An analytical C3-crop growth model for precision farming

Abstract

A simple and transparent analytical model for C3-crop biomass accumulation is introduced. The model is aimed to be used as a decision tool in precision farming. It is valid when growth is limited only by radiation or water and gives the optimal (maximum) biomass. It contains 8 fixed parameters, all with a clear basis in physics, chemistry and physiology. As a function of time, the growth is divided into two phases: exponential and linear. At an early stage of growth, the growth is exponential due to the expanding leaf area of the crop. At this stage, the model needs 6 parameters. The growth becomes linear when the leaf area is adequate to use all possible radiation. The model needs 2 parameters at this later stage. Water-limited growth needs an additional set of 4 parameters to describe phenomena of water related processes. When water is a limiting factor, the root-growth model becomes critical because the daily root growth determines the crop's growth directly. The model was tested first against field data at one point where all relevant inputs and parameters of the model were measured. Despite the simplicity of the model, there was a good agreement between simulated and measured values of biomass and leaf area. A scenario is described to show how the model may be used in practice and what kind of field data is needed. In on-line precision farming the key factor is the amount of radiation used by the crop, which can be measured adequately with two sensors, one above and one below the canopy.

Testing the use of an analytical and mechanistic C3 - biomass accumulation model for precision fertilization

“…The analytical crop growth model (Hautala and Hakojärvi 2011) with parameter values from Table 1 (essentially the same as in Hautala and Hakojärvi (2011)) and measured radiation (I) and precipitation as inputs was used to simulate the total biomass (BM) accumulation during the experiment period. The crop growth model simulates the highest attainable (maximum) biomass yield in prevailing moisture and radiation conditions.…”

“…Therefore the most parameters in Table 1 were measured in actual field conditions or were taken from literature. Monteith and Moss (1977), 2) Hautala and Hakojärvi (2011).…”

“…1 and 3 give the radiation limited crop growth. The amount of water available for crop growth is calculated from crop root growth, soil properties and rainfall (Hautala and Hakojärvi 2011). Initially the soil moisture content is assumed to be at field capacity (FC).…”

“…Furthermore, the simulated potential biomass yield should be very close to the biomass yield in actual farming when the temperature is optimal and precipitation is sufficient during the growing season. We simulate the potential biomass accumulation with a process based and mechanistic crop growth model (Hautala and Hakojärvi 2011) that was developed to describe the maximal biomass accumulation in prevailing growing conditions. The model has as few parameters as possible, which has been found to be beneficial in modelling studies (Boote et al 1996, Sinclair and Seligman 1996, Brooks et al 2001, Lark 2001) and further should be advantageous for spatial data sufficiency (model parameter values) and for practical farming applications (Adams et al 2000, Morison et al 2008.…”

Bayesian methods for predicting LAI and soil water content

“…Up to now, despite the wide development of agricultural technology, decisions regarding field management are still made by the farmer (Hautala and Hakojarvi, 2011). There is thus a need for decision making systems furnishing strategies for effective management of inputs, such as fertilizers and irrigation water.…”