Bone Meal in Hydroponics

Bone meal plays a major role in hydroponics industry!

how bone meal can be used in the hydroponics industry?

The key to successful hydroponics systems is nutrient management within the water source since the water is responsible for providing all of the nutrients the plants need. Phosphorus is recommended at 30-50 ppm elemental P in the nutrient solution; calcium is needed in
higher concentrations and recommended at a level of 80-240 ppm in the nutrient solution. Bone meal has gained popularity in hydroponic systems because of its organic nature. Historically many of the fertilizers or nutrient sources used to create the proper growing solution have been synthetic, rendering them unusable in an organic setup. Finely ground bone meal meets the criteria for an organic fertilizer and is highly water soluble so phosphorus and calcium are available to the plants quickly.

Adding bone meal to a hydroponics system isn’t quite as straightforward as it is when used as a soil amendment. This is partly because hydroponics systems can be quite temperamental and vary wildly based on the individual system. Because of this, there isn’t a
standard recommendation like the 10 pounds of bone meal per 100 square feet recommended for soil.

Bone meal needs to be added to hydroponic solutions carefully, similar to any other nutrient source. It’s important to test the nutrient solution and measure the parts per million of both phosphorus and calcium in the water, adding nutrients as needed and watching the resulting concentrations.

Precautions when working with bone meal

Just like any other source of nutrients, there are some precautions to heed when applying bone meal as a soil amendment. These precautions should be noted to maximize its benefits while minimizing any possible negative side effects.

1. Check the soil pH before application

One of the most important things to consider is the pH of the soil you are working with. Soil pH needs to be below 7.0 for the nutrients in bone meal to be available for plant uptake. Alkaline soils won’t see any benefit from its addition because of their high calcium content;
the phosphorus and calcium bind to create calcium-phosphate which is unavailable to plants.

2. Applying too much can hinder root uptake

Organic sources of fertilizer often rely upon fungi in the soil to make the nutrients bio available for plant uptake through the roots. In the case of phosphorus, mycorrhizal fungi penetrate the plant roots and break down the organic compounds for easier absorption and utilization of phosphorus. In turn the plant supplies sugars made via photosynthesis to the fungi, establishing a symbiotic relationship. Over application of phosphorus can lead to problems with mycorrhizal fungi and nutrient uptake into the roots. The plant senses the overload of phosphorus in the soil and prevents the mycorrhizae from penetrating the roots; the soil quickly adsorbs the phosphorus as it is released from the bone meal, making it unavailable for plant uptake.

The Truth about Phosphates and Mycorrhizal Fungi

One of the well-documented benefits from mycorrhizal fungi is the increase in the uptake of phosphates by the host plant. Mycorrhizal fungi increase the amounts of phosphate appearing in host plant tissue, and radio tracer studies have confirmed that this phosphate is being provided via the mycorrhizal fungi.

High available Phophate reduces root colonization

Interestingly, research has also shown that, when soils contain high levels of available phosphate, the degree of root colonization by mycorrhizal fungi diminishes. The higher the level of available phosphate in soils, the lower the level of root colonization by mycorrhizal
fungi. This effect is documented both for ecto- and endomycorrhizal plants. Note that this effect only applies to available phosphates. Insoluble phosphates are unavailable, and do not affect mycorrhizal development. 

Phosphate does not kill Mycorrhizal fungi

Oddly, many people have erroneously concluded that phosphate kills mycorrhizal fungi. In fact, there is no killing effect going on here. Instead, in soils having high available phosphate, the host plant apparently opts to restrict fungal colonization. The fungi and their spores are still alive. They are simply experiencing a higher level of restrictions from the host plant. In fact, there is ample evidence to show that the host plant has significant control over when and where mycorrhizal fungi may enter root tissue. Theoretically, under conditions of high available phosphate, the restrictions are increased. So the levels of soluble phosphate in the soil can affect whether the host plant opens the door to the root widely or narrowly. But the mycorrhizal fungi are not killed by phosphates. This misunderstanding has been promoted by various companies who attempt to blend and sell mycorrhizal products with no real grasp of their biology.

  • Phosphates, both available and unavailable forms, do not kill mycorrhizal fungi.
  • High levels of available soil phosphate (soluble phosphates) result in reduced root colonization by mycorrhizal fungi.
  • Insoluble phosphate does not affect mycorrhizal development. The insoluble phosphate in natural soils can represent as much as 99% of the soil’s total phosphate content.

What does this mean in practice?

From a practical standpoint, this phosphate effect has significant ramifications. When applying mycorrhizal fungi inoculants, it is important to avoid applying high levels of soluble phosphate. High soluble phosphate can effectively close the door (partway) to root colonization by these fungi. This effect can be turned into a benefit, because you can save money by using less fertilizer. Mycorrhizal fungi can effectively increase phosphate uptake by converting insoluble phosphates to soluble, available forms, thereby requiring much less fertilizer application.

There are various options at your disposal. If your soils contain significant amounts of unavailable phosphates (like insoluble rock phosphate), then you will not need to add much soluble phosphates, since mycorrhizal fungi will gradually mobilize (i.e., solubilize) this
phosphate source. Mycorrhizal fungi will take advantage of the rock phosphates that would otherwise have been unavailable to your plants. So you can save on your fertilizer budget.

If your soils have low levels of total phosphates (available and unavailable), then you will want to apply some phosphates. But you will have to avoid applying high levels of soluble phosphate at the same time you apply the mycorrhizal fungi inoculant. The best approach would be to apply only low levels of phosphates initially, and then spread out your phosphate applications, so you are not dumping a high level on the soil all at once. That is a bad practice anyway, since soluble fertilizers will readily leach away with each rainfall. One
of the main reasons for using mycorrhizal fungi inoculants is to reduce your dependence on high fertilizer applications. So don’t shoot yourself in the foot by combining high amounts of soluble phosphates with a mycorrhizal fungi inoculation program.

How much Phosphate is too high?

The amount of soluble phosphate needed to inhibit mycorrhizal fungi colonization is quite variable. It is different with different plants, with different fungi, with different soils, and it is affected by environmental factors such as light intensity, soil moisture and soil pH.

Mycorrhizal fungi and their host plants both need phosphates, and both work hard to accumulate this important mineral nutrient. But when soluble phosphates are abundant, the host plants tend to increase their restrictions to mycorrhizal fungi, resulting in lower levels of root colonization. So avoid applying high levels of soluble phosphates at the same time that you apply mycorrhizal fungi. Instead, consider reducing your total phosphate fertility, and spread your phosphate applications out more broadly.

3. Minimize pollution of nearby water sources

Having too much phosphorus in the soil can also cause many problems for nearby waterways and underground water sources through runoff. Phosphorus can either attach to the soil particles and move via erosion, or can dissolve in the runoff water directly. Once phosphorus gets into water sources it can cause eutrophication — an excess of nutrients in a body of water that triggers a dense growth of algal and plant life and depletes the oxygen within the water.

4. Incorporate well into the soil to prevent attracting animals.

As mentioned previously, bone meal is either applied by broadcasting it across the soil surface or mixed into the bottom of holes when planting. When it used as a top dressing the bone meal can attract dogs, coyotes, raccoons and other carnivorous or omnivorous animals because of its smell. If consumed in large amounts it can clump together in the animal’s digestive system, obstructing the intestinal tract. Make sure to work it into the soil well by either tilling or raking and then watering it in thoroughly to dissolve any powder left on the surface.

5. Importance of Soil test Before applying fertilizer

Before reaching for a bag of bone meal, you’ll need to determine whether your soil needs it in the first place. The first step is to conduct a soil test. This will show you your garden’s current phosphorus levels. Compare that information to the recommended phosphorous levels for your preferred vegetables, and you’ll see whether you need to make up the difference. For example, potatoes are heavy phosphorus feeders while leafy greens and nitrogen-fixing plants like legumes need much more nitrogen.

As a general rule, sandy soil requires more phosphorus than loam or clay does. It’s best not to guess whether your soil needs phosphorus, as too much can lead to problems. For instance, excess phosphorus might impair chlorophyll production, which leads to yellowing leaves.

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