Soil is a precious resource that requires special care
By Wilma Trujillo
Soil is fundamental to crop production. Without soil, no food could be produced on a large scale, nor would livestock be fed. Because it is finite and fragile, soil is a precious resource that requires special care from all of us. Many of today's soil and crop management systems are unsustainable. At one extreme, overuse of fertilizer has led to nutrient deposition that threatens environmental sustainability. At the other extreme, the under-use of fertilizer means that soil nutrients exported with crops are not being replenished, leading to soil degradation and declining yields.
How did the current situation arise? The main driver was the rapid increase in world population over the past 100 years, which demanded a fundamental change in soil and crop management in order to meet the food demand. That was achieved thanks partly to the development and massive use of mineral fertilizers, especially nitrogen.
The impact of mineral fertilizers on the environment is a question of management related to how much is applied compared to the amount exported with crops, or the method and timing of applications. In other words, it is efficiency of fertilizer use, especially of nitrogen and phosphorus, which determines if this aspect of soil management is a benefit for crops or a negative for the environment.
Thus, the challenge is to abandon current unsustainable practices and move to farming practices that can provide a sound foundation for sustainable crop production intensification. The new approaches focus on the management of soil health.
The Soil Science Society of America defined soil health as "the capacity of a soil to function within ecosystem boundaries to sustain biological productivity, maintain environmental health, and promote plant and animal health." Healthy soils maintain a diverse community of soil organisms that help to control plant disease, insect and weed pests and form beneficial symbiotic associations with plant roots to recycle essential plant nutrients, improve soil structure for better soil water and nutrient holding capacity, and ultimately improve crop production.
Soil properties that determine soil health include texture, depth, infiltration, bulk density, water-holding capacity, organic matter, pH, electrical conductivity, microbial biomass and respiration. Soil is a living factory of macroscopic and microscopic organisms that need food to eat and place to live. Without these organisms, soil does not function efficiently. These organisms control soil's ability to supply water and nutrients to plants and they ultimately determine how successful ranching and farming operations will be.
Functional interactions of soil biota with both organic and inorganic components, air and water determine a soil's potential to store and release nutrients and water to plants, and to promote and sustain plant growth. To achieve the higher productivity needed to meet current and future food demand, it is essential to ensure nutrient availability in soils and to apply a balanced amount of nutrients from organic sources and from mineral fertilizers, if required.
A combination of ecosystem processes (water cycle, energy flow, nutrient cycle, and community dynamics) and judicious use of mineral fertilizers forms the basis of a sustainable soil health management system that has the capacity to produce higher yields while using fewer external inputs.
For more information on soil health, please contact your local Colorado State University Extension offices or visit us at http://www.ext.colostate.edu.