By: Fred Hulme, Ph.D., Published in GrowerTalks, November 2009
During these tough economic times, many growers are trying to sustain their businesses by rethinking growing practices and lowering production costs. The costs of many unavoidable expenses including fuel, containers, transportation, growing media and fertilizer have either widely fluctuated or soared over the last year. Although fertilizers may only represent less than 5% of the total direct cost of producing a plant, a growing operation’s annual fertilizer bill can add up to a significant sum. So, what’s a reasonable strategy for reducing your fertilizer costs? And perhaps more importantly, what are the possible ramifications that can develop when you change your fertilizer practices?
Focus on the goal
Your fertilizer applications should provide the correct amounts and ratios of all essential nutrients at the right time to meet crop plant requirements. Any practice that doesn’t achieve this basic goal will result in lower plant quality and, most likely, reduced revenues. Conversely, any practice that exceeds this goal can be wasteful or even potentially harmful.
The key is balancing fertilizer use with plant needs, which involves regular program assessment and an emphasis on best management practices. After all, you can use the best fertilizer in the world, but if it’s not being used wisely or correctly, crop quality and your bottom line will suffer.
You can ask yourself the following questions to help develop an accurate and objective assessment of your fertilizer programs – and discover any inefficiencies or gaps along the way:
- Is the fertilizer program well-adapted to the growing system when considering crop needs and accounting for any supplemental nutrients or other elements provided by irrigation water and growing media?
- Are excessive amounts of nutrients being lost through leaching, nutrients draw-down or poor root zone pH?
- Are the mixing and application of fertilizers being carefully monitored?
- Are tests being performed to make sure the current program is living up to expectations?
- As Production practices change (e.g. bringing in more pre-finished plants or reducing growing temperatures), are feeding practices being modified as well?
- Is fertilizer being lose when pots are inadvertently tipped over?
- Is fertilizer an important element of your plants’ post-production phase to improve survivability and quality at the garden center?
After honestly answering these questions, the next step is to consider what changes to management practices could reduce the cost of your fertilizer program while still producing good results.
Ways to Lower Overall Fertilizer Expense
The following options involve possible benefits and risks to any grower seeking to lower fertilizer expenses. Some options will only work under certain circumstances, so it’s important that you consider your unique situations before implementing any of these options in your fertilizer programs.
Option 1: Go Cheap. Cost per bag is an easy metric to compare. You can obviously cut down on fertilizer costs by purchasing a product with a lower cost per pound while using the same number of pounds. However, you must understand how these less expensive products are made and how they may perform.
Upon first glance, switching to less expensive products may seem to be an easy choice. Yet, if these lower-grade fertilizers are made with poor-quality raw materials or offer inconsistent and unpredictable results, crop performance may suffer significantly. In other words, as the old saying goes, “penny wise and pound foolish.” When used at all, this strategy probably makes most sense for use on lower-value crops in the short term.
Option 2: Change formulations in order to use less fertilizer. Instead of only considering a fertilizer’s cost per bag, it’s better to compare the unit cost per crop when using different products. One strategy currently popular with growers is to choose products containing a higher percentage of nitrogen (N). Since water soluble fertilizers (WSF) are applied in concentration units of parts per million (ppm) of nitrogen, growers will need less product per gallon when they start with a formulation that contains a higher percentage of nitrogen.
For example, if a grower needs to make a concentration of 200 ppm of nitrogen, that grower would only use about 75% as much fertilizer per unit volume when using a 20-10-20 formulation as compared to 15-5-25 formulation. If the cost per bag of each formulation is the same, using the 20-10-20 would result in significant cost savings. Changing to a fertilizer with a higher percentage of nitrogen also makes most sense for use on lower-value crops in the short term.
If changing formulations was that simple, this would be an easy decision. But beyond nitrogen, other nutrients are also important. It’s possible to equalize nitrogen, but switching formulations might easily lead to a shortfall of another nutrient. Many commercial fertilizer formulations contain specific nutrient ratios for specific reasons. Products containing a higher percentage of nitrogen will likely have a lower percentage of some other nutrient. Before making a change, study product labels carefully.
As shown in Table 1 and 2, the grower would apply significantly more potassium and magnesium when implementing the 15-5-25 treatment. Depending on the specific growing system in question, the extra potassium and magnesium in 15-5-25 could have a huge advantage on the growth and quality of a crop. Additionally, higher nitrogen formulations could contain higher levels of ammoniacal or urea nitrogen that are more acidic in nature and could injure crops under certain conditions.
Option 3: Use less of your current fertilizer. Some growers are successfully choosing to use the same fertilizer product while cutting their rates and concentrations dramatically. Doing this correctly can save money without negatively impacting crop quality. Current fertilizer programs may be providing more than adequate nutrition, so any extra is being wasted (a situation known as “luxury consumption”) or leaching out of the root zone. Chosen fertilizer rates should be adequate for a crop’s needs and no more.
Fertilizer label instructions are generic guides for a variety of possible scenarios. What works best in each unique situation may differ. For example, a medium label rate might be insufficient, wasteful or harmful in a particular growing situation depending on many factors such as environmental conditions, growing media types, crops, irrigation frequency and leaching fractions. To fine-tune label rates, conduct in-house research to see if rates can be reduced without also lowering crop quality.
Reducing fertilizer rates may limit some nutrients such as micronutrients. One possible compromise is to reduce N-P-K, but supplement with micronutrients. This can be a cost-effective way to maintain crop quality. With lower fertilizer rates, nutritional programs will offer less flexibility, making it critical for you to proactively monitor crops to detect incipient nutrition problems before they are expressed as deficiencies.
Option 4: Consider Controlled-Release Fertilizer (CRF). Some industry professionals have suggested migrating away from CRFs to WSFs as a way to save money. However, a simple cost analysis demonstrates otherwise. While CRFs certainly are more expensive per pound compared to WSFs, they work more efficiently, can be applied at lower doses per pot and can result in less leaching of nutrients. For example, a CRF rate of 6 lb. per cu. yd. costs less than a constant liquid feed program of 20-10-20 at 200 ppm (assuming 12 fl. oz. per watering, six applications of WSF per week for eight weeks). See Table 2.
CRFs can easily be incorporated into the growing media before planting so the fertilizer is in close proximity to the roots where it is needed. Nutrient release from CRF is temperature-based, as is plant growth, so its use can be tied to plant demand. Plus, CRFs that are fully coated are not subject to huge nutrient losses caused by leaching. CRFs feed continuously as crops are watered, so root zones have a more uniform nutritional supply.
CRF rates for greenhouse use should be conservative, especially for fine-textured, peat-based growing media that are less susceptible to leaching. CRFs are much easier to adapt for crop types as compared to WSF, and their rates can be increased for heavy feeders without having to zone plants nutritionally. Additionally, the selection of longer-term CRFs can provide valuable post-production feeding both in the garden center and at the consumer’s home, leading to better plant quality and customer satisfaction throughout the supply chain. CRFs work exceptionally well in combination with WSF, making combination feed programs an option worth investigating. However, media containing CRF needs to be used quickly after blending – preferably within two to four weeks – to avoid soluble salt buildup in the soil.
Fertilizers may be more expensive these days, but they can provide excellent value if used correctly. When trying to cut fertilizer expenses, consider not only the per-bag cost of fertilizers, but also the costs of application, waste and monitoring. A focus on per-bag cost alone can be deceiving. Only an analysis of both the cost-in-use and the resultant quality from a variety of fertilizer treatments will determine their true value.
This article was first published in November, 2009 in GrowerTalks magazine.