Abstract
Data relative to two soybean seasons, several irrigation scheduling treatments, including moderate and severe deficit irrigation, and rain-fed cropping were used to parameterize and assess the performance of models AquaCrop and SIMDualKc, the latter combined with the Stewart’s yield model. SIMDualKc applies the FAO56 dual crop coefficient approach for computing and partitioning evapotranspiration (ET) into actual crop transpiration (Tc act) and soil evaporation (Es), while AquaCrop uses an approach that depends on the canopy cover curve. The calibration-validations of models were performed by comparing observed and predicted soil water content (SWC) and grain yield. SIMDualKc showed good accuracy for SWC estimations, with normalized root mean square error (NRMSE) ≤ 7.6%. AquaCrop was less accurate, with NRMSE ≤ 9.2%. Differences between models regarding the water balance terms were notable, and the ET partition revealed a trend for under-estimation of Tc act by AquaCrop, mainly under severe water stress. Yield predictions with SIMDualKc-Stewart models produced NRMSE < 15% while predictions with AquaCrop resulted in NRMSE ≤ 23% due to under-estimation of Tc act, particularly for water stressed treatments. Results show the appropriateness of SIMDualKc to support irrigation scheduling and assessing impacts on yield when combined with Stewart’s model.
Highlights
Uruguay is characterized by a warm temperate and humid climate, where summer crops are commonly rain-fed
2011–2012, when a severe water deficit was applied from the vegetative growth to grain filling, a sensitive period to water stress; Figure 1c,d refer to FI in 2012–2013, where water stress was avoided; and Figure 1e,f are relative to rain-fed cropping in 2012–2013, where only a limited stress occurred during pod formation
Good predictions were obtained with AquaCrop for vining pea [59], which was cultivated without water stress, confirming that the use of AquaCrop predictions is only recommended when severe water stress is not considered
Summary
Uruguay is characterized by a warm temperate and humid climate, where summer crops are commonly rain-fed. Supplemental irrigation is often required for achieving high yields [1]. Adequate irrigation scheduling has to be considered for soybean production. Predicting soybean yield response to water is required for assessing irrigation management strategies to be adopted by farmers. Crop growth and yield models are often used. The CROPGRO-Soybean model is probably the most used to simulate soybean growth and yield. It is one of the Decision Support System for Agrotechnology Transfer-Cropping System Models (DSSAT-CSM) whose features are discussed in detail by Jones et al [5]. Because DSSAT-CSM are oriented to represent the growth and yield processes considering a variety of constraints and stresses, they are rarely used for assessing water use or for.
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