4 Keys to a Strong Organic Fertilizer Strategy

Questions about an organic fertilizer strategy are common in organic farming. How do I provide enough nutrients? In particular, nitrogen. How do I manage my crop and soil without using synthetic fertilizers?

Fertilizer can come from a variety of organic sources, including animal waste, decomposing plants, and nitrogen-fixing crops like soybeans and clover. So it’s possible to use them in combinations to provide nutrition while also improving soil health and fertility.

Here are the four key parts of a successful organic fertilizer strategy:

1. Manure and your organic fertilizer strategy

The chief source of fertility for organic farmers is manure.

While it’s possible to run an organic operation without manure, you won’t be able to achieve optimum yields. It’s likely you’ll deplete your soil fertility over time, too. For long-term success with organics, manure needs to be a key part of your nutrient strategy.

Hog and poultry manure are usually the best choices

Organic farmers use two main types of animal manure:

• Hog manure: Hog manure contains 70-90% ammonium that is readily available to plants. Of course, weeds are also ready to take it up. So you may get a quick, dense flush of weeds after you apply it. And that’ll require additional weed management field work.
• Poultry Manure: Poultry litter contains only 10-20% of nitrogen in ammonium form. Most of it is organic nitrogen. Only 40-60% of that will be available to your plants in the first year as it takes time for soil microbes to break it down into an available form. This provides less fertilizer. Be ready to apply more manure to be sure your crops get enough nitrogen.

While both hog and poultry manure are excellent options for organic crops, you’ll achieve the best outcomes by using a mix of the two.

What about cattle manure?

Cattle manure can also be used in organic farming. Be aware, though, that the nitrogen levels are generally too low to be your primary (or only) nutrient source. For example, you’d need 8 – 12 tons of cattle manure to get the same amount of nutrients contained in 2 – 4 tons of poultry manure. In addition, cow manure often contains weed seeds whereas hog and poultry manure are more or less raw.

It’s worth noting, however, that cattle manure is usually your best choice for alfalfa. It tends to be higher in potassium and lower in phosphorus than hog or poultry manure.

The amount of manure required for your fields will vary based on crop rotations and soils, and the manure used. For example, if you need to build up your soils, consider applying at higher than removal rates. Take soil samples every four years. It’s a good idea to monitor phosphorus levels and ensure they’re not too high.

Buying and taking delivery of organic manure

No matter which manure source you choose, shop around. Always get a second quote on price because you can leverage that for negotiation.

And make sure you’re paying a fair price by looking at the manure analysis. Some retailers charge a premium for composted manure. This happens even when the nutrient content and concentration is about the same as raw manure sources.  

It’s always best to take a sample and do an analysis when the manure is delivered. Invite the seller to be onsite with you. If the results are markedly different than expected, you can and should negotiate for a lower price.

Storing organic manure

If you have to store your manure prior to application, take another sample before using it. As a general rule, there won’t be a lot of nutrient loss but it is a good idea to check. Therefore, it usually makes sense to store manure if it helps you get a better price. Keep in mind that the nutrients in some manures, like poultry litter, can settle over time. In those cases, you’ll want to agitate the manure to redistribute the nutrients before application.

Spreading organic manure

The ideal time to apply manure is in the Spring. If that’s not possible given the weather or field work activities, aim for a time window between Fall and Spring. The soil microbes that break down nitrogen and make it available for plant uptake begin to slow down in the Fall. They’re nearly inactive over the Winter but become active again in the Spring.

There are several ways to protect even more of the nutrients. You can apply it using methods that incorporate the manure directly into the soil. Incorporating helps capture the ammonium nitrate before it volatilizes. Poultry manure incorporated within the first 12 hours after application can release upwards of 70% of the available nitrogen in the first year. If incorporation takes place after 96 hours, the rate drops significantly.

2. Stretch your organic fertility strategy with crop rotations

While manure is an key fertilizer source, it’s not the only way to improve soil fertility. Strategic, well-planned crop rotations can also have dramatic impacts on nitrogen levels and your field’s productivity. 

Both cash and cover crops can provide nutrients as part of a rotation plan. Legumes, in particular, can fix their own nitrogen. The amount of nitrogen derived from crop rotations depends in some cases on the location of your farm. For example, organic soybean crops in Iowa can provide a 50 pound credit while dropping to a 40 pound credit in Minnesota. If you rotate from soybeans into corn or wheat, take into account the nitrogen credit derived from the soybeans.

A final factor to consider in an organic fertilizer strategy is the length of crop growth. Four years of alfalfa can provide 150 pounds of nitrogen in the first year of the next crop, and 75 pounds the following year. Contrast this with alfalfa. It provides 40 pounds the first year and no second-year residual.

3. Grow your own nitrogen with cover crops

You can generate nitrogen credits from cash crops by growing organic cover crops. You can choose Austrian winter peas, clover, fava beans, hairy vetch, and others. Several species of these cover crops are available, with varying seeding dates and costs. They also provide a wide range of nitrogen, starting from 20 pounds and reaching up to 200 pounds.

The amount of nitrogen produced depends on the type of cover crop and how it develops, so it’s best to be conservative. Aim for a rate at the lower end of the range, maybe even less. This helps ensure your fields receive at least the minimum amount of nitrogen needed. As you keep growing cover crops, it will be easier to predict the amount of nitrogen they will deliver.

Keep in mind that the nutrients released from cover crops will be similar to poultry manure. The nitrogen becomes more available as the plant breaks down over time, and most of the nitrogen will become available in mid-Summer.

Finally, many states have programs that will cover a portion or specific amount of the cover crop seed. This can help defray the total cost to your operation.

4. The best organic plan include an organic fertilizer strategy

To have success with an organic fertilizer strategy, you have to plan and use good management. If you can determine your crop rotations well in advance, you can get the best price on your manure.

AgriSecure can help you develop a nutrient management plan that also increases your bottom line. The MyFarm tool lets you store your crop rotations and plans online. Working with an account executive, you can determine the best crop rotation, times to purchase your inputs, and even local sources. We can also provide expert guidance. As you get started with cover crops, we can help you select define that ones that best fit your plans and budget.

If you’re ready to create and implement a fertilizer strategy for your farm, contact us today for a free consultation.

By Kenn Jenkins, CCA, AgriSecure Account Executive and Owner of Goliath Ag Farms