Wondering what to do with the raked leaves? Turn it into composted leaf litter or leaves, and read on to see how one small farm put this natural plant food to the test.
At Peach Ridge Farms in Grand Rapids, Michigan, we know, “If the soil isn’t happy, no one is happy!”
Since 2002, we have used proven methods of environmental stewardship. We use low-cost, manageable practices, working with the soil to make it better every year. We have seen how the plants like it. This year, our kohlrabi was ahead and already the size of cabbage! We also noticed how giant garlic grown with our secret ingredient is compared to the same garlic grown without it. This is proof that soil management matters.
Our secret is to add leaf material (defined here as twigs and chopped leaves) or “leaf litter” in the fall. Some people wonder what to do with raked leaves in the fall. We let it sit over winter, then plow it into the ground in early spring as a free natural fertilizer for the plants. Hush! Don’t tell anyone, okay? Last year we added over 174,000 books. In many areas he was 4 feet tall! Needless to say, these leaves weren’t all from our backyard. The truck delivering these sheets was so loaded that it got stuck entering the wet field. We had to use a tractor and chain to get it for free.
What if the benefits of composted leaves were just speculation? Maybe we were trying to fit the facts to our assumption that we were onto something with our durability. After all, every aspect of farming is affected by a plethora of causes. We decided to subject the fertilizers to a scientific test.
On your marks, get set, test!
First, we needed money for this experiment. We applied for and received a USDA-NIFA North Central SARE Region grant through the University of Minnesota to purchase seeds, garden hoses, greenhouse gas, and other necessary supplies . As part of our preparations for the experiment, we did a study of the scientific literature. We found two academic papers on the use of leaf material, but none on its effect on basil. Like most academic papers, they have fairly long titles; one, for example, reads: “Effect of leaf mold mulch, biochar and earthworms on mycorrhizal colonization and yield of asparagus affected by Fusarium wilt and root rot”!
Our end of the bargain was to keep our Facebook followers up to date with the experience; to distribute flyers to customers of our Community Supported Agriculture (CSA) program and our Farmers Market; and report our findings at the annual Grand Rapids CSA Open House.
Having obtained the money, we were ready to plant. We planned to grow sweet and lemony basil in three different plots in our greenhouse. The first plot would have soil enriched only with leaf matter, while in the second the soil would be enriched with leaf matter and organic duck manure. Finally, the third plot would have soil with leaf matter and organic chemical fertilizer.
For this experience, we had several goals in mind: first, to savor the flavors of our basil plants; second, to increase our basil harvest; third, to help the environment; and finally, to save money. We also wanted the results of this experiment to be applicable to small farmers and home gardeners.
Basil is a delicious herb. Its smell makes it a pleasure to weed, pick and just be there. It is easy to use in dishes like pesto. It tastes better fresh than the dried weed you can get at the store. It also has low disease rates and is very nutritious. To bolster the validity of this experiment, we planted the sweet and lemony basil varieties, so we knew the winner wasn’t just a fluke.
How would we test the winner? We were unable to measure the flavor or health of individual basil plants, so our criteria for the winner would be based on the weight of basil harvested. After all, more basil means the plants have grown well.
Part of receiving the grant involved being a responsible steward of the Earth, a goal that aligned perfectly with our sustainability goal. Using leaves reduces yard waste. In addition to this, we hoped to show that using leaf material to supplement nutrients in the soil eliminates the need to add more unwanted chemicals. If leaf material was a good source of nutrients on its own or in combination with chemical fertilizers or duck manure, we knew our method would be really helpful.
Regarding money, we wanted to provide basil to customers at a reduced price. Most people have it at home, so we wanted to give them an even better deal. Additionally, if experience shows that leaf material is a good source of additional soil nutrients, other farms and individuals could also save the money typically spent on buying fertilizer.
May the best leaf litter fertilizer win
Here are three fertilizer combinations we chose to measure in the experiment.
1 Only the leaves count. This is what we typically use at Peach Ridge Farms. By digging up the topsoil from our fields and putting it in the buckets in the greenhouse, all six test areas had the same soil.
In the future, we plan to test soil enriched with leaf matter against soil that has not been enriched with leaf matter.
2 Organic duck leaves and manure. Most gardeners have heard of the benefits of manure, but is it necessary in addition to leaf matter? We chose duck manure simply because we have ducks. The manure was aged, so there was no danger of pests. Aging is necessary when using manure from some animals. (Read how to safely age your livestock manure.)
3 Leaf matter and organic chemical fertilizer. Commercial farms typically use chemicals, which can have negative side effects, so we avoid them at our sustainable farm. But we were curious if an organic chemical fertilizer was needed. After all, the price of organic chemical fertilizers is considerable, but the chemicals are specifically added to optimize production.
The experiment is in progress
In April 2021 we planted both kinds of basil in seed trays. The soil medium we used to fill the seed trays is useful for plant germination, but contains no nutrients. This allowed us to distribute the basil plants evenly among the three zones without affecting the results, instead of just growing whatever sprouted in that zone.
Finally, it was time to conduct our experiment. We had six plots, each with 25 remaining 2-gallon buckets of ice cream. We filled each bucket with leaves and soil. In the first zone, which only had soil enriched with leaf matter, we added nothing before planting and only water afterwards. In the second zone, 1 pound of duck manure was mixed with 5 gallons of water and applied to the soil for three days before planting. In the third, 3 ounces of organic chemical fertilizer per liter of water was added every other day for three weeks. This overlapped with the time of planting, so it was the only area that was fertilized after planting.
When the basil plants were a week old, we transplanted them from the seed trays into the buckets. We spaced the plants evenly and evenly divided the largest and healthiest seedlings between the six zones to make the experience as consistent as possible. As the basil grew, we weeded it weekly.
Customers who come to our farm are used to harvesting herbs from our greenhouse, so we kept a record of what was taken throughout the growing season. Finally, the day came to measure what was left.
The winners: the best natural fertilizer for plants
So what did we discover? There is still a lot to learn, much of which goes against conventional wisdom. Our results suggest that duck manure could be an incomplete fertilizer for sweet basil. Now I’m curious when to add duck manure to the soil – whether it depends on the plant or how often the manure is applied. This is another option for future study. Additionally, we have learned that some, but not all, crop varieties do better with organic chemical fertilizers. This is yet another future topic as to whether there is an ideal amount of nutrients for plants, after which more nutrients actually prevent optimal growth.
More importantly to us, this experiment shows that leaf matter alone can give plants the nutrients they need. Sweet basil grown only in soil enriched with leaf matter did almost as well as sweet basil grown in soil with leaf matter and an organic chemical fertilizer. Oddly enough, the lemon basil grown in the leaf-enriched soil did the best of all the lemon basils. Our hypothesis was supported. All those years of filling the fields with leaves was a wise decision!
Takeaway meals: what to do with the raked leaves?
It’s easy to reuse yard waste for healthy soil by composting the leaves. They can be discarded in the fall and left to sit all winter. Use a tiller or hoe to chop and mix them into the soil before planting. Your plants will benefit from soil with extra nutrients, while you’ll save money and feel good about helping the earth.
Peach Ridge Farms is a sustainable farm located in Grand Rapids, Michigan. We have restaurant sales, business accounts, charities and schools, classrooms and CSAs.