Are physiological days of potato calculated accurately?

Abstract

Physiological days (P-days) of potato (Solanum tuberosum) are used as an indication of plant maturity and for timing of disease onset. The accuracy of weighting minimum and maximum temperatures to estimate diurnal temperature effect was evaluated and errors in P-day values were compared to a new method. P-days were calculated over three growing seasons using observed hourly temperatures; calculated from observed Tmin and Tmax (a slight modification of the original derivation); and computed from estimated hourly temperatures, using another method that estimated diurnal temperatures based upon a sinewave function for daytime temperatures and an exponential decay for temperature decrement during the night. The original derivation significantly overpredicted the actual P-days in each year, whereas the sine-negative exponential model consistently underpredicted P-days. The latter model was the more accurate, with only one year in three having a difference significantly greater than zero. Average errors were on the order of 1 to 6% of the true P-day value. Improved accuracy of P-day computation by using a novel method was negligible relative to the variation in appearance of spores ofAlternaria solani experienced in nature. However, future users of P-days should exercise due caution since the original method of calculating P-days may be less accurate than their application demands. An alternative is a less simplistic, physiologically-based, mechanistic model of potato growth.

Cotnpendio

Los días fisiologicos (Días-F) de la papa (Solarium tuberosum) son utilizados como una expresion de la maduración de la planta y para estimar la aparición de las enfermedades. La exactitud para medir las temperaturas máxima y mínima con la finalidad de estimar el efecto de la temperatura diurna fue evaluada y los errores en los valores de Dias-F fueron comparados con los obtenidos siguiendo un nuevo método. Los Días-F fueron calculados en tres temporadas de cultivo utilizando las temperaturas observadas hora