Could working on your soil health reduce your fertiliser wastage?

With 40% of fertiliser lost to leaching and volatilisation, growers are being urged to improve soil health to increase nutrient use efficiency, protect the environment and maximise profit margins.

George Hepburn, biological soils expert at QLF Agronomy, explained that fertiliser is one of the biggest input costs on many farms, and as prices have risen by 31% on last year, it is important to ensure applications are as efficient as possible.

“However, poor soil health means that a lot of growers aren’t getting the most out of their fertiliser,” he said.

For example, as much as 40% of nitrogen can be lost to leaching, immobilisation by soil microbes, denitrification and volatilisation. This leaves growers out of pocket due to wasted resources and potentially reduced yields.

“In addition, there are the environmental impacts to consider, and these are likely to rise up the agenda in light of Brexit and the Agriculture Bill,” he added.

“For this reason, improving soil health should be a key consideration. It will help soil biology work properly, allowing better nutrient movement from the soil to plants, increasing nutrient use efficiency and therefore, reducing fertiliser wastage.”

George encourages growers to go back to basics to improve soil health and improving soil structure is the first step.

“Soil structure is the foundation of nutrient efficiency as it helps soil microbes thrive, meaning they’re able to mobilise nutrients more effectively and make them more available to the plant.”

Assessing your soil

As a starting point, George advises going out with a spade, or in extreme cases, a digger, to physically look at the soil.

“The presence of deep rooting systems, good soil aggregation and abundance of visible soil life are all key indicators of healthy soil structure,” he said.

To test this, look at how far rooting is going down and whether or not there are any fine hair roots. It’s also useful to smell the soil – healthy soil smells almost like dark chocolate, and anaerobic soils have an unpleasant smell.

“Assess the aggregation of the soil to see if it’s crumbly or compacted, and check for soil life, such as millipedes, beetles and worms, the latter should be around 10 to 20 per spade in a healthy soil.

“Compare soil in the field with that from under the hedgerow where soil health and structure won’t have been affected by cultivations or compaction.”

Once you’ve established the state of your soils you can start to put a plan in place to improve them.

“To improve soil structure, increase organic matter to an ideal level of 5% of the soil mass by incorporating OM sources such as farmyard manure, compost and digestate,” he said.

“Cover and companion crops can also help with organic matter, as well as helping to scavenge and fix nitrogen in the soil.

Feeding microbes

When it comes to improving soil biology, he recommends including a bio-stimulant with other inputs to feed the soil microbes.

“One option is a liquid carbon fertiliser, which feeds the whole spectrum of soil micro-organisms with a range of sugars and yeasts,” he said.

“This encourages micro-organisms to hold onto nutrients and make them more available to the plant, increasing the efficacy and efficiency of inputs and reducing losses.

“Ultimately it’s about knowing your soils, going out and looking at them to make positive changes to increase the productivity of the biological system.”