Nitrogen-fertilizer response curves can be used to evaluate, precisely, so-called refundable nitrogen credits (RNC). These N-credits are meant as a convenient and valuable alternative to current carbon-farming derived carbon-credits. RNCs are input oriented and reward at no cost to the user existing soil conservation efforts by inferring the amount of supplemental nitrogen left to the crop residues at harvest, nitrogen that could have otherwise been harvested for profit in the grain.
This residue-nitrogen is a valuable service to the environment and thus deemed … refundable, at par with the real-time market price of nitrate ammonium, for instance. This said, such refundable nitrogen-credits will be small as compared to publicized carbon-farming derived carbon-credits, but again at little or no additional cost to the farmer.
RNC generation also ensures additionality of soil derived carbon dioxide removal certificats. Farmers are refunded only that amount of nitrogen left in the crop residues and effectively returned to the soil. Farmers and thus not being paid to attain sustainability per se as a baseline but rather for intensifying sustainability to avoid leakage as a result of decreased yields.
AgroNum refundable N-credits thus ensure additionality since only residue nitrogen beyond baseline sustainability are valued. More so, this crediting scheme is perennial, thus circumventing the usual permeance issue. Leakage is no longer an issue since RNCs imply yield increases. Finally, there is no risk of mitigation deterrence, since RNCs reenforce existing behavior rather than speculate on SOC stocks & accrual rates.
Supplemental nitrogen returned to the soil by the crop residues will lead to SOC conservation or build-up. This supplemental N in response to cropping practice modification is precisely estimated by Polyor SAS's AgroNum AI & dbase with respect to local or regional environmental means across Europe. A tentative validation was attempled by pitting AgroNum RNC against estimated increases in soil organic nitrogen modelled over 21 years starting 2000 at numerous sites across Europe using an R-language implementation of the recognized Roth-C model.
