Abstract
Deep sands occupy globally over 900 million hectares. In addition, large areas of soils have sandy A horizons overlaying B horizons with significant amounts of clay. The sand content of these soils varies but more importantly variations in the minor clay and organic matter constituents have a major bearing on the edaphic properties of sands. The fundamental limitation of sandy soils is their low reactive surface area. The limited capacity to supply resources, water or nutrients, to the roots of crops is the core reason for the low productivity of crops and pastures on sandy soils. Sands commonly suffer from multiple limitations, including multiple nutrient deficiencies, acidity, dense packing, low water-holding capacity, low fertilizer use efficiency, and water repellence. In addition, leaching of nutrients and agricultural chemicals, acidification, subsoil compaction, and wind erosion are degradation risks of sands. Breakthrough technologies to increase the performance of sands involve permanent increases in the reactive surface area with added clay, recalcitrant organic matter, or both to address the inadequate supply of resources. There is still an incomplete understanding of why and when amendment options on sands will be effective. The opportunity exists to develop cost-effective, novel amendments with high reactive surface area for long-term amelioration of sandy soils.