Crop water use indicators to quantify the flexible phenology of quinoa (Chenopodium quinoa L.) in response to drought stress

摘要

Models can play an important role in agricultural planning andmanagement. Thermal time accumulationis a common way of describing phenological development in crop models, but the sensitivity of thisconcept to water stress is rarely quantified. The effect of pre-anthesis droughts on the timing of anthesisand physiological maturity was assessed for quinoa (Chenopodium quinoa Willd.) var. ‘Santa Maria’, withthe help of two field experiments (2005–2006 and 2006–2007) in the central Bolivian Altiplano. Varioustreatments with different sowing dates and irrigation applications were considered. To evaluate theeffect of drought stress on crop development, drought stress during the first 60 days after sowing wasassessed with three different stress indicators: the number of days that the soil water content of the rootzone was above a threshold, the average relative transpiration, and the sum of daily actual transpiration,standardized for reference evapotranspiration (P(Ta/ET0)). The best indicator to quantify the effect ofpre-anthesis drought stress on phenological development was P(Ta/ET0) cumulated until 60 days aftersowing. This indicator showed a significant logarithmic relation with the time to anthesis and time tophysiological maturity. Correlations of the drought stress indicator with thermal time accumulation werebetter than with calendar time accumulation. Due to an effect of post-anthesis droughts, the correlationsof the drought stress indicator with the time to anthesis were stronger than with the time to physiologicalmaturity. It was also demonstrated that deficit irrigation can contribute to a better agricultural planningdue to a better control of the phenological development of quinoa. The proposed relations can be used formodeling phenological development of quinoa in drought prone regions and for efficient deficit irrigationplanning.