Getting Smart with Nutrients

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Supporting soil life is the key Tim and Janet Oliver Tim and Janet Oliver bought their Karapiro kiwifruit block in 1982. They have always been among the top producers in their packhouse, both before and after converting to organic production, but their nutrient policy has changed considerably. “The aim of our fertiliser programme is not so much about bringing in the nutrients as it is about building soil condition, and providing food sources for beneficial soil life,” says Tim. “Once you have the basics right, it doesn’t take much of a tweak for the system to cycle and release nutrients for itself.” The Olivers have regular soil tests done, and use a fertiliser consultant who specialises in organic systems. Tim is also keen on direct observation, digging holes to assess soil structure and quality, worm life, and root depth. Recently the Olivers have gone even further with their monitoring, sending leaf and soil samples to Australia to have the fungal and bacterial life assessed. “Kiwifruit is a forest crop and it needs fungally dominant soils, whereas pasture needs bacterially dominant soils.” Compost is used to “kickstart” the soil microlife and build organic matter. The Olivers use organically certified commercial compost products made from plant material and duck and chicken waste. This has been applied at rates of 10 to 15 t/ha in the development phase. “At a cost of around $50 per tonne, it’s not a huge expense when you consider you can take off $40-50 000 worth of kiwifruit from one hectare,” says Tim. To help build the fungal component of soil life, the Olivers add manuka mulch to their mix of compost and worm casts. Seaweed and fish manures are also used. Lime is applied every four to five years at a rate of 1 t/ha, to maintain a pH of around 6.3 to 6.5 for vine and fruit health and fruit storage. A mixture of herbs and grasses is maintained under the vines to protect the soil, provide habitat for beneficial insects, and bring up different nutrients from the soil profile. Sheep are a key part of the nutrient cycling system, and the Olivers graze Romneys under the vines. The sward is also mown in strips during spring and early summer, but never more than a third is mown at one time to maintain the flowering and seeding cycle and provide host plants for insects. Moisture holding capacity has increased dramatically with higher soil organic matter and improved structure. “The soil is so soft now, if we get two inches of rain we will not get a puddle in the orchard, but on properties nearby the water can sit for 10 to 12 days.” Tim is happy with what he sees in his soils. “The clover nodulates in spring, our worm counts are going up, all the surface soil is processed and you can see the worm casts now. The topsoil is deeper, and the boundary between the topsoil and the subsoil is all wavy where the worms have been dragging stuff down.” Environmental Benefits ✔ Clover is maintained as a low input natural N source. ✔ Fertiliser use based on soil testing and professional advice reduces waste and potential for losses to groundwater and waterways. ✔ Addition of organic matter improves soil physical structure, nutrient and moisture retention and soil biodiversity, also reducing surface runoff.
Minimising losses to protect waterways Stuart Edmeades sees nutrient contamination of water as a key issue for the area around Putaruru, since water is a valuable local resource. He is determined to minimise the loss of nutrients from his own 165 ha dairy farming operation to protect ground water and the crystal clear Waihou River. “Dairyshed effluent is a huge problem - we generate 22,000 litres of it each milking time with our rotary shed. I don’t want to see that run off into our river. And I am concerned about nitrogen because our ground water is very shallow. Water from Putaruru is bottled and sold because it is so pure, and we have to keep it that way.” Stuart had an effluent irrigation system which was deemed adequate for his conditions, but his own observations led him to doubt its effectiveness. “We were spreading over the recommended area, but found it was still running off in a wet year. So we put in another kilometre of piping and added 35 hectares to the 25 hectares we could already spread on. Even though it’s pumice, the soil seemed to be sealing off, so now we plan to alternate four years on, four years off on the different areas to avoid runoff.” As Chairman of the Te Waihou Walkway Committee, Stuart feels he needs to set a good example on his own farm which has over 3 km of river frontage and sees many visitors each year appreciating the sparkling waters of the spring-fed upper Waihou. “Years ago, before the river was fenced, I used to watch 250 cows get into the river and as soon as they started to move, it would turn green. Now when I see any effluent reaching the water it upsets me.” To avoid the possibility of effluent spills contaminating the river, Stuart has a series of backstops to his effluent system. A new float switch has been fitted to the holding tank to prevent leaks. Stuart has created a wetland in a nearby gully so that any accidental effluent overflow can collect rather than flow straight to the stream below. He has also created a pond as an additional pollution trap, and fenced off grassy filter strips beside the stream where it joins the Waihou River. Other farmers in the district are also fencing and planting areas along the main river and its side streams. “The main benefit is to fence and prevent stock going in so the nutrients stay on the land, not in the water.” Stuart is also mindful of efficient nutrient application on the farm, working to a ten year strategic plan prepared by his brother, a fertiliser consultant and soil scientist. “We calculate that by keeping careful track and only putting on what is needed, we have saved $120,000 over standard practice, and we are only five years into our plan.” Stuart Edmeades Environmental Benefits ✔ Fertiliser use is based on nutrient budgeting and professional advice, helping to reduce waste and potential for losses to groundwater and waterways. ✔ Nutrients from farm dairy effluent are recycled back to paddocks using well-managed irrigation to prevent surface runoff. ✔ Nutrient losses to waterways reduced by careful fertiliser application and using wetlands and fenced grass margins beside waterways as filters.
Page 1 and 2: Getting Smart with Nutrients A bala
Page 3 and 4: Good planning gets results Matthew
Page 5: Using nutrients to suit soil types

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