Third Season Performance of Synthetic Ground Covers In Blackberries

Synthetic weed barriers, which have shown promise in a first fruiting season ‘Kiowa’ blackberry (Rubus spp) planting near Monte Alto, TX (Lat. 26º 26’N), were evaluated for a second fruiting season in 2008.  Weed removal times were significantly shorter and material integrity unaffected by time (Mar. 2006 to July 2008) in a black polypropylene with polyester blend (Dewitt Co., Sikeston, MO) and a nylon-reinforced white on black plastic (T-65, Reef Industries, Houston, TX).  The white plastic material improved early season and total season yield (49% relative to bare soil), early season berry weight, fruit soluble solids (%), sugar:acid ratio and generated the lowest harvest season (May 14 to June 25) soil temperatures at 10 cm compared to other weed barriers and the bare ground treatment.  The durability of the synthetic weed barriers, in an environment which typically receives about 0.15 MJ/m² of UV A + B per day in mid-summer, appeared to be proportional to product cost.  In a separate 8 week greenhouse pot experiment to evaluate the effectiveness of these materials to reduce water loss, all synthetic fabrics were better than bare soil and the white plastic was superior to all materials used.  When plants were introduced to the system, (in a parallel experiment conducted at the same time), the ability to measure these water use differences gravimetrically between  treatments was lost after four weeks; and no significant plant growth differences (P > 0.08) in top or root dry weight between bare soil and weed barrier materials were observed in the eighth week.