Simulating Yield Response of Quinoa to Water Availability with AquaCrop

Abstract

Th e modeling of yield response to water is expected to play an increasingly important role in the optimization of crop water productivity (WP) in agriculture. During 3 yr (2004)(2005)(2006)(2007), fi eld experiments were conducted to assess the crop response to water stress of quinoa (Chenopodium quinoa Willd.) in the Bolivian Altiplano (4000 masl) under diff erent watering conditions (from rain fed, RF, to full irrigation, FI). Crop physiological measurements and comparisons between simulated and observed soil water content (SWC), canopy cover (CC), biomass production, and fi nal seed yield of a selected number of fi elds were used to calibrate the AquaCrop model. Subsequently, the model was validated for diff erent locations and varieties using data from other experimental fi elds and from farmers' fi elds. Additionally, a sensitivity analysis was performed for key input variables of the parameterized model. AquaCrop simulated well the decrease of the harvest index (HI) of quinoa in response to drought during early grain fi lling as observed in the fi eld. Further-on, the procedure for triggering early canopy senescence was deactivated in the model as observed in the fi eld. Biomass WP (g m −2 ) decreased by 9% under fully irrigated conditions compared with RF and defi cit irrigation (DI) conditions, most probably due to severe nutrient depletion. Satisfactory results were obtained for the simulation of total biomass and seed yield [validation regression R 2 = 0.87 and 0.83, and Nash-Sutcliff effi ciency (EF) = 0.82 and 0.79, respectively]. Sensitivity analysis demonstrated the robustness of the AquaCrop model for simulation of quinoa growth and production, although further improvements of the model for soil nutrient depletion, pests, diseases, and frost are also possible. available water in the soil between fi eld capacity and permanent wilting point; WP, water productivity; WP*, water productivity, normalized for ET o ; Y, total seed yield; Z x , maximum rooting depth.

Economic assessment at farm level of the implementation of deficit irrigation for quinoa production in the Southern Bolivian Altiplano

“…The variation in maximum and minimum air temperatures is between 31.5 to 22.7°C and -1.7 to -8.3°C, respectively (Geerts et al, 2009b), with high risk of frost (between 174 and 220 d yr -1 ) (IBTA, 1994;Aroni et al, 2009). Soils in the region are poor and are composed mostly of volcanic ashes and lava.…”

“…With the purpose of capturing broader climate variability than previous studies (Geerts et al, 2009b) and also considering the low soil fertility in the region, quinoa yield simulation carried out in this study takes into account a longer historical climatic data, seasonal rainfall was classified in four instead of three different climate scenarios, and soil fertility levels in the model were assumed.…”

“…Quinoa yield was simulated with the AquaCrop model Steduto et al, 2009;Raes et al, 2012) as calibrated for quinoa by Geerts et al (2009b). Simulations were run using 27 years (1983 to 2010) climatic data from Rio Mulatos (19°41' S, 66°46' W, 3,815 m asl), which is an agro-climatic station representative for the quinoa production area in the Southern Bolivian Altiplano (Geerts et al, 2006).…”

“…In addition to the values used by Geerts et al (2009b) for soil water content 2 , biomass production of 50% that corresponds to 50% of the soil fertility stress was calculated through the calibration process in the crop mode of the AquaCrop model version 4.0.…”

“…For this, we used the AquaCrop model , previously calibrated for quinoa by Geerts et al (2009b), for simulating quinoa production under rainfed condition and different irrigation strategies. From the simulation results water production functions were derived for different climate conditions.…”