Predicting plant available water holding capacity of soils from crop yield
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Predicting plant available water holding capacity of soils from crop yield Di He
&
Yvette Oliver & Enli Wang
Received: 12 March 2020 / Accepted: 27 October 2020 # Springer Nature Switzerland AG 2020
Abstract Aims Quantification of variations in plant available water holding capacity (PAWC) of soils helps to improve yield forecast and inform spatially variable management practices in dryland agriculture systems. We developed and tested a general inverse approach to estimate PAWC from crop yield. Methods The APSIM model was used to simulate wheat yield on synthetic soils with contrasting PAWC and climates. The simulated results were used to develop an empirical model to relate simulated yield to PAWC. The empirical model was inversely used to predict PAWC from observed crop yield. Potential prediction ability was quantified using independently simulated wheat yield on actual soils. The actual ability was assessed with measured wheat yields and PAWC. Results The approach had higher accuracy for sites with high rainfall or dominant summer rainfall. It could potentially provide acceptable PAWC predictions across contrasting climate regions (prediction error < 37 mm, 33.5%). The prediction error using crop yield against measured PAWC was 80% of the wheat yield variations caused by climate, soil and management conditions. For three paddocks in Western Australia, APSIM simulated wheat yield with R2 = 0.86 and RMSE = 0.3 ~ 1 t ha−1 (He and Wang 2019). For all the simulations in the assessment of potential prediction ability, we assumed that no other stresses occurred apart from water stress under rainfed condition. We set nitrogen content in the top 60 cm soil layer to 100 kg N ha−1 during the entire growing season to eliminate any nitrogen stress. Wheat cultivar Scout, a planting density of 120 plant m−2 and representative sowing date or rules at each site were used to conduct continuous simulations from 1889 to 2017, with details of simulation setup in He and Wang (2019). Crop residue was retained and incorporated into the surface soil layer shortly before sowing. The results from the first
Plant Soil
Fig. 2 Hydraulic parameters for the six soil-class-based profiles (a-f, deepest 200 cm) and the five soils from the APsoil database (g-k). LL15, DUL and SAT are the water contents at 15 bar
suction, drained upper limit and saturation, respectively. CLL is the water content at lower limit of wheat
Plant Soil Table 1 Soil PAWCs measured at various locations and crop sequences from three paddocks in Western Australia Paddock
PAWC (mm)
Crop sequence
Field A
131, 128, 96, 88, 87, 75, 67, 65, 54, 52
1997–2005: lupin-canola-wheat-lupin-wheat-wheat-wheat-canola-wheat
Field B
111, 105, 88, 64, 61, 60, 43
1997–2005: wheat-lupin-wheat-canola-wheat-wheat-lupin-wheat-wheat
Field C
162, 110, 100, 57, 40
1998–2002: wheat-lupin-wheat-lupin-wheat
nine years were discarded due to the uncertain initial soil water conditions. For assessment of actual prediction ability in Western Australia, APSIM was run w
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