Modelling the optimal phosphate fertiliser and soil management strategy for crops James Heppell August 2014

My Research The aim of my research is to model water and P uptake by crop roots and to optimise a sustainable environment for the future, given uncertain climate changes and demands from farming restrictions.

My Research The long term goal is to provide a guidance tool for farmers/ the agricultural industry as to how and when to fertilise crops. ? ? ? ?

Why is Phosphate Important?

The model enables analysis of different P fertiliser strategies on grain yield, for different environmental conditions Group Model Overview

Model Overview After P is applied, the model 1.Tracks the movement of P and water through the soil 2.Includes the binding reactions of P to soil particles 3.Calculates the depth-dependent uptake of water and P into a developing root system

Model Overview Our model is based on the one for nutrient and water uptake by plant roots from unsaturated soil (Roose and Fowler, 2004). We estimate the phosphate and water concentration levels within the soil down to a depth of 2m. We set soil parameters such as water permeability and buffer power, for known characteristics of the soil measured by Bangor University. Climate conditions are taken from weather station data and root structures are known from pot experiments. The model inputs include; initial water and P concentrations in the soil, climate data and the fertiliser and soil cultivation strategy.

Scenarios to Consider Cultivation FertiliserClimate A very wet climate Site specific climate Banded 5cmBroadcasted Plough at 25, 20 or 10 cm Inverted plough Min till gradientNo cultivation No fertiliser

Problem Definition Q1. What is the optimal fertiliser and soil management strategy for maximising plant P uptake? Q2. Does this strategy change for different climate conditions?

Experimental Data P profile for an Olsen index 2, 3 and 5 soil.

Experimental Data Field Trial set up: –Initial P level is 9-10 mg P/l (P1) –Winter Barley measured at GS39 (19 th May) –Varying fertilise amounts of Trisodium Phosphate (TSP) via incorporation or placing Incorporated Placed

Model Validation If we assume P index 2 (20 mg P/l) with exponential decay, similar results are obtained Total available P is only increased by 7% Incorporated Placed

Scenario Testing Results The best scenario for uptake is to mix the soil to a depth of 25 cm or Inverted plough. Placed fertiliser is better than incorporated by roughly 11%. Site Specific Climate

Scenario Testing Results The best scenario for uptake is to mix the soil to a depth of 25 cm or Inverted plough. Placed fertiliser is better than incorporated by roughly 11%. If the climate is particularly wet, average P uptake is increased by 2% across all scenarios, 6% for just incorporated. A very wet climate

Effect of Buffer Power Results for an initial P index 1 soil (10mg/l P constant), 90 kg/ha P 2 O 5 added to the top of the soil and then mixed down to 25 cm) The model is very sensitive to the buffer power. Therefore, to ensure accurate model predictions, a field-specific buffer power is required.

Effect of Soil Water Content Results for an initial P index 1 soil (10mg/l P constant), 90 kg/ha P 2 O 5 added to the top of the soil and then mixed down to 25 cm. The model is less sensitive to the volumetric soil water content However to further improve the accuracy of the model, the volumetric soil water content profile in depth is required.

Root Model Conclusions Have incorporated temperature-dependent root growth which allows modelling of the winter period. The model outputs depend entirely on the model inputs –buffer power –initial soil P and water profile to depth –site specific climate data Completed set of scenario testing –best method is to invert plough and place fertiliser (banded) Different cultivation techniques and practices can lead to differences in soil P and water profiles –To improve model prediction, more accurate site-specific data is needed

Thank you. Any Questions?