Single Application of Biochar Increases Fertilizer Efficiency, C Sequestration, and pH over the Long-Term in Sandy Soils of Senegal

High erosion rates, limited fertilizer or nutrient inputs, and soil acidification directly impact soil biodiversity. Continuous mono-cropping systems and the removal of crop residues exacerbate soil degradation. Crop production in the SPB is primarily rain-fed, with recurrent drought stress and limited soil water holding capacity due to low SOM. This results in lower crop productivity, ultimately leading to food insecurity and lack of resilience. Major food grain crop productivity has stagnated over the years due to poor soil fertility. Regenerative agricultural practices and technologies are needed to lift smallholder farmers out of poverty. Pearl millet and peanut are the major cereal and legume crops for food security in Senegal, particularly in the SPB. Millet production has stagnated at around 0.8 t ha−1, while cropping system diversity has reduced to primarily millet monocropping or millet-peanut rotation. Continuous crop cultivation without sufficient organic inputs has led to soil degradation, often to levels where soils are "non-responsive to inorganic fertilizers" with low use efficiency of applied nutrients. The combinations of organic materials with inorganic fertilizers have been shown to have a synergistic effect on marginal cropland. Similarly, combinations of inorganic fertilizers and organic inputs have been shown to replenish soil nitrogen and phosphorus nutrient stocks in Africa and restore soil properties to original levels. Rotation of a cereal with a nitrogen-fixing legume contributes to the soil nutrient pool, but with significant removal of these leguminous residues, the overall N contribution is likely minimal. Inorganic fertilizers are rarely applied to millet due to socioeconomic constraints such as limited economic return, high prices, limited availability, low quality control, and low market price for millet. There is a need to find alternative sources of organic materials or carbon amendments or increase the efficiency of applied nutrients. Biochar has shown advantageous traits, including improving soil properties, increasing nutrient availability, and yield performance. Biochar applications in soils have received attention as a possible means of improving productivity and sustainability of farming systems. Past studies have shown that biochar amendments improve soil properties and increase nutrient availability and yield performance. Biochar use is effective in tropical regions. A study in Zambia showed that 4 tons ha−1 biochar in combination with conservation farming strongly increased maize yield and improved physical and chemical soil characteristics in sandy, acidic soils. A study in Ghana observed that 20 t ha−1 biochar amendment with wastewater irrigation reduced microbial stress and facilitated more efficient use of nutrients in the highly weathered soil.