nutrient management in subtropical tree crops the avocado model
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Nutrient Management in Subtropical Tree CropsThe avocado model
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Avocado Fertilization
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Tissue%Dry WtNew shoots36Leaves 40Fruit 33Small branches 38< 1 inSmall branches 551-2 inScion trunk 48Rootstock trunk41 Scaffolding roots37Small roots 35New roots4.6
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Figure 1.
N Uptake (lbs N/a)
(128 lbs Fruit FW/tree)
Chart1
14.26335352425.81497797366.29955947141.179607095426.167400881120.216740088150.8810572687
9.06318832611.629955947110.375356253820.063749204617.444933920719.97444933926.7189647577
Roots
Trunk
Canopy Branches
Green Twigs
Leaves
New flushes
Fruit
Sheet1
OFFN Content (g per tree)SpringEarly SummerLate SummerFall
Tree Component1-AugNov-01Dec-01Jan-02Feb-02Mar-02Apr-02May-02Jun-02Jul-02Aug-02Sep-02Oct-02Nov-02Dec-02Avg DecJan -MarApr-JunJul-SepOct-Dec
Fine Roots941061291531-Aug1273.8624398064OFF1105131015141611
Small Roots (1")110838383Jan-021364.4869456207409Roots
Rootstock trunk7171107107Feb-02950.66666666673810.5242290749ON333295370391
Reproductive333295370391Mar-0212270.8401189827OFF339323398353
Trunk (scion)48484872487296727296967272487260Apr-021172.74
Wood >6"1681268412612612612616884168168168168126168126May-021553.56CB765.1780750978808
Scaffold Branches (wood 4-6")183122183183122183244244183305244244244183183183Jun-021751.44Sm Bran117.191435101200
Branches 2-4"287123123123123143.5164164123205205164205164205164Jul-021734.958
Small Branches (wood 1/2-2")127.1780750978239.2764369614105.50458715614520013514575100130125192210120252178.752293578Aug-021379.481Fruit Harvest
New shoots (green twigs, 6"1688412616884126126168126126168168210126126168CB729755
Scaffold Branches (wood 4-6")305122183244122122122244244244244305305183244264Sm Bran165.1314398063170
Branches 2-4"20582205205123164164164164205164246205164164205
Small Branches (wood 1/2-2")516817811292160768512518090100140170155137Dec-FebMar-MayJun- JulAug- Nov
New shoots (green twigs, 6"0.400.300.200.300.30.30.30.40.20.40.40.40.40.30.4
Scaffold Branches (wood 4-6")0.300.200.300.300.200.300.400.400.300.500.400.400.400.300.3
Branches 2-4"0.700.300.300.300.300.350.400.400.300.500.500.400.500.400.5
Small Branches (wood 1/2-2")0.500.700.400.500.500.500.500.500.500.500.500.600.700.500.6
New shoots (green twigs, 6"14-14320Canopy Branches93100.0825688073
OFFDry WeightScaffold Branches (wood 4-6")-2081-1561Green Twigs5138
Tree Component1-AugNov-01Dec-01Jan-02Feb-02Mar-02Apr-02May-02Jun-02Jul-02Aug-02Sep-02Oct-02Nov-02Dec-02Branches 2-4"-142107Leaves150122
Fine Roots12121212Small Branches (wood 1/2-2")-2146925New flushes4652.3065
Small Roots (6"424242424242424242424242424242
Scaffold Branches (wood 4-6")616161616161616161616161616161RootsTrunkCanopy BranchesGreen TwigsLeavesNew flushesFruit
Branches 2-4"414141414141414141414141414141ON712212361132
Small Branches (wood 1/2-2")253426294027291520262532302442OFF2362493013
New shoots (green twigs, 6"424242424242424242424242424242
Scaffold Branches (wood 4-6")616161616161616161616161616161
Branches 2-4"414141414141414141414141414141
Small Branches (wood 1/2-2")172336282340191725301820283422.2
New shoots (green twigs, 6"1608059118597684155.479.8134.4126130.2113.4130.2155.4107.1
Scaffold Branches (wood 4-6")21411614617111017798201.3164.7170.8237.991.5140.3219.6189.1167.75
Branches 2-4"13516017216412398107164200.9135.3172.2151.7143.5172.2155.8164
Small Branches (wood 1/2-2")17015015316018411610287222135.2102.5192213153.6294223.4908256881
New shoots (green twigs, 6"160805911859768414310984151126139160168141
Scaffold Branches (wood 4-6")21411614617111017798323348195238250171195366205
Branches 2-4"13516017216412398107152185156180279131193246201
Small Branches (wood 1/2-2")1141002071551061726712412014495258193279200243
New shoots (green twigs, 6"0.310.310.20.20.190.20.220.370.180.320.30.310.270.310.4
Scaffold Branches (wood 4-6")0.310.190.110.20.160.230.30.330.190.280.390.150.230.360.3
Branches 2-4"0.480.270.250.270.270.290.350.40.270.330.420.370.350.420.4
Small Branches (wood 1/2-2")1.410.450.510.510.620.390.330.580.490.520.410.60.710.640.7
New shoots (green twigs, 6"0.380.190.140.280.140.180.20.340.260.20.360.250.330.380.4
Scaffold Branches (wood 4-6")0.350.190.240.280.180.290.160.530.570.320.390.30.280.320.6
Branches 2-4"0.330.390.420.40.30.240.260.370.450.380.440.410.320.470.6
Small Branches (wood 1/2-2")0.670.440.580.550.460.430.350.730.480.480.530.680.690.820.9
New shoots (green twigs, 6"424242424242424242424242424242
Scaffold Branches (wood 4-6")616161616161616161616161616161
Branches 2-4"414141414141414141414141414141
Small Branches (wood 1/2-2")253426294027291520262532302442
New shoots (green twigs, 6"424242424242424242424242424242
Scaffold Branches (wood 4-6")616161616161616161616161616161
Branches 2-4"414141414141414141414141414141
Small Branches (wood 1/2-2")172336282340191725301820283422.2
New shoots (green twigs,
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Figure 3.
Fruit Dry Wt (g/fruit)
Chart1
85.572.480.37
281963
352366
412678
4527810
42261010
43.123271010
58341212
66451214
67461214
83481318
86561422
Total
Flesh
Peel
Seed
Aug 17,2001
Aug, 17, 01. Hrvest Data Nutrient concentrations in tree components of mature, on (A) and off (B) Hass avocado trees, measured in August 2001.
Tree 101Nutrient Concentration (percent)PPM
Tree ComponentNPKSMgCaNaNO3FeAlMnBCuZnMo
Fine Roots1.000.220.240.120.191.220.3644914042097664115536
Small Roots0.400.090.210.060.080.460.21147270697938216131
Scaffold Roots0.400.090.200.060.070.470.1612615097532321471
Rootstock0.200.080.100.020.020.090.22625540410121
Trunk0.300.040.270.050.070.570.0589411610175219
Scaffold Branches0.400.060.380.070.10.680.058602022751919428
Branches 2-4"0.500.190.670.040.170.60.021081812471319741
Small Branches0.500.170.330.050.170.780.14815943755527226106
New shoots0.800.391.210.090.330.930.053185453612351166
Leaves2.000.210.890.30.511.510.022771902035643757
Fruit2.600.222.080.40.080.070.0073624174445220
Seed.1.500.241.120.160.090.240.04219531523892066
Flesh2.600.222.080.400.080.07
Flesh2.300.392.250.200.180.180.0170802531612711450
Flesh2.900.362.730.410.130.160.013116254959533
Flesh3.100.282.310.330.090.050.0110472214549229
Flesh3.100.482.600.380.160.170.0226073451153944
Flesh Avg2.600.352.390.340.130.13
Peel1.200.241.770.160.120.160.02236251581031134
Peel0.900.090.730.100.150.220.0127221141369742
Peel0.900.090.770.080.140.230.0229119121267739
Peel1.300.261.890.320.140.110.0130221108751049
Peel1.200.231.480.270.120.230.0233821131177839
Peel Avg1.100.181.330.190.130.190
Tree 102
B.Nutrient Concentration (percent)
Tree ComponentNPKSMgCa
Fine Roots0.800.230.390.090.271.390.12613810201357683610535
Small Roots0.700.110.210.150.120.870.347274.001144.001929.0048.0036.008.0080.00
Scaffold Roots0.400.080.270.060.060.490.0992953294801719417
Rootstock0.200.040.120.020.020.070.19297141641029
Trunk0.200.040.120.020.020.060.21516910123916
Scaffold Branches0.400.060.310.060.060.640.11913357642123453
Branches 2-4"0.300.190.480.020.130.420.036118981151929437
Small Branches0.700.541.410.060.250.860.03311517923331381563
New shoots0.800.571.550.110.331.060.02762463525391462
Leaves2.100.261.150.390.541.710.02428821019210449986
Immature Fruit1.900.312.080.380.130.15
Seed.1.30.271.270.180.10.330.0233225856399026211
Flesh0.80.221.780.350.080.10.015176742427
Flesh1.70.41.950.190.120.180.01668830613541544
Flesh1.70.331.940.320.120.180.017061941048830
Flesh1.90.312.080.380.130.150.0158732646711133
Flesh1.60.351.830.290.140.170.01248229613671943
Flesh Avg1.540.321.920.310.1180.156
Peel0.900.101.250.120.150.310.022363191018621045
Peel0.700.070.420.060.120.150.0124251261040625
Peel0.800.090.770.100.110.310.0133181681656739
Peel0.900.211.720.090.140.220.012416.0017.007.008.0062.0011.0035.00
Peel0.800.151.190.090.10.20.0173261261148933
Peel Avg2.440.121.070.090.1240.238
Nov 8, 01
8-Nov-01
Tree 1Nutrient Concentration (percent)PPM
Tree ComponentNPKSMgCaNaNO3FeAlMnBCuZnMoCl %
Fine Roots
Small Roots
Scaffold Roots
Rootstock
Trunk ( >6" )0.300.050.310.070.070.54126.0050.0024.0014162190.96
Scaffold Branches0.200.030.190.030.030.25
Branches 0.5- 2"0.400.070.330.030.080.280.01158.0014.0013.007222250.776596.6
Branches 2-4"0.300.040.270.040.060.28197.0014.004.006141190.59
Scaffold Branches 4"- 6"0.200.030.160.020.030.190.007234.0013.0011.006111100.516305.7
Small Branches0.700.180.570.060.20.820.001208.0046.0018.0012273400.91
New shoots0.800.421.060.150.3310.008182.0061.0022.0016426610.750.1
Leaves2.100.150.660.450.441.921159.00227.00112.0075355340.64
Fruit
Seed.0.80.191.060.120.080.0413592649156150.730.1
Seed.0.80.21.040.110.070.02132226242060.660.1
Seed.0.80.20.990.120.060.0814952658165150.591250.6
Seed.0.70.211.020.130.080.0913002321217719
Seed.0.90.21.060.120.080.061422249136140.560.1
Seed Avg0.800.201.030.120.070.06
Flesh1.600.251.820.240.090.061.008278.0022.001.006.00104.008.0036.000.533950.9
Flesh1.600.231.890.210.070.041.008359.0022.004.00103.008.0035.000.45589.7
Flesh1.400.211.440.190.100.091.008377.0026.006.0088.006.0025.000.433319.3
Flesh1.400.221.500.220.100.081.007940.0025.006.0088.007.0027.000.590.11
Flesh1.900.221.660.240.110.081.008782.0031.006.0098.007.0032.000.343346.70
Flesh Avg1.580.231.660.220.090.07
Peel1.200.241.530.100.070.071.00659.0026.005.006.0065.006.0023.000.543899
Peel1.300.251.700.090.070.04867.0027.005.004.0073.007.0025.0010
Peel1.000.191.150.050.080.121.00424.0022.004.006.0052.005.0015.0003359
Peel1.100.221.350.100.080.111.00606.0023.007.007.0060.006.0020.000.392761.10
Peel1.300.241.660.100.090.121.00513.0026.006.007.0070.006.0023.000.4801108.500
Peel Avg1.180.231.480.090.080.09
Tree 2
B.Nutrient Concentration (percent)PPM
Tree ComponentNPKSMgCaNO3FeAlMnBCuZn
Fine Roots
Small Roots
Scaffold Roots
Rootstock
Trunk0.200.020.030.020.010.080.0193.0036.0044.00369100.156293.2
Scaffold Branches 4- 6 "0.200.030.190.030.030.250.00683.0042.008.0081010.46
Branches 2-4"0.200.030.180.030.040.22192.0010.003.007810.19
Small Branches 0.5" to 2"0.300.120.440.050.160.690.002180.0043.0021.00131820.47
New shoots0.600.320.740.140.341.140.007145.0055.0022.0018304530.41
Leaves1.700.150.610.480.542.28643.00281.00142.0011228430.78
Fruit
Seed.0.70.160.860.10.050.0813161710173130.80.1
Seed.0.60.170.860.110.050.060.0065342611320512.221697.8
Seed.0.90.180.950.150.050.0819692319344180.96550
Seed.0.80.160.970.120.050.061241215115181.030.1
Seed.0.140.830.050.0714932210114181.16368.2
Seed Avg0.750.160.890.120.050.07
Flesh1.40.211.450.190.120.141842158844260.4
Flesh1.40.191.430.180.10.110.0026401247864270.547499.5
Flesh1.60.191.340.220.110.1217106247934260.57457.53
Flesh1.50.211.730.220.080.080.0027971198735270.512735.7
Flesh1.20.171.340.210.10.19613177596250.492720.4
Flesh Avg1.420.191.460.200.100.10
Peel0.900.140.940.070.070.131.00429.0017.002.008.0041.003.0014.000.436445.10
Peel1.000.181.150.070.070.12342.0019.001.008.0050.004.0017.000.557059.10
Peel1.100.151.120.080.080.14416.0018.002.007.0057.004.0015.000.50197.00
Peel1.000.181.280.070.070.10730.0020.003.008.0044.005.0026.000.594434
Peel0.900.181.180.070.080.121.00596.0019.002.008.0038.005.0015.000.586412
Peel Avg0.980.171.130.070.070.12
Dec 13, 01
December 13, '01Harvest Data
Tree 6 OFFNutrient Concentration (percent)PPM
Tree ComponentNSPKMgCaNaNO3FeAlMnBCuZn
Fine Roots
Small Roots
Scaffold Roots
Rootstock
Trunk0.200.030.050.120.030.250.014157077710237
Wood >6"0.200.010.050.20.070.490.015430271919218
Scaffold Branches (wood 4-6")0.300.040.030.110.020.140.0141121458111
Branches 2-4"0.300.060.050.250.060.350.0133715141016220
Small Branches (wood 1/2-2")0.400.050.210.510.180.630.0287435361727530
New shoots (green twigs, 6"
Scaffold Branches (wood 4-6")0.400.030.040.280.080.740.00910833314522328
Branches 2-4"0.500.030.050.40.10.760.00541385422337
Small Branches (wood 1/2-2")0.400.020.120.550.110.410.0183321212618422
New shoots (green twigs, 1")
Rootstock trunk0.300.040.040.290.030.140.0155910310714136110.51
Reproductive
Trunk (scion)0.300.040.030.190.040.170.036159322619114270.31
Wood >6"0.30.040.040.380.070.580.005227312342176271.45
Scaffold Branches (wood 4-6")0.300.030.030.320.050.27105311727128150.48
Branches 2-4"0.400.040.050.470.080.41118301642207211.1
Small Branches (wood 1/2-2")0.500.040.120.820.20.711695434683212491.48
New shoots (green twigs, 2"0.200.050.030.140.020.080.10614155315470.10.175
Small scaffold roots (1/2-1")0.300.070.060.190.050.320.1130921838616216140.870.116
large scaffolding roots 1-2"0.300.060.060.20.040.30.0916919737012236110.92
Scaffold Roots (>1")
Rootstock trunk0.300.060.040.160.040.240.0952027286165310.67
Reproductive
Trunk (scion)0.200.040.030.140.030.190.117419156115110.17
Wood >6"0.30.060.050.310.050.420.033221511175170.6
Scaffold Branches (wood 4-6")0.300.050.060.360.070.50.0054436142011180.87
Branches 2-4"0.400.050.090.420.10.540.0044134192210210.67
Small Branches (wood 1/2-2")0.500.070.170.640.180.80.009416150222812350.71
New shoots (green twigs, 6"0.40.10.070.40.070.730.01948413415229221.2447.41
Trunk (scion)0.30.10.090.30.10.40.027163.034.029.010.019.07.029.00.947.51
Fruit
Peel 11.10.10.171.40.120.110.021210281310707250.740.10247.1
Peel 21.10.10.211.50.120.090.01624526118838300.648.03
Peel 31
Peel Avg1.10.110.221.700.120.140.019159392611848240.7847.61
Flesh 11.70.390.282.410.110.050.0115498241510112271.120.25549.32
Flesh 22.10.40.332.730.10.050.0125627243512813321.310.01948.25
Flesh 31.40.320.262.20.10.060.016380211510010251.20.15446.24
Flesh Avg
Seed 10.80.150.271.320.120.060.0122582558248180.8742.65
Seed 210.170.321.590.120.050.0132252545289210.842.09
Seed 30.60.140.271.260.090.050.0153172059169190.7743.87
Seed Avg
Tree 38 ON
Tree ComponentNSPKMgCaNaNO3FeAlMnBCuZnMoCl %C %
New flushes
Reproductive
Canopy Leaves2.50.50.231.10.521.590.0121961401052005075310.82646.67
Green twigs10.20.531.40.41.110.027767659954917820.870.21944.75
Small Branches (wood 1/2-2")0.70.10.260.90.230.930.016129069783317652.3946.1
Branches 2-4"0.40.10.090.60.090.470.015437512011312.5346.76
Scaffold Branches (wood 4-6")0.40.10.080.60.090.680.0115039482410393.4447.07
Wood >6"0.30.10.060.40.060.450.013342436157261.8647.66
Trunk (scion)0.30.10.080.40.10.50.03928.038.032.035.018.07.057.01.948.21
Fruit
Peel 110.10.181.50.120.10.015291413719250.610.13947.59
Peel 210.10.141.60.10.070.01531129519280.490.01447.65
Peel 31.10.10.191.90.090.050.02491361577410310.6447.63
Peel Avg
Flesh 12.20.390.352.810.10.050.0145118265710816311.570.18446.37
Flesh 22.40.420.343.150.10.040.015606730169218401.670.01945.82
Flesh 32.40.40.282.170.070.020.021603330559917412.230.03745.63
Flesh Avg
Seed 10.90.170.331.570.120.050.00822224482110200.6642.3
Seed 210.160.291.580.160.050.01447305102712211.1142.22
Seed 310.160.241.480.130.020.011142245249160.8642.43
Seed Avg
149.52
188.16
31.36
24.924.9886621315
lbs
3.814.2672220521.336
1.131.265622056.328
2.783.1136220515.568
6.116.8432220534.216
3842.5622050
10000 kg/ha
11200
150
30047.3
181.818181818216.5
63.8
Mar 6, 03
March 6th, 2003
Tree 3Nutrient Concentration (percent)PPM
Tree ComponentNPKSMgCaNaNO3FeAlMnBCuZnMoCl %
Reproductive2.70.461.510.250.340.980.121471991651007022651.171
Leaves1.900.200.730.330.661.990.008240.0090.0066.00200366410.680.68
New shoot green twigs0.700.380.740.090.431.160.01993.0063.0034.0044427680.550.241
Branches(wood) 0.5- 2"0.600.160.510.040.190.690.0187.0053.0042.0028287430.641
Branches (wood) 2-4"0.300.050.280.080.060.310.0081.0020.0010.0015153150.581
Branches (wood) 4"- 6"0.300.040.250.070.050.40.0318.0023.0016.0017153170.981
Wood >6"0.200.030.130.090.030.160.1152.0013.008.00910280.321
Scion Trunk0.200.020.090.070.020.080.10472.0012.006.0068260.121
Rootstock Trunk0.30.040.210.120.030.170.08410465739133120.291
large Roots >2"0.30.060.250.050.050.240.02218616325720194150.770.755
large Roots 1- 2 "0.40.060.220.060.060.320.04617422234019215201.310.75
Roots 0.5- 1"0.40.070.290.070.070.360.05417132651225256291.760.115
Roots < 0.5"0.600.080.280.090.110.640.161288.00645.00997.004337101152.921.062
Very Fines Roots1.400.180.430.170.251.540.38381.00593.00885.005669239037.171.173
Fruit
NOT FOR N 15 .Seed 10.700.201.260.110.10.050.0062581636267190.551
NOT FOR N 15 Seed 20.500.170.770.070.090.060.0061741327145140.760.281
NOT FOR N 15 Seed 30.700.211.030.080.10.070.0052991628245150.671
Seed Avg0.630.191.020.090.100.060.01243.6715.002.337.0021.335.6716.000.660.76
from fruit 6 & 8
composite seed Fruit 6&80.700.221.100.110.100.080.01120.0019.003.007.0021.008.0020.000.641.00
NOT FOR N 15 Flesh 11.300.292.460.380.100.0449762048910260.421
NOT FOR N 15 Flesh 20.800.211.680.180.080.052990126795170.211
NOT FOR N 15 Flesh 31.000.272.270.250.100.052644198747220.321
Flesh Avg1.030.262.140.270.090.050.003536.6717.000.006.0080.677.3321.670.321.00
composite flesh Fruit 6&81.100.282.250.230.100.052868.0024.006.00102.007.0022.000.2901.000
NOT FOR N 15 Peel 11.300.171.550.090.220.200.013124221517769450.431
NOT FOR N 15 Peel 21.000.111.370.070.160.170.010139251415556250.3103.47
NOT FOR N 15 Peel 31.100.131.580.080.160.160.009175221117567280.42.23
Peel Avg1.130.141.500.080.180.180.01146.0023.0013.3316.3362.337.3332.670.372.18
composite peel Fruit 6&81.200.131.430.090.180.160.12146.0029.0017.0016.0077.008.0037.000.300.56
Tree 4
Tree Component
Reproductive2.80.51.580.260.310.810.013349115112365934801.371.00.
Leaves2.20.270.950.510.591.410.013373978262389530.710.53
New shoot green twigs0.90.531.240.130.451.010.0212477357204718930.810.16
Branches(wood) 0.5- 2"0.50.20.560.060.160.510.009145413311247411.201.00
Branches (wood) 2-4"0.300.080.310.090.070.280.005108.0021.0010.007174200.761
Branches (wood) 4"- 6"0.300.060.270.070.050.260.00676.0018.0012.006143170.811
Wood >6"0.300.040.240.070.040.260.027103.0016.0011.006133230.731
Scion Trunk0.300.040.200.090.030.180.039131.0012.007.004112230.391
Rootstock Trunk0.300.030.170.010.020.060.046173.008.005.0028280.181
large Roots >2"0.300.060.240.040.040.160.012122.0098.00158.00420380.681
large Roots 1- 2 "0.30.060.230.050.040.210.02131132217919390.831
Roots 0.5- 1"0.40.090.290.050.070.340.05223230350418276201.831
Roots < 0.5"0.60.10.320.090.130.680.19330669311403440111763.630.677
Very Fines Roots1.30.20.40.190.241.210.45540797916213956234256.790.582
FruitT
Seed 1R
Seed 2E
Seed 3E
Seed AvgN#
from fruit 6 & 8O4
composite seedH
Flesh 1FA
Flesh 2RD
Flesh 3U
Flesh AvgIN
composite fleshTO
Peel 1S
Peel 2
Peel 3
Peel Avg
composite peel
Jun 12, 03
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Fruit N content (mg/fruit)
Figure 4. Nitrogen content of Hass avocado fruit.
Each point is the mean between 5 and 12 fruit, with standard error bars.
JulAugSepOctNovDecJanFebMarAprMayJunJul
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1500
1000
500
0
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Fruit K content (mg/fruit)
Figure 5. Potassium content of Hass avocado fruit.
Each point is the mean between 5 and 12 fruit, with standard error bars.
JulAugSepOctNovDecJanFebMarAprMayJunJul
2000
1500
1000
500
0
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Table 1. Mineral balance (g per tree) of 20-year-old Hass avocado in California.LeavesProportion removed& twigsBranchesTrunkRootsFruitTotalby fruit (%)N559 65734293191173411.0P118 12913 85 53 39913.3K373 61056251377166522.6Ca575109395317 62086 0.3Mg183 47112 61 16 742 2.2S101 12014 65 45 34513.2Al1.1 4.40.732.70.0 39 0.1B1.8 3.60.4 1.71.4 915.9Fe3.4 6.40.922.00.3 33 1.1Mn3.0 3.60.3 1.30.1 8 1.1Na9.823.99.285.81.8 131 1.4Zn2.1 3.90.8 7.60.5 15 3.3In a 10,000 pound crop this translates into 30 # N and 50# K
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So how do you manage these nutrients?
Every year is going to be somewhat different, according to yield.
Over application can lead to too much vegetative growth and contamination.
Too little can result in lower yields.
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Start with the fall leaf analysis.Are you within the recommended range?
Look at crop load, is it higher or lower than last year.
If higher bump up N from last year by 20%, if lower drop it by 20%. K does not leach and does not need to be changed as long as within range.
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Avocado NutritionAvocado is unique in that it is very efficient in recycling nutrients from the leaf mulch Generally, nitrogen should be applied every yearOccasionally Zinc should be appliedPhosphorous? Potassium? (maybe)Iron in calcareous soils
Citrus is similar
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How much to apply?N and K should be based on leaf analysis in later summer, fall.
NOT soil analysis
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Because of high pH soils north of San Diego, not a good idea to apply Ca and K nitrate, which raise pH. Stick with ammonium based materials. Organics have slight acidifying effect, as well.
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Organics cost at least 10 X more than synthetics. And in coastal California release N in about 2 months. Warm soils.
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FertilizersN-P-K ratio is the grade and is required to be on all bags of fertilizer21-7-14 means that in 100 lbs of fertilizer you will get 21 lbs on N, 7 lbs of phosphate (P2O5) and 14 lbs of potash (K2O)
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New Growers Quick Guide - Nitrogen0.5-1.0 actual pounds of nitrogen required per tree, per yearUsually divided into 8 or 9 applications to be injected into the irrigation systemOr, use this suggested hand application3 lbs triple 15 in early March/April0.5 lbs urea in June0.5 lbs urea in September
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When to fertilize? An ExperimentExperiment conducted: control treatment was fertilized at 25 lbs N per acre in each time period (late January, mid April, mid June, mid July, late August and late October)An extra 25 lbs per acre was applied in January, or February or April or June or NovemberApril gave increased yield of 31% over control, and November gave increased yield of 39% over control (4 years of data)
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New Quick Growers Guide IronIf interveinal yellowing of leaf, most commonly is iron deficiency, caused by high pH or waterlogging. Gradually acidify soil, review irrigation program. Start iron chelates in the meantime
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New Growers Quick Guide - ZincYellow mottling between the veins of the leaves, small leaves, short internodes, rounded fruit, apply zinc sulfateHand, 3-5 lbs zinc sulfate per tree, every 3-5 yearsIrrigation with liquid zinc, 1-2 gallons per acre
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New Growers Quick Guide Potassium
Leaf tip and marginal burn, starting on mature leaves, small brownish spotsSmall fruit, shriveled seedsSlow growthThin twigs, diebackConfused with chloride tip-burn which is much more common
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Salt/Chloride Tip-BurnNot a nutrient deficiencyCaused by:Saline water (from wells, ponds or reclaimed water)Poorly leached soils that accumulate saltsUnder-irrigationToo much manureCombinations of above
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Application MethodsLiquid application of fertilizers is best due to ease of application and reduction in labor costs. Hand application to soil - Many small groves still do not have fertilizer injection, Many growers still like to use triple 15 to get P and K, this is not water solubleFoliar, not suitable for Nitrogen or other materials due to thick waxy leaf surface in avocado, but very effective in citrus
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Injection EquipmentBackflow prevention deviceInjectorTank that will not corrodeDifferential pressure tanks, or batch tanksVenturi devicePositive displacement pump, gas, electric or water powered
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Nutrient Availability and UptakeThe atmosphere contains 78% N2 gasSome soil organisms and root nodules on legumes convert N2 to NO2Lightning also converts N2 to NO2Fertilizer companies use natural gas to convert N2 to NH3 (under high temperature and pressure). Prices going upOrganic manures are slowly converted to NH4 and NO3 for plant uptake
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Nutrient Availability and UptakeAmmonium to nitrate takes 1-2 weeks at 75FAmmonium to nitrate takes 12 weeks or more at 50FAmmonium to nitrate is optimum at pH between 5.5 and 7.8Under anaerobic conditions, nitrate is lost from the soil as nitrous oxide, nitric oxide and N2 gases
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Nutrient Availability and UptakeMost of N is taken up as nitrate (NO3-Some may be taken up as ammonium (NH4+)Nitrate is highly mobile in soil and moves to the roots quickly (and is leached out readily)Ammonium binds to soil particles and is converted to nitrate by bacteriaVery poor uptake when soils are cold, and as as nitrate readily leaches
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Nutrient Availability and UptakePhosphorus (P)Most P in soil is tied up chemically, less than 1% may be available for uptake into plant. Mycorrhizal fungi help uptakeP taken up as phosphate ions: H2PO4-, HPO4--, or PO4Note: phosphorous acid is a phosphonate, not readily used as a nutrient- Rare documentation of supplemetal P in CA trees
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Nutrient Availability and UptakePotassium (K)Taken up as K+ ions and remains in ionic form in the plant90-98% of K occurs in primary materials and is unavailable to the plants1-10% is trapped in expanding lattice clays and is slowly available1-2 % is in soil solution and readily availableDoes not readily leachMost fruit trees require 2x as much K as N
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Nutrient InteractionsExcess K+ may compete with Mg and Ca uptakeExcess P interferes with Zn uptakeExcess Fe can induce Mn deficiencyIncreasing K fertilization can reduce B in the leaf analysisUSE LEAF ANALYSIS
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SUMMARYNitrogen applications are typically 1 lb of N per tree per year as an acid-based source, and best applied in spring early fall AVOID winter applicationsPhosphorus is rarely called forPotassium as hand or helicopter applied can go on anytime as K2SO4Zinc and Iron as sulfate or chelate go on in the warm months
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