Assessing when stock needs more fertiliser, before symptoms of deficiency appear, can be difficult without analysing samples of growing media or plant tissue. Being able to directly measure the nutrient status of plants would mean that growers could monitor uptake and adjust fertiliser applications.
In project HNS 193, a range of crops grown at various nursery locations in the UK and elsewhere in Europe are being monitored using novel nutrient-monitoring equipment and techniques to validate their usefulness under commercial conditions, with the aim of developing on-site monitoring schemes.
In its first year, the project has focused on Buddleja davidii, Chamaecyparis pisifera, Prunus laurocerasus and Viburnum tinus to see how each responds to increasing levels of fertiliser, how this information is presented by the tests and how the results compare to laboratory analyses. The work was undertaken at PCS in Belgium and Greenmount College in Northern Ireland because of their contrasting climates.
The test methods vary from simple handheld dipsticks for measuring sap nitrogen to smartphone apps that relate leaf colour to nitrogen content. Others are portable meters that assess either tissue nitrogen content or leaf chlorophyll fluorescence as indicators of plant health.
So far, the trials have revealed a problem extracting sufficient sap from plant material for some of the devices to test. Another issue with the dipsticks is that the colour of the sap samples makes it difficult to distinguish or interpret the colour reaction on the test strip.
You can read more about project HNS 193 on the AHDB Horticulture website.