Simulating Soil Moisture with Temperature in Clay-Based Agriculture

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Discussion Overview

The discussion revolves around simulating soil moisture in clay-based agriculture and how temperature affects moisture levels. Participants explore the variables involved in this simulation, including temperature, humidity, and soil characteristics, while seeking equations or models to facilitate their understanding.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant seeks a general equation to simulate soil moisture decrease at specific temperatures, particularly in clay soil.
  • Another participant suggests that factors such as air temperature, vapor pressure, humidity, wind speed, and diffusion equations are relevant to the simulation.
  • A different viewpoint emphasizes the variability of soil types and the need for laboratory testing to accurately predict soil properties, challenging the notion of a universal definition of "clay."
  • One participant expresses a lack of background in soil science and requests guidance on assumptions and equations to use for their simulation.
  • Another participant highlights the importance of understanding water migration through soil and its evaporation rates, noting that this is determined through field testing.
  • There is a suggestion that while complex models exist, simpler equations may suffice if high accuracy is not required for the simulation.

Areas of Agreement / Disagreement

Participants generally agree that soil variability complicates the simulation of moisture levels, and there is no consensus on a simple equation that can be universally applied. Multiple competing views on the necessary complexity of the model remain unresolved.

Contextual Notes

Limitations include the lack of clarity on specific soil characteristics, the dependence on various environmental factors, and the absence of a universally accepted equation for the simulation.

whitenight541
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Hi all,

I'm not sure if this is the right thread to post this topic.

I want to simulate soil moisture and how much it decreases given a certain temperature.
For example at temperature 25 degrees Celsius , what is the rate of decrease of the soil moisture? The kind of soil is clay suitable for agriculture.
Is there a general equation for this?
Please guide me.

Thanks in advance
 
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I remember calculating this many years ago. I believe you need to know the air temperature (as you stated), vapor pressure of the moisture (does this depend on soil?), the humidity, the wind speed (maybe), and the diffusion equation. If you can cover the soil with straw or corn stover, the diffusion will be less.
Bob S
 
There is nothing really cut and dried because soils vary so much. What you call "clay" wouldn't be what I would call clay, if it is indeed suitable for agriculture. I'm used to speccing and testing blue marine clays for the construction of clay-core dikes for waste treatment ponds, and for the isolation of leachates from solid wastes. You wouldn't want to try to grow anything in that.

Clay as a generic term can mean a high concentration of fines, some silt, some sand and some organic materials. That could possibly describe the soil in my garden-spot when I initially moved here (neglecting the ever-present rocks). What I'm getting at is that soil-classifications are not monolithic and need to be backed up with quite a bit of laboratory testing before you can predict their properties with any confidence.
 
Thanks so much for replying.

The problem is I'm a computer-science graduate and I don't have any knowledge regarding this topic. I'm not even sure it is called clay (as you stated it shouldn't)

All I know is it is a soil suitable for agriculture, the temperature varies from 20 to 30 degrees Celsius throughout the year. Humidity is moderate, it can be a coastal city though.

I don't know anything about the diffusion equation.

What assumptions should I make about the rest of the parameters you stated? and what equation should I use in calculating the moisture?
 
One thing that you are missing (and it is critical) is "how fast can water migrate through the soil and evaporate if the soil is wetter than the air?" This is something that is determined through testing in the field. When building clay-core dikes, we had to test the clays in the lab, in situ, and as-deposited because for the layers of clay to bond well, their moistures had to match well. Some soils that can be characterized as "clays" dry fairly well, while others develop a rather hard external crust that helps resist migration of water and retains the moisture in the underlying soil. I'm not a theorist, but spent a few seasons in the trenches as a soil scientist in construction, so most of my work was practical and driven by experimentation.
 
I tried reading the PDF and I didn't understand a single word. I think it needs a vast background on geophysical issues.

Is there a simple equation for this with simple variables that I can find and assume? I don't need the model to be accurate. Just accurate enough to model the soil in general, it is a simulation using wireless sensor networks. I can make any number of assumptions within the model.

I'm sorry for my laziness but I really couldn't get anything.

Thanks in advance.
 
whitenight541 said:
Is there a simple equation for this with simple variables that I can find and assume?

I don't think so. People go to school for years to answer these kinds of questions. I knew a civil engineer who specialized completely in soils.
 
I totally agree with you .. but usually complexity comes for accuracy. If accuracy is not required simple equations are formed. right?
 

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