Soil texture, one of the most fundamental properties influencing fertiliser management, may be overlooked in day-to-day decision-making. In soil, texture refers to the relative proportions of sand, silt, and clay. This proportion plays a large factor in how soil behaves in terms of water holding capacity, nutrient retentions, drainage, and workability.
Sandy soils, common in New Zealand, are characterised by large particles and wide pore spaces. These soils drain quickly and are easy to work, but have a low capacity to hold nutrients, particularly Nitrogen (N) and Sulphur (S). As a result, fertiliser applied to sandy soils is more prone to leaching, especially during periods of high rainfall or irrigation. In these situations, smaller, more frequent applications of fertiliser are more efficient than large, single applications. This approach reduces the risk of nutrient loss and improves plant uptake.
At the other end of the soil specturm, clay has very fine particles and a much higher capacity to hold nutirents. Their higher Cation Exchange Capacity (CEC) means they retain nutirents such as Potassium (K), Calcium (Ca), and Magnesium (Mg) more effectively. However, clay soils are prone to water logging and compaction, limiting root growth and reducing the plant's ability to access nutrients. Timing of fertiliser applications is critical. Applying nutrients when clay is saturated leads to losses through runoff or denitrification.
Loam soils, a balanced mix of sand, silt, and clay, are generally considered ideal for plant growth. They offer a good compromise between drainage and nutrient retention, making fertiliser management more forgiving. However, even within loam soils, variations in organic matter and structure influences how nutrients behave, so they should not be treated as uniform.
Understanding soil texture helps inform practical decisions around fertiliser use, particularly in relation to soil wetness and paddock access. Usually wetter for longer, clay soils have limited opportunities for fertiliser applications without causing damage such as pugging or compaction. This restricts timing windows and reduces flexibility, increasing the risk of missed applications, or applying nutrients in less-than-ideals conditions. In contrast, lighter soils provide more consistent access, to allow better alignment of fertiliser applications with plant demand, but this must be balanced against their higher leaching risk.
In practice, tailoring fertiliser programmes to soil texture means matching application rate, timing, and product choice to the soil's ability to retain and supply nutrients. When combined with soil testing and an understanding of seasonal conditions, this significantly improves nutrient use efficiency, reduces environmental losses, and supports consistent pasture or crop performance.
TECH TIPS
- Only apply N strategically when soil temperature means pasture growth is still responsive.
- Avoid applying fertiliser to saturated soils to reduce the risk of runoff, denitrification, and soil damage.
