Glozer Dr, Kitren

Ingels, Chuck

Garcia Suarez, Maria Paz :

Efficient Nitrogen Fertilization for Control of Vegetative Growth and Optimum Cropping , 2009 Kitren Glozer , Department of Plant Sciences , UC Davis Chuck Ingels , UC Cooperative Extension , Sacramento County Maria Paz Garcia Suarez , Dept . Ciencias Agroforestales , University of Sevilla , Spain Abstract This project addresses two of the main concerns in nitrogen Best Management Practices ( BMP ) : efficiency of nitrogen use to optimize cropping and control of vigor through nitrogen management . Current cropping of pear in California tends to be much higher than when N recommendations were first developed and while it is logical that more crop â?? removes â?? more N , higher N also tends to decrease storage life of pome fruits and much more of the current pear crop is produced for fresh market than in the past . Improved knowledge of optimum timing , form , and amount of N to produce pears to todayâ??s standards is warranted . Because pear trees may respond gradually to changes in applied nutrients ( Raese , 1996 ) ; Ingels , 2005 ) , a practical approach toward comparing N levels is to identify and use orchards with existing â?? low â?? and â?? high â?? N practices . We began evaluating N partitioning to vegetative and reproductive tissues in March , 2009 in â?? High N â?? and â?? Low N â?? orchards . These orchards have similar yields ( 25 - 30 t / A / yr ) , tree age , density , soil and growing conditions . ï?· The â?? Low N â?? orchard has not had â?? full N â?? ( 120 # N / A / yr ) applied since 2007 as a cost - saving act measure , whereas the â?? High N â?? orchard receives 120 # N / A / yr . act ï?· We sampled tissues during bud swell ( March 9 ) , preharvest ( July 7 ) , and postharvest / preleaf fall ( October 1 ) . ï?· We have found that in March and July there are no differences between â?? low â?? and â?? high â?? N orchards , but only between tissue types . ï?· Spur buds have significantly higher N than shoot buds and while bearing spur leaf N declines up to July , shoot leaf N rises . Non - bearing spur leaf N is intermediate to these . ï?· Current recommendations for N analysis vary , depending on the information source o Pear in Calif ( DANR Bulletin # 1879 , 1978 ) â?? spur leaves in June - July ; deficient in N is < 2.3 % N , with 2.3 - 2.8 % adequate o Shear and Faust , 1980 - - non - bearing spur leaves or shoot leaves from mid - portion of terminal shoots sampled at cessation of terminal growth ( July - August ) deficient is < 1.8 % and adequate is 1.8 - 2.6 % ï?· October N values will be added for shoot buds , spur buds , shoot leaves and spur leaves when analyses are completed . This project is exploratory in nature and has afforded the opportunity to apply for , and receive a 3 - year grant from CDFAâ??s Fertilizer Research and Education Program to continue and expand this work , for a total of $ 150,000 . Introduction N fertilization recommendations for California European pear trees have been modified from 1991 ( moderate amount = 75 to 125 lb actual N applied to the soil per acre â?? Integrated Pest Management for Apples & Pears ) to 2007 ( 2 lb actual N / ton of crop / acre ; Pear Production and Handling Manual ) . The 2007 recommendation establishes two physiological premises for N management . The first is based on cropping , so that a 30 ton / acre orchard should receive 60 lb actual N per acre per year . The second premise , based on controlling vegetative vigor is to apply no nitrogen if the average shoot length is greater than 12 inches . These criteria address two of the main concerns in nitrogen Best Management based on cropload and control of vigor through nitrogen Practices ( BMP ) : efficiency of nitrogen use management . Reproductive and vegetative growth tend to be competitive processes , i.e . , as one increases , the other declines . Both are highly subject to nitrogen ( N ) level , with high N tending to favor vegetative growth , yet good cropping depends on a certain level of N as well . Excessive canopy production shades the inner and lower canopy , reducing flower production and fruitfulness with permanent consequences to cropping . BMP should reflect N partitioning spatially in tissues and temporally during the growth and rest cycles , with emphasis on application of N in forms and at timings that minimize over - usage , increased vigor , and ground water leaching . Yet , growers tend to perceive reduction in N use as an unacceptable risk for reduced cropload and smaller fruit size and that critical leaf N values are outdated as they were established when tonnage was lower , tree density per acre was lower and most fruit went to processing ( thus fruit size was less important ) , or fresh fruit were not stored ( often stored 2 + months at present ) . Knowledge of BMP for Californiaâ??s Delta orchards may be inadequate , where most trees are 30 to 100 + years old , are often inter - planted to increase tree density , may retain tissue nitrogen for years without applied N and crop well ( 1997 - 2000 unpublished study , Ingels ) , and are intensively farmed ; alternatively , BMP may already be well - understood by many growers , based on their experience , but are not reflected in the current recommendations . Because pear trees may respond gradually to changes in applied nutrients ( Raese , 1996 ; Ingels , 2005 ) , a practical approach toward comparing N levels is to identify and use orchards with existing â?? low â?? and â?? high â?? N practices . Similar gradual change in K status has been reported in apple ( Moulton et al . 1998 ) . Thus , we have begun monitoring nitrogen levels in two orchards in which â?? low â?? and â?? high â?? N use ( the extremes found in the recent survey conducted in the â?? Delta â?? ( Ingels , 2008 ) , preparatory to more intensive studies . Objectives : 1 . Develop baseline data on seasonal N tissue levels and N demand in European pear . 2 . Compare â?? low â?? and â?? high â?? N orchards to test assumptions about N critical levels . Plans and Procedures : Orchard information and fertilizer levels Two orchards were identified as â?? high â?? and â?? low â?? N application orchards from the survey results ( Ingels , 2008 ) . Both orchards are â?? Bartlett â?? , on the immediate west side of the Sacramento River and within approximately 5 miles of each other . The â?? High N â?? orchard was originally planted at 20 â?? x 20 â?? , more than 100 years ago ; interplants are more than 30 years old at 10 â?? spacing in the row . The rootstock is unknown . Yields are typically about 30 tons / acre . Total actual N applied is 120 lb / acre / year , The â?? Low N â?? orchard was planted about 100 years ago , probably on â?? Winter Nelis â?? rootstock at an original spacing of 16 â?? x 17 â?? and interplants have been continually added for approximately 30 years , as trees are removed , and to decrease the in - row spacing . Yields are typically about 25 - 30 tons / acre . This orchard has had 120 lb actual N / acre until 2007 , and has since had 60 lb / acre . Both orchards received KNO in spring ; in the â?? High N â?? orchard , KNO is routinely applied in spring ; its use 3 3 this year was â?? typical â?? , at the growerâ??s discretion and orchard - wide . KNO was applied to the â?? Low N â?? 3 orchard this year at first cover spray , at 5 lb / acre . Different forms of nitrogen are used by California pear growers : CAN17 , CaNO , KNO , NH NO , UN - 32 , and urea ( 2008 survey ) . KNO is often added to blight 3 3 4 3 3 sprays ( 3 - 6 lb / A ) until oil sprays after petal fall and may be added to codling moth sprays until leaves harden off in spring ( B . Zoller , personal communication ) . KNO may suppress hatching European red 3 mite nymphs when applied at this timing ( B . Zoller ) and has been reported to inhibit pear psylla in Europe ( personal communication , S . Carruthers ) . Thus there is interest in incorporating KNO applications into 3 an experimental design for N applications testing rate , form and timing of N fertilization . KNO in spring 3 will be a treatment incorporated into the new CDFA FREP project next year . Tissue sampling Samples were obtained from the oldest trees in each orchard , from 20 trees selected at random and spaced well - apart throughout the orchard , avoiding â?? problem â?? areas . Spur buds and spur leaves were sampled from spurs no more than 4 â?쳌 in length , at approximately 3 - 6 â?? above ground level , on all sides of the canopy and at the canopy periphery for maximum light exposure . Terminal shoot buds were selected at the tips of 1 - year old wood , in similar locations as the spur samples . Sampling terminal vegetative shoot buds and spur buds prior to bloom provides an early picture of N status ; sampling the same buds in fall prior to leaf drop will show both N status due to cropping and N status due to longer - term postharvest N uptake than mid - summer sampling of leaves would . Thus , our sampling schedule included three collection timings and five tissue sample types : 1 . Timing 1 = â?? budswell â?? ; shoot and spur ( mixed floral and vegetative ) buds â?? approximately 15 - 20 buds per sample collected March 9 2 . Timing 2 = preharvest ( late June , early July ) ; shoot , non - bearing and bearing spur leaves â?? 10 leaves per replicate tree of each type collected July 7 3 . Timing 3 = pre - leaf fall ( late September , early October ) ; shoot and spur ( mixed floral and vegetative ) buds and leaves from shoots and spurs collected October 1 Leaves were washed in a mild soap solution , rinsed and dried in an oven at ~ 55 ° C , and ground . Percentage of tissue nitrogen has been determined from a subsample on a dry weight basis . Data analysis and statistics Treatment effects for the two - site comparison were evaluated using Proc GLM in SAS ( SAS Institute Inc . , Cary , NC ) in which the experimental design was a CRD ( completely random design , replicated by â?? site â?? with 20 replicate trees sampled randomly and â?? replicate tree â?? nested within â?? orchard â?? ) ; estimation of fixed effects was based on Least Means Squares ( LSM ) tests for main effects of â?? orchard â?? and â?? % N â?? and interaction of â?? replicate â?? X â?? sample type â?? . Proc Mixed was used to test â?? replicate â?? and â?? orchard â?? as random effects with â?? sample type â?? as a â?? fixed â?? effect . Where significant effects were found , within - orchard N levels were compared by t - tests ( SAS Proc Ttest ) when only two sample types were collected , and by LSM when more than two were collected , correcting treatment means for â?? replicate â?? effects by the use of Type III Mean Squares and F - test , level of significance P = 5 % . Outliers were plotted with distributions in Proc BoxPlot . Results and Discussion March buds had tissue levels that differed significantly between shoot and spur buds , but not between orchards ( Table 1 ) ; average shoot bud level was 1.60 - 1.62 % N and average spur bud level was 2.42 to 2.60 % N . The range in values for shoot buds in both orchards was much greater than for spur buds ( Figure 1 ) . It has been our experience in previous trials for vigor control , using Apogee ( BASF ) that pear extension shoots are of two types , in that one type continues to grow vigorously for 2 - 3 months , while the other type grows no more than 1 - 3 â?쳌 before setting a terminal bud . Perhaps the range in values for the terminal shoot buds reflects this pre - determined growth difference . When sampled in early July , terminal shoot leaves had much higher N values ( 2.64 and 2.75 % ) , while bearing spur buds had declined in tissue N to 2.09 - 2.15 % ; non - bearing spur buds were intermediate , but much closer to shoot leaf values ( 2.41 - 2.48 % ; Table 2 ) . No significant differences were found for â?? orchard â?? , thus , these values were similar for both orchards , despite N application differences for two years that amounted to half - rate N in the â?? Low N â?? orchard . The range for different leaf N values was similar and relatively small for all leaf types ( Figure 2 ) . In addition to N values being highly significant among the leaf types , there were also highly significant â?? replicate â?? differences , indicating that the range from tree - to - tree was contributing to differences among tissue N ; the two populations of trees ( each orchard is a â?? population â?? ) exhibit large tree - to - tree differences in tissue N level for the same kind of leaf . This is typical in orchards in general , regardless of what response or characteristic is sampled , often obscuring treatment differences due to high replicate variance . We will use harvest blocks as replicates rather than individual trees in subsequent trials to reduce variance , although some sampling may still be tree - by - tree . Thus , because there are no differences between the orchards , despite different levels of applied N , the values are plotted together to show change in tissue N over time ( Figure 3 ) , illustrating the reverse change between shoot tissues and spur tissues . The first increases from budbreak to preharvest while the latter decreases , probably due to higher demand by the growing fruit on the tissues immediately subtending the fruit . October tissue samples should provide additional information about N removal by the crop . Tissue sampling in mid - summer is too late to make adjustments for current season needs , thus , sampling both early and later in the season may provide more opportunity to make adjustment and anticipate inadequacies in the following year , particularly after a very heavy cropload when reserves may be insufficient to support a high - cropped condition . A clear understanding of which tissues sampled will give the best information of N levels relative to cropping in pear is lacking ; the leaves sampled are recommended to be from non - fruiting spurs , although fruiting spurs may have the highest demand for N . Ingels â?? 4 year study ( 1997 - 2000 ; CPAB report ) of N management included a 0 - N treatment ( no N applied for 4 years ) , yet leaf N only slightly declined during the study period , never reaching inadequate levels ( 2.2 - 2.4 % leaf N is considered adequate ; IPM manual ) . Our recent study that utilized 2 % ( v / v ) foliar urea for defoliation and dormancy - induction found leaf N levels in the excessive range , regardless of leaf type , treatment type or analysis timing ( Ingels et al . , 2008 ) . Despite recommended guidelines for N application and growers â?? use of leaf analysis to manage N applications , it is possible that N fertilization is excessive in many Sacramento River Delta orchards , and possibly pear orchards in other districts as well . The harvest of pears removes 1.3 lbs . N / ton ( Weinbaum , 1992 ) , thus , a 20 - ton crop removes only 26 lbs . N / acre . While additional N is required for vegetative growth , even assuming 50 % efficiency of uptake from soil - applied N and equal amount of N required for vegetative and reproductive growth , a typical River Delta orchard may require no more than 100 lb N / A annually if all were applied to the soil ( especially if top - dressed ) . Foliar feeding and / or fertigation may be more effective means to deliver N and other nutrients . Our up - coming FREP trials will attempt to develop more information about N form , application timing and amount that provides the best balance for high cropload and vigor control . Pertinent references Aguirre , P.B . , Y.K . Al - Hinai , T.R . Roper , and A.R . Krueger . 2001 . Apple tree rootstock and fertilizer application timing affect nitrogen uptake . HortScience 36 ( 7 ) : 1202 - 1205 . Ayala , M . and G.A . Lang . 2004 . Examining the influence of different leaf populations on sweet cherry fruit quality . Acta Hort . 636 : 481 - 488 . 3 - Dong , S . , D . Neilsen , G.H . Neilsen and L.H . Fuchigami . 2005 . Foliar N application reduces soil NO - N leaching loss in apple orchards . Pl . Soil 268 : 357 - 366 . 15 Lea - Cox , J.D . , J . P . Syvertsen and D.A . Graetz . 2001 . Springtime Nitrogen uptake , partitioning , and leaching losses from young bearing Citrus trees of differing nitrogen status . J . Amer . Soc . Hort . Sci . 126 ( 2 ) : 242 - 251 . Sanchez , E.E . 2002 . Nitrogen nutrition in pear orchards . Acta Hort 596 : 653 - 7 . Sánchez , E.E . and Righetti , T.L . 1990 . Tree nitrogen status and leaf canopy position influence postharvest nitrogen accumulation and efflux from pear leaves . Amer . Soc . J . Hort . Sci . 115 : 934 - 937 . Sanchez , E.E . , T.L . Righetti , D . Sugar , and P.B . Lombard . 1991 . Recycling of nitrogen in field - grown â?? Comice â?? pears . J . Hort . Sci . 66 ( 4 ) : 479 - 486 . Sánchez , E.E . , Righetti , T.L . , Sugar , D . and Lombard , P.B . 1992 . Effects of timing of nitrogen application on nitrogen partitioning between vegetative , reproductive , and structural components of mature â?? Comice â?? pears . J . Hort . Sci . 67 : 51 - 58 . Southwick , S.M . , W . Olson , J . Yeager , and K.G . Weis . 1996 . Optimum timing of potassium nitrate spray applications to French prune trees . J . Amer . Soc . Hort . Sci . 121 : 326 - 333 . van den Ende , B . 1996 . Nitrogen fertilizer for pears - - Apply it at the right time . Horticultural Tech . Bulletin , Calif . Pear Growers . May 1 , 1996 . AKNOWLEDGEMENTS We appreciate the participation of Dr . Maria Paz Suarez - Garcia in this project during her stay at UC Davis as a Visiting Scholar to the Department of Plant Sciences . We appreciate the ongoing support of the California Pear Advisory Board . Without the growers â?? participation and generosity of time , cooperation and effort in getting our field trials planned and executed , we would not have been able to do this project â?? Many thanks to Chuck Baker and Richard Elliot , their managers and field personnel . Thom Wiseman deserves exceptional gratitude for his insights , suggestions , recommendations and expertise as a PCA . Thom provided much of the information needed to â?? steer â?? us in the right direction for this trial and the upcoming FREP trials . Broc Zollerâ??s recommendation to include KNO as an important component of â?? choice â?? and â?? multiple 3 benefits â?? for nitrogen BMP is also very much appreciated . The contribution by SQM Specialty Plant Nutrition of KNO helped to keep our costs down â?? thank you for 3 your support . Table 1 . Tissue N ( % nitrogen ) in expanding pear buds , March 9 , 2009 y Orchards ( Low N vs High N ) Shoot terminal bud Spur bud Significance x 60 units nitrogen / years 1.60 b 2.50 a * * * 120 units nitrogen / year 1.62 b 2.42 a * * x Means separation by Studentâ??s ttest , P = 0.05 ; means with the same letters within rows ( a given orchard ) do not significantly differ . y * * * , * * = significance at 0.001 and 0.01 , respectively . Analysis of Variance of Nested Model testing differences between Orchard High N and Orchard Low N ; N = orchard rep ( orchard ) bud rep * bud Source df MS III Model 59 0.32 * * * Orchard 1 0.1 Rep ( orchard ) 38 0.06 Bud type 1 14.5 * * * Rep * bud type 19 0.07 Error 20 0.04 X ANOVA by SAS Proc GLM , P = 5 % ; * * * is significant at P = 0.1 % . Figure 1 . Box plots for shoot and spur buds , respectively , for Low N and High N orchards , March 9 , 2009 . The line within each boxplot indicates the mean for the treatment , the upper box edge is the 75 % limit and the lower edge is the 25 % limit for the treatment means . The â?? whiskers â?? extending above and below each box represent the range of the data . Outliers are identified by open circles above and below the whiskers , where present . Table 2 . Tissue N in pear leaves , July 7 2009 . Within and between orchard comparison of % N in shoot leaves ( current year extension shoots , mid - shoot sample ) , bearing , and non - bearing spur leaves . Spur leaf Significance Within each orchard Shoot leaf Leaf ( Low N or High N ) Nonbearing Bearing Replicate ( tree ) type 60 units nitrogen / years 2.64 a 2.41 b 2.15 c * * * * * * 120 units nitrogen / year 2.75 a 2.48 b 2.09 c * * * * * * Means separation by LSMeans , P = 0.05 . Means with the same letters within rows ( a given orchard ) do not significantly differ . Error term is rep * leaf type . Significance Comparison within both orchards ( combined ) and between orchards Leaf ( compared ) testing leaf types for significant differences in % N Orchard type Combined orchards ( Low N + 2.70 a 2.44 b 2.12 c * * * High N ) Compared orchards ( Low N vs NS Hi N ) Means separation by Proc Mixed , â?? leaf type â?? as fixed effect , orchard and replicate as random effects . LSMeans , P = 0.05 ; means with the same letters within row ( leaf types combined across orchards ) do not significantly differ . Error term is rep ( orchard ) ; * * * , NS = significant at 0.1 % , non - significant , respectively . Analysis of Variance of nested model N = orchard rep ( orchard ) leaftype rep * leaftype ; error term is rep ( orchard ) . Source df MS III Model 79 0.105 * * * Orchard 1 0.049 Rep ( orchard ) 19 0.033 * * * Leaf type 2 3.322 * * * Rep * Leaf type 38 0.008 Error 40 0.009 Figure 2 . Box plots for leaves for Low N and High N orchards , July 2009 . The line within each boxplot indicates the mean for the treatment , the upper box edge is the 75 % limit and the lower edge is the 25 % limit for the treatment means . The â?? whiskers â?? extending above and below each box represent the range of the data . Outliers are identified by open circles above and below the whiskers , where present . Shootleaf Bearingspurleaf Non â?쳌 bearingspurleaf spurleaf Figure 3 . Change in % nitrogen for shoot and spur buds to leaves ( shoot , bearing and non - bearing spur ) over time , 2009 . Sample dates were March 9 ( expanding buds ) and July 7 ( preharvest ) . 2.2 - 2.4 % leaf N is considered adequate ( IPM manual ) for pear , measured from shoot leaves midsummer . Note that the October values will be added as they are made available .