13Blueberry roots at three soil depths for two soil treatments Soil depth (inches)Soil treatmentPercent of total roots0 to 3.5Bark bed44Bark incorporated464 to 7.037457.5 to 10.5198
14Plant water potential during the fruit ripening period - 2010 OBJECTIVESMATERIALS AND METHODSThe objective of this study was to evaluate plant drought stress during the final stages of fruit development of blueberry grown in several soil management systems without irrigation.Predawn and solar noon plant water potential of ‘Emerald’ SHB was measured with a pressure chamber during a dry period of fruit development and no irrigation was applied.
29Daily plant water use of mature ‘Emerald’ blueberry plants by month averaged across treatments and years.Monthly means + SE of daily water use of mature ‘Emerald’ southern highbush blueberry plantsaveraged across treatments and years from April, 2010 to Sept*Means for one year due to complications from overhead irrigation for freeze protection.
31Monthly crop coefficients (Kc) for mature ‘Emerald’ blueberry plants Averaged across treatments and years from April, 2010 to Sept. 2012Monthly Kc means + SE for mature ‘Emerald’ southern highbush blueberry plants averaged across treatments and years fromApril, 2010 through September, Kc values are based on 3 ft. in-row by 10 ft. between row plant spacing (1452 plants/a.).*Mean for one year due to complications from overhead irrigation for freeze protection. Mean annual Kc = 0.65.
32Estimated per acre water use of mature ‘Emerald’ blueberry plants at 3’ by 10’ spacing (1452 plants/a)JanFebMarAprMayJunJulyAugSepOctNovDecgal/day6251452209122652875264328463151268618881496842gal/month19,37540,65664,82167,95089,12579,29088,22697,68180,58058,52844,88026,102Yearly water use = 757,214 gal. per acre or acre-inches inthe planted field. Assuming 4 ft. wide beds with 10 ft. row spacing≈ inches in the row bed (area with root system).
33ConclusionsSouthern highbush blueberry plants are shallow-rooted and drought susceptible. 80+% of roots were in the top 7 inches of soil.Frequent, light, irrigations are needed during the growing season.Bark, applied as either a bed or incorporated into the soil reduced drought stress.Regardless of soil treatment, plant water stress increased significantly after 3 days without irrigation.
34ConclusionsMonthly averages for daily plant water use of mature ‘Emerald’ blueberry plants ranged from about 0.6 gal/day (winter) to over 2 gallons/day (mid to late summer).Water demands increased rapidly in the spring (March) and peak water demands occurred during the late stages of fruit development (late April and May) and in mid to late summer (July – Sept.). Maximum monthly averages≈ 2.0 – 2.25 gal./plant/day.Monthly averages do not reflect the day to day variation in water demand which is heavily influenced by weather and can be considerably greater or less than the monthly averages.Summer pruning significantly reduced plant water use for 3 to 4 weeks until plant canopies were re-established.Kc values can be used with reference ET to determine general water requirements. Soil moisture monitoring devices along with a knowledge of rooting depth, distribution, and soil water holding characteristics are useful when developing irrigation schedules.