Comparison of an Antitranspirant Spray, a Polyacrylamide Gel, and Wind Protection on Early Growth of Muskmelon

Field experiments were conducted over 4 years to evaluate the effects of antitranspirant (Folicote,Aquatrollnc., Paulsboro, N.J.) and polyacrylamide gel (SuperSorb, Aquatrollnc., Paulsboro, N.J.) on early growth oftransplanted muskmelon grown either protected by tree windbreaks or exposed to seasonal winds. A randomized complete block design (RCBD) with split plot arrangement was used with wind protection (sheltered and exposed) areas as the main treatment and use of an antitranspirant spray or gel dip as subtreatments. Based on destructive harvests in the field, treatments and subtreatments did not affect dry weight or leaf area index in the first 2 years. Specific contrasts, however, showed that gel application significantly increased fresh weight, dry weight, and leaf area index over that of the untreated transplants whereas the spray application tended to reduce these factors during the first 3 weeks after transplanting. Significant differences between gel and spray subtreatments disappeared by 5 weeks after transplanting. Shelterbelts ameliorated crop microclimate thereby enhancing plant growth. Significantly, wind velocity at canopy height was reduced 40% on average and soil temperatures were about 4% warmer in the sheltered plots compared to the exposed plots during the first 5 weeks post-transplant. Muskmelon plants in the sheltered areas grew significantly faster than the plants in the exposed areas in 2 of the 3 years reported, with the 3-year average fresh weight increased by 168% due to wind protection. Overall transplanting success and early growth were enhanced the most by wind protection, followed by the polyacrylamide gel root dip, and least by the antitranspirant foliar spray. We conclude that microclimate modification by wind speed reduction can increase early muskmelon plant growth more consistently than the use of polyacrylamide gel as a root dip at transplanting or the use of an antitranspirant spray. A polyacrylamide gel root dip generally will provide more benefit during early muskmelon growth than the use of an antitranspirant spray. Transplanted plants may be subjected to water stress soon after planting due to wind, heat, cold, or a combination of these climatic factors. While these conditions can occur in any production area, wind and large fluctuating temperatures are particularly characteristic of the continental climate in the Great Plains. Water stress during early plant development can affect plant establishment and may reduce yield. Avoidance ofwater stress can reduce the risk of crop loss. There are two main methods to reduce water stress in transplanted crops: Received for publication 17 Oct. 2005. Accepted for publication 16 Nov. 2005. Journal series 14707 NebraskaAgricultural Researcb Division, University of Nebraska. Use of trade names does not imply endorsement oftbe products named nor criticism of similar ones not named. Research was supported by CSREES Project NE20-050 and the Mcintire-Stennis Cooperative Forestry Research Program. We thank Linda 1. Young for statistical support. 'Associate professor. To whom reprint requests should be addressed; [email protected]. 'Fonner graduate student. JProfessor. HORTSCIENCE VOL. 41(2) APRIL 2006 Reduce water loss through the leaves by reducing transpiration or maintain adequate moisture in the root zone. This research compared the use ofa wax-based antitranspirant foliar spray (Folicote, Aquatrol lnc., Paulsboro, N.J.) with the use of a polyacrylamide gel slurry (SuperSorb, Aquatrol Inc.) applied to the root ball at transplanting on early growth of muskmelon transplants in the field. In much of the previous work with antitranspirants and polyacrylamide gels, the emphasis was on reducing water stress over the entire growing season, e.g., Gehring and Lewis, 1980. Previous work with antitranspirants that did emphasize early growth and development found increased seedling water potential and increased plant growth throughout the growing season (Nitzsche et al., 1991). Shelterbelts, rows of trees that reduce wind velocity to the leeward side, benefit vegetable production through microclimate amelioration often resulting in earlier and higher yields, improved pollination, reduced disease pressure, and less wind damage (Baldwin, 1988; Brandle et al., 2004; Hodges et al., 2004; Van Eimem et al., Materials and Methods Research was conducted during the growing seasons of 1991, 1992, 1993, and 1994 at the University of Nebraska Agricultural Research and Development Center at Mead, Nebr. (lat. 41 long. 96°23'W, 354 m above mean sea level). The soil was a Typic Argiudoll (Sharpsburg silty clay loam). A randomized complete block design was used with a split plot arrangement of subtreatments. The main treatments were areas protected from the wind using replicated shelterbelts (tree windbreaks) and comparable replicated areas exposed to the wind. These are described in more detail below. Seven subtreatments were applied randomly to the muskmelon transplants in each main treatment in 1991. The subtreatments consisted ofantitranspirant foliar spray (Folicote, Aquatrol Corp.) and polyacrylamide gel (SuperSorb.Aquatrol Corp.) applied singularly and in combination as follows: 1) control (without any chemical treatment); 2) dip (SuperSorb gel polymer at transplanting); 3) spray (1'01 icote antitranspirant at transplanting); 4) dip and spray at transplanting; 5) spray at transplanting and again after 2 weeks; 6) dip at transplanting and spray after 2 weeks; 7) spray once 2 weeks after transplanting. In years subsequent to 1991, the number of replications was increased to four and the seven subtreatments were reduced to three: control (without chemical treatment); dip (transplant root ball dip in polyacrylamide gel slurry at transplanting); and spray (foliage spray with antitranspirant at transplanting and again 2 weeks after transplanting). For simplicity, only the subtreatments in common across years are included in this report. Folicote was prepared as a 5% solution in water (1 :20 v/v dilution). Warm water was added to the Folicote, stirring slowly to form an emulsion. Then a nonionic surfactant [Biofilm (alkylarypolyethoxethanol), Aquatrol lnc., Paulsboro, N.J.] was added to make a 0.5% concentration of surfactant. The antitranspirant spray was applied over the top of the transplanted muskmelon to runoff using a backpack sprayer at 3.9 MPa, walking about 0.45 m-s ' with the spray nozzle about 30 em above the muskmelon foliage. A slurry of SuperSorb (polymer gel) was prepared as 85 g/3.78 L of water. Roots were dipped in the gel suspension to the top of the root ball immediately before placement in the soil. The mixture was stirred frequently to maintain suspension of the gel. Wind protection for the main treatments was provided by replicated systems ofmature mixed 361 HortScience (April 2006) 41(2): 361-366.