Acidity More Acidity Soil acidity is a challenge to soil health and limits yields due to low P availability and excess Al availability. It is a particularly issue in humid subtropical and tropical climates with old soils and high rainfall. Erosion More Erosion Soil erosion is a major threat to agricultural productivity and soil health, with 10 million ha of cropland lost each year to this process. Global soil loss is estimated to be occurring at 10 to 40 times the rate of formation. Excessive Water and Poor Drainage More Excessive Water and Poor Drainage Excessive water and poor drainage may reduce yields for many crops due to a lack of oxygen in the water logged root zone. Such anoxic conditions also promote the reduction and gaseous loss of nitrogen, decreasing nitrogen use efficiency and releasing potent greenhouse gases, threatening soil health. Low Available Phosphorus More Low Available Phosphorus Low available phosphorus is responsible for reduced agriculture productivity in many regions globally, hindering soil health, especially in tropical regions with highly weathered soils. Low Organic Matter More Low Organic Matter Organic matter (OM) comprises a small percentage of most soils by volume, however, it plays a crucial role in soil health and ecosystem services because of its interaction with many other soil properties. Soil OM increases the soil’s water holding capacity, cation exchange capacity, fertility, microbial abundance and diversity, and soil structure. Soil OM is the largest pool of terrestrial carbon, containing 77% more carbon than above-ground vegetation, playing a significant role in climate regulation. Nutrient Management More Nutrient Management Nutrient deficiency occurs when an essential nutrient is not available in sufficient quantities to meet the requirements of a growing plant. Healthy soils have a functioning biogeochemical cycle that supplies nutrients in the required amounts for crop growth. Overcoming nutrient limitations in modern agricultural systems is one of the main obstacles to producing quality and yield increases worldwide. Pollution More Pollution Soil pollution occurs when a soil becomes enriched in a contaminant exceeding the naturally existing level or contains a contaminant that poses a threat to living systems and soil health. While many pollutants come from human activity, some are present in soils due to natural processes or local geology. Salinity More Salinity Soil salinization can greatly reduce crop yields and water quality leading to negative effects on human nutrition and livelihoods. Globally, it is estimated that 20% of irrigated land is salt affected. Climate, soil parent material and subsequent rock weathering, groundwater, flooding of land by seawater, land management and equilibrium reactions control sources of salinity. Soil Borne Diseases More Soil Borne Diseases Soil borne diseases are those plant diseases caused by pathogens who inoculate the host by way of the soil (as opposed to the air or water). Unhealthy soils can have issues with high levels of disease incidence and pests. Common soil borne diseases include damping-off, root rot and vascular wilt; and can exhibit symptoms such as tissue discoloration, wilting of foliage, root decay and sudden death. Structural Degradation More Structure Degradation Soil structure refers to the arrangement of mineral and organic soil particles and the spaces between them. Soil structure in a healthy soil allows for both movement and retention of water and nutrients, as well as providing space for root growth. Structural degradation of the soil most commonly refers to compaction, the compression of soil particles so that the space between them is diminished (especially large pores), but can also refer to the lack of cohesion that occurs in sandy soils. Water Scarcity More Water Scarcity Water scarcity is a major global challenge, particularly in arid and semi-arid climates, with half a billion people facing severe water scarcity year round. Unsustainable use of freshwater for agriculture has led to an increase in the risk of food insecurity. Drought frequency and severity, especially in arid and semi-arid locations, is increasing due to climate change, and water will need to be carefully managed before, during and after drought to mitigate its negative impacts and to secure healthy livelihoods.