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DIVISION S-2-SOIL CHEMISTRY

Modeling nutrient uptake using a moving boundary approach

Comparison with the barber-cushman model

^a Dep. de Química-Física, Facultad de Ciencias Físico-Químico y Naturales, Río Cuarto, Argentina
^b Dep. de Ecología Agraria, Facultad de Agronomía y Veterinaria, Univ. Nacional de Río Cuarto-Ruta 8- Km 601, (5800) Río Cuarto, Argentina
^c Facultad de Ciencias Agrarias, Univ. Nacional de Cuyo, Almirante Brown 500, (5505) Chacras de Coria, Mendoza, Argentina
^d Dep. de Matemática-Conicet, Facultad de Ciencias Empresariales, Univ. Austral, Paraguay 1950, (2000) Rosario, Argentina

jreginato{at}exa.unrc.edu.ar

Single nutrient uptake by a growing root system is often estimated by the Barber-Cushman model. The model solves the coupled equations of transport in the soil and absorption of nutrient by roots in fixed domains. This study was conducted to determine whether a moving boundary model that accounts for increasing root competition could improve predictions of nutrient uptake. Our model includes assumptions of the Barber-Cushman model and the moving boundary approximation. The model predicts nutrient uptake by coupling nutrient flux to roots and nutrient absorption on a variable domain in time. The model output was compared with measured uptake of Mg, K, P, and S by various crops and soils using experimental data obtained from the literature. Predicted Mg, K, and P uptake by pine seedlings was close to that observed for K and P, although for Mg the predicted uptake showed deviations similar to those of the Barber-Cushman model. Sulfur uptake by wheat in different soils was better predicted by the moving boundary model in at least 10 out of 18 measured cases. The model prediction was also compared with measured K uptake by three maize hybrids grown on typic Hapludult of Río Cuarto, Argentina, in a growth chamber. The moving boundary model appears to provide a better description of coupling between transport, absorption of nutrient, and root growth than the Barber-Cushman model, and it improves the prediction for nutrient uptake in some tests.