I am doing a science project trying to figure out which types of plants retain the most moisture in soil, as an attempt to combat desertification.
A garden expert suggested different plants for me to use, based on the fact that they use little water and provide a lot of shade. But, he suggested to me for my setup, to use grow lights, accompanied by an under-plant heating pad, rather than a heating/grow light.
Now that I think about it, don't his choices for plants seem moot? What is the point of using plants that create a lot shade, if the heat is coming from under the plant, rather than rays from above it?
The plants I am using are Bermuda Grass, Evening Primrose, and Bergenia (winterglow)
I am also aiming to maintain a heat of about 80-90 degrees F
What kind of set up do you think I should use, and do you have any other comments on the experiment?
Not quite sure I understand, but I don't see the point of the heat mat under the plants. That is usually used for sprouting seeds ONLY. Many seeds do need that warmth to sprout. Once sprouted they don't need it. Since I do use heat mats for sprouting seeds, I can tell you that they are very drying. The heated soil dries out way faster than the same soil, watered the same way without the heat mat.
Why do you need to maintain a temp of 80 - 90 deg? Is this going to be in a greenhouse? Where are you located?
What we know about retaining moisture in soil doesn't so much have to do with the kind of plants, but the quality of the soil (lots of organic matter, good tilth) and keeping the soil mulched all the time. No till practices help, because tilling opens up the soil so that the moisture can escape.
As I said before, I am relating this project to combating desertification.
I am trying to match the high levels of heat found in areas that are at risk for desertification.
Also, most areas suffering from desertification do not have the money and resources to produce the required mulch/compost, or modify the type of soil that they are using. In these conditions, the easiest and most likely variable to be altered is what crop/plant you are planting, as an attempt to regain moisture in the soil.
There have been different projects proven to regain moisture levels in previously arid soil, simply by planting certain crops. Although I do not agree with all of his "Facts", Allan Savory has done a good job at re vegetating desertified areas by planting feeder crops, and using absurdly high levels of livestock. The Livestock is too high, that they do not eat all the plants before moving on, and they leave dung which acts as a fertilizer. Here you can see his TEDTalk presentation discussing his processes
DoubleDogFarm wrote:"DarlesCharwin" Thats Funny
Desertification is mostly caused by human disturbance. Stop deforestation, overgrazing and bad farming tecniques.
And rather than trying to get people to change their lifestyle (which obviously doesn't work), I'd like to see what other minor changes can help. Such as farmers planting certain crops to retain moisture. Later on, I would like to also test which plants de-salinate soil most efficiently, and which ones contribute most to nitrogen fixation.
This is just my senior year in highschool, so I expect my life plans to change, but at this point I would like to go to college for Environmental science, and eventual try to find a career in field research for Habitat Repair and sustainability
Your ambitions are admirable and your project is a good one.
But if people both in industrialized countries and poor ones won't change their lifestyles, then civilization as we know it is probably pretty doomed and you will be living through some pretty hard times (I'm old and probably won't live to see it all for which I'm thankful).
EVERYONE has the resources to improve their soil - it is known as humanure, composted waste from bucket toilets. In the primitive version that kept soils in China fertile for thousands of years, it is just "night soil" applied directly to the fields, but of course there is a lot of risk of disease transmission in that. But composted humanure added to sandy soils would improved the moisture holding dramatically.
Most everyone has some kind of wastes from cooking and from fields (corn stalks, etc) that can be chopped up and composted.
If your project is about moisture and desertification. I do see the point of the light and the heat mat. You will be trying to simulate desert conditions. You would probably need to use different soil medias for your test plants.
desert soils are warm (hot)= increased evaporation
desert soils are low in organic matter, more sandy=reduced water holding capacity
few trees in deserts = plants have high light requirements. No hostas here.
Adaptable plants = high light heat tolerant, with deep roots to reach the water table and/or water storage capacity, or adaptation (gray leaves, few leaves or stomata, waxy leaves, designed to collect and store water or dew) to collect or limit evaporative losses.
Improving soil = Don't cut down the trees (provide shade, water storage habitat for wildlife, cools the surrounding air and ground with shade),
diversity = trees, shrubs, grassses = prevent erosion of soil from wind and rain, eventually will add organic matter to the soil
How to get there faster. Take desert soil add organic matter, cover crop with drought tolerant plants. If you are planting. Use no till methods. Cut the tops of the plants over seed using seeds of plants that originate from areas that are naturally hot and dry. Grow melons not tropical grasses. Practice water conserving farming methods. In Egypt a fedan (about an acre) is productive requires that the topography be graded to promote the collection of water when it does rain and channels that water toward the crop.
Plant trees, plant crops around the orchard. Trees can provide fruit or nuts and windbreaks, lower the temperature of the area providing a more amenable microclimate. Drip irrigation, add organic matter and mulch. Dry garden.
For project you will need to use media that resembles desert soil= sandy and low in organic matter
you will need to measure water in and out. Set up a terrarium. and use a moisture meter = create a microcosm. If you can weigh the system at the start and in between you will be able to measure how much water is lost from the system
measure the water going into the system.
Heat mat or element under soil= simulates water evaporation from desert soils
High light, heat from the sun= light, evaporative losses from the sun is simulated
Plants in system will need to be adaptable in either catching morning dew (good thing a terrarium does actually mist up) or put down deep roots or have some adaptation hairy gray leaves, no leaves, water collecting adaptations (spines on cacti), waxy succulent leaves, storage in roots or stems, canopies that can shade the soil and cool the immediate area and slow down evaporation. drought resistant grasses and shrubs in marginal conditions can help to prevent erosion of soils from wind as well as add organic matter to the soil.
Experiment with mulching to help retain moisture in soil, cool and slow evaporative losses. Use materials that may be available.
Happy gardening in Hawaii. Gardens are where people grow.
So to answer your questions; I don't think that a grow/heat light would warm up the soil sufficiently to simulate the temperature of desert soil. That may be the point of the heat mat. But you're right; the shade of the plant will have less or even no impact on the temperature of the soil (and perhaps evaporation) if heated from below.
May I suggest that shade is not the most important contributor to water retention and that organic matter and soil structure are. Soil that has a high humus content holds water and prevents evaporation to some extent. Soil that has pathways for water to enter a deeper level will less likely lose it to evaporation.
Shade will reduce the soil temperature though and part of your experiment should actually show whether or not the reduced temperature actually reduces evaporation in various types of soil (sandy desert soil and 'modified' desert soil with some organic matter). I.e. you have made an assumption that shade, temperature and evaporation have a certain relationship but you need to back this up - either in your literature review if someone else has proved this relationship or with your own work.
You don't have to only warm the soil up form above though, you could investigate the relationship between temperature and evaporation and state the assumption that shade and temperature have a direct relationship (fairly logical). It depends what you can actually do with your resources and how complicated this should be. Research should be kept simple and rather of better quality that over-doing it but then running out of time. I have this problem keeping my research limited!
Concerning the advice given, his suggestions come from a background of gardening, not necessarily science and perhaps you should consult your supervisor?
It sounds like a great project and we would love to see the results.