What PSNT result indicates that no additional sidedress nitrogen is required?

The correct choice indicating that no additional sidedress nitrogen is required is when the nitrate-nitrogen (NO3-N) concentration is greater than 21 ppm. This threshold is based on research and guidelines that suggest plants have adequate access to nitrogen for optimal growth when NO3-N levels exceed this concentration.

When soil tests, particularly the Pre-Sidedress Nitrate Test (PSNT), reveal nitrate levels above 21 ppm, it indicates that the soil already contains sufficient nitrogen to meet the needs of the crop during its critical growth phase. Adding more nitrogen at this stage could potentially lead to nutrient leaching and water quality issues without providing any additional benefit to the crops.

Understanding these nitrate levels helps farmers and agricultural professionals make informed decisions about nitrogen application, supporting both crop health and environmental stewardship.