Valencia Advanced Production System [APS] Rootstock Trial, LaBelle

Dr. Bill Castle
Dr. Fred Gmitter
Dr. Jude Grosser

March 24, 2021 - updated
November 18, 2020 - updated
November 22, 2019 - updated
September 6, 2019 - posted
CREC Citrus Plant Improvement

Valencia APS Rootstock Trial, LaBelle - Description

To evaluate rootstock potential for higher density planting [10 x 20 ft.; 218 trees/acre], Valencia trees on 31 rootstocks were established in the cooperator’s old field nursery site in the flatwoods west of Highway 29, south of LaBelle.  The site was first surrounded with a windbreak combining Eucalyptus and red cedar plants, then a fertigation system operated via drip irrigation was installed.  The Valencia trees were propagated onto rootstocks from California, Spain and the CREC.  This trial is part of a larger set of trees involving Vernia and Valencia planted on US 897, C-35 or Swingle at either 8 x 15 feet or 10 x 20 feet.

Valencia APS Rootstock Trial, LaBelle - Summary

• Location:  Felda, Hendry County
• Scion: Valencia
• Rootstocks: 31
• Date planted: November 2009 and March 2010
• Design: Randomized complete-block; 4-10 replications
  • Plot size: 4 trees
  • Spacing: 10 x 20 ft. = 218 trees/acre
  • Drip fertigation
• Data:
  • 2012/13: Yield [pounds fruit/tree]
  • 2013/14: Yield [boxes/tree], juice quality, PS/acre
  • 2014/15: Yield [boxes/tree]
  • 2015/16: Yield [boxes/tree], juice quality, PS/acre
  • 2017/18: Yield [boxes/tree]
  • 2018/19: Yield [boxes/tree], HLB rating, juice quality, PS/acre
  • 2019/20: Yield [boxes/tree], HLB rating
  • 2020/21: Yield [boxes/tree], HLB rating, juice quality, PS/acre
  • 7-year cumulative yield [boxes/tree]
  • 4-year cumulative PS/acre
• Trial status: ACTIVE

Valencia APS Rootstock Trial, LaBelle - Interpretive Summary

This summary covers the period from the beginning of cropping to the 2020-21 season.  The Valencia trees on 31 rootstocks were planted in November 2009 at 10 x 20 ft. in a replicated trial.

• Yield in the 2nd crop year ranged from 0.5 to 2.0 boxes/tree; in later years, yield ranged from 1.0 to 2.5 which probably represents tree cropping at a mature stage, i.e., canopy containment for the 10 x 20 ft. spacing. Maximum yield of 3.0 boxes/tree was obtained in the 2018-19 season when the trees were about 8 years old.  Thereafter, 2 to 3 boxes/tree appeared to be a reliable, stable yield which @ 218 trees/acre is about 430-650 boxes/acre. 
• Cumulative yield over 7 seasons ranged from 6 to 11 boxes/trees with trees on 7 rootstocks producing 9 or more boxes [Fig. 38].
• Juice quality. The outcomes were not greatly influenced by rootstock. Brix was usually around  8-12 and varied only 10-15% among the trees on 31 rootstocks.  Typical PS/box were generally low, about 5-6.  Because sampling took place between February and May in any given year, it was likely a factor exceeding the effect of rootstock on juice quality.
• HLB visual symptoms were rated in 3 seasons.  The results were variable within rootstock, but the relationship among rootstocks was unchanged from season to season, i.e., the trees on those rootstocks that rated low [more HLB symptoms] remained in that position and likewise for those trees that rated high [Figs. 18, 27, 29].
• Rootstocks used in this trial with Valencia scion did not produce dramatic differences in the variables measured; nevertheless, considering primarily cumulative PS and cumulative yield, there were some consistencies suggesting the following rootstocks be evaluated further:
  
  
  • UFR 4
  • 11-5-6  
  • 6-6-29
  • RB 24-16 
  • B11-R1-T37