What to Add to the Field in March

by Sarah Jay, Modern Farmer
March 10, 2026

In March, winter is waning, even if your region has a long, cold season. In southern regions, March signals the end, whereas in the North, there may still be a few months of cold weather. Unless the ground is frozen solid, it’s a good time to include some March amendments. 

If you’re on the edge of winter, use a thermometer to determine whether or not it’s a good time to amend your soil. Wait for a minimum temperature of 40°F (4°C). If temps are still too cold, use the time to source and gather your amendments. 

Much of what you need is likely available on your land, but you might need to get some amendments from external outlets. If you need more than you have on hand, you can use this time to plan how to source from within the farm rather than outside it.

Most of the amendments listed here are useful for any farmland, no matter the dedicated use. Many are available on the farm already and don’t need outsourcing. But it’s likely there’s a farm nearby that has extra on hand. This is where making friends with your neighbors is beneficial. You can always do a search on online marketplace platforms to see if people are giving some of these away.

Compost

Adding compost to the fields is beneficial, no matter what you are growing on your land. This part organic, part abiotic amendment feeds the soil and supports the microbiome. The beneficial fungi, bacteria, and archaea present in compost support an even and consistent exchange, making nutrients easily available to plants. 

The only thing to note is that compost is slightly acidic, so if you’re working with a highly acidic soil, it could lower the pH over time. However, compost is among the most gentle March amendments, providing fertility that releases slowly over time, rather than all at once like a synthetic fertilizer would. 

If you don’t have a compost heap on your land, now is a great time to site one in cold areas. If you’re moving swiftly into spring in March, get one started. Piles are easy. Simply scrape the surface of the earth, and start piling a 3:1 ratio of carbon materials to green ones. Then let the stuff turn into gold for your farm. If you haven’t incorporated compost into the fields yet, you will see a noticeable difference once you do.  

Mulch

No matter where you live and what the weather is like, mulch is a great March soil amendment. You don’t have to work it into the soil, so there’s no minimum temperature requirement. Simply lay down a mulch to prevent erosion in your fields, suppress weeds, and to regulate the soil temperature. 

If you’re already growing plants, use mulch to suppress weeds in the bare areas. Spread a two to three-inch layer around the base of the plants, keeping the mulch away from any stems or trunks. Use organic mulches for a slow release of nutrients that nourish plants as it locks in moisture. 

Leaves (shredded or whole), wood mulch (chips, bark, shredded), and even grass clippings will do what mulch does best. All of these can be sourced from the farm itself or from a nearby farm. This saves you money and gives your fields the boost they need to get going in spring. 

One important note: if you’re germinating seeds in a bed, wait to mulch it until your plants are fully emerged and have their first set of true leaves. 

Worm Castings

Just like the other March amendments do, worm castings provide a gradual and gentle release of nutrients to your farm’s beds. They may contain up to 4% more nitrogen than compost, and increase porosity and water holding capacity. The excrement of worms may also contain trace minerals you can get with standard bulk soils. 

Farmers can even start their own vermicompost system. In these, worms are contained in a tiered system of bins and fed kitchen scraps, paper, and other organic items. Then, their excrement is harvested and used as needed. Worm bins can be kept in areas with hot summer seasons, but they’ll need to be indoors if temperatures climb above 85°F (29°C). Beds in cold areas need hefty insulation to protect worms. 

You only have to work in a little bit of worm castings into the existing soil. Simply scrape the surface with a trowel or hand rake and work the casting in. You can find these at farm and garden stores all over if you don’t have your own or a nearby source. Your farm’s fields will be healthier and more productive as a result. 

Leaf Mold

Farms on the edge of woodlands would do well to include one of the forest’s greatest lessons in nutrient cycling. Leaf mold is the result of decaying fallen leaves. The leaves on the forest floor provide insulation for the little guys who live near the soil, and lock in moisture and nutrients for the plants and trees that remain. 

These are all over the place at the end of winter, as long as deciduous trees are nearby. Instead of bagging them up and giving them to your local municipal waste management department, rake them into your rows and beds. Wet them, and as they decay, they make leaf mold. 

Leaf mold prevents erosion and improves moisture and temperature regulation. You can layer leaves on your rows and add moisture. Then, let them do their thing. Or you can gather them, contain them in bags or bins, and moisten them to make leaf mold before applying. 

Fertilizers

Before adding any fertilizers to your rows, beds, and fields, always do a soil test. An excess of any one nutrient could spell disaster for your crops as the season goes on, and it takes time to come back from imbalances. Especially for synthetic fertilizers, careful additions are so important. In-ground beds often have some of the native composition as well, and there could be imbalances you need to correct. 

Most tests tell you how to amend your soil and which nutrients are lacking or overabundant. One safe bet for most situations: you can sprinkle a little bit of full-spectrum organic powdered fertilizer. Go light if you’re unsure that your garden needs it.

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