How to Correct pH With Soil and Soilless Mixes.

This post deals with soil mediums but i would be a good idea to read related posts for background material.  I have written about checking the pH with hydropoincs as well as  correcting the pH in hydroponics.

Once you test the pH, if it is below 5.9 or above 7.0 you may want to adjust the pH. One way to adjust for minor pH changes is to change the pH of the water you use to water your plants. You can buy pH up or down from HTGSupply.com and use it like in a hydroponics system to water your plants.

If you have a severe problem I recommend you transplant or pot up the plants using new soil. This often is all that is needed. However, if you can’t put your plants into a new bigger container you can remove the first inch or so of soil,( try to minimize root damage while doing this) and sprinkle lime into the pot, at a rate of 1 teaspoon (5 ml) of lime per gallon of soil. Give your plants a good watering to work the lime throughout the soil. You can replace the soil you removed earlier, but I have found adding new soil on top is better. Put the old soil in the compost pile.

Check the soil pH next time your plants need watering to check that everything is fine. You should only need minor adjustments to the water if any.
Good Growing,
Dr. E.R. Myers


How To Measure the pH of Soil or Soilless Mediums.

I have written about checking pH for hydroponics growers.  Soil growers have less problems with pH than people growing with hydroponics, but good growers also measure the soil pH to see if it in the optimum range for growing the best plants. Once you grow successfully, you need to keep trying new products and techniques. Keep testing things with scientific tests so you don’t get mired in mediocrity.

You will need to wait until your medium is dry and ready to be watered. Use the same water you use for your garden and adjust the pH to around 7.0. You must know the exact pH of the water going into your soil, so really anywhere from 6.5 – 7.0 will suffice.

Second, place your plant/container in some sort of tray to catch the runoff water, and water slowly (with your pH known water) until the water drains into the tray.

It’s the first drops of water that will give you the best reading of your soil, so make sure to water slowly. Then, remove the pot from the tray to eliminate excess water entering the tray. It is a good idea to have a second tray to put the plant into as more water drips out. Then, perform the pH test on the runoff and compare it to your initial test. (You can get pH tests kits at many places including HTGSupply.com)

The results of the runoff test will likely be lower than your starting value of 7.0. If this is the case, a small drop of 0.5 pH to 6.5 pH (example) would be ok and your soil needs no further alterations at the moment.

I would recommend doing this for all plants in your garden, but if you get about the same reading for all plants the first time you do this, you may only need to test one or two plants each time you check the pH. I’d check the pH once a month or at a minimum at the beginning of vegetative flowering stages of growth.


How Are Nutrients Lost From the Soil?

I get a lot of questions about what fertilizer is the ‘best’ and there is a lot of buzz online about various fertilizers and their myriad of benefits. So, one thing you want to think about is once you add fertilizer, how will they be lost from your soil or grow medium.
The first way to lose nutrients is root absorption. This is what you want, the nutrients to go into your plants to promote growth and increase yield. I have written about factors that can limit growth and good growers know that too many nutrients are just as bad as too few. This Goldilocks factor of biology is why you need to do scientific tests to see what amount of fertilizer you should use. ALWAYS start with the manufactures suggestion; they should have done some tests to give you this starting point. Some plants will do better with a bit more, others may actually grow better with a bit less fertilizer. If you do not get improved growth with more fertilizer, then that can save you money, and prevent nutrient build up over a long time.
   Another way for you to lose nutrients is through leaching. This is when water soluble nutrients are dissolved in water and as the water moved down and out of the pot (or out of the root zone outdoors). Many growers do a ‘flush’ after they are done with vegetative growth; the idea is to wash out any excess nitrogen which can interfere with flowering. This is why you want to waer your plants only when the top layer is dry, so they can use the nutrients in the soil, and you only want a small amount of water to run out the pots when you water. If you notice a white ring on the trays that catch water overflow or on the bottom of your pots, that is most likely salts/fertilizers residue. This is a sign of leaching. Leaching is not a problem with hydroponics since the water is cycled over the roots many times, but you do have to deal with the pH with hydroponics or the nutrients will be unavailable no matter how much you add to the solution. If you are growing outside, another way to lose nutrients is erosion, when pieces of soil are washed away in a rain storm or blown away by wind the nutrients attached to that soil are lost too.

Good Growing,
Dr. E.R. Myers


E-mail - Using Small Pots for Big Yield

     I have read your posts in growing in small spaces. I do not have a lot of space and I was thinking if I keep the plants in small pots and keep them well watered, I will have more plants and get the biggest harvest from a small area. I am going to try to grow plants from veg. through flowering in 1 gallon pots. What do you think, any suggestions you have would be great.

Thanks for the E-mail and reading the other posts, it makes me happy to know I can help. Theoretically you are right, if you keep the soil moist but not soggy and give the plant all the nutrients it needs you should get good growth. That is the basic idea of hydroponics. However, if you grow in soil, it will be harder to keep the whole soil moist, but not too moist (see my post on water retention in soils). Also, once the roots hit the container edges, they will be restricted in growth and restricted root growth means restricted plant growth. You might want to try a bubble boy or two instead of using small pots. I think you might get a bigger yield with that vs. several small containers. This depends on the plant species you are growing and light you are using, you did not mention that. I do not know what type of height restriction you have. If you do not have a lot of height, I’d recommend a T-5 fluorescent or a LED from HTGSupply.com.

Last, you could do a scientific experiment and grow a few plants in the gallon pots, and try others in a 2 gallon pot. I find most growers use 2 gallon pots or larger when trying to get fruit. Many plants need to get a certain size before they flower, so if you are growing larger plants, you might want to go with 2-3 gallon pots.
Let me know if you have any other questions, and how things turn out,

Good growing,
Dr. E. R. Myers


Water Availability in Soil Mediums II

 I will continue to talk about water availability in soil mediums. Most soils have about 50% pore space. This may surprise you. It is the pore spaces that are important and various mediums will increase or decrease the pore space, meaning they will increase or decrease the amount of water a soil/medium can hold. Please see my posts on sand, perilite, vermiculte coir, coir and soil  and more to determine what you should be adding to your medium.

When soil is saturated it means, all the pores are full of water, but after a day, all gravitational water drains out, leaving the soil at what is called field capacity. Plants then draw water out of the small pores which hold the water against the force of gravity. The longer the soil goes without water the greater the difficulty the plants will have at getting water, until no more can be withdrawn. The soil is then at what is termed the wilting point and without water additions, plants die.  Like I tell my students, most things in Biology go by the 'Goldilocks Principle'  Not too much, not too little, but just the right amount is what is needed.  You don't want a saturated soil, you will get reduced growth and often have yellow leaves as a first sign you are aver watering.

The amount of soil water available to plants is governed by the depth of soil that roots can explore (the root zone) and as I said the nature of the soil material.  Taller containers will allow roots to grow deeper.  A wide short pot may have the same volume, but it won't hold as much water once the gravitational water is gone.   Because the total and available moisture storage capacities are linked to porosity, the particle sizes (texture) and the arrangement of particles (structure) are the critical factors. I will discuss these terms in the next post..

Good Growing,
Dr. E. R. Myers