Modelling the optimal phosphate fertiliser and soil management strategy for crops

Abstract

12Aims The readily available global rock phosphate (P) reserves may be depleted within the next 50-13 130 years warranting careful use of this finite resource. We develop a model that allows us to assess 14 a range of P fertiliser and soil management strategies for Barley in order to find which one 15 maximises plant P uptake under certain climate conditions. 16Methods Our model describes the development of the P and water profiles within the soil. Current 17 cultivation techniques such as ploughing and reduced till gradient are simulated along with fertiliser 18 options to feed the top soil or the soil right below the seed. 19Results Our model was able to fit data from two barley field trials, achieving a good fit at early 20 growth stages but a poor fit at late growth stages, where the model underestimated plant P uptake. 21A well-mixed soil (inverted and 25 cm ploughing) is important for optimal plant P uptake and 22 provides the best environment for the root system. 23Conclusions The model is sensitive to the initial state of P and its distribution within the soil profile; 24 experimental parameters which are sparsely measured. The combination of modelling and 25 experimental data provides useful agricultural predictions for site specific locations. 26 27

Use of a coupled soil-root-leaf model to optimise phosphate fertiliser use efficiency in barley

“…The experimental data includes different rates of P application (0,5,10,20,30,60, 90 kg P ha −1 for spring barley; 0 15, 30, 60, 90, 120 kg P ha −1 for winter barley) and both sites were classified with an Olsen P index 1 soil (Defra 2010). The protocol for this is described in Heppell et al (2015). In addition, we use the climate data, from the UK Met office Integrated Data Archive System (MIDAS), to accompany the spring barley (Inverurie, Scotland) and winter barley (Cambridge, England) data sets for the specific fields in the trial.…”

“…In this paper we extend a root-soil model (Roose and Fowler 2004b;Heppell et al 2015) which estimates plant P uptake, with an above ground leaf model which estimates above ground dry mass (based on Thornley 1995), to produce a whole crop model. We first describe the root-soil model (hereafter called the root model), followed by the leaf model and then our coupling process to create a whole crop model.…”

“…To model the root system we follow the same approach as described in Roose and Fowler (2004b) and Heppell et al (2015) by modelling two orders of root branches only (main and first order branches). First order roots branch off the main order roots at a given density(ψ 1 ), branching angle (θ), and each order of roots has a given maximum length and radius (L0, L1 and a, a 1 for main and first order roots, respectively).…”

“…First order roots branch off the main order roots at a given density(ψ 1 ), branching angle (θ), and each order of roots has a given maximum length and radius (L0, L1 and a, a 1 for main and first order roots, respectively). As in Roose and Fowler (2004b) and Heppell et al (2015) we let the root growth slow down as the root becomes longer. Following Heppell et al (2015) we also let the root growth rate (r) be dependent upon air temperature T, we detained from the MIDAS database,…”

“…We hope to address some of these problems by creating a model that links the above and below ground processes in such a way that they rely on one another. Our whole crop model is based on a below ground plant-soil interaction model (Roose and Fowler 2004b;Heppell et al 2015) coupled with an above ground leaf growth model based on the seminal work of Thornley (1995).…”