Research update - nitrate sensor

Published 13 February 14

Research Update:

Using nitrate soil sensors to increase sustainability

With rising costs of feed and fertiliser, combined with changing climatic conditions, maximising resource use efficiency has never been more important to maintaining sustainable farm systems.

Nitrogen fertiliser is expensive, and there are a number of factors such as: soil type, temperature, plant demand, soil moisture and soil structure, which can influence how effectively applications of nitrogen are utilised.

To help improve our understanding, Rory Shaw, a DairyCo joint-funded* PhD researcher at Bangor University, is currently investigating how to develop new sensors to help make the most of our nitrogen fertiliser applications.

“Knowing the level of nutrients in soil will help to achieve optimal yields using inputs most efficiently however, for soil nitrogen ensuring, supply meets, but does not exceed, demand is extremely tricky,” says Rory.

 “Nitrogen application levels in excess of crop requirements are costly to the farmer and in some situations can result in harmful effects on the environment. In comparison, under-fertilisation risks a reduction in yield and can incur extra costs buying in expensive supplementary feed.”

Due to the dynamics of the nitrogen cycle, soil nitrogen concentrations can vary and change quickly in response to inputs, weather changes and crop uptake. Currently testing soil nitrate concentration is costly, time consuming and there is a delay between sampling and application which can make results difficult to interpret.

Nitrate sensors

Rory is currently working on developing new sensors to continuously monitor the presence of nitrate in soil solution (Figure 1).

Figure 1.

Nitrate sensor

“The sensors consist of ion-selective electrodes which detect and convert the activity of a specific ion dissolved in solution into an electrical potential, which is then measured by a voltmeter and converted into a reading of the amount of nitrate in soil solution,” explains Rory. “These sensors could be coupled with a wireless devise to allow farmers or agronomists to remotely monitor soil nutrients.”

So far, most of Rory’s work has been in the lab, building and testing the sensors and this spring, he will begin trialling the sensors in the field.

Trials will be taking place at Bangor University, comparing grass and clover receiving no N fertiliser to pure ryegrass swards receiving inorganic N fertiliser. The study examines the effect of clover inclusion on grass yields and greenhouse gas emissions. The trial will also aim to determine equivalent rates of N fertilisation at different clover densities. 

Rory will be using the nitrate sensors within this study to better understand N dynamics in the soil of grass clover swards.

In the future, sensors may be implemented as sensor networks within fields, to allow real-time monitoring throughout the growing season. More detailed monitoring around times of fertiliser application will help understand how to maximise resource use efficiency.

The applications for this type of technology are endless. It is extremely useful in research programmes but could also be the starting point for targeted fertiliser applications based on real time-data, meaning nitrate is only applied exactly when and where it is needed.

This new development of precision in agriculture makes more efficient use of nitrate, potentially reducing both farm input costs and environment impact from over application.

* This project is co-funded by DairyCo, EBLEX, HCC and QMS.

For more information about this project, watch the ‘Measurement of soil nitrates’ video on our YouTube channel.

For more information on fertiliser application, download Grass+ Chapter 11: Optimising Fertiliser Practice .