The in-field sap testing of high value crops, such as potatoes and beet, is now being recommended by agronomists as a means of ensuring that best use is made of all applied nutrients throughout the growing season.

Simon Fox, from Emerald Research Ltd. said: “For optimal nitrogen [N] uptake in potatoes, the levels of magnesium and potassium need to be maintained; any drop in these will lead to inefficient uptake and a reduction in overall crop performance.  

“Testing these levels can be easily done with in-field sap testing kits. 

"The results can be used to tailor any additional magnesium or potassium foliar applications, thereby only applying what’s needed at the most appropriate time.”

Fox added that while the decision to apply less N may be driven by cost and supply rather than for the good of the environment, in the long run, it is where UK agriculture needs to move to.

“The strategies that will need to be applied this year to achieve the best tonnages possible, will need to become part of every season’s planning, if farmers and growers are to produce more with reduced inputs," he explained.

Fertiliser for high value crops

Quite a number of root crops have yet to be planted out in 2022. According to Fox, now is the time for growers to start thinking of how to get best value from the various fertiliser options that can be applied.

“Now is the optimum time to apply nitrogen, phosphate and potash to the soil, as they encourage the tap root to reach a pocket of nutrients when they are needed to boost root development, resulting in better rooting," Fox continued.

“It is important to remember that while nitrogen is water soluble and can move through the soil, phosphate is immobile and will only travel 1mm a year, making it imperative that it is placed where it can be reached easily.

“The key to crop success is early establishment and early crop vigour to create a robust root system. With the current season hike in fertiliser prices, now is the time to ‘cash in’ on any ‘banked’ nutrients from previous seasons.”

Fox explained that planting is also the ideal opportunity to place specialist soil microbial mixes next to the seed that stimulate and promote root growth from the start.

“These microbes will help to provide an extensive root network that allows the crop to exploit any nutrients in the root zone," he stated.