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SWEET SPOT, " ... an optimum point or combination of factors or qualities". When it comes to sustainable agriculture and soil organic matter conservation, the sweet spot is when & where nitrogen-fertilizer use efficiencies are neither too high, nor too low. Excessively high NfUE lead to soil-mining because nitrogen deprived crop residues cannot be properly humified; excessively low NfUE prime soil organic carbon mineralization by nitrogen rich soil microflora in dire need of such carbon substrates.

ADDITIONALITY, along with leakage & permanence, have become conundrums for carbon-farming. The latest round coming from Don et al. 2023 and De Rosa et al. 2023. The former, at the risk of making things even more byzantine, introduce still more new terms such as SOC accrual, negative emissions, etc. De Rosa et al. 2023 infer leakage since the “accrual” (sic) of SOC stocks in European croplands are said to come from their conversion to … grasslands.

The latest in a series of Polyor SAS innovations for the intensification of sustainable agriculture. The European EP patent has just been granted. The idea is to minimize the nitrous oxide emissions from cellulosic crop residues by applying minimal amounts of nitrogen, phosphorus & sulfur directly to the crop residues.

COST & PRECISON. Carbon farming can be way too costly in comparison to the market value of the carbon-credits. A France Agricole article states that C-credits should be 200€ to cover costs of innovative cropping practices & carbon-farming implementation. To get around such costs is to do away with error prone sampling. More so given the inherent heterogeneity of all soils.

PERMANENCE: Last but not least, the issue of permanence can plague carbon-farming & sequestration efforts. For instance, see Dynarski et al. 2020 or Paul et al. 2023. Paul et al. 2023 state that; “While increasing SOC is a cornerstone for more sustainable cropping systems, carbon certificates fall short /.../ as permanence of SOC sequestration cannot be guaranteed.”

LEAKAGE. Sustainable agriculture through carbon-farming & sequestration often advocates grain yield reductions to lower N-fertilization rates responsible for GHG emissions. This extensification leads to “leakage” since these missing yields need to be produced elsewhere, often on marginal. This said, yield gaps across Europe indicate that yields should increase, not decrease.

Polyor SAS’s AgroNum approach to SOC conservation is inherently ergonomic. N-fertilizer response curves provide baseline sustainable grain-N target yields, along with their corresponding N-fertilization rates. Farmers only provide the plot's centermost GPS coordinates and current target yields and N-fertilization.

ADDITIONALITY is one of the many issues concerning carbon-farming. Additionality implies that some sort of soil organic carbon (SOC) baseline easily set at the plot level is known and recognized. Lack of will lead to a sentiment of unfairness and free-riding.

Carbon-farming derived carbon-credits imply baselines. This is a major limitation given that such baselines are very difficult, if not impossible to obtain. This critique also applies to conventional carbon-farming. Polyor has circumvented this conventional baseling problem by redefining soil organic matter baselines in terms of nitrogen refundable nitrogen credits (RNCs).

Are all increases in soil organic carbon (dSOC) creditable? Probably not. Put simply, AgroNum considers sustainability as the baseline from which refundable N-credits attributable to pTEC are calculated.

Soil organic carbon conservation using Polyor SAS's AgroNum approach (https://lnkd.in/exiTpR5a) to sustainable agriculture? A simple validation using the Roth-C model of carbon turnover in soil.

Again, how can N-fertilizer recommendations cater to the needs of both field-crop AND the ensuing crop residues precursors of SOM? As stated previously, an article by Kirby et al. 2016 recalled the stoichiometric C/N limitations imposed by SOM. In the same vein, Richardson et al. 2014.