Soil solution analysis transcript.

Soil solution analysis is a great way to monitor the movement and status of certain nutrients in the soil and soil salinity.  It can help you identify if you are fertilising or irrigating too heavily and washing and wasting your nutrient past your root, or under irrigating and concentrating salts within the rootzone and improve the environmental sustainability. 

This video will provide a brief introduction into this technology. Soil solution analysis is the extracting of the soil water by various instruments and then analysing the soil solution for nutrient concentrations.  There are currently two methods to extract soil solution.  The first is the wetting front detector and the second is the ceramic sampler.

The commercial model of a wetting front detector is the full stop and it is a type of inverted funnel that when water moves down the profile it concentrates in the funnel and fills the reservoir at the base of the instrument.  When the reservoir fill a small indicator at the top of the unit pops up to indicate that moisture has reached this level.  

The indicator is great because it can help growers identify how many hours of irrigation are required to reach at a certain soil depth.  The soil solution sample can also be extracted via a pipe.  The fullstop can only be placed to a maximum depth of about 50cm because wetting fronts below 50cm are generally not strong enough to concentrate in the funnel.

There are various types of ceramic sampler’s on the market such as this 20mm wide sampler and 40mm wide sampler and you can even make your own. The ceramic samplers can be installed at any depth in the soil.    
                                                           5B To extract a soil solution from the soil air needs to be sucked out of the tube by a syringe so then soil solution can be pulled into the tube over a day or so through the ceramic tip by negative air pressure.

There are slightly different specifications on the ceramic tips characteristics between manufactures and models and you need to make sure you get one that suits your conditions.

The limitation of the soil solution extraction devices is that they require an irrigation or major rainfall event for a sufficient volume sample to be taken.  The results can also be variable within a block due to the complex nature of soils and how water and nutrients move and interact in the soil.  It advisable to install at least three sites in a block until you can gain confidence that the sampling sites are generally providing similar results.  For research purposes you might require five of more sites.

Soil solution analysis should be used in conjunction with soil moisture monitoring devices such as tensiometers or capacitance probes, because although you might know the concentration of a nutrient at a certain depth, you need soil moisture data to help you determine if water and nutrients are moving fast or slowly past the rootzone
Soil solution analysis is especially good at identifying when soil salinity levels begin to rise so you can apply leaching irrigation to move the salts out of the rootzone before any visual symptoms occur and continue to grow a health crop.  Once you see salt damage, crop and yield damage has already occurred
Soil solution analysis has been around for over 100 years. 

It has been used in many research projects, but it is now starting to be used by growers of a wide variety of crops as a crop management tool. For more information on soil solution sampling you can watch other soil solution videos that include information on installation, sampling, manufacture, analysis methods and interpretation.

You can also download the Soil solution report and factsheet from the NSW industry and investment web site and more information on the Full Stop wetting front detector is available from the Full stop website.