Effect of Different Plastic Sheet Coverings and Pruning Time on Yield and Yield Components of Table Grape "cv. Superior"

This study was carried out during two successive seasons in 2007 and 2008 on five years old "cv. Superior"
grape cultivar in a private vineyard at El-Noubarya city, Behaira Governorate, Egypt. The vines were grown in sandy
soil with spacing of 2m within rows and 3 m between rows under drip irrigation system and trained to cane pruning
under baron trellis system. The main factor was the three pruning times [(1st December (P1), 15th December (P15) and
30th December (P30)] carried during dormant season to ten canes per vine with 12 nodes per cane. Four renewal spurs
(2 nodes) were tretained per vine, while the sub main factor was four mulching treatments with sheet cover sleeves air
white plastic (WSCT), air yellow plastic (YSCT), soil white plastic (WSCS) and soil yellow plastic (YSCS). The
control was the rest of the field (no mulch with pruning 20th December).The (P30YSCS) and (P30WSCS) treatments
gave the highest yield (kg/vine) in the first and second seasons compared with control treatment. Also the treatments
(P1YSCS), (P1WSCS), (P1YSCT) and (P1WSCT) gave the lowest value of yield as compared with control. All
treatments significantly decreased number of berries/cluster in both seasons, except the treatments (P1YSCS),
(P1WSCS), (P15YSCS), (P15WSCS) and the control. The increasing of cluster length and decreasing of berries number
in the treatments (P1YSCT), (P1WSCT), (P15YSCT), (P15WSCT), (P30YSCT) and (P30WSCT) caused a significant
reduction in cluster compactness as compared with control treatment. Furthermore, increasing of cluster compactness
significantly under the treatments (P1YSCS), (P1WSCS), (P15YSCS), (P15WSCS), (P30YSCS), (P30WSCS) and the
control caused by decreasing cluster length and increasing berries number compared with all treatments. Accumulation
of high temperatures by (P1YSCT), (P1WSCT), (P15YSCT), (P15WSCT), (P30YSCT) and (P30WSCT) increased total
sugars in both seasons compared with control treatment, but the treatments (P1YSCS), (P1WSCS), (P15YSCS),
(P15WSCS), (P30YSCS) and (P30WSCS) did not affect total sugars compared with control treatment.