The first step in planning a successful growing season for your next line of crops and plants is choosing a suitable fertilizer. However, there are many factors to consider when searching for the best fertilizer choice, including:
- Crop needs
- Desired growth
- Nutrient ratios
- Water quality
First focusing on the final point of water quality, a good place to start is determining what is, isn’t, and should be in the water you’re providing for your plants. Annually, growers should conduct a water test to gauge alkalinity and the concentration of other elements in their water supply. Once you’ve determined the contents of your water, you’ll know what type of fertilizer pairs best with it.
Fertilizers can be categorized into one of the following three:
According to Patrick Veazie and Brian E. Whipker of North Carolina University in a recent e-Gro alert, the above category a fertilizer falls into is often dictated “by the ratio of ammoniacal (NH4+) (acidic) or nitrate (NO3-) (basic) nitrogen source,” with every fertilizer blend having “a different amount of potential acidity or basicity.” Therefore, for crop needs, it’s important to choose a fertilizer that balances out the alkalinity levels present in your water supply to prevent pH substrate levels from rising above recommended ranges.
Additionally, as discussed, the factor of desired growth also plays into your choice of fertilizer. For more lush growth, a fertilizer higher in ammoniacal nitrogen is preferred. Meanwhile, a fertilizer with a higher nitrate ratio will produce more compact growth.
Growers should also consider the phosphorous percentage of any given fertilizer and its impact on plant growth regarding nutrient ratios. A fertilizer with a high phosphorous percentage “will produce plants with greater internode length and can reduce anthocyanin (red) color for foliage plants.” Understanding the phosphorous fertilization rate can allow growers to delay or promote plant growth. However, Veazie and Whipker stress that “most substrate blends have limited nutrient holding capacity and P deficiency symptoms can be induced within two or three weeks if a zero P program is used.”
Lastly, pairing a fertilizer with an appropriate substrate is also a vital consideration, especially with more alternative substrate options now available on the market. For example, “peat generally has a pH of 3.0-4.5 while peat alternatives such as coconut coir (5.5-6.5) and wood fiber (5.5-6.5) are much higher.” Therefore, growers using high-pH substrate components should routinely monitor their substrates to prevent pH levels from increasing above the suggested threshold. Additionally, employing the use of an acidic fertilizer to balance out the increase in substrate pH levels is also a viable option.
For more information, details, and tips on the effectiveness of pot and container height regarding water capacity, please read the full e-Gro (Electronic Grower Resources Online) alert “Considerations When Selecting a Water-soluble Fertilizer.” Additional e-Gro alert pieces from Volume 13 (2024) can be found online.
