What is the best fertilizer for the garden? This issue is regularly discussed on social media and warrants a wide range of opinions. Some say chicken manure is great, but others say it's too hot and can burn your plants. Horse manure can be used almost fresh, but cow manure must be composted. Sheep manure is more nutritious and sheep digest their food better. This is important? Some swear by rabbit dung.
Many of these discussions consist of many opinions but are very poor indeed. In this post, I'm going to dive into the science and try to determine which manure is best.
What is the best fertilizer for your garden?
“better” needs to be defined
Online discussions of manure suffer from two main problems. They lack facts, making it difficult to draw a conclusion, but more importantly, they never define the word "best".
Does better mean high nutrient content? Lower costs? Easier to apply? greener? Does it contain less herbicides or antibiotics? Is the best manure the one you can get the shortest way to save time and cause less pollution?
These are all valid definitions of best, but without agreeing on something, you can't come to an intelligent conclusion.
Do you want tartar or well-done manure?
You can use manure in three ways; fresh, aged or composted. Fresh manure is something that is less than a month old. If you leave that crap out for a while, it gets old. It hasn't been composted yet and you can clearly see the individual components, but it's not as hot as fresh manure.
The composted manure passed through ahot composting processand now it looks like healthy black soil.
Farms and large gardens can use fresh or probably aged fertilizers, but this is not available to most home gardeners, so I will ignore this type of fertilizer in this post. Instead, I will focus on hot compost manure.
The gardener should be aware of the fact that, in most places, there are few, if any, regulations regarding the naming of manure. Words like "manure", "aged manure", "rotten manure" and "compost" don't mean much. You certainly cannot compare products based on the descriptions used.
When one supplier was asked the difference between bagged cow and sheep manure, he replied, "Do you really think we're dealing with two piles?"
Mud factors to consider
In order to compare the benefits of different fertilizers, it is important to understand the factors or properties that affect a garden.
- soil improvement
- Pasta NPK
- herbicide content
- antibiotic content
- Degree of digestion by the animal.
- weed seeds
There are two main reasons for adding compost to the garden; organic matter and nutrients.
Many soils have been overburdened by agriculture or damaged by construction and are now low in organic matter. The addition of organic matter improves the structure of the soil, increases its water holding capacity, increases its nutrient holding capacity and increases the microbial population.
The second reason to use manure is to add nutrients to the soil. They take two different forms. The inorganic component, which people call salts, is what plants can use. These include nitrate, phosphate, calcium, potassium, magnesium and a variety of micronutrients. The second form consists of organic nutrients that are not available to plants. Slowly over time, as decomposition proceeds, these organic nutrients are converted into the inorganic form so that they can be used by the plants.
Organic matter in manure
manure dry matter,Building Soils for Better Crops, Sustainable Soil Management Third Edition. SARE Handbook 10, 2009 | Michigan State University Extension
ANDmost important reason for fertilizationfor the garden is to increase the organic matter content, but discussions of the best fertilizer never seem to mention differences in organic matter.
In fact, I couldn't even find organic matter values for different compounds. The closest I found are values for dry matter content, which should be very close to the organic matter content. Chicken is key, probably becauseMuch of their manure consists of bedding material..
So which fertilizer is best for organic matter? We have almost no data to compare manure with and commercial products often don't provide this kind of information, but this is one of the main reasons to buy manure. I don't think the gardener has a way to evaluate fertilizers for this property.
Fresh manure contains a significant amount of inorganic nutrients, but when composted it consists mainly of organic nutrients.
Try to find the NPK of the composted manure. I couldn't find a reliable source for this information. So why do discussions on social media always compare the nutrient levels of manure from different animals? HeFresh manure NPK values are readily availableand this is what most people use to compare fertilizers. But these comparisons only apply if you use fresh manure.
I noticed a variety of commercial products in bags with the words "mud" and "compost". One had an NPK of 1-1-1 and all the others had an NPK of 0.5-0.5-0.5 or 0.3-0.3-0.3. I haven't found a single product that has a different ratio. Many products do not have their NPK listed on the packaging or in online information, and none of the mass-produced products have the NPK.
The NPK value for everyoneA specific type of manure can vary greatly depending on the type of animal., type of feed, age of the animal, degree of composting and amount of urine collected. The most important factor is diet, as 50% to 90% of what you eat ends up in manure. Therefore, a horse fed grass will produce different manure than a horse fed alfalfa and grain. Composted manure manufacturers do not want to print new bags for each batch of product, so they are looking for a value close to the final value.
The important point here is that when you buy composted manure, they all have roughly the same NPK. The fact that the fresh cow might have a better NPK than the fresh horse is irrelevant.
What happens when you start with fresh manure and hot compost? Your raw material depends on the source, but a large amount of nitrogen is lost during the composting process. Even P and K are lost. hot fertilizer has alow C:N ratio and composting properlyYou have to add more carbon, which has the effect of lowering the relative nitrogen content. I suspect the end product won't be much different for all paste types at 0.5-0.5-0.5.
Rabbit manure may be the exception, as it does not need to be composted before use. But one product I looked at was $40 for two pounds. I bought 12 yards of horse manure (hundreds of pounds) for about $60 and I can get composted manure in bags for about $4 for 35 pounds.
Herbicide content in manure
Herbicides are used to control weeds in the forage (animal feed) and this plant material is then fed to the animals. SomeHerbicides can survive the entire process including composting, resulting in manure that damages crops, especially seedlings.
It is important that the manure is free of herbicides, so this is one of the most important selection criteria. How do you know it's herbicide free? Most certified fertilizers have been tested for herbicides, but a large number of commercial fertilizers are not certified.
you can make aSimple test if finished compost contains herbicides.
Antibiotic content in fertilizer
All cattle can be given antibiotics, and none of these animals fully digest antibiotics, so they end up in their manure. Organic manure must not contain antibiotics.
Antibiotics affect microbial populations but do not appear to inhibit the composting process. The high heat of the heatCompost breaks down antibiotics. Cold composting is much less effective.
Fresh manure and cold composted (ie aged) manure contain higher levels of antibiotics. cold weatherComposted manure has much less content, but it still contains something.
Do plants absorb antibiotics from the soil?
The answer is a resounding yes, and it looks like it.Higher concentrations in soil lead to higher concentrations in plants. You might think that certified organic vegetables don't contain antibiotics, but you're wrong. ANYOrganic farms use manure from animals that have been given antibiotics..
The level of antibiotics in vegetables is very low and should not be a cause for concern. However, keeping antibiotic levels low in your soil is a worthwhile goal.
pathogens in manure
"LevelManure contains a variety of bacteria, viruses and protozoa.and some of them are known for their adverse effects on humans. Bacteria that are known human pathogens include certain strains ofE coli, including 0157:H7,salmonellaspp.,Listeria,streptococcispp.,Campylobacter,Clostridiumsp. Belongs to the protozoanGardenjKryptosporidium. Most viruses found in animal dung do not infect humans."
Type and amount of pathogens are very different. For exampleE coli0157:H7, one of the most important foodborne pathogens worldwide, known to cause life-threatening conditions, is most common in cattle but has also been found in the dung of other mammals.Camplyobacterit is common in bird dung, but can be found in all species. When you use manure you are potentially exposed to pathogens - no fresh manure is free of them.
Most pathogens die on their own within a year, and many die sooner. InAt higher temperatures, their life expectancy is reduced to weeks or even days.. Two weeks of hot composting at 55°C (130°F) will kill almost all pathogens.
For those still thinking about using compost teas: “Add sugar or molasses when addingThe soaking process has been reported to increase the incidence of pathogens.in compost tea. "
Warm compost manure, especially certified manure, must be free of pathogens.
Degree of digestion by the animal
I see claims that the degree of digestion is an important factor. Some say that manure from ruminants such as cattle, sheep and goats is better because it passes through a more efficient digestive system. Horses, for example, have less efficient systems and much of what goes in comes out undigested.
If you take plant matter and compost it by taking the animal out of the loop, you'll get good compost. This seems to indicate that the degree of digestion is not an important factor. The type of food the animal eats is probably more important.
Manure is rarely manure. It is almost always mixed with some type of bedding material. The amount and type are also important, and most of it is not digested.
I don't think the degree of digestion is an important factor.
From an environmental and cost point of view, the best fertilizer is one that is readily available. There's really no point in worrying about getting some crap that's marginally better than what's at hand. For many gardeners, that means buying prepackaged manure from your local grocery store or nursery.
Free fertilizer is great. Lower costs for you and you recycle a waste product.
Some fertilizers contain more weed seeds than others, but this isn't a problem in a properly covered garden. Hot composting also kills most weed seeds.
Mango manure can have higher levels of weed seeds, and sheep have even lower levels than cows.
Which crap is better?
Let's go back to the assumption I made at the beginning, namely that we only have to think about composted manure. If you decide to use fresh or aged manure, you may need to consider some minor differences. Sheep dung is produced into small nuggets that are easier to handle than large cow pies. Fresh manure has different NPK values depending on the animal source, but these vary greatly. So unless you measure NPK you don't know what it is. Using fresh manure early in the garden adds more nutrients and organic matter to the soil than using a hot compost process.
The risk with fresh manure is pathogens. Personally, I think the risk is very low, but the authorities should be more cautious and recommend composting.
Looking at the above criteria for composted manure, it is clear that many online discussions do not come to the right conclusion. These are not NPK values as most composted manures have the same value. Even itching is not a problem as it is eliminated by composting. Herbicides and antibiotics are a problem with any type of animal manure, and weed seeds are not a problem.
Assuming you want to reduce the risk of pathogens, all that's left is to use composted manure, and then there's only one parameter left to consider; Availability.
Some brands may be better than others, but the producer cannot evaluate and compare one product with another. Online tips that say sheep manure works great are useless.
The best option is to compost and use your own plant waste. If that's not enough compost, buy locally. Don't send a special bag of alpaca manure across the country just because someone online said it was better. Once composted, it's all black shit!
Choosing the best soil
The following posts will help you choose the best soil:
Soil and compost: the right choice
Flooring for raised beds: which is the best?
Topsoil, compost, triple mix: what's the difference?