This invention relates to a sub-irrigation system for growing plants and more particularly to a system of linked reservoirs that can be placed beneath the soil to facilitate sub-irrigation by capillary action.
Historically, cultivated plants have been watered using various sprinkler or open canal-based systems. Unfortunately, these traditional irrigation methods are associated with numerous drawbacks. Water conservation, especially in more arid climates, is a major concern with such irrigation methods. Spraying is particularly problematic, because water droplets are dispersed into the air, thereby increasing the surface area of the water and facilitating evaporation. In addition to the loss of water through evaporation, water applied by surface irrigation methods may also be lost to the underlying ground water via percolation through the soil. Besides poor water conservation, further disadvantages of sprinkler-based surface irrigation methods are: 1) leaching of nutrients and fertilizers away from the root systems and out of the soil, 2) washing of pesticides off the leaves and out of the soil, 3) contamination of ground water with environmentally hazardous levels of fertilizer and pesticides, 4) erosion of soil, 5) damage to building surfaces, walkways and flooring (staining, rotting, hard-water deposits, etc.) from misdirected sprinklers and inadvertently sprayed water, 6) damage to walkways and flooring from excess water draining from planters, beds, and pots, and 7) personal injury liability from slippery flooring surfaces. Thus, surface irrigation methods, especially sprinkler-based systems are inefficient in terms of water conservation and associated with numerous disadvantages and potentially harmful effects.
A variety of subirrigation methods and devices have been developed to address some of the problems associated with surface irrigation. Most subirrigation systems take advantage of attractive forces that exist between water molecules themselves (adhesion) and between water molecules and other polar or hydrophilic substances (cohesion). In nature, the adhesive and cohesive properties of water permit continuous columns of water to rise hundreds of feet through narrow conductive elements, like capillaries, from the roots beneath the soil up into the leaves, from where the water evaporates through tiny pores in the leaves. Such movement is known as capillary action. Typically, prior art subirrigation systems provide water to plants via capillary movement of water from a lower reservoir, through some conducting means and into the soil in a planter, wherein the reservoir, conducting means, and planter comprise an integrated system. Generally, such systems also incorporate a means for providing air and water to the lower reservoir, as well as a means for permitting aeration and drainage of the planter.
In particular, U.S. Pat. No. 4,160,342 to Dryer, U.S. Pat. No. 4,231,187 to Greenbaum, U.S. Pat. No. 4,356,665 to de Oliveira, U.S. Pat. No. 4,962,613 to Nalbandian, U.S. Pat. No. 4,991,346 to Costa, (incorporated herein by reference) all teach variations of two-compartment, integrated subirrigation systems for growing plants, comprising a lower reservoir and an upper planter, with an airspace in the reservoir between the bottom of the planter and the surface of the water. The planter compartments are in fluid communication with the lower reservoirs via a variety of water conducting elements, such as wells, troughs or tubes, etc., which extend from the bottom of the planter to below the surface of the water in the reservoir. The conducting elements are perforated below the surface of the water and open to the soil in the planter compartment so that water in the reservoir may move into an adsorptive medium within the conducting element and subsequently rise up into the soil by capillary action.
The bottoms of these prior art planters also typically have holes through which excess water in the soil may drain into the reservoirs and through which oxygen can migrate from the airspace up into the soil. The means for adequate drainage and aeration are critical to a healthy root system and plant. Roots submerged in soil saturated with water deteriorate from lack of sufficient oxygen. These references also generally provide a vertical tube or channel between the lower reservoir and the air above the soil, through which water can be added to the reservoir and through which air may move freely between the atmosphere and the airspace in the reservoir.
While the prior art subirrigation planters described above address some of the disadvantages seen with surface irrigation methods, these integrated two-compartment systems are not well suited for large-scale commercial use. Each planter requires individual monitoring and care. Although the nursery industry typically employs overhead sprinklers to water large numbers of plants, there have been some attempts to secure the benefits of subirrigation technology on a commercial scale. For example, Whitcomb (U.S. Pat. No. 4,729,189) discloses an automatic subirrigation mat having attached thereto a plurality of fluid-conveying channels, which are connected along one edge of the mat, to a main water pipe. Each channel has a number of outlets or holes designed to align with the center holes in the bottom of standard nursery pots, such that water conveyed by the channels moves under pressure through the outlets directly into the soil within the pots. Whitcomb teaches a variety of specialized valves and outlet structures for regulation of water flow. While the reference teaches watering of many plants, through a network of coupled channels, it does not describe a passive watering mechanism (i.e. via capillary action), nor does it provide means for drainage and aeration.
Bednarzik (U.S. Pat. No. 5,020,275) also teaches an automated subirrigation system comprising an inner planter having a nozzle extending downward from an opening in its bottom, and an outer pot, having a sealing means which closes off the nozzle when the planter rests in its lowest position within the outer pot. The outer pot has a water inlet line for conveying water into the outer pot. The inner planter will float as the water level in the outer pot rises, thereby opening the nozzle and permitting irrigation of the soil. As the water content within the planter increases, it sinks, thereby sealing the nozzle and preventing further watering. Subsequently, as water is used and evaporates from the planter, it begins to float, once again opening the nozzle and causing water to enter the planter under hydrostatic pressure, as well as via capillary action. The water level in the outer pot is regulated by an external float valve. Bednarzik discloses the interlinking of many such automatic watering pots to a central, regulated water line. However, Bednarzik, like Whitcomb, does not provide a means for drainage and aeration. As mentioned above, adequate drainage and aeration are critical to healthy roots and plants.
Thus, there is a significant need for a commercial scale planter system that affords the excellent water conservation of subirrigation, avoids the many disadvantages of sprinkler systems, is adaptable to automated operation and nutrient supplementation, and provides adequate drainage and aeration.