Blog & News

How to increase nitrogen-fertilizer use efficiencies (NfUE) and avoid the “mining” of soil organic matter? Interesting insight from Kirby et al. 2016 – "Inorganic Nutrients Increase Humification Efficiency and C-Sequestration in an Annually Cropped Soil" concerning the so-called “nutrient-use efficiency” paradigm.

Lots of talk about AI. This said, AI is really about implementing collective intelligence (CI). This AI/CI conjunction has been extensively reviewed. Polyor SAS's AgroNum approach to sustainable agriculture and soil organic matter conservation is also a form of CI implemented by AI.

Polyor SAS has updated it's AgroNum Rationale & Positioning paper (https://lnkd.in/eBmfT3NM) to include recent advances; * refundable nitrogen-credits as an alternative to carbon-credits, * a brief introduction to the mathematical basis of RNCs, * soil carbon-deficits versus carbon-debts correlation.

Soil carbon debt? Soil carbon deficit? Carbon DEBTs as defined by Wuepper et al. 2021 compare present day soil carbon levels to those of pristine soils that may have existed in the past. Polyor SAS's AgroNum approach to sustainable agriculture & SOM conservation defines soil carbon DEFICITs as the difference between soil carbon levels over time when crop residues returned to the soil are nitrogen sufficient to those when crop residues are deemed deficient in nitrogen.

Polyor SAS is developing an alternative to conventional carbon-credit & carbon-farming approaches to sustainable agriculture. A pTEC index ("progrès technique") indicates the amount of supplemental nitrogen allocated to the humification of crop residues into stable SOM.

The recent Carbon Farming Workshop sponsored by the EC's CR expert group was enlightening. My take was that carbon-farming is for the time being probably most implementable at the regional/national level, not as agricultural consultancy at the farm/plot level. More so, field-sampling & in situ monitoring costs, along with (im)precision issues make carbon-credit issuing a bit of a guessing game.

Precise grain yield & nitrogen fertilization recommendations require precise input data. This said, at the field level, very few such data are easily available. In fact only grain-yield dry-matter & nitrogen-content, along with kg-N_fertilizer/ha are known precisely. The rest - soil organic matter stocks, soil physico-chemical analyses, clay contents, texture, etc., are at best error prone averages.

Robert Höglund's "Removing Carbon Now" paper, cf. soil carbon sequestration section (pp 10-12) reminds us that there is no consensus as to how to measure soil carbon sequestration at the plot level, let alone which cropping practices are necessarily most effective in any given place or time. More so, there is the risk of non-additionality since farmers should be adopting soil conservation & best cropping-practicies anyway, with or without payments.

How accurate are process-based dynamic field-crop models? On average, pretty good, I hear. For instance herein, Wallach et al. 2018. Polyor SAS's AgroNum approach to sustainable agriculture & soil organic matter/carbon conservation has more of an AI/artificial intelligence bent to it. Probably more ergonomic & precise when it comes to agricultural consultancy. Time will tell.

Nitrogen fertilization, Nf, is often incriminated, said to be linked to soil organic matter and nitrogen (No) depletion. Data from Mulvaney et al. 2009 clearly shows that No depletion is in fact correlated to Nf. This said, data from Table 5 in Mulvaney et al. 2009 indicate that if the % Nf use efficiency, %NUE, of these same N-fertilizers is increased, soil organic nitrogen (No) is conserved, i.e. organic N losses are reduced if not reversed.

Azotobacterial fertilization (AZB). Non-bactericidal control/slow release fertilizers can be applied directly to soil borne crop-residues. This targeting of crop-residues with otherwise conventional nitrogen (N), phosphorus (P) & sulfur (S) soil and/or foliar applied fertilizers will enhance the activity of indigenous & inoculated azotobacteria.

Sustainable agriculture via carbon-farming must account for the cost of building soil organic carbon. Eg. 1000 kg of stable soil organic carbon will need to sequester 100 - 120 kg of N. This nutrient cost of carbon-farming has been explicated by Richardson et al. 2014. AgroNum is a simple way around this so-called dilemma (van Groenigen et al. 2017 by ensuring that crop residues are sufficiently rich in N to be properly humified into stable SOC.