History
Use of Geotextiles
Geotextiles were used for capillary irrigation not long after World War II. However, it was not until 1995 that extensive research was conducted at the CSIRO Division of Land and Water in Griffith, Australia, by Grain Security Foundation Ltd, that SSTI was established as a serious commercial alternative to drip.
Polyester geotextile of specific thickness and manufacture is required to ensure the system has the appropriate flow characteristics and so that it does not become hydrophobic (repels water).
Solving Typical Subsurface Problems
Summary
Studies were done on many forms of geotextile using various dripper rates and configurations to evaluate water flow for the major soil texture types and to determine if SSTI had the same problems experienced by subsurface drip systems (SDI). Specifically, considerable focus was placed on the problem of root intrusion, tunnelling, dripper blockage and insect damage (serious problems associated with SDI).
Root Intrusion
Research data showed that roots could invade the geotextile but did not thrive nor thicken in the polyester geotextile [2] : 17 and, therefore, caused no damage. The roots were deterred from entering the dripper area because that area is dry relative to the rest of the system. Roots simply went elsewhere.
Tunneling
Tunneling (the process whereby water works its way up to the surface) was nearly eliminated by the narrow reflective impermeable tape above the drip line. [4]
Blocked Drip Emitters
Drippers are often blocked in bare drip systems due to soil lodging in the emitters and/or soil crusting around the emitters when the system is not operating. SSTI eliminates this problem because there is a physical barrier presented by the geotextile and due to the fact that the soil remains moist for much longer than drip systems (i.e. the soil does not form a crust anyway).
Insects
Similarly, insects are deterred from damaging SSTI systems because of the geotextile barrier.
Water Delivery
Initially solid, thick-walled drip pipes were used in trials at the CSIRO but subsequent trials between 1995 and 1998 demonstrated that drip tapes (thin-walled, flexible pipe) could be used very effectively. The loss of strength from using thin-walled drip tapes was countered by the additional tensile strength of the entire system (base layer, drip tape and geotextile). While significantly reducing the cost of SSTI, the use of drip tapes also permitted the use of large diameter drip lines (of up to 35mm) allowing for run lengths up to one (1) kilometre. The thin, flexible wall of drip tape also meant that master rolls of manufactured product could be much larger (over 600m in length).
Optimal Width and Wetting Patterns
The width of SSTI products varies based on the application. However, at the University of Queensland, Australia [3] trials were conducted to discover the optimal width of the SSTI in black cracking clay with alfalfa sown across a single SSTI line. The SSTI line was 20 cm wide and was installed 30 cm below the surface. The alfalfa germinated directly above the SSTI line but covered 75 cm either side (a total of 1.5 m) in uniform lines. As a result of this research, most SSTI systems are between 6 cm and 20 cm wide. However, some products are up to 2 m wide.
Installation Technologies
In 1997 the first SSTI plow was tested at CSIRO Griffith [5] using a standard three point linkage behind a tractor. This demonstrated that SSTI could be installed at 20–40 cm deep quickly and easily using the plow. SSTI plows are now available to install 1, 2 or 3 lines (more lines are possible).
Other Uses of SSTI
In 1996 the first ebb and flow mat technology for potted plants was commercialized based on SSTI technology using drip tapes to control the water delivery. This ebb and flow mat form of SSTI proved very effective in producing potted plants, sprouted wheat and barley for animal production and for research purposes in producing seed varieties without the use of any overhead irrigation. [5] It also provided an effective fertilizer delivery platform.
Irrigation is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has been developed by many cultures around the world. Irrigation helps to grow crops, maintain landscapes, and revegetate disturbed soils in dry areas and during times of below-average rainfall. In addition to these uses, irrigation is also employed to protect crops from frost, suppress weed growth in grain fields, and prevent soil consolidation. It is also used to cool livestock, reduce dust, dispose of sewage, and support mining operations. Drainage, which involves the removal of surface and sub-surface water from a given location, is often studied in conjunction with irrigation.
Drainage is the natural or artificial removal of a surface's water and sub-surface water from an area with excess of water. The internal drainage of most agricultural soils is good enough to prevent severe waterlogging, but many soils need artificial drainage to improve production or to manage water supplies.
An aquifer is an underground layer of water-bearing, permeable rock, rock fractures, or unconsolidated materials. Groundwater from aquifers can be extracted using a water well. Aquifers vary greatly in their characteristics. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology. Related terms include aquitard, which is a bed of low permeability along an aquifer, and aquiclude, which is a solid, impermeable area underlying or overlying an aquifer, the pressure of which could create a confined aquifer. The classification of aquifers is as follows: Saturated versus unsaturated; aquifers versus aquitards; confined versus unconfined; isotropic versus anisotropic; porous, karst, or fractured; transboundary aquifer.
The water table is the upper surface of the zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with water. It can also be simply explained as the depth below which the ground is saturated.
A French drain is a trench filled with gravel or rock, or both, with or without a perforated pipe that redirects surface water and groundwater away from an area. The perforated pipe is called a weeping tile. When the pipe is draining, it "weeps", or exudes liquids. It was named during a time period when drainpipes were made from terracotta tiles.
Drip irrigation or trickle irrigation is a type of micro-irrigation system that has the potential to save water and nutrients by allowing water to drip slowly to the roots of plants, either from above the soil surface or buried below the surface. The goal is to place water directly into the root zone and minimize evaporation. Drip irrigation systems distribute water through a network of valves, pipes, tubing, and emitters. Depending on how well designed, installed, maintained, and operated it is, a drip irrigation system can be more efficient than other types of irrigation systems, such as surface irrigation or sprinkler irrigation.
Nutrient management is the science and practice directed to link soil, crop, weather, and hydrologic factors with cultural, irrigation, and soil and water conservation practices to achieve optimal nutrient use efficiency, crop yields, crop quality, and economic returns, while reducing off-site transport of nutrients (fertilizer) that may impact the environment. It involves matching a specific field soil, climate, and crop management conditions to rate, source, timing, and place of nutrient application.
The vadose zone, also termed the unsaturated zone, is the part of Earth between the land surface and the top of the phreatic zone, the position at which the groundwater is at atmospheric pressure. Hence, the vadose zone extends from the top of the ground surface to the water table.
Sewage farms use sewage for irrigation and fertilizing agricultural land. The practice is common in warm, arid climates where irrigation is valuable while sources of fresh water are scarce. Suspended solids may be converted to humus by microbes and bacteria in order to supply nitrogen, phosphorus and other plant nutrients for crop growth. Many industrialized nations use conventional sewage treatment plants nowadays instead of sewage farms. These reduce vector and odor problems; but sewage farming remains a low-cost option for some developing countries. Sewage farming should not be confused with sewage disposal through infiltration basins or subsurface drains.
Fertigation is the injection of fertilizers, used for soil amendments, water amendments and other water-soluble products into an irrigation system.
Groundwater models are computer models of groundwater flow systems, and are used by hydrologists and hydrogeologists. Groundwater models are used to simulate and predict aquifer conditions.
Soil salinity control relates to controlling the problem of soil salinity, with the aim of preventing soil degradation by salination and reclamation of already salty (saline) soils. Soil reclamation is also called soil improvement, rehabilitation, remediation, recuperation, or amelioration.
Alkali, or Alkaline, soils are clay soils with high pH, a poor soil structure and a low infiltration capacity. Often they have a hard calcareous layer at 0.5 to 1 metre depth. Alkali soils owe their unfavorable physico-chemical properties mainly to the dominating presence of sodium carbonate, which causes the soil to swell and difficult to clarify/settle. They derive their name from the alkali metal group of elements, to which sodium belongs, and which can induce basicity. Sometimes these soils are also referred to as alkaline sodic soils.
Alkaline soils are basic, but not all basic soils are alkaline.
SahysMod is a computer program for the prediction of the salinity of soil moisture, groundwater and drainage water, the depth of the watertable, and the drain discharge in irrigated agricultural lands, using different hydrogeologic and aquifer conditions, varying water management options, including the use of ground water for irrigation, and several crop rotation schedules, whereby the spatial variations are accounted for through a network of polygons.
Sand-based athletic fields are sports turf playing fields constructed on top of sand surfaces. It is important that turf managers select the most suitable type of sand when constructing these fields, as sands with different shapes offer varied pros and cons. Regular maintenance of sand-based athletic fields is just as important as the initial construction of the field. As water and other aqueous solutions are added, a layer of thatch may accumulate on the surface of the turf. There are different ways to manage this level of thatch, however the most common are aeration and vertical mowing.
Surface irrigation is where water is applied and distributed over the soil surface by gravity. It is by far the most common form of irrigation throughout the world and has been practiced in many areas virtually unchanged for thousands of years.
Groundwater remediation is the process that is used to treat polluted groundwater by removing the pollutants or converting them into harmless products. Groundwater is water present below the ground surface that saturates the pore space in the subsurface. Globally, between 25 per cent and 40 per cent of the world's drinking water is drawn from boreholes and dug wells. Groundwater is also used by farmers to irrigate crops and by industries to produce everyday goods. Most groundwater is clean, but groundwater can become polluted, or contaminated as a result of human activities or as a result of natural conditions.
Agricultural hydrology is the study of water balance components intervening in agricultural water management, especially in irrigation and drainage.
A subsurface dyke is a structure that is built in an aquifer with the intention of obstructing the natural flow of ground water, thereby raising the ground water level and increasing the amount of water stored in the aquifer. Acting as an underground barrier impermeable to water, it controls the groundwater flow in an aquifer and raises the water table.
Micro-irrigation, also called Micro-spray,localized, low-volume, low-flow, or trickle irrigation, is an irrigation method with lower water pressure and flow than a traditional sprinkler system. Low-volume irrigation is used in agriculture for row crops, orchards, and vineyards. It is also used in horticulture in wholesale nurseries, in landscaping for civic, commercial, and private landscapes and gardens, and in the science and practice of restoration ecology and environmental remediation. The lower volume allows the water to be absorbed into slow-percolation soils such as clay, minimizing runoff.
