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Mapping Plant Available Water-Holding Capacity (PAWC) using EM and Radiometric Surveying

Mapping Plant Available Water-Holding Capacity (PAWC) using EM and Radiometric Surveying

  • Author: Wheatbelt NRM
  • Date Posted: Dec 3, 2015
  • Category:

Project Details

Project Delivery: Wheatbelt NRM, Individual Landholder, Precision Agronomics

Contact: Lizzie von Perger

Ph: 96703100


Website: Wheatbelt NRM Website

Start Date: 2015                       End Date: 2017

Site ID: SA00351SA1

Area (Ha): 156 ha


Project Aim

To evaluate the use of variable rate technology for optimizing nutrient and water use efficiency relative to traditional farming practices.


This will be done using spatial radiometric and electromagnetic (EM) surveys, with soil testing to map PAWC and nutritional status of the soil and identify zones for VRT input.  The soil zonation mapping will then be incorporated with yield data and Yield Prophet modelling to optimize inputs using VRT and evaluate the impact on whole of paddock input budgets and overall profit.


Given the textural variability within these paddocks, and consequently PAWC and yield potential variability such practice is likely to greatly enhance the efficiency of nutrient use and whole of paddock profit.


Project Description

The most limiting factor of a crop’s yield potential is the soils ability to store plant available water. This is mainly determined by the soil texture and the roots ability to penetrate down the soil profile.


Plant Available Water-holding Capacity (PAWC) is difficult to measure directly but is an important soil property that determines yield, deep drainage and nitrate leaching in our Mediterranean-type environment.  Properly ground-truthed geophysical surveys can be used estimate the spatial distribution of soil types and approximations of PAWC.


By using radiometrics and electromagnetics (EM) surveys, soil testing, yield data and Yield Prophet to determine soil’s PAWC and nutritional status we can develop variable rate maps to apply inputs using satellite guidance (GPS) technology. This in turn can be used to tailor fertiliser application rates to soil type and increase overall nutrient use efficiencies.


Many farms in the Western Australian grain-belt are equipped with yield mapping technology and have the ability to apply fertilizer at variable rates across paddock, but farmers are unsure how to determine rates for different zones.


Project Outputs

Project outputs will be added once the trial has been completed.


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