One of the first steps towards good nitrogen (N) management is to take soil nutrient samples. Soil sampling gives you valuable information about your N management planning, such as how much N should be applied for optimal yields and minimal excess.
Timing of the soil sample matters
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Different sample timing helps to answer different questions about N management.
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One of the potential times to take a soil sample is near the end of growing season, also referred to as “post-harvest.”
What does a post-harvest sample tell you about N?
It tells you the amount of unused N (in the form of nitrate) that has remained in the rooting depth of the soil that the crop didn’t take up.
How can you use the post-harvest nitrate sample to inform your N management planning?
Feedback:
- This provides a “report card” on how effectively your N inputs were taken up by the crop – a high value means the crop left behind a substantial amount of N in the soil.
- Based on this feedback, you can then adjust your N inputs (e.g. timing, rates, sources, placement) the following season to minimize the amount of N left over in the soil.
Prediction:
- In regions where winters are mild with high rainfall (i.e. the South Coast), post-harvest nitrate testing can be used to determine N inputs for the coming crop and can replace N sampling in the spring.
