Date of Graduation
Bachelor of Science in Agricultural, Food and Life Sciences
Nalley, Lawton Lanier
This thesis examines the effects of shade on ‘Prime-Ark 45’ blackberries (Rubus spp.) in greenhouse (GH) and field (FD) experiments aimed at improving fruit production in the southern United States Ozark Plateau region. Primocane blackberry production in the southern United States is limited in acreage of production as well as low yields by high temperatures during the bloom and early fruiting period, resulting in poor fruit set and poor fruit quality. Shade may have the potential to delay bloom and flowering to a more favorable season or by reducing temperatures that cause a poor fruit set and quality. Both the GH and the FD experiment was established in the June 2014 to evaluate the effects of shade on primocane fruiting blackberry growth, physiology and fruiting. The research objectives were experimenting the timing and intensity of shade on the potential for delayed flowering and fruiting. The GH experiment analyzed four treatments using 50% shade cloth: 1) an untreated nonshaded control [CK], 2) unshaded for 29 days then shaded for 30 days [US], 3) shaded for 29 days then shaded for 30 days [SS], and 4) shaded for 29 days and unshaded for 30 days [SU]. Each treatment had 11 single plant replicates. The number of flower buds, flowers, and individual fruits did not vary significantly among treatments in the greenhouse experiment. The last to bloom was the SU, 26 days after the CK on 28 July. These findings are significant because fruit could be shifted to 5 Sept. compared to the CK which would fruit approximately 10 Aug. A FD experiment was conducted to study the effects of various levels and time of shade treatments on ‘Prime-Ark 45’ blackberries. The FD experiment differs from the GH experiment because it included two levels of shade 30% and 50% implemented at different times throughout the growing season. The FD experiment consisted of seven treatments with varying levels of shade and differing dates of treatment implementation: 1) an untreated nonshaded control [CK], 2) early shade 30% [ES30], mid shade 30% [MS30], 4) late shade 30% [LS30], 5) early shade 50% [ES50], 6) mid shade 50% [MS50], 7) late shade 50% [LS50]. The 30% and 50% treatments began 16 June [ES], 1 July [MS] and 15 July [LS]; there were 5 replications per treatment. Growth measurements were taken weekly for both experiments to measure estimated leaf chlorophyll content and leaf assimilation. No significant differences for cane length, cane diameter, node number, internode length, number of lateral branches or number of fruit clusters were observed among treatments. Field treatments ES30, MS30 and ES50 had less fruit than LS treatments during the experiment period. It is possible that flowering and fruiting of the ES treatment could have continued after the end of this experiment due to the delay in flowering and fruiting as observed in the GH experiment. In the future shade should be applied 1 May as opposed to 16 June and could be coupled with season-extending high tunnel systems to protect fruit against freezing autumn weather.
Caillouet, Olivia C., "The Effects of Shade on Growth, Development and Yield of a Primocane Fruiting Blackberry, ‘Prime-Ark 45’ to Extend the Market Season" (2016). Horticulture Undergraduate Honors Theses. 4.