Evaluating the Impact of Superabsorbent Polymers on Grapevine Water Management

The United States ranked 4^th with total grape yields of 6,692,950 metric tons in 2011. Oklahoma’s wine industry has grown from three wineries in 2000 to over 50 wineries in 2012. Most of Oklahoma suffered extreme, severe, or moderate drought during the past several years. Growth, yield, and fruit quality of grapes depend on grapevine water status. Hence it is necessary to promote soil moisture by means of an integrated system that includes efficient irrigation and other water-saving production techniques. Super-absorbent polymers (SAPs) are one type of water-saving agents, which have segments of hydrophilic groups that can absorb and retain liquids and last 4 to5 years, which makes them very cost effective for long term maintenance situations. The SAPs can absorb natural water at around 100 to350 times its own weigh. In this experiment, five transplant grapevine cultivars (Cynthiana, Rubaiyat, Chardonel, Noiret, and Chambourcin) were used with four different levels of SAPs (0, 50, 100 and 150 g) in two particle sizes (small (s) = 0.8-1 mm and large (l) = 2-4 mm). Water absorbing capacity (WA), electrolyte absorbing capacity, relative water content (RWC), and assessment of soil water were carried on in order to evaluate the impact of SAPs on grapevines in the first year. Significant correlations were observed among the height and number of leaf at week 12 as well as week 16 after planting. Small SAP showed higher WA with 151 in comparison with 29 in L-SAP. The highest RWC were observed using 100 g L-SAP (73%) followed by 50 g S-SAP (72%) after 16 weeks. Large-SAP showed a lower charge (10.45 g/g) and thus a decrease in absorbing capacity compared to that of S-SAP (33.25 g/g) which has a higher charge due to smaller particle size. Thus, the particle size has negligible effect on absorbing capacity of SAPs. Soil water content had an inverse relationship with the amount of added SAP, meaning that plots with higher superabsorbent remained at higher moisture levels. The average soil matric potential (an indicator of soil water content) during the growing season decreased from 27.1 centibars for the control treatment (no SAP) to 10.3 centibars at 150 g L-SAP treatment. A similar trend was observed at plots where the grapevine did not survive, with matric potential ranging from 13.6 to 5.0 centibar for the same treatments, respectively.