Banding Fertilizers in Pecan Orchards Michael Smith Department of Horticulture & L.A. Oklahoma State University
Necrotic leaves near shuck split on Pawnee July leaf P 0.114% and leaf K 0.62%
September Leaf P and K Concentrations and Leaf Necrosis Ratings Nut count, kernel %, kernel grade and return bloom improved with higher leaf P and K concentrations.
Cultivar: PawneeAge:9 years Soil: Dennis silty clay loam Irrigation: subsurface drip Treatments: Control – N only; P – N + P; K – N + K; PK – N + P + K 2009 All trees: March 52 lb/acre N May 88 lb/acre N P: March 131 lb/acre P2O5 K: March 69 lb/acre K2O PK: March P rate + K rate 2010 All trees: March 104 lb/acre N P: March 262 lb/acre P2O5 K: March 138 lb/acre K2O PK: March P rate + K rate 2011 All trees: March 104 lb/acre N P: March 262 lb/a P2O5 K: March 138 lb/acre K2O PK: March P rate + K rate 2012 All trees: March 52 lb/acre N May 75 lb/acre N P: March 131 lb/acre P2O5 K: March 69 lb/acre K2O PK: March P rate + K rate
July leaf P 2011 2012
Drought started in 2010 and has continued to intensify. Trees on survival irrigation ration Surface water irrigation source Non-irrigated 2 miles south
July leaf K 2011 2012
P deficiency symptom in July Leaf symptoms Rating 1 Rating 3 Rating 5 Symptoms appear closely linked to P shortage, even in July.
2011 1-year-old branches with fruit 2010 branch type
N & P on ‘Chickasaw’ near Baconton, GA Treatments: March 0 or 50 lb/a N Late July 0 or 100 lb/a N Late July 0 or 150 lb/a P2O5 N source: (NH4)2SO4 P source: Triple super phosphate Reps: 6 single trees
Late July N & P application on next year current season shoots fruiting
P & K in the rest of the field 18-46-0 (DAP), 0-46-0 (TSP), or 0-0-60 banded increases availability of those nutrients. Broadcast applications are generally ineffective. Applied with spinner off Note K band Healthy trees without deficiency symptoms as a result of banding 18-46-0 banded in March
Potassium banding on ‘Desirable’ in GeorgiaWood, Wells & Funderburke, 2010 • ≈25 years-old on Elliott rootstock • Faceville sandy loam soil • 30’ x 60’ spacing • Drip irrigated from 1 line on each side • 0-0-62 applied March in ≈ 6” wide band spanning several emitters. Applied on each side of the tree within the herbicide treated area. • Rates from 0 to 53 lb/tree K2O • Measurements were at the end of stage 2 fruit drop, i.e. June drop.
Potassium concentration in leaves, retain fruit and aborted fruit of ‘Desirable’ the 1st year following application Retained fruit Aborted fruit
Zinc banding of ‘Desirable’ in GeorgiaWood, 2007 • 15’ x 30’ (97 trees/acre) • 4-years-old at beginning of study • Faceville fine sandy loam • Drip irrigated • Buried line 4’ from trunk on each side of tree • Water delivery on surface 3’ apart • 1 gph operated 8 to 12 hours/day • Irrigation lines within herbicide strip • Single application of ZnSO4 or ZnO banded 4” x 13’ over drip line • 0 to 9.3 lb Zn/tree (0 to 25 lb ZnSO4; 0 to 12 lb ZnO)
Leaf Zn following a single applicationWood considered 50 ppm as threshold 1st year 2nd year 4th year 3rd year
Summary • Applying phosphorous, potassium and zinc in bands within the wetted area of drip irrigated trees is effective. • Phosphorus and potassium can be applied as a bulk blend. • Do not apply zinc in the same area where phosphorus was applied. • Similar results will probably be obtained when applied within the wetted area of micro-sprinkler or sprinkler irrigated orchards. • Banding about mid-way between the trunk and dripline should be beneficial on non-irrigated orchards, but the effectiveness will probably be reduced.