Glozer Dr, Kitren

Grant, Joseph A

Southwick, Stephen :

Effects of fall applications of urea and zinc sulfate to > Bing = sweet cherry spring budbreak , 2005 1 2 3 , Joe Grant and Stephen M . Southwick Kitren Glozer 1 Plant Sciences Department , U . C . Davis 2 Farm Advisor , San Joaquin County 3 formerly with the Pomology Department , U . C . Davis Summary : A single treatment of nutrient / defoliant chemicals was found to advance bloom significantly in the first half of the bloom period ; this treatment was applied on 25 October . This treatment advanced bloom from 4 % to 73 % in 5 days ( March 3 to March 7 ) , compared to the control ( 0 - 40 % ) and the hand defoliation on the same date ( 0 - 11 % ) . Hand defoliation tended to result in a bloom progression that was equivalent to , or delayed , compared to the untreated control . Chemical nutrient / defoliant treatments did not remove leaves very far in advance of normal leaf fall , although leaves were â?? burned â?? . The treatments did result in bloom advance that was equivalent to , or slightly ahead of , the control . By March 9 , bloom had progressed so far that treatments generally did not differ in the percentage of truss buds open . All truss buds opened and no vegetative or reproductive bud death was found . The significance of the results is discussed as they relate to previous defoliation work and the use of the Dynamic model for calculating chill accumulation . Problem and its Significance : While rest - breaking agents have become commonly used in California cherry production , application timing continues to involve a certain amount of uncertainty from year - to - year . In order to use any chilling model adequately and thereby schedule rest - breaking treatments , both the beginning point of dormancy and the beginning point of chill accumulation must be understood . One method of testing dormancy onset is tree defoliation , which may be used to alter the pattern of budbreak and regrowth in spring ( Couvillon and Lloyd , 1978 ) . Originally , we believed that California sweet cherry growers might benefit from fall defoliation with regard to helping trees adapt to less than adequate chilling conditions . With that in mind , we conducted a preliminary experiment in Fall , 2002 , investigating the effects of fall defoliation on budbreak and fruit set in the subsequent growing season . We found that chemical defoliants ( 20 lb per acre each of zinc sulfate and urea ) tended to advance bloom and increase the percentage of reproductive buds that opened , compared to hand defoliation and the control , despite the fact that leaves were removed slowly . . Three timings were applied in October , 2002 , and the last timing ( October 30 ) resulted in the greatest number of open buds and the greatest advance in bloom . Hand defoliation tended to reduce the percentage of open - flower truss buds , tended to delay bloom and increase both vegetative and reproductive bud death . Defoliant / nutrient treatments of zinc + urea ( 10 and 15 lb per acre , respectively ) in 1996 and 1997 had improved pollen viability in these â?? low chill â?? years ( with chill portions of 58 and 52 , respectively , and chill hours of 695 and 424 , respectively ) , which appears to be reduced when chill accumulation is inadequate ( Weis et al . , 1996 ) . We repeated our trial in 2004 - 2005 season and evaluated budbreak as a result of treatment . Objectives : Test chemical defoliants and hand - defoliation in the fall and evaluate the effects on budbreak and fruit set in > Bing = sweet cherry . Plans and Procedures : The experiment was carried out in a mature commercial orchard west of Lodi , CA , in a block of > Bing = cherries ( Prunus avium L . ) on Gisela 6 rootstock , planted 10 â?? x 16 â?? . Treatments consisted of an unsprayed control and two types of defoliation treatments applied on 4 , 12 , 18 , 25 October , or 2 November . Defoliant treatments included a chemical application of 20 lbs urea + 20 lbs basic ZnSO ( urea + Zn ) and hand - 4 defoliation . Urea and zinc were applied in combination using Stihl mistblower with a spray volume of 100 gallons per acre to simulate conventional air - blast sprayer application . Treated trees were separated by guard rows and guard trees within a treated row . Treatments were applied to single trees randomized within a replicate â?? block â?? ; four replicate blocks were used for data collection . The Dynamic model was applied to climatic data collected by Watchdog data - loggers placed in the orchard . Bloom development was assessed by measuring the rate of individual truss bud opening ( progression of flowering ) in spring , 2005 . To that end , two limbs per tree were tagged prior to bloom . Progression of flowering bud opening was measured on each selected limb by calculating the percentage of emergent or open truss buds ( â?? emergent or open â?? = mid - popcorn to petal fall stage ) on 28 February ( no bloom ) and 3 , 7 , 9 , 11 , 14 and 16 March . No dead buds were found . Analyses of variance were performed with Proc GLM procedure of SAS ( SAS Institute Inc . , Cary , NC ) and mean separations were tested by Duncan = s Multiple Range Test ; P = 0.05 . Results and Discussion : A single treatment of chemical defoliants / nutrients was found to advance bloom significantly in the first half of the bloom period ; this treatment was applied on 25 October ( Table 1 ) . This treatment advanced bloom from 4 % to 73 % in 5 days ( March 3 to March 7 ) , compared to the control ( 0 - 40 % ) and the hand defoliation on the same date ( 0 - 11 % ) . Hand defoliation tended to result in a bloom progression that was equivalent to , or delayed , compared to the untreated control . Chemical defoliant / nutrient treatments resulted in bloom progression that was equivalent to , or slightly ahead of , the control , with the exception of the 25 October treatment . By March 9 , treatments generally did not differ in the percentage of truss buds open . All truss buds opened and no vegetative or reproductive bud death was found . Defoliant / nutrient treatments in this trial appears to partially replace chilling accumulation , resulting in a bloom advancement and compression of bloom ( fewer days to achieve full bloom , defined as 80 - 90 % of reproductive buds open ) . Bloom advance and compression was more pronounced than in 2002 - 2003 . However , these trials were performed in different years , sites , and rootstocks , all of which could explain such differences . When comparing the results of â?? best â?? treatment in two years , we might conclude that defoliant / nutrient treatments in the last week of October would be a reasonable timing for future consideration , however , we did not apply later than October 30 in 2002 , so do not know whether a later treatment would have been more or less effective . When evaluating the temperature data from 2004 , we found that the Dynamic model indicated an accumulation of 3 chill portions at the effective timing . When CIMIS data ( from the Winters station ) was also evaluated for the 2002 experiment , we found that 3 chill portions had been accumulated by October 30 as well . In both cases a similar amount of chill accumulation at effective defoliant / nutrient treatment timings may be interpreted to mean that defoliant / nutrient treatments may be used for rest - breaking when chill accumulation has begun and is in the range of 3 CP . We might also suggest from this data that the Dynamic model be used to â?? fix â?? the onset of chill accumulation , rather than a calendar date . We believe that these results and interpretation should be further tested , particularly as this technique may provide a â?? safe â?? alternative to later rest - breaking treatments and may answer the question of > When should we start calculating chill accumulation ? â?? Selected References Anstey , T . H . ( 1961 ) Prediction of full bloom date for apple , pear , cherry , peach and apricot from air temperature data . Proc . Amer . Soc . Hort . Sci . 88 : 57 - 66 . Couvillon , G . A . and Lloyd , D . A . ( 1978 ) Summer defoliation effects on spring bud development . HortSci . 13 : 53 - 54 . 2 George , A . P . and Nissen . R . J . ( 1988 ) Chemical methods of breaking dormancy of low - chill nectarines : preliminary evaluations in sub - tropical Queensland . Austral . J . Expt . Agr . 28 : 425 - 429 . Lang , G . A . , Early , J . D . , Martin , G . C . and Darnell , R . L . ( 1987 ) Endo - , para - and ecodormancy : Physiological terminology and classification for dormancy research . HortSci . 22 : 371 - 377 . Lloyd , J . and Firth , D . 1990 ) Effect of defoliation time on the depth of dormancy and bloom time for low - chill peaches . HortSci . 25 : 1575 - 1578 . Richardson , E . A . , Anderson , J . L . and Campbell , R . H . ( 1986 ) The omnidata biophenometer ( Ta45 - P ) : a chill unit and growing degree hour accumulator . Acta Hort . 184 : 95 - 90 . Richardson , E . A . , Seeley , S . D . , Walker , D . R . , Anderson , G . L . and Ashcroft , G . L . ( 1975 ) Pheno - climatography of spring peach bud development . HortSci . 10 : 236 - 237 . Weis , K.G . , S.M . Southwick , and M.E . Rupert . 1996 . Abnormal anther and pollen development in sweet cherry cultivars resulting from lack of winter chilling . ASHS 93rd Annual Meeting ( Abstract 700 ) We wish to acknowledge the cooperation of the Grupe ranch in the execution on of this project . 3 4 14 a a a a a a a a a a a 98.8 99.8 99.6 99.3 99.6 99.6 98.1 99.4 98.9 99.4 100.0 March 11 open . ab ab ab ab ab ab b a a a a Y March 2005 . 80.5 94.3 85.7 90.8 93.0 89.8 92.8 97.6 98.3 96.7 97.3 buds in truss progression ab ab ab 9 b a a a a a a a March of 54.3 64.5 70.1 71.1 84.3 80.2 85.9 80.6 80.2 82.4 88.7 percentage bloom bcd bcd abc bc bc 7 cd ab ab ab d a as cherry March 11.0 30.4 35.0 25.5 55.6 55.1 43.5 55.4 40.2 73.0 45.2 measured sweet 5 bc bc bc bc bc bc bc bc > Bing = Bloom b c a March 11.1 3.1 2.1 3.4 3.3 4.4 8.1 6.4 3.5 0.0 21.4 gal / acre . on hand - defoliation 3 x March 100 b b b b b b b b b b a 0.0 0.4 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.3 3.9 0.05 . was volume = portions P and Test , sprays spray 0 0 0 3 7 Range Chill acre ; 4 ZnSO Multiple per date 2 + 12 18 25 4 November lb urea Application October October October October Duncan = s 20 ( 2004 ) at applied fall by 4 of separation x ZnSO defoliation defoliation defoliation defoliation defoliation Effect 4 4 4 4 4 SO SO SO SO SO Treatment and Zn Zn Zn Zn Zn 1 . Control Mean Urea + + + + + Table hand hand hand hand hand urea urea urea urea urea Y x 5 open . a a a a b b b 6 April 94.9 93.9 96.2 97.8 87.4 87.1 83.0 Y 2003 . buds in truss progression of ab 1 a a b b b b percentage April 85.8 90.3 94.2 80.1 71.4 74.3 65.7 bloom as cherry measured 27 bc sweet a c e b c d March 67.9 15.2 40.8 45.2 52.6 39.0 21.1 significant . Bloom â?? Bing â?? gal / acre . on non 21 hand - defoliation x ab ab ab ab a b b March = 3.2 11.9 5.2 4.3 1.2 6.1 0.7 100 ns 0.05 ; was volume = P and portions Test , sprays spray Range 0 1 3 Chill acre ; ZnSO4 Multiple per + lb Application urea 16 23 30 20 Duncanâ??s October October October date ( 2002 ) at applied fall by ZnSO4 x of separation defoliation defoliation defoliation Effect SO4 SO4 SO4 Treatment and Zn Zn Zn 2 . Control Mean Urea + + + Table hand hand hand urea urea urea x Y