Soil health key to food security, biodiversity

Throughout history, humans have worked the fields, and land degradation has occurred. Many civilizations have collapsed from unsustainable land use, including the cultures of the Fertile Crescent in the Middle East, where the agricultural revolution first occurred about 10,000 years ago. The United Nations estimates that 2.5 billion acres have suffered erosion since 1945 and that 38% of global cropland has become seriously degraded since then. In the past, humankind survived because people developed new lands.

But a few decades ago the total amount of agricultural land actually began to decline as new land could no longer compensate for the loss of old land. The exhaustive use of land is combined with increasing populations; greater consumption of animal products produced in large-scale facilities, which creates less efficient use of crop nutrients; expanding acreages for biofuel crops; and the spread of urban areas, suburban and commercial development, and highways onto agricultural lands.

Despite the high productivity per acre and per person, many farmers, agricultural scientists, and extension specialists see severe problems associated with our intensive agricultural production systems.With conventional agricultural practices heavily dependent on fossil fuels, the increase in the price of energy—as well as the diversion of crops to produce ethanol and biodiesel and other trends—will cause food prices to be higher in the future, resulting in a worldwide upsurge in hunger.Too much nitrogen fertilizer or animal manure sometimes causes high nitrate concentrations in groundwater. These concentrations can become high enough to pose a human health hazard. Many of the biologically rich estuaries and the parts of seas near river inflows around the world, including the Gulf of Mexico, are hypoxic (have low oxygen levels) during late summer months due to nitrogen enrichment from agricultural sources.

Phosphate and nitrate in runoff and drainage water enter water bodies and degrade their quality by stimulating algae growth.

Antibiotics used to fight diseases in farm animals can enter the food chain and may be found in the meat we eat. Perhaps even more important, their overuse on farms where large numbers of animals are crowded together has resulted in outbreaks of human illness from strains of disease-causing bacteria that have become resistant to many antibiotics.

Erosion associated with conventional tillage and lack of good rotations degrades our precious soil and, at the same time, causes the silting up of reservoirs, ponds, and lakes.

Soil compaction reduces water infiltration and increases runoff, thereby increasing flooding, while at the same time making soils more drought prone.

In some parts of the country groundwater is being used for agriculture faster than nature can replenish this invaluable resource. In addition, water is increasingly diverted for urban growth in dry regions of the country, lessening the amount available for irrigated agriculture.

With the new emphasis on sustainable agriculture comes a reawakening of interest in soil health. Early scientists, farmers, and gardeners were well aware of the importance of soil quality and organic matter to the productivity of soil. The significance of soil organic matter, including living organisms in the soil, was understood by scientists at least as far back as the 17th century. John Evelyn, noted that their fertility could be maintained by adding organic residues. Charles Darwin, the great natural scientist of the 19th century who developed the modern theory of evolution, studied and wrote about the importance of earthworms to the cycling of nutrients and the general fertility of the soil.

It should come as no surprise that many cultures have considered soil central to their lives. After all, people were aware that the food they ate grew from the soil. Our ancestors who first practiced agriculture must have been amazed to see life reborn each year when seeds placed in the ground germinated and then grew to maturity.

Although we focus on the critical role soils play in growing crops, it's important to keep in mind that soils also serve other important purposes. Soils govern whether rainfall runs off the field or enters the soil and eventually helps recharge underground aquifers. When a soil is denuded of vegetation and starts to degrade, excessive runoff and flooding are more common. Soils also absorb, release, and transform many different chemical compounds.

Soils also provide habitats for a diverse group of organisms, many of which are very important such as those bacteria that produce antibiotics. Soil organic matter stores a huge amount of atmospheric carbon. Carbon, in the form of carbon dioxide, is a greenhouse gas associated with global warming. So, by increasing soil organic matter, more carbon can be stored in soils, reducing the global warming potential.

(Write is President of Praja Science Vedika and Dean, TKR Engineering College, Meerpet, Hyderabad)