Soils support life. And without soils, many of the world’s living organisms will find it difficult to survive and thrive. Besides forests and grasslands, this includes economically important plants like rice, which feeds more than half of the world’s population.
Soils also allow plants like rice to grow upright and turn towards the sun. They also provide needed nutrients to ensure enough yields, and store and supply water to plants. It is estimated that 99% of the food and fiber we produce grows on soils and only 10-12% of the earth's surface is covered by soils available for agriculture. Soils also provide many more essential services for humans. They help filter water; they immobilize many toxic substances, they mineralize crop residues and store carbon, as well as exchange gases with the atmosphere.
Soil is made up of air, water, mineral particles, organic matter, and organisms. About half of it is pore space that can be filled equally with water and air while most of the solid portion is made of mineral particles. Even though organic matter usually makes up about 2% of a top soil’s weight, it binds soil particles together, stores nutrients, and feeds soil organisms. Organic matter is created by tiny, living organisms that decompose dead plants and animals, creating nutrients that plants can use.
Although these nutrients already come from the soil, some plants like rice may still need supplemental nutrients (those added to the soil with fertilizers) especially when higher yields are required for a growing population. IRRI works on four areas that encompass soil and rice, including managing of nutrients.