Per Water Board guidance, growers must measure soil-N and maintain this information in their records. For the TNA report that is due by 3/1/22, growers that did not measure the N present in soil for their 2021 crops should do the following:
It is fine to report “0” pounds applied if you did not apply any fertilizer-N to a crop, provided this is an accurate reflection of your practices. This is an acceptable value and will not be flagged as a true “Error.” You may, however, receive a “Warning,” which is simply a prompt to double check and confirm that your entry was correct and not a typo. Your final report will be accepted, even if you do not make any changes in response to the Warning.
In this case, simply select “NR” (Not Recorded) from the drop-down menu to indicate that the value is unknown. You cannot leave this item blank.
For now, C:N ratio is an optional field that will be used in the future as part of the INMP summary report to determine the organic fertilizer discount factor for the amount of nitrogen mineralized during the first 12 weeks in the year it was applied.
Update 2/14/22: Quite a few growers have this question, and we expect to have a response from the Water Board shortly. In the meantime, one option is to calculate a “weighted average C:N ratio,” based on all fertilizers applied to the crop. This way, the crop can be entered as a single line-item, with a single weighted-average C:N ratio.
For example, if you used Fertilizer A for half of your total N-application, Fertilizer B for one-quarter of your total N-application, and Fertilizer C for the rest (i.e. one-quarter), then multiply the C:N ratios by 0.5 (Fertilizer A), 0.25 (Fertilizer B), and 0.25 (Fertilizer C) prior to summing to get the weighted average.