More organic matter and better soil health and fertility can come from adding compost to your soil. But too much compost can be bad for your plants and the environment.
In the past few years, growers have had trouble with methods like using deep compost mulch, adding extra compost to high tunnels, and growing plants in raised beds with only pure compost. Learn how to assess the condition of your soil and ways to remedy excessive compost applications.
As a gardener, using horse manure as a fertilizer can significantly boost your vegetable yields and soil health. Horse manure improves soil structure, increases nutrient availability, and promotes microbial activity But can you put too much horse manure in your garden? The short answer is yes Over-application of horse manure can lead to issues like excessive salinity, nutrient imbalances, and contamination. In this article, we’ll look at how much horse manure is too much, the potential risks, and best practices for using horse manure safely and effectively in your garden.
How Much Horse Manure is Too Much?
Determining the right amount of horse manure for your garden takes some careful consideration. Application rates often recommended are 1-2 inches of manure tilled into the top 6-8 inches of soil before planting But even these seemingly modest amounts can be problematic if the manure is applied year after year
With repeated heavy applications, nutrients like phosphorus, potassium, magnesium and sodium can build up to excessive levels in your soil. This can inhibit the uptake of other nutrients and cause deficiencies. High salinity from over-applied manure can also damage plants and create physiological drought conditions.
So how do you know if you’ve put down too much horse manure? Signs of over-application include:
- Visible manure chunks in soil
- Strong manure odor
- Excessive salinity and high pH
- Nutrient deficiencies in plants despite high soil fertility
- Lush, weak growth and pest/disease problems
- Nutrient runoff and contamination issues
Routine soil testing will alert you to any unfavorable nutrient accumulations or pH/salinity issues from over-use of horse manure. Testing every 1-2 years provides useful feedback on the effects of your manure applications and soil amendment practices.
Potential Risks of Too Much Horse Manure
Using excessive amounts of horse manure carries several potential risks:
Nutrient Imbalances and Deficiencies
Too much manure can throw off nutrient ratios in the soil. High levels of phosphorus, potassium, magnesium and sodium can inhibit the uptake of nutrients like nitrogen and calcium. This can induce deficiencies and reduce plant growth and quality.
Excessive Salinity
The salts present in horse manure can accumulate to excessive levels with repeated heavy applications. High soil salinity makes it difficult for plants to take up water, creating drought stress. It can scorch and burn plant roots, leaves, and fruits.
Contaminants and Pollution
Over-application of manure increases the risk of contaminants like weed seeds, pathogens, antibiotics, and heavy metals building up in your garden soil. This creates health hazards for crops and the surrounding environment. Nutrient runoff can also pollute nearby water sources.
Rank Growth and Pest Problems
Too much manure encourages excessive, weak growth in plants. This makes them more susceptible to diseases and insect infestations. Overly rich soils also tend to have issues with nematodes and other soil-borne pathogens.
Best Practices for Using Horse Manure
To harness the benefits of horse manure while avoiding over-application, follow these best practices:
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Test your soil – Regular soil tests will tell you what nutrients you have enough of or too much of. Adjust manure and fertilizer applications accordingly.
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Use aged manure – Composting manure kills pathogens, weed seeds and reduces odor. Avoid using raw manure near food crops.
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Limit heavy applications – 1-2 inches per growing season is sufficient in most soils. Avoid piling on 3+ inches of manure at a time.
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Rotate manure with other amendments – Alternate seasons of manure use with green manures, compost, and mineral fertilizers. Don’t rely solely on manure year after year.
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Till into soil – Thoroughly incorporate manure into the top 6-8 inches of soil to prevent nutrient runoff.
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Account for other soil nutrients – Reduce fertilizer inputs based on nutrients supplied by the manure. Too much on top of manure causes imbalances.
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Monitor salt and pH levels – Test soil salinity/pH yearly. Adjust practices to prevent excessive alkalinity.
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Prevent contamination – Keep freshly applied manure away from crops. Follow safe harvesting, handling, and washing practices.
The nutrients and organic matter in horse manure can profoundly enhance soil health and plant growth. But horse manure is a powerful soil amendment. Used judiciously and in moderation, it boosts the garden ecosystem. Over-applied, it can be equally destructive. Regular soil testing, proper application rates, and integrating manure with other organic and mineral amendments helps strike the right balance. Monitor your soil closely, and let your plants and test results guide you in determining if you’ve put down too much horse manure in your garden.
Adjust the pH, alkalinity, and salt concentrations in your soil
The ideal pH range for growing fruits and vegetables is 6. 0 – 7. 0 (with the exception of a few specific plants such as blueberries, which thrive in acidic conditions). Soils that are too acidic (below 6) can be amended with agricultural lime. A basic soil test will provide instructions for the amount of lime needed to adjust your soil.
More commonly, soils that have received excess compost tend to be too basic (pH above 7). To make soil more basic is easier than to make it more acidic, but growers can still do the following:
- If you don’t want to keep adding cations (nutrients with a positive charge) to your soil, stop adding compost. Soils that have a lot of compost tend to also have a lot of phosphorus in them. Until your calcium, potassium, and phosphorus levels drop again, use only nitrogen-based fertilizers like ammonium nitrate or ammonium sulfate, urea, and blood meal. Based on your soil test, talk to an Extension educator in your area about the best fertilizer sources to add. Test your soil every year until conditions stabilize.
- Adding sulfur to your soil can bring down the pH. A list of sulfur products can be found in the nutrient management guide for commercial growers. Adding sulfur will probably have to be done more than once to keep the pH low, and it could take months or even years to see results. To drop the pH by one unit, use the following amounts of sulfur: g. from 8 to 7: Add 0 to sand, loamy sand, and sandy loam soils. 8 lb / 100 sq. feet, 8 lb / 1000 sq. feet, or 1 lb per cubic yard. In loam or silt loam soils, add 2. 4 lb / 100 sq. feet, 24 lb / 24 sq. feet, or 3 lb per cubic yard. Because clay soils have a high buffering capacity, it is hard to lower their pH. It is not a good idea to lower the pH of clay soils because acidifying amendments can cause salt to build up and the soil doesn’t drain well. The Soil Test Interpretations and Fertilizer Management for Lawns, Turf, Gardens, and Landscape Plants guide has more information on how to make your soil more acidic. However, we don’t have good advice on how much sulfur to use to lower the pH of a tunnel yet because it depends on the type of soil, how wet it is, and how much calcium is in it.
- Low pH can also be reached by making your irrigation water more acidic. This is especially important in high tunnels, where salts build up in the soil when it doesn’t rain. Acidic water can help to neutralize these salts. To do this right, you need to know both the pH and alkalinity of the water you use for irrigation. For $10, the University of Minnesota Soil Testing Laboratory will test your water. The pH of your irrigation water should be between 5 and 7, and the alkalinity should be between 37 and 38. 5 to 130 ppm (but no more than 65 ppm for seedlings). The AlkCalc tool can help you figure out how much acid you need to add to your water once you know its pH and alkalinity.
- If you are growing in a raised bed or another small space, you might want to take out some of the compost and spread it out over a bigger area.
- If you flood your land a few times a year, it can help get rid of salts. It is very important to do this in tunnels and other enclosed areas where rainwater can’t get in.
Assess the nutrients in your soil
High levels of nutrients like ammonium, calcium, magnesium, potassium, and sodium tend to build up in soils that have too much compost, especially manure. These soils can also develop high concentrations of bicarbonates, carbonates and hydroxyls.
Too much of any nutrient can inhibit the uptake of other nutrients, resulting in deficiencies.
- Too much ammonium can stop calcium, magnesium, and potassium from being taken in.
- More alkaline soil is found where there are lots of base cations, such as calcium, magnesium, potassium, and sodium.
- Soils that are very alkaline tend to have a high pH, which is a measure of acidity. In high pH soils, many nutrients are less available. So, even though there are plenty of nutrients in the soil, your plants may show signs of nutrient deficiency.
Another problem with soils that get too much compost is that soluble salts might rise to levels that are harmful (salt toxicity).
- When leaching is low in high tunnels, soluble salts can build up to too high of levels.
- Most of the time, composted manure has more salts than composted plant matter.
- It is not a good idea to use raw manure in high tunnels because it can have a lot of salts and ammonium in it.
The first step to remediate an excessive application of compost is to test the soil. The basic series should be on your soil test, which includes pH, organic matter, phosphorus, and potassium. Soluble salts like calcium, magnesium, sodium, and ammonium should also be on the test.
Read more about Interpreting soil tests for fruit and vegetable crops.
Is Horse Manure Good for the Garden?
FAQ
How much horse manure should I add to my garden?
What happens if you use too much manure?
When should you not use horse manure?
What vegetables don’t like horse manure?
Can you put too much horse manure on plants?
There are a number of reasons as to why your plants can suffer from too much manure being applied; exceedingly high levels of nitrogen and salt, herbicides and bacteria such as E.coli can all be reasons as to why you shouldn’t put too much horse manure on your plants. Where can I buy organic horse manure?
Can you put horse manure in a garden?
Adding fresh horse manure to your garden will add a lot of nutrients but also carry bacteria and weed seeds with it, which can cause damage to your garden in the long run. The best way to use horse manure is to compost it first before using it on your garden.
Is horse manure better than garden compost?
Horse manure is often regarded as more nutritious than garden compost, however this is a broad generalisation as compost quality varies, depending on the type of waste material and composting method used. When using horse manure, ensure it’s well rotted or composted, and at least six months old.
Can horse manure be used as mulch?
Often combined with stable bedding and allowed to rot down for a couple of years, horse manure is perfect for digging in or spreading as a mulch. Fresh manure mustn’t be used directly on the garden as it can actually remove nutrients from the soil and scorch plants, but it can be added to compost heaps. What is horse manure?
Is horse manure safe for vegetables?
A: Yes, horse manure is safe for vegetables when applied in proper proportions and after being properly composted. When working with manure, always be sure to wear protective clothing such as gloves and a mask to avoid coming into contact with any potentially harmful bacteria. Q: Can I Use Fresh Horse Manure in My Garden?
How much horse manure do I Need?
The amount of horse manure needed will depend on how much compost you want to make, as well as the size of the area that you are going to fertilize. The general rule is that you need about 20 lbs (9 kg) of horse manure for every cubic yard (about 1 m³). Does composted horse manure smell?