Abstract:
A fertigation system includes a circulation pump positioned in-line in a closed-loop, low-flow tubing delivery means. The circulation pump acts to agitate and substantially equalize a concentration of nutrients in fluid within the tubing, thereby preventing a concentration gradient from being established by upstream plants receiving preferential exposure to the nutrients relative to downstream plants. The circulation pump should preferably be configured not to substantially raise a fluid pressure within the tubing.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present invention claims priority to provisional patent application Ser. No. 61/329,867, filed Apr. 30, 2010. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to systems and methods for providing fertilizer to plants, and, more specifically, for providing fertilizer via low-flow irrigation systems. 
         [0004]    2. Description of Related Art 
         [0005]    It has been found during the use of low-flow systems, such as are typical with porous membranes, that most commercial fertilizers, even though water soluble, often fall out of solution, or “settle out.” When this happens, the amount of fertilizer available for plant use decreases in proceeding farther and farther from the fertilizer injection point. 
         [0006]    In the case of systems using porous membranes, such as taught in commonly owned U.S. Pat. Nos. 7,198,431, 7,712,253, and 7,748,930, it may be that, as a plant pulls fertilizer from the porous membrane, the fertilizer concentration inside the membrane decreases, thereby decreasing the amount of fertilizer available to plants downstream. 
         [0007]    Such a phenomenon is not an issue with high-flow, as the flowing fluid (water and fertilizer) carries the nutrients to the plant along with the water. However, with the systems such as the low-flow porous membrane system, this flow rate can be down to a level of extraction at the rates at which plants absorb water and fertilizer. 
         [0008]    In testing the feeding system and method of the above-referenced &#39;431 patent and &#39;827 and &#39;863 publications, a decrease in fertilizer concentration was noted. With tomato plants placed along a 100-ft membrane  1  in. in diameter, plant growth was seen to decrease at a distance of approximately 50 ft downstream of the fertilizer injection point, with continuing decrease further downstream. In recent tests, with the current pull rates of nutrition and water, it has been found that it takes approximately 30 days for water and/or nutrient to pass from the membrane feed inlet to the opposite end of the membrane. While this time is a function of environmental and biological factors, it serves as a demonstration of how substantially low the flow rates can be. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention is directed to a system and method for increasing an efficacy of a fertigation system, wherein the fertigation system comprises a low-flow system including a tubing-based delivery apparatus. 
         [0010]    The fertigation system of the present invention comprises a circulation pump positioned in-line in a closed-loop, low-flow tubing delivery array. The circulation pump acts to substantially equalize a concentration of a substance such as a nutrient in fluid within the tubing, thereby effectively preventing a concentration gradient from being established by upstream plants receiving preferential exposure to higher concentrations of the substance relative to downstream plants. The circulation pump should preferably be configured not to substantially raise a fluid pressure within the tubing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a cross-sectional view of a first embodiment of a fertigation system. 
           [0012]      FIG. 2  is a cross-sectional view of a second embodiment of a fertigation system. 
           [0013]      FIG. 3  is a close-up view of a return feed portion of the embodiment of  FIG. 2 . 
           [0014]      FIG. 4  is a cross-sectional view of a third embodiment of a fertigation system. 
           [0015]      FIG. 5  is a cross-sectional view of a fourth embodiment of a fertigation system. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0016]    A description of the preferred embodiments of the present invention will now be presented with reference to  FIGS. 1-5 . Although a number of embodiments will be presented herein, it will be understood by one of skill in the art that departures from the exact constructions illustrated and discussed are intended to be subsumed within the present invention. 
         [0017]    A first embodiment of a fertigation system  10  is illustrated in  FIG. 1 . A feed inlet  11  is positioned in fluid communication with a tubing inlet  12 , leading to outbound tubing  13 . The outbound tubing  13  is connected at a distal end  14  to a distal end  15  of return tubing  16  using, for example, a “U” fitting  17 , although this is not intended as a limitation. Simple connectors can be sealed by welding, for example, using a hand-held welder, or by clamping. A slide assembly can also be used at the tubing ends, which would require no tools in the field for connecting and sealing. 
         [0018]    A proximal end  18  of the return tubing  16  is connected to an inlet  19  of a pump  20 , such as, for example, a peristaltic-type pump, although this is not intended as a limitation on the invention. The pump  20  should preferably have the attribute of adding no substantial additional pressure to circulating fluid within the tubing lumen  21 . 
         [0019]    An outlet  22  of the pump  20  can connected adjacent the tubing inlet  12 , thereby providing circulation and substantial fertilizer concentration equalization within the tubing lumen  21 . 
         [0020]    A second embodiment of a fertigation system  30  is illustrated in  FIGS. 2 and 3 . A feed inlet  31  is positioned in fluid communication with a tubing inlet  32 , leading to outbound tubing  33 . The outbound tubing  33  is connected at a distal end  34  to a distal end  35  of return tubing  36  using, for example, a “U” fitting  37 , although this is not intended as a limitation. 
         [0021]    A proximal end  38  of the return tubing  36  is connected to an inlet  39  of a pump  40 , such as, for example, a peristaltic-type pump, although this is not intended as a limitation on the invention. The pump  40  should preferably have the attribute of adding no substantial additional pressure to circulating fluid within the tubing lumen  41 . 
         [0022]    A difference between this embodiment  30  and that  10  discussed above comprises that an outlet  42  of the pump  40  is connected with the tubing inlet  32  at an acute angle  43  ( FIG. 3 ), which decreases agitation in the low-flow-rate system. Again, this embodiment thereby provides circulation and substantial fertilizer concentration equalization within the tubing lumen  41 . 
         [0023]    In a third embodiment  50  ( FIG. 4 ), the feed inlet  51  is positioned in fluid communication with a tubing inlet  52 , leading to outbound tubing  53 . The outbound tubing  53  is connected at a distal end  54  to a distal end  55  of return tubing  56  using, for example, a “U” fitting  57 , although this is not intended as a limitation. 
         [0024]    A proximal end  58  of the return tubing  56  is connected to an inlet  59  of a pump  60 , such as, for example, a peristaltic-type pump, although this is not intended as a limitation on the invention. 
         [0025]    A difference between this embodiment  50  and those  10 , 30  discussed above comprises that an outlet  62  of the pump  60  is in fluid communication with tubing  63  that leads back to a storage tank  64 . Here the pump  60  can deliver a higher-pressure feed, as the effect of any agitation would be delivered to the storage tank  64  and not the irrigation tubing  53 , 56 . Thus the pressure within lumina  65 , 66  of the tubing  53 , 56  is maintained at a substantially constant value determined at least in part by an elevation head of the storage tank  64 . 
         [0026]    In a fourth embodiment  70  ( FIG. 5 ), the feed inlet  71  is positioned in fluid communication with a tubing inlet  72 , leading to respective inlets  81   a , 81   b , . . . of a network  73  of parallel outbound tubing sections  73   a , 73   b , . . . . The outbound tubing network  73  is connected at respective distal ends  74   a , 74   b , . . . to a manifold  75  leading to a proximal end  76  of return tubing  77 . 
         [0027]    A distal end  78  of the return tubing  76  is connected to an inlet  79  of a pump  80 , such as, for example, a peristaltic-type pump, although this is not intended as a limitation on the invention. 
         [0028]    As with embodiment  50  discussed above, an outlet  82  of the pump  80  is in fluid communication with tubing  83  that leads back to a storage tank  84 . 
         [0029]    As discussed above, the pumps  20 , 40 , 60 , 80  can comprise any type of pump usable in the target setting, although a peristaltic pump is believed to represent the best mode at the time of filing. 
         [0030]    In use, the pump  20 , 40 , 60 , 80  can run continuously or can be triggered intermittently depending upon the pump displacement and the length of the run. To ensure the fertilizer is kept in solution, and the concentration is substantially consistent, at least one full fluid rotation is believed preferable to be completed every several hours, the cycle time preferably designed to maintain a substantially constant concentration and keep the fertilizer in solution. Since the pump is run under low pressure and at a flow rate large enough to just cycle the fluid, the pump could be powered by a small solar panel when placed remotely. 
         [0031]    Additional embodiments and elements can include the use of filtration in the system to help extend membrane lifespan. 
         [0032]    Tubing membranes can be made as a unitary element having parallel sealed channels, or they can be separate tubing elements. If together, the tubing elements could be separated by perforations to enable easy separation.