Abstract:
A plant protection system which is economical, and quickly installed and removed and which can be used on row crops such as strawberries to protect against frost, freezing, and insects. The system includes a series of frames placed along a crop row wherein each frame has at least one twine engaging loop on the upper portion of the frame. Twine is tensioned along the upper sides of the frames by drawing the twine into an open end of the loop, looping the twine completely around the loop and proceeding to the next frame with the twine held in tension at the loop. A protective cover is draped over the frames and tensioned twine and anchored in the crop furrows. The tension of the twine between the frames prevents the cover from sagging and touching the crops.

Description:
BACKGROUND OF THE INVENTION 
     This invention is generally related to a plant protection system that can be quickly and easily assembled in a field for protecting a crop of plants against adverse environmental conditions such as frost and freezing as well as insects or other pests. This invention has particular application to row crops such as strawberries and similar plants, but can be modified for other crops. 
     Cultivated crops have always been subject to the forces of nature and unseasonable climatic conditions such as frost or freezing can destroy a crop. Likewise, excessive or insufficient rainfall during the growing season can have a devastating effect on crops. Other natural threats such as insects are also a serious concern. Ideally, all these adverse conditions could be eliminated in a greenhouse enclosure, but that is obviously impossible and economically infeasible where thousands of acres are under cultivation. 
     In an attempt to replicate the benefits of a greenhouse but at a significantly reduced cost, several methods of covering crops in the field have evolved which involve draping a pliable cover such as plastic sheeting or other types of fabric over the crop to afford protection to the plants from external elements and propping up the pliable cover with a frame to keep it away from the plants. While this type of cover can be easily placed over a field of crops by unrolling across the field, if the cover touches the plants, their foliage, blossoms or fruit, damage can occur. This is commonly called “burn”. 
     Because of their flexibility and pliability, such covers will naturally sag between rigid frames, making it difficult to prevent touching the plant. While it may be possible to stretch a cover to eliminate sag, this is generally not feasible because of the large field areas involved and the difficulty in securing the perimeter of the cover. Adding more rigid frames to shorten the distance between frames will alleviate the problem of sag to some extent but then the cost begins to increase, defeating the intended purpose of providing protection to the plants in an economical way. It is apparent that the covers must be supported in two directions, with the rigid frame providing support in one direction and support between the frames in the other direction being provided by another means. 
     SUMMARY OF THE INVENTION 
     It is an object of this invention to provide an economical plant protection system which can be installed easily and quickly over a field of crops without special tools or equipment and can be removed easily and quickly and stored for future use. 
     It is an object of this invention to provide a plant protection system for a row of plants in soil having a first row end and a second row end wherein the system includes a plurality of frames each having a first soil engaging end, an upper portion and a second soil engaging end. Each frame spans the row of crops with the first soil engaging end and the second soil engaging end pressed into the soil in the furrow on each side of the row. The frames are spaced along the row of plants from the first row end to the second row end. On the upper portion of each frame is at least one twine engaging loop formed as a circular loop of the upper portion of the frame with a loop open end and a loop closed end wherein there is a gap between the loop open end and the upper portion of the frame and the loop closed end is in contact with the upper portion of the frame. At least one twine, having a first twine end and a second twine end, is fixedly secured in the soil at the first row end and successively engaged under tension in a twine engaging loop on the upper portion of each frame extending along the crop row and the second twine end is fixedly secured in the soil at the second row end. The twine first engages the twine engaging loop at the loop open end, loops completely around the circular loop over the closed loop end and exits the twine engaging loop at the loop open in tension to engage the twine engaging loop on the next frame along the crop row. 
     The inventive plant protection system further comprises a cover having an inner surface and an outer surface, wherein said cover is draped over the frames and twine with the inner surface facing the plants but only in contact with the upper portion of each frame and twine. 
     It is a further object of this invention to provide an frame for spanning a crop row as part of a plant protection system wherein each frame has a first soil engaging end, an upper portion and a second soil engaging end and at least one twine engaging loop located on the upper portion, and wherein the twine engaging loop further comprises a circular loop of the upper portion of the frame with a loop open end and a loop closed end, wherein there is a gap between the loop open end and the upper portion of the frame and the loop closed end is in contact with the upper portion of the frame. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of the inventive system in place. 
         FIG. 2  is an elevation of a frame. 
         FIG. 3  is a perspective view of a twine engaging loop. 
         FIG. 4  is a perspective view of a twine first engaging a twine engaging loop. 
         FIG. 5  is a perspective view of a twine having engaged the twine engaging loop and being looped around the twine engaging loop. 
         FIG. 6  is a perspective view of a twine fully engaged around the twine engaging loop and being tensioned to engage the next twine engaging loop. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a perspective view of the inventive plant protection system  1  in place over plants  2  in a crop row  3  with furrows  4  and  4   a  on both sides of the crop row  3 . Frames  5  span the crop row  3  and are set in a plurality of positions along the crop row  3  from the first row end  10  to the second row end  11 . Each frame has a first soil engaging end  12  and a second soil engaging end  13 . The first soil engaging end  12  is pressed into the soil  9  in the furrow  4  and the second soil engaging end  13  is pressed into the soil  9  in the furrow  4   a  on the other side of the crop row  3 . Although the first soil engaging end  12  and second soil engaging end  13  are shown pressed into the soil  9  in the furrows  4  and  4   a , the soil engaging ends  12  and  13  can be pressed into the soil  9  on the crop row  3  itself depending on the width of the frame  5  and the width of the crop row  3 . 
     Each frame  5  has an upper portion  13   a  with at least one twine engaging loop  6 . As depicted in  FIG. 1 , the frames  5  have two twine engaging loops  6 , which would normally be used. The number of twine engaging loops  6  would determine the number of twines  7  needed. In this depiction there are two twines  7 , each having a first twine end  14  and a second twine end  15 . Each first twine end  14  is fixedly tied to a stake  16  driven into the soil  9  at the first row end  10 . Although two stakes  16  are depicted, one stake  16  could be used as well as any other method of tying off the first twine end  14 . Once the first twine end  14  of each twine  7  is secured in this fashion at the first row end  10 , each twine  7  is successively engaged in tension on the twine engaging loops  6  of the next frame  5  going from the first row end  10  to the second row end  11  and the second twine end  15  of each twine  7  is fixedly tied to a stake  16  driven into the soil  9  at the second row end  11  or otherwise tied off at the second row end  11 . 
     With each frame  5  in place along the crop row  3  and each twine  7  tensioned between frames  5  at the twine engaging loops  6  and each first twine end  14  fixedly tied at the first row end  10  and each second twine end  15  fixedly tied at the second row end  11 , a cover  8  with an inner surface  17  and an outer surface  18  is draped over the frames  5  and twines  7 , with the inner surface  17  in contact with the frames  5  and twine  7 , and held above the plants  2  to prevent contact between the inner surface  17  and the plants  2 . The cover  8  can be draped in a direction across the length of the crop row  3  or draped along the length of the crop row  3  depending on the width and length of the cover  8  which would normally be supplied in rolls. The cover  8 , once in position, can be easily held in place at the ends of the cover and in the furrows  4  by any suitable method such as soil weighting. 
       FIG. 2  is an elevation of an embodiment of the frame  5  with a first soil engaging end  12 , a second soil engaging end  13 , an upper portion  13   a , and two twine engaging loops  6 . A suitable material for the frame  5  would be galvanized steel wire of approximately 5 gauge, although other materials and coatings could be used. The embodiment of frame  5  shown in  FIG. 2  would be approximately 20 inches wide and approximately 10 inches high, to suit the width of the crop row  3  and the height of the crop row  3  and plants  2 . This general size is intended for strawberry crops but can be adapted to suit other plants. In a normal application for this embodiment of frame  5 , a frame  5  would be placed along the crop row  3  approximately 10 feet apart. 
       FIG. 3  is a perspective view of a typical twine engaging loop  6  on one side of the upper portion  13   a  of a frame  5 . As can be seen in  FIG. 3 , the twine engaging loop  6  is formed by creating a circular loop  19  in the upper portion  13   a  of the frame  5 . There is a loop open end  20  on one side of the circular loop  19  and a loop closed end  21  on the other side of the circular loop  19 . In this embodiment the loop open end  20  is on the side of the circular loop  19  facing the upper portion  13   a  and the loop closed end  21  is on the side of the circular loop  19  closest to the first soil engaging end  12 . Another twine engaging loop  6  on the other side of the upper portion  13   a  would be a mirror image of the twine engaging loop  6  shown in  FIG. 3 . 
     At the loop open end  20 , the bottom  25  of the circular loop  19  is apart from the upper portion  13   a  of the frame  5  by a gap  24 . At the loop closed end  21 , the bottom  25  of the circular loop  19  is in contact with the upper portion  13   a.    
       FIG. 4  is a perspective view of a twine  7  first engaging a twine engaging loop  6 . In this depiction, the twine  7  is being drawn from left to right with a twine tensioned end  22  and a twine looping end  23 . The twine tensioned end  22  is already engaged in the twine engaging loop  6  of another preceding frame  5  along the crop row  3  or, in the case of the first frame  5  at a first row end  10 , the twine tensioned end  22  would be engaged at a stake  16  or otherwise tied off at the first row end  10 . As can be seen in  FIG. 4 , the twine looping end  23  does not pass through the circular loop  19 , but engages the twine engaging loop  6  at the loop open end  20  and is drawn into the gap  24 , which should be of a dimension no less than the thickness of the twine  7 . A suitable material for the twine  7  would be non-stretchable polypropylene although other materials may be used. 
       FIG. 5  is a perspective view of a twine  7  having engaged a twine engaging loop  6  and being looped around the twine engaging loop  6 . The twine looping end  23  has been drawn into the gap  24  at the loop open end  20  and is being looped around the circular loop  19  at the loop closed end  21 . 
       FIG. 6  is a perspective view of a twine  7  having fully engaged a twine engaging loop  6  and being tensioned to engage a twine engaging loop  6  on a successive frame  5  along the crop row  3 . As can be seen in  FIG. 6 , the twine looping end  23  is looped completely around the circular loop  19  and exits the circular loop  19  at the loop open end  20  crossing over that portion of the twine looping end  23  first drawn into the gap  24  at the loop open end  20 . Once fully engaged at a twine engaging loop  6 , the twine  7  can be drawn tightly towards the twine engaging loop  6  on the next successive frame  5  along the crop row  3 . The twine looping end  23  then becomes a twine tensioned end  22  for the next twine engaging loop  6 . Because the twine  7  is in tension between frames  5 , the twine  7  provides full support for the cover  8  along the length of the crop row  3 , while the frames  5  provide full support for the cover  8  across the crop row  3 . 
     Because the twine  7  does not pass through the circular loop  19 , the twine  7  can be rapidly engaged with the twine engaging loop  6  by a simple looping motion. Likewise, the twine  7  can be rapidly disengaged from the twine engaging loop  6  by a reversal of the looping illustrated in  FIGS. 4 ,  5  and  6 . 
     The simple placement and removal of the frames  5  can done in conjunction with the engagement and disengagement of the twine  7  with the twine engaging loops  6  or separately. For example, a person could walk along a crop row  3  and easily install frames  5  at the required spacing by simply pressing the first and second soil engaging ends  12  and  13  into the furrows  4  and  4   a  on either side of the crop row  3 . Once a frame  5  is in place, twines  7  running from the twine engaging loops  6  of the previously installed frame  5  can be quickly engaged and looped about the twine engaging loops  6  of the present frame  5  by the same person who installed the frame  5 . Alternatively, one person could walk along the crop row  3  and install the frames  5  at the required spacing, while another person could follow and engage the twines  7  with the twine engaging loops  6  of each successive frame  5 . 
     Once the frames  5  have been installed along a crop row  3  and twines  7  have been successively engaged in tension on the twine engaging loops  6  on the frames  5 , a cover  8  can be draped over the frames  5  and twines  7  and the inner surface  17  of the cover  8  will not touch the plants  2 . It is also intended that the cover  8  may be draped over more than one crop row  3 , depending on how many crop rows  3  has been fitted with frames  5  and twine  7 . The direction of draping of the cover  8  will depend on the width and roll length of the cover  8  as well as the length of the crop rows  3  and the number of crop rows  3  in a field. Once the cover  8  is in place over the frames  5  and twine  7  it can be held in place by weighting it down in the furrows  4  and at the edge of the field. 
     Although there are several materials available for the cover  8  such as plastic sheeting which may provide immediate protection against an imminent problem such as freeze or frost, most of these materials would have to be removed quickly to allow sunlight and water to reach the plants. There are now frost protection materials such as woven and non-woven synthetic polymeric fabrics which are porous to air and water and allow sunlight to pass through, but still provide protection against severe weather conditions and insects. Covers  8  of these materials can be left in place over the crop rows  3 , thereby eliminating the need and cost of installation and removal more than once throughout the growing season.