question: why is it that if the soil is too dry, it will burst open
comment: Water has volume. Water in soil adds to the volume of the soil. As soil dries, the water is no longer within it. Reduced volume means the soil contracts. This causes cracks.
passages: BULLET::::- Drainage: In soils of bad drainage the water delivered through rain or irrigation may pool and stagnate. As a result, prevail anaerobic conditions and plant roots suffocate. Stagnant water also favors plant-attacking water molds. In soils of excess drainage, on the other hand, plants don't get to absorb adequate water and nutrients are washed from the porous medium to end up in groundwater reserves.
   Major effects on soil properties due to soil compaction are reduced air permeability and reduced water infiltration. Main physical negative effects to plants are restricted plant root growth and accessibility of nutrients due to increase in bulk density and reduced soil pore size. This may lead to an extremely dry topsoil and eventually causes soil to crack because the roots absorb water requiring for transpiration from the upper part of the soil where plants can penetrate with their restricted root depth.
   In moist climates, soils may be adequate for cropping with the exception that they become waterlogged for brief periods each year, from snow melt or from heavy rains. Soils that are predominantly clay will pass water very slowly downward, meanwhile plant roots suffocate because the excessive water around the roots eliminates air movement through the soil.br
   Insufficient soil moisture produces stress in plants, and water availability is one of the two most important factors (temperature being the other) that determine species distribution. High winds, low atmospheric relative humidity, low carbon dioxide, high temperature, and high irradiance all exacerbate soil moisture insufficiency. Soil moisture availability is also reduced at low soil temperature. One of the earliest responses to insufficient moisture supply is a reduction in turgor pressure; cell expansion and growth are immediately inhibited, and unsuberized shoots soon wilt.
   Organic materials in the soil (including plants and animals) all increase the infiltration capacity. Vegetation contains roots that extent into the soil which create cracks and fissures in the soil, allowing for more rapid infiltration and increased capacity. Vegetation can also reduce surface compaction of the soil which again allows for increased infiltration. When no vegetation is present infiltration rates can be very low, which can lead to excessive runoff and increased erosion levels. Similarly to vegetation, animals that burrow in the soil also create cracks in the soil structure.
  
  Section::::Factors that affect infiltration.:Land cover.
   In soil science and agronomy, soil compaction is usually a combination of both engineering compaction and consolidation, so may occur due to a lack of water in the soil, the applied stress being internal suction due to water evaporation as well as due to passage of animal feet. Affected soils become less able to absorb rainfall, thus increasing runoff and erosion. Plants have difficulty in compacted soil because the mineral grains are pressed together, leaving little space for air and water, which are essential for root growth. Burrowing animals also find it a hostile environment, because the denser soil is more difficult to penetrate. The ability of a soil to recover from this type of compaction depends on climate, mineralogy and fauna. Soils with high shrink-swell capacity, such as vertisols, recover quickly from compaction where moisture conditions are variable (dry spells shrink the soil, causing it to crack). But clays which do not crack as they dry cannot recover from compaction on their own unless they host ground-dwelling animals such as earthworms — the Cecil soil series is an example. 
   Groundwater
  
  Another off-site effect can be seen with regard to groundwater. The infiltration rate of grassland soil without traffic is five times higher than on soil with severe traffic. A consequence might be a reduced recharge of groundwater. Especially in dryer regions suffering from a lack of water reserves, this poses a crucial risk. In regions where “the subsoil provides a significant proportion of the water required by crops to meet transpiration demands”, often being dependent on agriculture, this danger of compaction is most present.
   Most crops require specific soil moisture conditions, and do not grow well in wet, mucky soil. Even in soil that is not mucky the roots of most plants do not grow much deeper than the water table. Early in the growing season when water is in ample supply, plants are small and do not require as much water. During this time, the plants do not need to develop their roots to reach the water. As the plants grow and use more water water becomes more scarce. During this time, the water table begins to fall. Plants then need to develop roots to reach the water. During periods of dryness the water table can fall faster than the rate at which plants grow roots to reach it, which condition can gravely stress the plants.
   Waterlogging (agriculture)
  
  Waterlogging refers to the saturation of soil with water. Soil may be regarded as waterlogged when it is nearly saturated with water much of the time such that its air phase is restricted and anaerobic conditions prevail. In extreme cases of prolonged waterlogging, anaerobiosis occurs, the roots of mesophytes suffer, and the subsurface reducing atmosphere leads to such processes as denitrification, methanogenesis, and the reduction of iron and manganese oxides.
   Soils that have an udic moisture regime commonly occur in areas of humid climates that have well distributed rainfall: i.e. they have adequate summer or winter rains, and generally cool summers.
  
  Aridic
  
  The moisture control section in the aridic moisture regime is dry when the temperature of soil, at a depth of 50 cm from the soil surface, is above 5 °C for more than half of the cumulative days per year and moist when it’s above 8 °C for less than 90 consecutive days. Soils that have an aridic moisture regime normally occur in an arid or a semi-arid climate.
  
  Xeric
   The introduction of deep rooting plants are a natural way to regenerate compacted soils. Deep rooting crops provide crop induced wetting and drying cycles that crack the soil, break up impermeable layers of soil by root penetration and increase organic matter[80] .
   Section::::Consolidation analysis.
  
  Section::::Consolidation analysis.:Spring analogy.
  
  The process of consolidation is often explained with an idealized system composed of a spring, a container with a hole in its cover, and water. In this system, the spring represents the compressibility or the structure of the soil itself, and the water which fills the container represents the pore water in the soil.
  
  BULLET::::1. The container is completely filled with water, and the hole is closed. (Fully saturated soil)
   Hardsetting has been defined this way: ""A hardsetting soil is one that sets to an almost homogeneous mass on drying. It may have occasional cracks, typically at a spacing of 0.1 m. Air dry hardset soil is hard and brittle, and it is not possible to push a forefinger into the profile face. Typically, it has a tensile strength of 90 kN. Soils that crust are not necessarily hardsetting since a hardsetting horizon is thicker than a crust. (In cultivated soils the thickness of the hardsetting horizon is frequently equal to or greater than that of the cultivated layer.) Hardsetting soil is not permanently cemented and is soft when wet. The clods in a hardsetting horizon that has been cultivated will partially or totally disintegrate upon wetting. If the soil has been sufficiently wetted, it will revert to its hardset state on drying. This can happen after flood irrigation or a single intense rainfall event.""
   Other soils may have an impervious layer of mineralized soil, called a hardpan or relatively impervious rock layers may underlie shallow soils. Drainage is especially important in tree fruit production. Soils that are otherwise excellent may be waterlogged for a week of the year, which is sufficient to kill fruit trees and cost the productivity of the land until replacements can be established. In each of these cases appropriate drainage carries off temporary flushes of water to prevent damage to annual or perennial crops.
   Surface drainage systems are usually applied in relatively flat lands that have soils with a low or medium infiltration capacity, or in lands with high-intensity rainfalls that exceed the normal infiltration capacity, so that frequent waterlogging occurs on the soil surface.
  
  Subsurface drainage systems are used when the drainage problem is mainly that of shallow water tables.
  
  When both surface and subsurface waterlogging occur, a combined surface/subsurface drainage system is required.
   BULLET::::- Water content: Without soil moisture there is no transpiration, no growth and plants wilt. Technically, plant cells lose their pressure (see osmotic pressure and turgor pressure). Plants contribute directly to soil moisture. For instance, they create a leafy cover that minimizes the evaporative effects of solar radiation. But even when plants or parts of plants die, the decaying plant matter produces a thick organic cover that protects the soil from evaporation, erosion and compaction. For more on this subject see mulch.
   If the soil temperature is 22 °C and above annually, or if winter contra summer soil temperatures vary by more than 6 °C at a particular depth of 50 cm below the soil surface, the soil moisture control section of ustic soil is dry, in some or most parts, for at least 90 or more cumulative days in a normal year. Although it is not dry in all parts for more than half of these cumulative days, at a soil depth of 50 cm the soil temperature is greater than 5 °C. In the event that the moisture control section is moist in all parts for 45 or more consecutive days in the four months after the winter solstice, the moisture control section is then dry in all parts for less than 45 consecutive days in the four months after the summer solstice.
   In agriculture, soil compaction is a complex problem in which soil, crops, weather and machinery interact. External pressure due to the use of heavy machinery and inappropriate soil management can lead to the compaction of subsoil, creating impermeable layers within the soil that restrict water and nutrient cycles. This process can cause on-site effects such as reduced crop growth, yield and quality as well as off-site effects such as increased surface water run-off, soil erosion, greenhouse gas emissions, eutrophication, reduced groundwater recharge and a loss of biodiversity.
   BULLET::::- Try avoiding soil compaction as it creates wet spots in the soil that can increase plant stress and SDS infection rates
  
  BULLET::::- Managing for SCN as this nematode often occurs alongside "F. virguliforme"
  
  BULLET::::- Deep tillage to break up compaction and help the soil warm faster
  
  One common management tactic used in other pathogen management plans is crop rotation. In some cases, disease severity can be reduced but most often it is not effective. This is because of chlamydospores and macroconidia as they can persist in soils for many years.
   Pores that are too small to be penetrated by most microorganisms. Organic matter in these pores is therefore protected from microbial decomposition. They are filled with water unless the soil is very dry, but little of this water is available to plants, and water movement is very slow. Size 0.1 μm.
  
  Section::::Modelling methods.
   Some soils are too high in permeability, allowing water to quickly pass through it, hindering purification effectiveness and allowing contamination to spread to nearby water sources or ecosystems. . 
  
  Areas of low soil permeability, such as areas with high water tables and limited soil cover over porous bedrock, can result in contaminated surface pooling.
  
  Section::::Design.
   Cool, wet field conditions shortly after planting favor the infection of soybean seedlings. This increases disease establishment and poses a higher threat to the crop yield. In addition to early cool and wet conditions, frequent or heavy rains in the middle of the growing season can speed up the expression of SDS symptoms. Being that this pathogen favors these wet conditions, increased risk is acquired when fields are irrigated as well as low-lying fields that are at risk of flooding and having soil compaction issues.
  
  Section::::Disease Development.
   When a soil becomes too dry, plant transpiration drops because the water is increasingly bound to the soil particles by suction. Below the wilting point plants are no longer able to extract water. At this point they wilt and cease transpiring altogether. Conditions where soil is too dry to maintain reliable plant growth is referred to as agricultural drought, and is a particular focus of irrigation management. Such conditions are common in arid and semi-arid environments.
   Section::::Effect on the land.
  
  The mounding building causes disturbances that build nutritional value as well as improving drainage and fertility. All of these improve vegetation and thus herbivore concentration in an area. Oftentimes these disturbances can be strong enough to switch the ecosystem from a grassy vegetated area to a tree, shrub, and pioneer species landscape.
   Expansive soils are the most problematic in regions with very defined wet and dry periods, as opposed to areas that maintain a certain level of moisture throughout the year, as this annual cycle causes the soils to expand and swell every year. Water can also be introduced into the soil through people, or their infrastructure. Damage is quite often caused by differential swelling which is caused by pockets of wet soil situated right next to dry soil. Examples of localized water sources include sprinkler systems, cesspools, leaky pipes, and swimming pools.
  
  Section::::Identification.
  