As we were finishing our new hoophouse and encouraging everybody in the neighborhood to start gardening, I asked in Steve Solomon’s Yahoo group about a general organic fertilizer for alkaline desert soil.  He asked for a soil test and it turned into a most interesting experience.

I’m very confused about what to do and I will be updating this page with questions and answers.

We tested TWO areas

This spring we started our new “lower garden”.  We screened the rocks out of the soil along the west fence and as just about everywhere we garden, caliche is about a foot down.  The lower garden has a dry wash and it is sandier than the other gardens, but that west bed dirt looks a lot like the dirt in the hoophouse except that it has fewer rocks.

We sourced free wood chips from a landscaper last winter and MIXED them with the screened dirt along with aged horse manure, some acidic organic mulch (Star Nursery in Vegas, $29/yd), a little Espsom salt and probably some coffee grounds from Starbucks.

I’ve since watched Back to Eden (free online) and they say NOT to mix chips into the dirt because the decomposition causes nitrogen deficiency.   However, it worked out great and there were no indications of nitrogen deficiency.

We fertilized with ACT tea (fish emulsion, kelp, vermicompost) a few times.  We only have one of those 5 gallon buckets with a little WalMart air pump brewer, so i didn’t expect  much.

The burlap on the fence protected the plants from our ferocious winds.  I never expected the plants to do as well as they did in the first year (click for larger pictures):

8/1/11 west bed - flowering chaste tree

We’d had the chaste tree for a year in a pot and it was AMAZING to see how it took off and flowered after we planted it in the ground.

The bed is probably around 40 ft long and the south half had several varieties of sorghum (test growing for sorghum syrup and ethanol).

8/9/11 west bed with cukes, melons, amaranth, chaste tree and tomatoes

Unfortunately, the gophers finally found me. It took them 5 years. And it took us way too long to order traps and figure out how to work them. The gopher killed off just about all melons and cucumbers and then moved on to the sorghum when we finally got him (or her).

Apparently gophers don’t care for tomatoes and those were by far the most prolific tomatoes I’ve ever grown. There were two plants by the chaste tree that started producing great tasting good sized cherry tomatoes (the labels had faded) just when it got really hot in August after a (relatively) cool summer. Despite the heat, they kept on flowering and setting fruit until they froze.

11/22/11 soil test sampling

Here are the holes for the soil samples and this is the ONLY place where we didn’t hand water. We turned the sweat hoses on manually while watering the rest of the garden with the garden hose and watered every 2nd day until August when it got so hot we had to water every day (eve).  Definitely not consistent, sometimes forgot to turn it off and overwatered and we don’t wear watches.

I enjoyed being in the garden in the evening to water and look at all our plants.  I never dreamed that we would have such a lush garden in the first year.

Our new hoophouse

Last winter we turned our abandoned carport turned shadehouse into a greenhouse and we liked it so much, we decided to build a hoophouse.  Our growing season was very short this year with worries about frost throughout May, although we got lucky and didn’t have hard freezes in October as last year. But the melons didn’t get done – again.

We also had FANTASTIC tomatoes in our little greenhouse and they just froze in early December and were still FULLY LOADED.  Between the lower garden tomatoes and the greenhouse we haven’t had to buy any tomatoes at the store since July and we both love tomatoes.  I would have never thought that tomatoes would set fruit with temps over 120 F every day. The Armenian cucumbers did ok too, but we got them started too late.  So we decided on a 20 x 40′ hoophouse.

The hoophouse is on a slight slope (the only place we have on our 1 acre lot)  and it was much more work than I had expected to clear, dig up 100+ lb rocks and to get it somewhat level (our tools were shovels, rakes and picks). We’re still over a foot lower on the east side.

Our prevailing summer winds come from the south and the front is facing SW (on contour), so it’s not hit directly by the winds but we’ll still have great ventilation.

11/21/11 -- finally got the plastic on.

As everywhere else we garden, we screen the rocks out and then amend with wood chips, pine needles, horse manure, acidic mulch, coffee grounds …

Preparing the dirt

We took NATIVE soil samples from various areas in the hoophouse. This area has not been irrigated.

About our property

I bought the place in 2006 and it was VIRGIN DESERT.  Nobody could have polluted and there is no gold (no mining).  I don’t have runoff from neighors (no neighbors).   However, we built the house on the top of the lot and there is lots of exposed caliche from grading and piles of caliche around the basement of a yet to be built “main” house.  I had big plans and ran out of cash.

We’re at 4000 ft in NW AZ between the Grand Canyon Skywalk and Lake Mead in the Joshua Tree forest near Meadview.  In winter 2010/2011 we had lows of 9 F on Thanksgiving, 9 F in December and then 4F in January.  It’s not usually that cold and all the trees we planted in fall 2010 froze.  We haven’t received many summer rains and most monsoon clouds circle around us.

We HAUL our water from a co-op well about 1.5 miles away in a 300g pickup tank and we use our gray water for trees. During the relentless hot August we spent about $40 on water and drove about 50 miles to get it (another $20 or so in fuel).  We had 3 raised beds, 50 ft of grapes w herbs and veggies, 5 garden beds with another about 60 ft of fence beds with herbs and veggies, the lower garden with about 100 feet of beds along the fences, 2 hugels and I don’t know how many trees, 20?  And we take LONG showers.

The soil tests

As per Steve’s recommendation, we got the $20 test at Logan Labs.


Since I know nothing about soil tests and I find them rather confusing, I prepared a spreadsheet to compare the results of the two tests and I added my questions:

(couldn’t upload the .xls)

Since the lower garden did so well, I was very surprised by the 8.7 pH and excessive calcium.  I didn’t think we had a problem.

I’m also surprised that the pH is identical to the native soil in the hoophouse.    Of course we have more organic matter in the lower garden, but I thought it would be a lot higher than the apparently perfect 5.45%.

Now I want to do a test of native dirt outside of the lower garden just to see how our amendments changed the dirt.

I’ve gotten lots of advice such as:

  • “Move the hoophouse” and that we shoudn’t grow anything in that soil.
  • Add sulfur.
  • Apparently the high pH can result in incorrect test results.

I’ve done a lot of reading and here are a few pages I saved:

From the Arizona master gardener program:

Explanation of various soil types.

… Most soils in Arizona are alkaline and have a pH of between 7 and 8.5.

The Effect of PH on Plant Nutrient Availability

The major impact that pH extremes have on plant growth is the availability of plant nutrients and concentration of plant-toxic minerals. In highly alkaline soils, micronutrients such as iron, zinc, copper and manganese become chemically tied up and are sparingly available for plant use. In highly acidic soils, calcium, phosphorous, and magnesium become tied up and unavailable, and manganese and aluminum can reach toxic levels. The application of certain materials to the soil can be made to adjust the soil pH value.

Reclamation of highly alkaline soils which are also high in sodium content can be accomplished using gypsum or other soil amendments. Once excess sodium is leached away the soil pH can decline, but not below about 7.5. Applications of acids or elemental sulfur to lower soil pH are usually not effective. This is because most Arizona soils contain the mineral calcium carbonate (free lime). This mineral buffers the soil pH at about 7.5 to 8. Nearly all of the calcium carbonate would have to be neutralized with a strong acid to even begin to drop the soil pH appreciably. …

… Another consideration is organic matter. Most western soils are low in organic matter under virgin conditions but it commonly increases appreciably with the application of irrigation water and cultivation. The most important factor regarding organic matter is that it has very favorable effects on the physical properties of soil. Particularly, organic matter tends to counteract the unfavorable effects of exchangeable sodium on soils. Simply put, heavy applications of organic mulches will increase water holding capacity, infiltration rate, tilth and soil aggregation. It has also been proven that organic matter will prevent deterioration of the physical properties of the soil by serving as an energy source (i.e. food) for microorganisms which promote stable aggregation of the soil particles.

Use caution when applying manures as a source of organic matter because they typically contain appreciable amounts of soluble salts and are usually somewhat high in pH as well. If the soil pH is too high, elemental sulfur or commercial gypsum can be added to the soil to rid the soil of excess sodium and indirectly reduce alkalinity.

Most ornamental plants require slightly to strongly acidic soil. These kinds of exotic (imported) plants are often very difficult to grow in our alkaline soils. These species frequently develop iron chlorosis when grown in soils in the alkaline range. Iron chlorosis can be confused with nitrogen deficiency since the symptoms (a definite yellowing of the leaves) are similar. The two nutrient deficiencies can be distinguished by observing where on the plant the deficiency symptoms appear. With iron deficiency, the symptoms appear at the shoot tips and on the newest growth. With nitrogen deficiency it is the older, lower leaves that are most affected. Foliar sprays of iron can alleuicte iorn deficiency. Also, iron chlorosis can be corrected by applying a chelated iron product to the soil to add plant available iron. be beneficial.

Soil Testing

Soil testing is done to determine nutrient status, pH, electrical conductivity (EC, a measure of salt content), soil structure, and sodium absorption ratio (SAR), or exchangeable sodium percentage (ESP). A basic soil test should include nitrogen, phosphorus, and potassium status, pH, and EC. Also, a SAR or ESP should be done for alkaline or sodic soils. Testing for secondary and micro nutrients is usually not needed and is expensive to conduct. A current list of testing facilities can be requested from the Cooperative Extension office. Home soil testing kits are not as accurate as lab testing. Some kits are very poor. More expensive kits are not necessarily more accurate. …

From the AZ Cooperative Extension:

… Calcium carbonate is a basic (high pH) substance, and where caliche is present the pH may be high enough to cause iron to be unavailable to plants. The symptoms of iron deficiency appear on the youngest, newest leaves, the area between the leaf veins becoming pale yellow or white. No physical deformity occurs, but in severe cases the youngest leaves may be entirely white and stunted. …

Spectrum Analytic:

Calcium in the Soil

Cation Exchange Capacity (CEC)

More info

Primal Seeds on nutrient deficiencies — how to identify and remedy

I’ll be THRILLED if I can get the lower garden to look as good as in its first season again.

We got a worm factory in spring and 4 lbs of red wigglers, but I don’t think we put any worms in the lower garden and I saw none when I got the soil samples.  The raised beds and greenhouse have lots of worms now and next year we’ll definitely put wigglers in the lower garden.  People say they’re only good for compost, but we found them thriving in the raised beds and they even lived through the cold winter.

What else should I do with the lower garden for the next planting season?

Update 12/29/11:  We had our gardening club meeting yesterday and another local organic gardener had tested his soil at 8.7 pH 3 years ago.  He used a little sulfur once a year and now it’s 7.8.   While he used a home testing kit that’s not as accurate as lab tests, the TREND is what’s important.   Aside from sulfur he recommended LOTS of organic amendment.  So it looks like we’re on the right track.