Using Whey in Your Garden

It’s summer and some of us don’t do much cooking this time of year. But, we’re making cheese while the milk is flowing and, as always, we have a lot of whey.

We can strain it and it will keep for months in the fridge. Or, we can freeze it, up to the limit to how much we can fit in our freezers.

Of course, whey is useful in a hundred ways, but, in this post, we are exploring it’s role in gardening. We’re assuming that you are a home cheese maker and not a commercial business, although many farmers buy whey from cheese businesses in order to use it in their fields. (Example – click here)

Salt

We use unsalted whey because salt is not useful in the garden. Fortunately, most of the time, when we make cheese, we salt the curds after we drain off the whey, so this is usually not an issue.

Acid whey vs sweet whey

We need to bear in mind that there is a difference between acid whey and sweet whey: Sweet whey comes from cheese we make with rennet. Acid whey is a byproduct when we make dairy products that don’t involve the use of rennet – yogurt, buttermilk, kefir, etc. (There is sub-category of acid whey called “cooked whey” which is the whey leftover from making panir, queso fresco and ricotta. It has less protein and less vitamins and minerals than the other wheys but it can still be used in the garden.)

Acid whey is more acidic than sweet whey. This is because some of the lactose in it has been converted to lactic acid. Sweet whey has a pH greater than or equal to 5.6, whereas acid whey has a pH less than or equal to 5.1 (from Wikipedia). Another difference is that acid whey has slightly more vitamins and minerals in it than sweet whey.

Many articles erroneously recommend using only sweet whey in gardening and not acid whey. That is based on the idea that you might go out and throw a gallon of acid whey onto your tomato plant with no regard for the acid content. That would not be good for your plants. In fact, some people pour acid whey on their weeds to kill them! (We’re assuming here that you understand the difference between the two kinds of whey and that you will follow the directions below when using it.)

Both kinds of whey can damage the environment when large quantities of it are dumped into bodies of water because changing the pH of the water effects the fish, etc.

Changing the pH of the soil

For those of you who don’t generally consider this aspect of gardening, the pH of the soil is the level of acidity. The lower the pH, the more acidic the soil is and the higher the pH, the more alkaline it is.

This is important because plants can’t get the nutrients they need from the soil unless the soil has the right amount of acidity. Different plants prefer different levels, so, soil that is good for one type of plant, is not good for another. There are many good charts online showing optimal pH ranges for plants; here’s one from the Farmer’s Almanac – click here.

How do you know the pH of your soil? Most universities have soil testing labs and you can send samples to them for a small fee. The information you receive is absolutely invaluable. Or, if you already have the type of pH meter we sell (click here) to use when making cheese, you can use the same pH meter to test your garden’s soil.

If you don’t know the pH of your soil, you don’t really know whether whey will be good for it. Odds are it will be for the acid-loving plants, but if your soil is already very acidic (5 – 5.5), whey would not be a good choice.

Generally speaking, it’s a fool’s errand to try to change the acidity of your soil; it’s preferable to simply plant the right plants in the right place. However, that isn’t always possible (because we just have to have that gorgeous hydrangea in our alkaline soil). So, most of us make amendments of one kind or another.

We use various products for this – whey, vinegar, sphagnum peat, sulfur or any acidifying fertilizer. In any case, it is not wise to change the pH too rapidly.

Fertilizing value

As stated, you would usually use whey on your acid-loving plants to change the pH. However, whey has some value as a fertilizer in itself.

It actually has small quantities of nitrogen, phosphorus and potassium (as well as calcium and magnesium). The N-P-K ratio is typically 0.15-0.05-0.17. (Acid whey has less protein than sweet whey, but it still contains many of the same vitamins and minerals in sweet whey.)

This is low enough for you to use it regularly without fear of over-fertilizing.

Directions for use:

Strain your whey in cheesecloth or butter muslin so there are not big pieces of curd floating in it.

Dilute it before adding it to your soil. This is an inexact science, but we suggest you dilute it in the same amount of water to start, so you have a 50:50 split.

Pour it around the base of your plants and not on the plants themselves.

Try not to give your plants a total of more than 1″ of diluted whey per week. (You will need a rain gauge for this.) A common recommendation is to use 1 gallon of diluted whey per 10 square feet of garden space every seven to 14 days.*

Controlling powdery mildew

Some folks spray whey onto their plants to prevent the spread of fungal diseases like powdery mildew.

Directions: Strain your whey, dilute it (50 parts water:50 parts sweet whey or 70 parts water:30 parts acid whey) and spray it on your plants bi-weekly. You can also use it as a deterrent in advance if you feel that your plants are highly susceptible to powdery mildew.

Adding to your compost

Whey is a great supplement to your compost because the carbon:nitrogen ratio averages 20:1. (UMN.edu)

Strain it and, after you add it to your compost, turn the pile so the whey doesn’t heat it up too much.

If you are worm composting, add only a few diluted tablespoons per week – the worms don’t like too much acidity.

Any other ideas?

If you are using whey in your garden, we would love to hear from you. Either make a comment here or send stories and pics to info@cheesemaking.com.

*This is from Hunker: An all-purpose fertilizer with an N-P-K ratio of 24-8-16 is diluted at a rate of 1 tablespoon per 1 gallon of water. This supplies 0.1 ounces of nitrogen, 0.03 ounces of phosphorus and 0.06 ounces of potassium per application. To apply the same amount of nitrogen using whey, mix the whey half-and-half with water. This will supply 0.1 ounces of nitrogen, 0.04 ounces of phosphorus and 0.12 ounces of potassium per gallon. Use the mixture in place of regular fertilizer every other time you fertilize. Use 1 gallon of diluted fertilizer or whey per 10 square feet of garden space every seven to 14 days.