Ways to reduce nitrate leaching
- Apply no more nitrogen fertiliser than the crop needs for good growth.
- Do not over-water. Excessive applications of water infiltrate through the soil and leach nutrients away. Small frequent waterings are best on sandy soils, keeping the root zone moist without excessive water drainage.
- Ensure that your irrigation system applies water evenly. Uneven application leads to over-watering in some areas to supply enough water to the drier spots. Excess water drains below the root zone, taking nutrients with it.
- On sandy soils, apply nitrogen fertiliser in small, regular doses throughout the life of the crop. This will limit leaching caused by heavy rain or over-watering to the most recent application.
- Slow-release nitrogen fertilisers can reduce leaching because they supply nitrogen at a steady rate over an extended period. This can result in efficient nitrogen use by crops, with fewer nutrients available for leaching. These forms of nitrogen are generally expensive.
- Match nitrogen application rates with crop growth stage. Young crops require lower rates of nutrients than in mid-growth. Apply nutrients in more frequent, smaller doses when crops are young, because their root systems are smaller. Reduce nutrient applications as the crop approaches maturity.
- When plants are young, place nitrogen fertiliser with droppers immediately adjacent to plants. When crops develop more extensive roots they are better able to extract nutrients spread over the whole growing area.
- Use tissue testing to determine whether the crop has sufficient nitrogen and adjust nitrogen applications. Sap testing kits provide a quick method to determine the nitrogen status of a crop.
Acknowledgement
Neil Lantzke authored the original version of this material.