Holmen has been using arginine as a liquid fertiliser in its nurseries for fifteen years, but the organic fertiliser Argrow is now available in solid form too. This enables seedlings to continue being fertilised once they have been planted in the forest.
"This could be a revolution in silviculture," predicts Daniel Hägglund, head of Holmen's nurseries.
Classic fertilisers contain high amounts of nitrates as a source of nitrogen. The disadvantage is that nitrates easily leach out, with a negative impact on watercourses and wells as a result. Unlike nitrate, arginine is organic and has a positively charged molecule that is bound in the soil. This means that the nitrogen, essential to plant growth, is not washed away by rain or watering.
Research results have shown that forest seedlings much prefer arginine to nitrate as a source of nitrogen. Arginine produces better root systems, rapid growth and a high survival rate. The discovery was patented and the company SweTree Technologies (STT) has worked with Holmen to produce the new fertiliser Argrow. Development and marketing is now managed by the company Arevo AB.
"Argrow is a liquid fertiliser that produces a large number of fine, small roots and efficient and eco-friendly nitrogen usage," says Daniel Hägglund, head of seed and seedling operations at Holmen. "Argrow is now used for the 35 million seedlings we grow in our nurseries every year."
Holmen's nurseries in Friggesund and Gideå have long used the organic fertiliser. The fact that it is now available in solid form makes it possible to also add the fertiliser when the seedlings are planted in the ground. Photo: Karl Nordlund.
To further improve the effects of organic nitrogen on the seedling, Arevo has sought forms of the new fertiliser that have a longer, slow-release action. The solution emerged when crystals containing the substance arginine phosphate were found by accident. The crystals formed spontaneously in the fertiliser tanks at Holmen's nurseries. They were ground into a granulate, which releases the nitrogen bound in the arginine over a long period.
Under the working title Argrow Granular, the granulate makes the work of the nurseries much easier. However, it also gave rise to the idea of sending the fertiliser along with the delivered seedlings. In 2016 and 2017 trials of the granulate were conducted on seedlings in the field. And according to Daniel Hägglund, the trials are looking promising. If the results in 2018 are equally positive, he thinks the method is here to stay. What stands out after using the solid fertiliser is that a very strong root system develops, up to seventeen times larger than in the reference seedlings.
Daniel Hägglund, while emphasising that much remains to be done before all the cards are on the table, says that the seedlings are already looking better after only a year.
"I personally believe that this may herald a silviculture revolution in Sweden," he says.
Arginine as a source of nitrogen in nurseries
- Organic amino acid (arginine occurs naturally in forests and in the soil) instead of ammonium nitrate.
- Eliminates nitrogen leaching.
- Creates seedlings with a better balance between root and shoot.
- Produces active root systems with more mykorrhiza. Mykorrhiza is an interaction between subterranean fungal threads and the roots of the seedlings. The trees depend on mykorrhiza to help them take up valuable nutrients that they would not otherwise be able to reach with their own roots.
Use of arginine fertiliser in the field
- Higher seedling survival.
- More even regeneration. Giving the seedling a dose of fertiliser at planting gives all seedlings the same conditions for growth. The amount of fertiliser is the same, the plants are still too small when planted to be able to detect any individual differences.
- After one season in the field, produces a major increase in new roots.