Fertilizer - Between Green Grass and Clear Water?

The terms “organic” and “natural” can be confusing, and they don’t always correspond to “sustainable.” In terms of lawn care and nutrient pollution, organic fertilizer has a specific definition with clear benefits.

Plants need a combination of roughly 13 different nutrients to thrive: nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, iron, zinc, manganese, copper, boron, molybdenum, and chlorine. In agriculture and lawn care, we focus on the big 3—nitrogen (N), phosphorus (P), and potassium (K)—because adding them has the greatest impact for increasing plant growth, as they play vital roles in growth, respiration, photosynthesis, and resistance.

In the wild, each of these nutrients has its own cycle, where they’re stored in rocks, air, or water, absorbed from soil by plants, and released back into the environment when these plants die and are decomposed by bacteria. But, this process is slow: limited by nutrients, commercial crops and residential grasses couldn’t keep up with our growth needs.

So, chemists created synthetic fertilizers, with high, standardized concentrations of these nutrients. They harnessed nitrogen from the air, hydrogen from natural gas, and phosphorus and potassium from ore, combining them in known quantities. With this standardization, fertilizers are marked with N-P-K values, signifying the percent by weight of each nutrient. Because these fertilizers are cheap, convenient, and have an instant, measurable impact on growth, they make up a majority of the fertilizer market.

Synthetic fertilizers have some issues though: First, they’re energy and resource intensive to produce, which is itself unsustainable. And when applied, synthetic fertilizers allow all their nutrients to be instantly available. Since plants can’t absorb and use all these nutrients at once, they “burn” grasses or are left vulnerable to be picked up by water, leaching through soil into groundwater or flowing as runoff into storm drains and waterways, unfiltered. The nutrients fuel an overgrowth of aquatic plants and algae, blocking off sunlight and producing toxins while they’re alive and depleting oxygen from water when they die and are decomposed by bacteria in a process that uses oxygen. Toxic and hypoxic water can kill aquatic life, birds, and surrounding plants. 

Organic fertilizers are a solution. They’re made of organic matter—like manure and dead plant matter—and slowly decomposed by microorganisms in a process that frees up their nutrients. Plants get the nutrients they need at a gradual pace, reducing the risk of burning, leaching, and polluting stormwater runoff. 

Upfront, organic and slow-release fertilizers are more expensive, but they can save money over time with a few advantages:

  1. Fewer applications – Since organic and slow-release fertilizers release their nutrients gradually, they only need to be applied a few times per year: less labor
  2. No growth spike – applying synthetic fertilizers to grass fuels explosive growth in the initial period because of the instantly-available nutrients: this means extra mowing and maintenance efforts. Gradual release solves this problem.
  3. Water retention – organic matter holds water, reducing irrigation use and costs: 1 1% increase in soil organic matter can hold an extra 20,000 gallons of water per acre of land. This is especially helpful during droughts, where we limit our irrigation use.
  4. pH buffering – by acting as a buffer, organic matter reduces the risk of soil acidification, protecting plants
  5. No burn – With gradual release, the margin for overfertilizing, thus hurting your plants, is more forgiving.

Organic fertilizers are readily available at home improvement stores. They’re sustainable, while saving time and money in the long run⁠—a reasonable deal…

References

Li, Jiajia, et al. “Association between Maternal Exposure to Chemical Fertilizer and the Risk of Birth Defects in a Rural Population in Northern China: A Population-based Study.” International Health, 6 May 2022, https://doi.org/10.1093/inthealth/ihac027.

Lines-Kelly, Rebecca. “Plant Nutrients in the Soil.” Wollongbar Agricultural Institute, Oct. 1992, www.dpi.nsw.gov.au/agriculture/soils/soil-testing-and-analysis/plant-nutrients. Accessed 15 Aug. 2022.

National Oceanic and Atmospheric Administration. “What Is Nutrient Pollution?” National Ocean Service, 26 Feb. 2021, oceanservice.noaa.gov/facts/nutpollution.html. Accessed 11 Aug. 2022.

Sullivan. “Drought Resistant Soil. Agronomy Technical Note. Appropriate Technology Transfer for Rural Areas.” National Center for Appropriate Technologies, 2002. Accessed 11 Aug. 2022.

Uchida, R. “Essential Nutrients for Plant Growth: Nutrient Functions and Deficiency Symptoms.” Plant Nutrient Management in Hawaii’s Soils, Approaches for Tropical and Subtropical Agriculture, 2000, www.ctahr.hawaii.edu/oc/freepubs/pdf/pnm3.pdf. Accessed 15 Aug. 2022.

United States Environmental Protection Agency. “Nutrient Pollution.” EPA, www.epa.gov/nutrientpollution. Accessed 11 Aug. 2022.