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Functionality of Soils Understanding Moisture Cycle Throughout the Irrigation Interval |
Garden Tip TB1485 |
Technical Bulletin Series
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Soil is measured in a number of ways that makes this determinatiuon
possible. Saturation is the point where there is zero air in the soil.
Field Capacity is that level where moisture begins to be useful
for plant life, and the Wilting Point is the level at which moisture
content to too low for root systems to utilize.
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Soil Composdition and soil Amendments are often overlooked,
as the value and importance of soil functionality is
not known or understood.
The more functional a soil is, the healthier the plant growing in that soil becomes. Obviously a totally dysfunctional soil will not support living plants. Additionally; soils with a low functional rating will produce plants with little to no growth, lack of fruit, and a high incidence of disease and infestation. True, some plants can tolerate a greater level of dysfunction than others. This hardly makes the case for not attempting to improve soil function during the planting process.
No plant
PREFERS Dysfunctional Soil!
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The Garden Galaxy Pro-I Irrigation Matching Calculator for New Plantings
calculates both the Native Soil Function and the Amended Soil Function,
and presents them as a percentage (from less than 10% to 90%.
The higher the percentage, the more functional the soil.
A 10% ratings means that for only 10% of the time in between irrigations,
the soil is fuinctional. A 90% rating indicates that for 90% of the time between
irrigations, the soil will support plant life.
The Pro-I reports ach functional rating - Side-by-Side - in order to see and understand the difference between properly amended, and unamended native soil.
The goal of the Pro-I is to Educate while making specific recommendations! Armed with knowledge... Helping make landscapers and gardeners more successful! |
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DYSFUNCTIONAL SOIL
At a certain point, soil becomes completely dysfunctional; It Doesn't Drain! In addition to improving the functionality of the soil surrounding our new plant, we need to verify that the hole we dig will in fact drain. Just because we put good soil into the hole, doesn't assure that the water we add to this good soil will be able to drain away and allow for the plant root system to breathe. To demonstrate this point; Imagine that we fill a pot with no holes at the bottom with sand. The sand is a very permeable soil, yet this water can not drain because the pot has no holes where the water may exit. The same is true for landscapes where the hydraulic condcutivity is less than 1 inch in 24 hours (0.04 in./hr.) Even with great amendments, there is nowhere for the water to go, other than transpiration of the plant. The result is plant failure and disappointment. In this situation, the alternatives are growing in a raised bed, or creating drainage bu channeling water through a french drain towards a downhill location.
Make sure you Jar Test Your Soil Know the Soil [HCR] Avoid a Future of Trouble
Organic material like compost and other blends of planting mix,
are recommended to be mixed in with the native soil. When the
percent of clay in the Native soil exceeds 20%, then it becomes necessary
to "remove" some of the Native completely in order to get a final product
amended soil that has the right properties.
High Clay CAN NOT be amended down.
Adobe bricks are made of high clay and straw/mulch. A percentage of the clay MUST be removed, then the soil amended! The amendments should include SAND, as this will not compress during time, and adds greatly towards increasing HCR. |
A Jar Test will provide the soil details needed in order to know the Hydraulic Conductivity [HCR] of the soil. This is the speed (inches per hour) that water will move through this soil when completely wet. If the soil's HCR is greater than 0.14 in/hr, then we likely have enough drainage to plant. However, if your soil is less than 0.08 in/hr you may want to also do a 24 hour Drain Test to make sure. Holes that won't drain kill plants! |
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When blending the soil for planting; a portion of any High % clay Native soil may need to be set aside (not used for planting) as the goal is to create a soil composition that favors the growth of new roots. The Garden Calculator Pro will specify what percent of the Native can be used, as well as the quantities of the other amendments needed (based on the size hole it specifies for planting). Once, having dug the planting hole, the amendments and remaining Native soil can be mixed together and used to surround the new plants rootball. Whatever amended soil is placed under the new plant should be packed firmly. Avoid situations where the rootball "sinks" after being planted. |
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The Garden Calculator Pro-I will actually specify the amount of Native soil, and each of the various amendments to add and mix for surrounding your new plant during the planting process. It calculates the permeability of this "NEW" soil mixture in order to provide the correct number of emitters and the irrigation run time. It is IMPORTANT to amend according to these specified formula! Putting in way too little amendment changes the new soil mix composition to the extent that irrigation moisture may not reach the bottom of the planting hole. Too much amendment can create a soil so different from the soil in the Nursery pot, that the new plant root system may not be able to grow past its' initial size. In the case of sandy native soil; insufficient amendment may cause premature wilting of your new plant between waterings.
THE SUCCESS OF A NEW PLANT DEPENDS CRITICALLY ON PROPER AMENDMENT.
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