Sunday, October 4, 2020

Citizen Science: Experimenting with Kitchen Trash to Remediate Soil

I have learned a lot from Master Gardeners - especially their virtual lectures on soil. But to be honest, I have had a few gripes about past presentations where they suggested the use of herbicides to keep out "weeds" or recommended plants that require too much water in our drought-stricken desert.  To their credit, more recent presentations have included rainwater harvesting and permaculture in addition to irrigation systems. So that's good. But there was one statement that really bothered me. The master gardener proclaimed that there was very little organic matter in the desert. I couldn't resist leaving a comment in chat that there could be if we didn't pull all of our native plants and grasses (i.e. "weeds") and left leaves and other debris on the ground to nourish the soil rather than covering everything with gravel. He admitted with a shrug that that was a good idea.   

It is no secret that I am an advocate for returning our yards (as much as possible in an urban environment) back into a native desert habitat.  Dan and I dug up all the plastic and gravel and replaced it with earthwork basins and woodchip mulch in an effort to sink in the rainwater, nourish the soil and grow native and drought-tolerant edible trees. But after 25 years at this location, our yard is still negatively impacted by the weed killers from previous owners.

Scraping out poison green gravel

Even after digging out a layer of green (we believe poisoned) gravel to make a greywater basin for our heritage fig trees, those poor little trees are barely holding on after three years. As an advocate for greywater harvesting, it pains me deeply to admit our failure. And it's not for lack of trying.

I baby those little guys. I get up early to water the organic mulch around the basin (with rainwater when we have it.) I am experimenting with a makeshift "no waste" fertilizer made from kitchen trash that would have otherwise ended up in the landfill or our slow working compost pile. 

I started with a mixture of coffee or tea and crushed organic egg shells - until someone informed me that Tucson dirt already has too much calcium. That made sense since I had dug up some calcium buildup and even some caliche in our yard. (I can still see egg shells in one of the basins since it takes so long to break down...) So now I just use the used coffee grounds and tea leaves...

I also pour all of my vegetable and pasta cooking water in the basin to add minerals. And even the slime water left when preparing nopalitos (prickly pear cactus.) 

After drying my moringa leaves for tea, I put the stems in the basin for mulch. If moringa is good for us, it must be good for the plants too, right? 

I figured banana peels would add potassium.

I read that legumes add nitrogen to the soil, so I started soaking and planting cowpeas and other beans around my fig trees, curry plants and jujubes. The cowpeas actually bloomed under our curry plants and some even grew bean pods. 

But lately the lizards eat the leaves off of the beans. It may be the definition of insanity, but I keep trying.

I heard that hair was good for gardens, so I started adding our pets and even our own hair to the mix. I cut the hair up into tiny bits and mix that with used tea leaves.  I'm not sure it's breaking down to nourish the soil, but at least it's making mulch. 

I've always taken a lot of pics of my process and different experiments in our yard. I like to fancy myself a "citizen scientist."  But since that disturbing statement about our lack of organic matter, I have been really trying to remediate the soil.  

Another comment I heard was that if there is fungus growing in your soil, you are watering it too much. We planted three jujube trees at the same time. I have observed that the jujube tree that is doing the best has little mushrooms growing in the organic mulch around it and clumps of white organic matter. I think that's a good sign.

The other two jujubes have no mushrooms and none of the white stuff and they seem to be struggling. They are less than half the size of the big jujube and much less full. Dan said that those two were planted in the basin where he had dug up oleander shrubs. So the poison from the oleander may still be in the ground there. He also discovered some asphalt along the edge of the basin. First, the weed killer in the green gravel and now this!  Please, keep in mind that what you put in your yard can impact the soil for future owners. 

big jujube in foreground, smaller in background

I finally looked up what kind of ground our jujube preferred to better understand why the one tree was doing better than the others.  I found...

Dig up a bit of soil at the site where you plan to plant or have a jujube growing. Squeeze some in your hand and open your hand again. If it stays in a tight clump that doesn't break up under light pressure, it is clay and you need to steer clear. If it doesn't hold together at all, it is sand and probably doesn't hold enough nutrients. If it breaks up under light pressure, you have loam, and the plant should thrive. When there's a little sand in the loam that's even better for the jujube, which needs a well-drained soil. Make sure you're not at the bottom of a hill or near where your home's downspouts release either because these plants prefer dry feet.

One video I watched had very productive plants growing in red clay soil. According to my copy of Fruits of Warm Climates, sandy loam is the preferred soil type for jujubes, but the plants must be fairly adaptable to do so well there.

Inspired by the screening of "Kiss the Ground" - a doc about how saving our soil could help fight climate change. I decided to do some research on whether my little additions were actually doing anything to remediate the soil. To really know, I would need to get the ground in different areas of our property tested to see if there were any deficiencies. Since that wasn't an option, I did conduct a fascinating google search.

First, I found out there was indeed organic matter in desert soil. To learn more about desert soil, check out this article from the Desert Museum.

But what was my "no waste" fertilizer adding to the soil? Here's what I found out.... Most plants need nitrogen, phosphorus and potassium.

Coffee grounds have a high nitrogen content, along with a few other nutrients plants can use. In compost, they help create organic matter that improves the ability of soil to hold water. We've got a keeper, folks! 

Used tea grounds and fresh tea leaves contain nutrients and tannic acid that, when added to the soil, create a more fertile environment for garden, landscape and container plants. Because tea grounds are natural, organic matter, they increase nutrient levels and improve soil quality as they decompose.

Banana peels contain nutrients that are essential for healthy potted plants. However, they don't contain everything your plant needs. As they decompose, banana peels add potassium as well as small amounts of nitrogen, phosphorus and magnesium to the soil in a similar fashion as a slow-release fertilizer. Not only do they add nitrogen to the soil, balancing any carbon-rich materials that might already be in there, they also add to soil structure and improve drainage.  It adds Tannic acid that slightly lowers soil pH to acid loving plants (best for flowering plants like roses). It also creates good drainage and moisture retention. GONGA! Another keeper! 

Human hair is a rich source of nitrogen. Human hair is good for plants when combined with compost since it takes too long to break down. 

In addition to water and sunlight, plants need certain nutrients to grow, particularly nitrogen. While nitrogen is abundant in the Earth's atmosphere (composing about 78 percent of it), it is in the form of molecular nitrogen (two nitrogen atoms bonded together), which is unusable to plants. For plants to take up nitrogen, it must be "fixed" into compounds such as nitrate (one nitrogen and three oxygen atoms), which plant roots can absorb from the soil.

Were the beans I was planting doing any good? 

While some plants, such as legumes, get their nitrogen through symbiotic relationships with nitrogen-fixing bacteria, others rely on fertilizers, whether organic (composted plant waste or animal manure) or inorganic (the man-made stuff you buy at the gardening center).

Legumes, including beans and peas, are able to have a symbiotic relationship with a specific family of bacteria called rhizobia. The plant roots form nodules (little bumps), which house the bacteria. The nodules provide protection for the bacteria and the root provides them with sugars as a food source. In return, the bacteria take atmospheric nitrogen, which plants can’t use, and through a process called nitrogen fixation they convert it to ammonia. The ammonia is converted to nitrate as it is absorbed by the plant.

In a green plant before flowering, 60% of the fixed nitrogen is found above ground in leaves and stem and 40% below ground. The same plant with mature pods has 80% of the plants fixed nitrogen in the seed, 9% in leaves and stem, and remainder in the roots.

Forage crops that are harvested and removed from the land provide almost no nitrogen for future plants because “roots and crowns add little soil nitrogen, compared to the above ground biomass“. About 80% of a plants nitrogen is found above ground.

The most efficient way of fertilizing soil with legumes is by using them as a green manure. Just as legumes start to bloom, which is when they’ll be richest in nitrogen, work them into the soil where they’ll decompose and release the nitrogen they stored. Don’t let them flower fully and go to seed, as the nitrogen will largely migrate into the seeds. (That’s why legume seeds are high in protein, of which nitrogen is a prime component.) So, with the green mature method, you don’t get to eat your beans and peas or whatever else you sowed: you have to turn the mother plants under.

However, you can have your nitrogen and eat it too, to a certain degree. Grow your peas, beans, broad beans, etc. the way you usually do, harvesting (and eating) their seeds, but don’t pull the plants out in the fall. Instead, cut off the leaves and stems if you want to (although you could work them into the soil as well), but leave the roots in the ground to decompose. Not all the nitrogen moves to the seeds, so the rotting roots still contain a decent share of nitrogen that future vegetables will be able to harvest.

So here's what I learned about the beans I planted. The ones that grew bean pods actually fixed less nitrogen in the soil than the ones with just leaves, so I shouldn't let them flower. Dan disagrees about turning the growth under because it is tilling. He suggested that since I don't want to disturb the microbial growth, that I should just let them rot in the ground to fix the most nitrogen. 

Dan also mentioned that native legumes like mesquite and palo verde fix nitrogen. And they don't require a lot of water and the lizards don't eat the leaves off of them. The green seeds of the palo verde are edible. And the seed pods on the mesquite can be ground into a yummy and nutritious flour. But that's another blog...leave those pods where they land for a natural mulch that doesn't wash away as easily in the monsoon floods (like woodchip mulch can.) Yet another reason to grow native plants in your yard - to leave organic matter for living soil - desert style! 

What I leaned from our desert farming friends Donald and Cristina : The soil is high red clay in a hard calcium carbonate pan. Alkaline soil is just part of the lower desert soil make up. The alkalinity in desert soils will generally start at a pH of 7.8 and goes up from there. The problem is when the soil pH is higher than 8.5 it indicates the start of a saline situation. Calcium is one of the main elements that contribute to high pH. It is hard to lower. Adding organic matter greatly helps. Organic matter when it starts to break down by the bio activity releases organic acids. The acids attaches to elements that raise the pH. This acid make the elements more water soluble so it can be leached out at a lower depths in the soil. It is Important to add soil sulfur along with organic matter. This really helps lower lower pH. It is organic. I have been gardening with a high clay soil for about 40 years, would not trade it for anything else. Again Organic Material (which includes your kitchen scraps, chicken manure mixed with hay, in ground composting etc) helps open up the soil for water and plants roots. Learning how to mange high clay soils can be your friend. Clay has some characteristics that are helpful growing plants in the deserts. Clay retains more water helps extend the periods between irrigations. Clay soils believe it or not are more fertile. It retains nutrients a lot better. In the desert you will not get rid of calcium. In our soil the calcium is well disseminated to hard pans in the soil like cement. Our soil when we moved here the upper inches was a little over 8. Now with Organic Materials-and soil sulfur the pH is now about 7.8.

Organic material is the best cure for all types and textures of soil. There are elements in the soil that make it alkaline, the biggest ones are calcium and sodium. Sulfur helps. Use organic materials that do not include calcium like egg shells, ashes, and salt bush, tamarisk or salt cedar leaves.

To find out what kind of soil you have, use the NRCS Soil Survey Web Platform:

How to use the NRCS Soil Survey Web Platform to find information about your soil using the NRCS Soil Survey web application.

I don't know about you, but I've learned a lot from my efforts as a "citizen scientist." I will definitely keep using my beneficial "no waste" mulch of coffee, tea, banana peels and hair! While being grateful for our edible forest of native desert plants that don't require so much care to provide us with shade, food and a habitat for critters. 

More information: 

Are Coffee Grounds Good for Plants?

Do Legumes Add Nitrogen to the Soil? -Garden Myths

Recommended by a facebook friend: DIY soil analysis jar

To be continued...