The 4 per 1000 initiative.

Soil organic matter is at the nexus of global challenges: food security, climate change adaptation and mitigation, soil security. The 4 per 1000 initiative, launched at the Climate COP21 within the Lima-Paris Action Agenda proposes to increase soil organic carbon (SOC) stocks to simultaneously address all these challenges. It directly addresses three sustainable development goals: SDG2 ?no hunger?, SDG13 ?Climate action?, and SDG15 ?Life on land? and indirectly concerns several others. The initiative targets agricultural soils in priority, which are often the most degraded soils and because of the high expected benefits in terms of soil fertility and hence of productivity. A range of agricultural practices are available that allow to increase SOC stocks while ensuring a resilient, productive and environmentally friendly agriculture, so that a large-scale deployment can be aimed at. Here, we review and discuss the main limits and criticisms addressed to the 4 per 1000 initiative

Block LU Factors of Generalized Companion Matrix Pencils

We present formulas for computations involving companion matrix pencils as may arise in considering polynomial eigenvalue problems. In particular, we provide explicit companion matrix pencils for matrix polynomials expressed in a variety of polynomial bases including monomial, orthogonal, Newton, Lagrange, and Bernstein/Bézier bases. Additionally, we give a pair of explicit LU factors associated with each pencil and a prescription for block pivoting when required

Studies from global regions indicate promising avenues for maintaining and increasing soil organic carbon stocks: The Scientific and Technical Committee of the 4 per 1000 initiative

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