Soil is always at risk from degradation by erosion, salinity, contamination and other results of mismanagement. Some 17% of the land surface has already been strongly degraded and the affected area is still growing. This eventhough there is a wealth of know-how related to land management, improvement of soil fertility, and protection of soil resources.
At present, soil is a threatened natural resource. Some 17% of the land surface has been strongly degraded. Overexploitation, overgrazing, inappropriate clearing techniques and unsuitable land use practices have resulted in severe nutrient decline, water and wind erosion, compaction and salinization. The resulting decrease in productivity has especially affected marginally suitable lands that was taken into cultivation due to population pressure, or that was not given the opportunity to recuperate for a sufficient long time after prolonged cultivation.
Cultivating the soil always results in a decline of fertility. Part of the nutrients that are taken up by the plants is removed by harvesting. To keep the soil productive, its nutrient levels need to be replenished on a regular basis. Crop residues should be returned to soil to maintain or even increase their organic matter status. A sufficiently high organic matter level is important to increase soil stability, soil water holding capacity and the nutrient holding capacity and supply. However, additional organic and/or inorganic fertilization is inevitable to restore and maintain the optimal productivity of the soil.