Skyrocketing fertiliser prices are prompting farmers to rethink how they manage soil health and fertility.
Avoca Group managing director Bryce Manderson urged farmers and lifestyle block owners to make sure every fertiliser dollar was spent wisely by adding more lime to the mix.
The Northland-based company is a leading provider of lime and fertiliser mixes in Northland, South Auckland and Waikato.
Prices for fertiliser components have gone up recently. Magnesium, sulphur and potash are all up about 50 per cent and other basics like urea have doubled in price.
Avoca sources its own lime but imported other components for its fertiliser mixes.
Manderson said lime was an important way to "sweeten the soil" by boosting pH levels. This would release nutrients locked in the soil to be available to grass and plants.
"Lime maximises returns from money spent on fertiliser, reduces soil acidity and significantly increases the availability of important plant nutrients," he said.
"If soils are too acidic or alkaline, nutrients remain locked up. Lime, which is calcium carbonate, provides calcium to soil and plants. Calcium ensures efficient plant uptake of water and nutrients, carbohydrate storage in plant leaves, nodulation and nitrogen fixation in legumes, and encourages earthworm activity.
Lime increased the availability of important plant nutrients such as phosphorus, nitrogen, potassium, calcium and magnesium and trace elements like boron and molybdenum.
"I liken lime to a superhero because it fosters optimum availability of all other nutrients. It provides great bang for your buck. You only have to talk to farmers who have a regular liming programme to understand the benefits."
Manderson said it was important to maintain a pH of 6.3-6.5 to optimise the availability of all these nutrients.
Northland farms tended to need more fertiliser than other areas of New Zealand because of the high rainfall and old gumland soils which were prone to leaching.
"Rainfall and plant-soil chemical interactions naturally increase soil acidity. On top of that, landowners are responsible for acidification through the abundant use of fertilisers on our agricultural land.
"All of these factors drop our soil pH levels below the optimum required for maximum nutrient availability. Applying lime will increase the pH of your soils, creating conditions for greater nutrient availability and therefore increased productivity," he said.
Avoca is celebrating "quite a big year", marking 75 years in operation and Manderson's 40th year with the company started by his late father, Jim.
The lime rock is no longer quarried from the Avoca valley near Dargaville - instead it is sourced from quarries in Moerewa, Whangārei and Wellsford. The company has bulk stores at each of those sites as well as Dargaville and Te Kauwhata.
"We've been in the Waikato for the last three years and our lime/fertiliser mixes are proving popular as our Northland lime is softer and more reactive,'' Manderson said.
Slow-release fertilisers were a good trend for farmers and the environment, he said.
"Avoca has components like sulphur, magnesium, nitrogen and potassium in slow-release form, taking up to a year to break down."
For phosphate, Avoca has replaced superphosphate which was 80 per cent water-soluble, with modern mixes of dicalcic phosphate which is much less water-soluble, at 0.2 per cent.
"Slow-release means there is less chance of leaching in high rainfall areas,'' he said.
A recent development is to add biological products into fertiliser mixes to further boost soils. Fungi and bacteria are sprayed into small absorbent chips to make a product which is then included in fertiliser mixes.
"Dairy farmers are finding it works well to rebuild soil structure which has been damaged by pugging. Trials have shown there is less product required when it is added with urea.
"It's all about building resilient soils,'' he said.