How to Condition and Fertilize Straw Bales

Conditioning and Fertilizing

Straw bales make a fantastic choice for raised bed gardens. Once you’ve decided on the layout and design, it’s time to prepare them for growing your vegetables. In this guide, we’ll discuss how to condition straw bales for planting using water and fertilizers, how the process works in cooler vs. warmer climates, and what are the best fertilizers to use for straw bale gardening.

How Do You Prepare Straw Bales for Planting?

Before you start growing vegetables using the straw bale gardening method, you’ll need to prepare your bales by conditioning them. The goal is to gradually turn the straw into compost, and create a nutrient-rich growing medium that allows your plants to thrive.

Straw is not hay, which means it has a low nutrient count. This is one of the reasons it’s rarely used to feed animals, and the main reason you can’t plant seeds directly in it. Without conditioning, your bale won’t be able to support plant growth, and you’ll have nothing to harvest by the end of the growing season.

The bale conditioning process requires three things: fertilizer, water, and time. Keeping the bales moist the entire time is crucial, yet you also need to pay close attention to the types of fertilizers you use, the quantities, and when to use them. With that in mind, let’s take a look at what the process actually entails.

Conditioning the bales is an essential step in straw bale gardening

The Straw Bale Conditioning Process

There are two main methods you can use to condition your straw bales, depending on whether you live in a warm or cool climate. Here’s what you need to know.

Conditioning Straw Bales in Warm Climates

This is the easy way to condition your bales. It works best in warmer climates, or if you’re starting the conditioning process in spring. The principles behind it are simple. Start by getting the bale soaking wet, then gradually add nutrients into it. This is what the timeline should look like.

Day 1: Give your bales a deep soak, until they’re saturated with water. If you live in a very warm and dry area, check the bales in the evening, and water them again if they’ve dried out.

Day 2 and 3: Keep watering the bales each day. You can check if the bales are evenly damp by pushing your hand inside the straw. By day 3, your straw bales should also start getting warmer, as the composting process begins.

Day 4: It’s time to add fertilizer to your straw bales. Add 3 cups of organic nitrogen fertilizer per bale, then water the bale slowly and evenly. You want to push the fertilizer into the straw and keep it there, not wash it into the ground below.

Days 5 and 6: Continue adding fertilizer to the top of the bale and watering it daily. Around day 6, you’ll also want to check the temperature inside the bales. The easiest way to do that is using a thermometer. If all is going well, the temperature inside the bale should reach 150°F (65.5°C) by day 6 or 7.

Days 7 to 9: Reduce the amount of fertilizer to half, and continue to water regularly.

Days 10 to 13: You can stop adding fertilizers, but keep watering the bales every day.

Day 14: Stick your hand inside of the bale or use a thermometer to check the temperature. If it’s dropped to 99°F (37°C) or if it feels warm but cooler than your hand, your straw bale is ready for planting. If it’s still a bit hot, give it another couple of days to reach an optimum temperature.

You can use a compost thermometer to check the temperature in your straw bales

Conditioning Straw Bales in Cool Climates

If you live in a cooler climate, your straw bales will take longer to break down. You will also need to use more fertilizers to kick-start the decomposition process. This second method relies on a higher level of fertilizer, added on alternate days in order to get the decomposition going quickly.

Day 1: Sprinkle 3 cups of organic fertilizer with nitrogen on each bale and water it well, ensuring the fertilizer disappears inside the straw tubes.

Day 2: Give the bales a good soak, but don’t add any more fertilizer.

Day 3: Water and fertilize the bales.

Day 4: Skip the fertilizer, but continue watering the bales.

Day 5: Give your bales both water and fertilizer.

Day 6: Water the bales.

Day 7: You can reduce the amount of fertilizer to one and a half a cup per bale. Pour it evenly on top of the bale, then give it a good watering. At this point in the conditioning stage, you should also notice a drastic increase in temperature. Use a thermometer to check that it reached 150°F (65.5°C).

Day 8 and 9: Continue adding 1.5 cups of fertilizer per bale and keeping the straw moist by watering it daily.

Day 10: By now, your straw bales should have a good amount of nitrogen in them. That means it’s time to add in other nutrients. You can switch to an organic fertilizer with potassium and phosphorous, then water it in.

Days 11 to 14: Keep watering your straw bales, but don’t add any more fertilizers. Check the temperature inside the bale each day. Wait until the straw feels warm to the touch but cooler than your hand before you start planting.

Once your straw bales are ready and if you live in an area where winter temperatures never drop below freezing, such as USDA hardiness zones 10 b to 13 b, you might as well start sowing. Brassicas and cruciferous vegetables like broccoli, cabbage, and Brussels sprouts can be sown in outdoor air temperatures as low as 45°F (7°C) using the straw bale method.

Otherwise, let’s discuss what happens to your straw bales over winter.

How Do You Condition Straw Bales Over Winter?

If you want to start the straw bale conditioning process in late fall or winter, try starting before temperatures drop below freezing, using the cool climate method mentioned above. Once it gets going, the microbes in the bale will take care of the rest.

Don’t worry if your bales get covered in snow while you condition them. If the composting process has already started, the heat it generates will keep the bales from freezing solid. The snow will also help insulate the bales, and once it melts, it will provide them with much-needed moisture.


Straw Bale Covered in Snow

In areas with very cold winters, you can protect your bales by covering them with black plastic sheeting. But, again, don’t worry too much about the bales freezing. The microorganisms in the bales will go dormant, and when the bales thaw, they will continue to decompose the straw.

What Fertilizer is Best for Straw Bale Gardening?

There are two main types of fertilizers you can use for your straw bale garden: organic and synthetic. Synthetic fertilizers are cheaper, easier to dose, and they don’t produce unpleasant smells. But if you’re aiming for organic gardening, organic fertilizers are a must.

Before we dig deeper into the topic, it’s important to understand how different fertilizers affect the bale conditioning process, and why using them in the right order matters.

A straw bale is a sterile soilless mix. If left to its own devices, it will turn into compost in about 2 years. That’s a very long time to wait before you start planting, which is why you need to add a nitrogen-rich fertilizer in the beginning to speed things up. Once the microorganisms in the bale get enough nitrogen from the fertilizer and carbon from the straw to start the composting process, they can turn your straw into compost in as little as two weeks.

Learn how to condition and fertilize straw bales

After composting starts, you will need to add the extra nutrients in the second half of the process. Once your vegetables are planted and begin growing, they will also benefit from regular applications of phosphorous and potassium fertilizer. Check out chapter 5 for an in-depth look at how often should you fertilize a straw bale garden.

In the meantime, let’s take a look at which fertilizer types to use for conditioning a bale, and when.

Best Organic Fertilizers for Straw Bales

Blood Meal

Blood meal is a slow-release fertilizer made out of dried and powdered animal blood. It has a very high nitrogen ratio, which makes it a perfect candidate for conditioning straw bales in an organic way. You can use a blood meal fertilizer from the start to the end of the process.

Fish Fertilizers

Made out of whole fish as well as bones, scales, and skin, fish fertilizers can be found in several forms: oil, emulsion, fish meal, and hydrolysate. They are high in nitrogen and amino acids, as well as potassium and phosphorus. They are quick-acting organic fertilizers, and can also be used in all stages of the conditioning process.

Bone Meal

Bone meal is another type of slow-release fertilizer, made from steamed animal bones ground into a powder. It has a high phosphorus and calcium content, but lower amounts of nitrogen and potassium. You can use this in the second half of the bale conditioning process, which calls for an organic phosphorus fertilizer.

Some manufacturers also sell pre-made organic fertilizer mixes


Seaweed fertilizer is typically made from kelp and sold in a liquid, easy-to-use form. It’s a fertilizer high in potassium, but it also contains many enzymes and minerals that improve fruiting yields and healthy plant growth. Use it in the second half of the bale conditioning process.

Compost Tea

Compost tea is literally a mix of compost and water, ready to use in just 2 days after mixing. Given the fact that it’s diluted, it has a lower nutrient score than actual compost. However, it contains valuable microorganisms, which will help boost the bale composting process especially if you’re using slow-release fertilizers. The best way to use compost tea is in combination with another organic fertilizer. Simply add one cup per bale per day.

Wood Ash

Wood ash provides a lime and potassium boost, and can also be sprinkled around your plants for pest control. Using it is not mandatory, but if you do, use it sparingly. When it gets wet, it produces salts that can damage your plants. You can avoid this by adding it to your compost first, to give the salts a chance to drain away.

Organic fertilizers can be sold in either liquid, powder, or granule form

If you’re using granule fertilizers, try dissolving them in a jug of water first. Then pour the solution on top of the bale. By dissolving them, you also prevent fertilizer burn issues when the plant roots come into contact with the granules.

Synthetic Fertilizers

Also known as inorganic fertilizers, these are any types of fertilizers that are chemically manufactured. They contain nitrogen, phosphorus, and potassium that have been synthesized and designed to give your plants an instant nutrient boost. Synthetic fertilizers are also easier to dose and use compared to organic fertilizers.

If you’re planning to use synthetic fertilizers to condition your straw bales, there are no rules against this practice. You can use a liquid fertilizer for grass, or other pre-made mixes. Lawn fertilizer, for example, has a high nitrogen ratio. And because it’s synthetic, it can drastically speed up bale conditioning.

The downside is that synthetic fertilizers can have a negative impact on your garden. They can lead to a buildup of fertilizer salts in the bale, which will damage the plant’s roots later in the growing season. Also, if your aim is to grow in organic straw bales, this type of fertilizer should have no place in your garden.

Urea Fertilizer

How Much Water Should I Use?

Straw bale gardening requires a lot of water throughout the conditioning process. For example, an entire bale can use one or two gallons per day at the start of the process, when it needs a very good soak. Water the bale using a hose until you see water draining through the bottom of the bale. Once you start adding fertilizers, water slowly to allow them to seep deep inside the bale. You can also install a drip irrigation system or put a soaker hose on top of the bale, to keep it evenly and constantly moist.

Around day 5 in the conditioning process, when the bales start getting hot inside, switch to warmer water if possible. If your tap water is too cold, you can try leaving it in barrels overnight, and use a watering can to water the bales.

You can also use mulch to help the bales retain moisture once your plants start growing

How Long Does it Take to Condition Straw Bales for Gardening?

On average, the straw bale conditioning process takes 14 days. This time frame isn’t set in stone though. If you live in a warm climate or get started when ambient temperatures are high enough, the process can be done in 10 days. Meanwhile, in a cooler climate, it can last almost a month.

The sun exposure in your garden can also impact how fast bales condition. A bale sitting in direct sunlight will turn to compost faster, and can be used for planting sooner. Meanwhile, a straw bale positioned in partial shade will take longer to break down. As with any gardening technique, there are no hard and fast rules, so you’ll need to adapt to your growing conditions.

How Do You Know When the Straw Bales are Ready for Planting?

Here are the main signs that the straw bale composting has been a success and that you’re ready to start planting:

  • The straw feels damp and warm to the touch.
  • The top of the bale begins to look like actual compost, with small, dark clumps that break up between your fingers.
  • You start seeing seeds sprouting in the bale. Sometimes, straw bales can have cereal seeds left over from the harvesting and threshing process. Simply pluck them out by hand, before they start using the valuable nutrients you want saving for your vegetables.
  • Mushrooms emerge in the bale. This is a great indicator that your straw bale is not just ready, but also healthy. Although some of the mushrooms growing in straw are edible, it’s best to err on the side of caution and avoid eating them.

Ink cap mushrooms love growing in straw bales

If your straw bale is hotter than 100°F (38°C) by the end of day 14, always wait until it’s cooled down before you start planting seeds directly in it. Similarly, if by day 6 or 7 in the curing process the temperatures have failed to rise, you’ll need to consider ways to warm up your bale. We’ll discuss troubleshooting straw bales that are either too hot or too cold in Chapter 6.

Picking the Right Plants

Once your bales are ripe with necessary nutrients and moist with water, it’s time to delve in to the fun part: picking the plants for your garden. In chapter 4, you’ll learn about the vegetables, fruits, and flowers that thrive in straw bale gardens.

Share your thoughts

  1. Brenda Shumpert

    My bales never got warm Above 70 degrees Fahrenheit but I have mushrooms galore! May have used the wrong fertilizer because I have grass growing all over the bales. The bales have decomposed and appear to be ready for my plants. But the temperature never rose… it ready? (Yes I did get organic fertilizers and followed the watering and fertilizer schedule listed in the how to guide). Waiting for the reply

    • Lisa Row

      Hi Brenda!

      If you are in a cooler area it may take longer for the bales to decompose. But if they seem ready they probably are. Grass can be pulled out fairly easily before planting.

      Good luck!

  2. Loretta Andry

    On 13th day how much potassium and phosphorus do I add per bale?

    • Erica

      1/2 cup per bale

  3. Marianne whitehouse

    I have calcium nitrate to use as a conditioner. Is that OK and how much do I use?

  4. Dave

    Can I use last year’s straw bales again this year

    • Patrick

      Yes you can, as long as the bales are still stable. Mostly they won’t last for much longer than 2 seasons.

  5. Michelle Fitzhugh

    What does it mean if I don’t have any mushrooms growing but I have followed the directions? I live in South Alabama. We are having uncharacteristically cool weather right now. Not sure if this is a factor. Thanks for your reply.

  6. Kelly Kozicky

    Hi, Can I use blood meal as a nitrogen source?

  7. Doug

    What is the best fertilizer to use after you have planted and once a month or when ?

    • Greg

      I’ve had good results using a 10-10-10 weekly or bi-weekly depending on a particular plantings needs. I also top dress with dolomite lime on day 5 of bale prep. Then once a month during the growing season. Using 1 cup each time. I have found this particularly important when growing tomatoes and peppers.

  8. Tom

    I’ve decided to try the straw bale gardening this year. I started conditioning them with a 10-10-10 fertilizer. Could not find the 34-0-0. Will this be a problem? Is it okay to keep this conditioning method going through the 14 days before planting?

  9. Lu Anne Mason

    Question: I’m trying straw bale gardening for the first time. I’ve started conditioning my bales using the Easy Method. I watered the bales first 3 days, then started feeding. On the first feeding day, I sprinkled the straw with blood meal, and watered that in with liquid seaweed and fish fertilizer. Days 5 I just watered with seaweed and kelp. Today is the 6th day, and I sprinkled organic fertilizer on the bale, and watered in with seaweed and fish water. I don’t detect much heat in the bales.

    Is it possible the bales could be too tight, and there isn’t enough air for the reaction to start? Thanks!

  10. Arthur

    This is a very interesting article, thanks for sharing a lot of information!

    • Admin_86433420

      Thank you 🙂

  11. Maricela

    This article is great. Im just learning as I go.
    Thank you so much!

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