The main reason to sow green beans through plastic is the yield increase. The plants are more vigorous than bare ground beans. The beans produced are longer therefore more eye appeal and the yield increase is substantial.
Normal yields on green beans in Pennsyvlania are between 100 and 150 bushels per acre on bare ground. In 1986 using the Polyplanter, a test plot of green beans was sowing using clear plastic and dropping two seeds every eight inches. Herbicides were used for weed control. Fifty pounds of nitrogen was used for fertilization. Also a bare ground check plot was planted under the same condictions. The green beans planted through plastic yielded 400 bushels per acre. The check plot yielded 80 bushels per acre.
In 1987 green beans were planted through plastic on May 20. The first picking was on July 5 and the yield on these beans was 580 bushels per acre. From 1988 to 1992 the yield of green beans on clear plastic has been over 450 bushel per acre, with the highest around 700 bushel per acre. Let it be noted that under optimun conditions green beans have exceeded 400 bushel per acre on bare ground.