación mediante el trasplante de plántulas de papa de 3–4 cm cv. Agata de brotes. Hubo efectos significativos de los tratamientos de N en todas las variables medidas (peso seco de raíz, hoja, tallo y planta, y número y peso de minitubérculos). Para obtener el número máximo de minitubérculos de rendimiento, 9.51 minis/planta, correspondiendo a 67 minis/m2, la concentración ajustada de N posterior a los 21 días fue de18.4 mmol/l. El tratamiento 4 promovió el más alto rendimiento de minitubérculos de semilla básica de papa en un sistema hidropónico trifásico.ResumoNa hidroponia, o gerenciamento de nutrientes é o fator limitante para a obtenção de produção ótima sendo o nitrogênio (N) o componente chave a ser considerado ao otimizar o gerenciamento de nutrientes nesses sistemas. Assim, o objetivo desse trabalho foi avaliar diferentes combinações de concentrações de nitrogênio para a otimização da produtividade de tubérculos de batata-semente básica em sistema hidropônico de três fases. Os tratamentos consistiram de cinco combinações de concentrações de N até 21 dias após o transplante (DAT) e após 21 DAT (13 e 13 - controle; 13 e 0; 13 e 7,8; 13 e 16; 13 e 26 mmol L−1). O material de propagação utilizado foi broto da cultivar Ágata, com 3 a 4 cm de comprimento, em média. Houve efeito significativo dos tratamentos com N sobre todas as variáveis avaliadas (matérias de raiz, folha, caule e planta secas e número e massa de minituberculos). Para obter o número máximo de minitubérculos na colheita, 9,51 minitubérculos/planta, correspondendo a 67 minitubérculos/m2, a concentração de N ajustada foi de 18,4 mmol/L. O tratamento 4 propiciou a mais alta colheita de minituberculos da classe básica de batata-semente em um sistema hidropônico trifásico.
Modelling of Mooney viscosity relaxation in natural rubber
Abstract Better assessment of natural rubber (NR) quality and processability, through the identification of new attributes, is still a major challenge. With this scope, 12 model samples of natural polyisoprene and two of synthetic polyisoprene were characterized in terms of Mooney torque relaxation, using the standardized ISO289 method (ML(1+4)100, explained later in the Section 1 ). The main purpose of this study was to identify a model that gave a better fit for the experimental decay of Mooney torque over time (ML(t)=f(t)) than the usual power law model used before (Y=at−b, [G.M. Bristow, A.G. Sears, The use of novel parameters in the assessment of natural rubber processability, NR Technol. 18 (1987); H.G. Burhin, W. Spreutels, J.M. Campbell, MV2000 Mooney viscometer: Mooney relaxation measurements on raw polymers and compounded rubber stocks, Kautsch. Gummi Kunstst. 43 (1990) 431]). The results showed that a generalized Maxwell model, and the Wu–Abbott empirical model ( Y = 1 − a Ln ( t ) − ( b t / ( c + t ) ) ) [T. Wu, J.A. Abbott, Firmness and force relaxation characteristics of tomatoes stored intact or as slices, Postharvest Biol. Technol. 24 (2002) 59–68], recently used for describing stress relaxation of tomato flesh, allowed a better description of the relaxation curve for the samples studied than the power law or stretched exponential traditionally used. Moreover, the total relaxation time (τm) given by the generalized Maxwell model showed good correlation with the total gel content of the samples studied.