Last year was designated the International Year of Soil by the Food and Agriculture Organization (FAO) to shine a light on the importance of soil quality in improving food security and resilience to floods and droughts. The educational outreach and events that made up the Year of Soil also aimed to educate that globally soil degradation is happening.
According to the FAO, studies show that about 33% of the world’s soils are facing moderate to severe degradation. Some studies indicate half of the topsoil on Earth has been lost in the past 150 years. The current rate of soil degradation threatens the capacity to meet the needs of future generations. Soil degradation comes in various forms, including erosion, salinization, nutrient depletion, loss of biodiversity, pollution, compaction, and loss of organic matter. Any one of these factors directly impacts the productivity of crops being grown on a particular piece of land.
In the U.S., modern agriculture has maintained the productivity of crops compared to other places in the world where newer technology and practices are not available. But, even here growers are realizing a more balanced approach and paying attention to soil health is important to the sustainability of agricultural lands.
Getting It Right
The use of fertilizers has helped keep yields up in Florida fields. But, there can be too much of a good thing. Overuse of fertilizer leads to soil and water contamination and a reduction in microbial activity.
The fertilizer industry and agricultural associations have done a good job promoting the 4Rs Nutrient Stewardship program to promote the correct application of nutrients. The four Rs include: The Right source (match fertilizer type to crop needs); Right rate (match the amount of fertilizer to crop needs); Right time (make nutrients available when crops need them); Right place (keep nutrients where the plants can use them).
The 4Rs program provides detailed training modules on how to implement the program on farms on its website. The experts who developed 4Rs note the program is not a single set of practices and reminds growers careful nutrient management must be accompanied by a package of other production and conservation techniques to be successful.
Fertilizer can increase yields as well as increase the nutrient density of crops. But, other factors can influence yield and quality. According to the International Plant Nutrition Institute (IPNI), the same can be said of the health of soils. Soil health depends on maintaining nutrient reserves as well as practicing soil conservation practices.
IPNI notes overemphasis on nutrient-use efficiency can lead to nutrient-depleted soils and lost productivity. Too much emphasis on productivity can lead to poor nutrient-use efficiency. The organization suggests following the 4Rs guidelines allows growers to balance the needs of nutrient-use efficiency and productivity.
A World Of Biodiversity
Soil is more than just a static substance that holds the roots of plants in place. Well-managed soils are teaming with life and activity. There are billions of microorganisms such as bacteria, fungi, and protozoans in the soil, as well as thousands of insects, mites, and worms. According to the FAO, 25% of the planet’s biodiversity is found in soils.
Many of these microorganisms have beneficial effects to plant health. Mycorrhizae fungi have long been associated with plant health. Dr. Jim Graham, a Professor of Soil Microbiology for UF/IFAS, has studied mycorrhizae in citrus. Graham published research on the benefits and interactions with pathogens of citrus mycorrhizae in the journal HortScience.
In the publication, Graham noted that mycorrhizae are the “normal” condition of roots on citrus trees and most other horticultural plants. However, he adds many “normal” horticultural practices such as the use of fertilizers and pesticides, soil sterilization, and plant production in sterile soilless media can reduce soil microorganisms. These technical advances have led to the rapid production of pathogen-free plants, but mycorrhizae have been sacrificed in the process. This may be especially true in citrus production today given all the actions take to fight HLB.
Graham goes on to note that growers should consider how to reintroduce mycorrhizae into soils given the demonstrated benefits.
The are a number of industry suppliers of soil supplements that contain mycorrhizae and other beneficial soil microorganisms. Florida-based companies include Pathway BioLogic; EcoMyc; Quantum Growth; Life Soils; and BioWash.
“Growers are realizing benefits of incorporating biological-based solutions within their management practices,” says Mike Gans, director of operations with Pathway BioLogic. “Pathway’s proven biological fertility solutions increase nutrient uptake and utilization, improving plant performance, ultimately impacting crop yields. This will help us take another step toward our collective goal of feeding the growing world population.”
Why Are Soils Important?
- Soils are a key enabling resource for human well-being, central to the creation of a host of products and essential ecosystem services.
- Soils are the basis for the production of food, fibers, fuel, and medicinal products.
- Soils absorb, store, alter, purify, and release water, both for plant growth and water supply.
- Soils interact with the atmosphere through absorption and emission of gases (e.g., carbon dioxide, methane, water vapor) and dust.
- Soils make up the greatest pool of terrestrial organic carbon (more than double the organic carbon stored in vegetation).
- Soils regulate carbon, oxygen, and plant nutrient cycles (N, P, K, Ca, Mg, etc.).
- Soil is the habitat of numerous animals and organisms such as bacteria and fungi and thus sustain biological activity, diversity, and productivity.
- Soil is the habitat for seed dispersion and dissemination of the gene pool.
- Soils buffer, filter, and moderate the hydrological cycle.