Frequently Asked Questions

There are so many water-soluble fertilizers. Which one is best for me?

Peters water soluble fertilizers from Scotts are designed to fit a broad range of different irrigation water types, crop types, growing systems and special uses. The easiest way to determine which formulation is best for your operation is to use the patent-pending Peters® A-B-C Selection System™. Simply enter your water type and select the crop, and you’ll receive a short list of recommendations.

The system starts with water quality, because water is the single most important factor in how well a fertilizer will perform in terms of solubility and nutrient uptake. If you don’t know your water type, the on-line Peters A-B-C Selection System offers a Water Type Approximator™, based on based on decades of research. Of course, the best way to determine your water type is testing all irrigation water sources at your greenhouse or nursery. The Scotts Testing Lab will assess the alkalinity, background nutrient content and other potentially problematic elements in the water source. With this information, Scotts’ expert professional field force can help you fit the best nutritional program to your operation. See our list of Territory Managers for additional assistance.

I have heard that Peters Excel® water-soluble fertilizer can reduce or eliminate the need to add mineral acid to my irrigation water. Please explain?

Peters Excel Fertilizers are patented and contain a unique component called urea phosphate. Urea phosphate forms phosphoric acid in solution that acidifies the stock tank allowing nutrient components such as calcium, phosphorus, magnesium and sulfates to remain soluble in the tank. If you are currently adding acid to reduce bicarbonates in your irrigation water, some Excel formulations (21-5-20 All Purpose, 20-5-19 Poinsettia and 15-5-15 Cal-Mag) can reduce or eliminate this need. As a rule of thumb, consider that every 100 ppm N of these formulations will neutralize approximately 16 ppm excess alkalinity.

How often should I feed with Peters® fertilizers and when should I provide a clear watering?

The Scotts Company recommends that growers select the correct fertilizer concentration based on the crop grown and apply this each time the plants are irrigated. This practice called continuous liquid feeding, ensures that the nutrient levels in the root zone are more uniform over time. If growers employing this practice are carefully monitoring soluble salts and pH levels in the growing media, there should seldom be a need to apply a clear water irrigation. While this practice can help mitigate a problematic high salts condition, generally it will result in washing out valuable nutrients from the root zone. This can be both wasteful and impactful on the environment.

Some growers choose to feed less frequently and therefore need to feed at higher concentrations to adequately feed the crop. While many growers manage to make this practice work, it can lead to “feast or famine” conditions over time. Soluble salts levels will be higher just after the fertilizer treatment, but will dramatically decline as plants take up nutrients and clear water leaches the growing media.

How much Peters® fertilizer should I use?

The correct fertilizer concentration for a particular operation will depend on a number of factors including: feeding frequency, crop type, crop stage, growing media, pot size, leaching fraction and environmental conditions. Generally fertilizer should be applied at concentrations necessary to sustain optimal root zone nutrient levels and quality plant growth. See the table below for The Scotts Company’s general recommendations for crop types. Consult your local Scotts’ expert for more details.

How do I mix up a small volume of fertilizer?

Our product labels contain mixing instructions for growers using concentrated stock solutions, specific injector ratios and target fertilizer concentrations expressed in parts per million of Nitrogen (ppm N). Often a grower only wants to make up a small volume of fertilizer solution in a watering can. While fertilizer should be added on a weight per volume basis to obtain precise concentrations, mixing small volumes of fertilizer to small volumes of water will suffice to get approximate target concentrations. For example: 1 level teaspoon of Peters® 20-20-20 General Purpose fertilizer added to 1 gallon of water will result in an approximate concentration of 240 ppm N. This would be an acceptable concentration for feeding flowering pot crops on a continuous liquid feed basis. If feeding less frequently, add 2 teaspoon of 20-20-20 per gallon. To obtain small volume recipes for other Scotts water soluble products, download the brochure on the Scotts fertilizer web page.

How much Peters® fertilizer should I use on flowerbeds or in the landscape?

Water-soluble fertilizer applications to landscapes can provide a quick boost of nutrients and significantly green up landscape crops. Peters 20-20-20 General Purpose is the formula recommended for this purpose. The trick to get good results is not to go overboard in concentration and to provide adequate volume to an area. It is best to apply fertilizer when the soil is moist and plants are not under stress like in the heat of the day.

For large jobs: apply no more than 5 lbs of 20-20-20 per 1,000 sq. feet of area per application. For maintenance this application can be repeated 2 to 3 times per growing season. If more water is mixed with the 20-20-20, this will ensure a more uniform and effective application. Dilute no more than 1 lb of 20-20-20 per 5 gallons of water for low volume applications.

For smaller jobs: generally flower beds or other ornamental plants will be safe with concentrations up to 3 pounds/100 gallons (711 ppm N) or 1 tablespoon per gallon (720 ppm N). To get adequate feeding, apply 1/4 to 1/2 gallon of fertilizer solution per 1 sq. ft of area. This treatment can be repeated as needed every 10 to 14 days.

If you have more specific questions, contact your nearest Scotts Territory Manager.