Global soil nutrient depletion and yield reduction

Nutrient depletion in soils adversely affects soil quality and reduces crop yield and consequently poses a potential threat to global food security and agricultural sustainability. With an emphasis on human-induced nutrient depletion, this paper described the causality among soil nutrient depletion, soil quality, crop production, socio-economic variables, and environmental condition. Then, global soil nutrient budgets of nitrogen (N), phosphorus (P), and potassium (K) were estimated for wheat (Triticum aestivum L.), rice (Oryza sativa), maize (Zea mays L.), and barley (Hordeum vulgare) production for the year 2000. As a result, there were unbalanced fertilization with surplus N in some developing countries and insufficient inputs in many developing and all least developed countries. Globally, soil nutrient deficits were estimated at an average rate (kg ha(-1) yr(-1)) of 18.7 N, 5.1 P, and 38.8 K, covering 59%, 85%, and 90% of harvested area in the year 2000, respectively, and annual total nutrient deficit was 5.5 Tg (1 Tg=10(12) g) N, 2.3 Tg P, and 12.2 Tg K, coupled with a total potential global production loss of 1, 136 Tg yr(-1). Besides socio-economic factors, the soil nutrient depletion can be attributed to insufficient fertilizer use, unbalanced fertilization, and nutrient depletion-induced soil fertility problems. Soil fertility problems associated with human-induced nutrient depletion are widespread worldwide.