The present paper proposes a bifactorial model obtained by a generalization of the unifactorial Mitscherlich model. After analysing the graphic representation of the experimental data and the theoretical curves, one can conclude that they present good concordance. Treatments with nitrogen fertilizers within the limits of 0-200 kg a.i. ha-1 determined different optimum and maximum values for each of the four fertilization variants with phosphorus and potassium (optimum value 97 kg ha-1 N on 0 0 with yield increase of 1224 kg ha-1 ; optimum 107 kg ha-1 N on 50 50 , with an increase of 952 kg ha-1 ; 111 kg ha-1 N on 100 100 with an increase of 968 kg ha-1 and 103 kg ha-1 N on 150 150 with an increase of 1413 kg ha-1). From an economical point of view, we will maximize the benefit corresponding to production value in the hypothesis that only one fertilizer is applied, namely a complex fertilizer of the type 15 15 15. For the actual price values = 0.2 € • −1 , = 0.6€ • −1 the solution of the equation above is = 221 • ℎ −1 .

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<p>Land cover, productivity and carbon stocks are among the widely acknowledged indicators of the land’s degradation and development status. The indicators’ assess-ability, however, differs across global ecosystems and location. Despite the complexity of carbon stocks, soil carbon in particular is receiving increasing attention for its potential in both climate change mitigation and economic growth in developing carbon markets. <br>The degraded drylands of Jordan have been targeted by multiple investment programs to rehabilitate their arid agro-pastures, including through the application of mechanized micro-water harvesting structures combined with the plantation of native shrub seedlings. Whilst both local and remote land cover and biomass change monitoring indicate variable rehabilitation success, the related carbon stock changes remain largely under-investigated and unclear.<br>An international research consortium designed and implemented a study to investigate the actual and potential future carbon stocks per ecosystem status at an agro-pastoral research site located in central Jordan’s ‘Badia’, considering both conventionally managed (degraded) and rehabilitated lands. Field experiments conducted by scientists and  local and former tribal community collaborators were combined with carbon modeling using RothC. This enabled the development of multiple scenarios considering both natural and enhanced, or human induced, processes; for example, through landscape modification (mechanized micro-water harvesting), vegetation plantation as well as optional soil amendment through biosolids. Preliminary results suggest that the implementation of water harvesting structures leads to a pronounced increase in soil carbon sequestration when compared to baseline conditions of between 15% and 45% over a 5 year period , with work ongoing to quantify the uncertainties around these results. The selected rehabilitation scenarios match the criteria for vast potential upscaling across global drylands. The study outcomes will eventually support a comprehensive ecosystem services valuation approach with (soil) carbon as an integral factor and moving towards reversing degradation and crediting the dry ecosystem’s values beyond their marginal agricultural services.</p>