May 2026

As Canterbury moves into autumn and winter, farms are entering the main leaching season. The period between April and October is when nutrient losses below the root zone are at their highest risk. During winter, soil temperatures drop, and pasture growth slows significantly. Once soil temperatures fall below around 6 °C, ryegrass growth becomes limited, meaning plants are not taking up nutrients efficiently. At the same time, rainfall continues moving water through the soil profile. When soils become saturated, drainage increases, carrying soluble nutrients deeper into the ground. Canterbury presents a unique challenge compared to many other farming regions in New Zealand. Naturally, much of the region only receives around 600–900mm of annual rainfall. However, once irrigation is added to farming systems, soil moisture levels become similar to much wetter regions of the country. When heavy winter rainfall occurs, nutrients can be flushed below the pasture root zone before plants can utilise them. Most farmers associate leaching with nitrate nitrogen, and rightly so. Nitrate is highly soluble and easily moves with water through the soil. However, nitrogen is not the only nutrient being lost during winter drainage. Important nutrients, including calcium, magnesium, potassium, sodium and sulphur, can also be leached from the soil profile. These nutrients are essential for both pasture growth and animal health. Research I was involved in showed that intensive grazing systems can lose significant quantities of magnesium and calcium annually through leaching. In some situations, approximately 30kg of magnesium per hectare per year was being lost below the root zone. If these nutrients are not adequately replaced, soil fertility gradually declines over time, which is what the Ministry of Agriculture found was occurring in the 1980’s and 1990’s. These losses equate to a large sum in terms of dollar value. One of the key lessons for farmers during the leaching season is to be careful with highly soluble fertilisers during periods when soils are cold, wet, and pasture growth is limited. If soluble nitrogen and sulphur fertilisers are applied when there is little plant uptake occurring, there is a much greater chance that nutrients will move beyond the root zone during drainage events. Timing fertiliser applications closer to active pasture growth periods can improve nutrient efficiency and reduce unnecessary losses. Soil texture, structure, and drainage pathways also influence leaching risk. Lighter soils and free-draining profiles allow faster movement of water and nutrients compared to heavier, more retentive soils. Healthy soils with good structure, balanced fertility and efficient irrigation management are better at holding nutrients and supporting plant uptake. Contact Dr Gordon Rajendram 021 466077 rajendram@xtra.co.nz www.gordonrajendramsoilscientist.co.nz Contact Media PA phillip@mediapa.co.nz 027 458 7724

New Zealand’s agricultural success relies on a careful balance between productive farming and environmental protection. Few figures illustrate this balance better than Dr. Gordon Rajendram, a respected soil scientist based in Hamilton, whose work in nutrient management and soil fertility has shaped farming practices across the country. His scientific approach aligns closely with the goals of Environment Councils, the regional authorities responsible for managing land, water, and environmental resources throughout New Zealand. Together, the insights of scientists like Rajendram and the regulatory oversight of Environmental Councils highlight how New Zealand can continue to advance sustainable land use. Science That Works on the Ground Dr. Rajendram has spent decades helping farmers understand how to optimise soil health while reducing environmental impacts. His work spans: What sets Rajendram apart is his focus on practical, measurable outcomes. He believes soil science must translate into real-world improvements — better yields, lower costs, and reduced environmental footprints. His ability to turn complex science into clear, actionable advice has made him a trusted figure in an industry navigating increasing regulatory expectations. Managing a Complex Landscape in Regions Like Canterbury As the regional council for Canterbury, ECan plays a central role in protecting the region’s natural resources. Its responsibilities include: Canterbury’s landscape — vast plains, braided rivers, and heavy reliance on irrigation — makes ECan’s work both challenging and essential. The region’s agricultural productivity is high, but so are the environmental pressures, especially around nitrate leaching and water allocation. Collaboration Is Key: Environmental Councils and Farmers Working Together One of the most important factors in achieving long-term environmental progress is genuine collaboration between Environmental Councils and the farming communities. Regulations alone cannot deliver the outcomes the region needs. Farmers understand their land intimately, while Environmental Councils bring regional data, environmental oversight, and long-term planning. For positive outcomes, both sides must work in partnership: When Environmental Councils work constructively with farmers — listening, adapting, and supporting — environmental improvements become far more achievable. The most successful initiatives like Canterbury have been those where farmers feel they are part of the solution, not simply being regulated. A Shared Path Forward New Zealand’s reputation for sustainable, high-quality production depends on the combined efforts of scientists, farmers, and regional authorities. Dr. Gordon Rajendram offers the scientific “how,” Environmental Councils provide the regulatory “why” and “what,” and farmers carry out the daily decisions that shape the land. Real progress happens when these groups work together. Collaboration, not confrontation, is the key to a resilient and sustainable agricultural future. Contact Dr Gordon Rajendram 021 466 077 | rajendram@xtra.co.nz www.gordonrajendramsoilscientist.co.nz Contact MediaPA Phillip Quay MediaPA 027 458 7724 phillip@mediapa.co.nz