Foliar N, P, K, B Studies on Almonds
Roland D. Meyer
Extension Soils Specialist, UC Davis
Research with foliar application of nutrients on citrus, avocado, peach
and almond has shown some potential for increasing yields. The primary benefits seem to
point to improved set and strength of newly developing fruit/nuts. It is also uncertain
what, if any, benefit may accrue from phosphorus, potassium, and boron applications along
with the nitrogen. The availability of a new material, mono potassium phosphate, along
with good nitrogen sources-urea and potassium nitrate provide additional motivation for a
more in depth investigation and reevaluation of this topic. Research during the 1995
through 1997 period with spring applied foliar treatments resulted in some favorable
effect upon yield, particularly with boron. It has been suggested that fall plus spring
applied foliar treatments may have an opportunity to increase almond yields. One other
material (PHT 12-26-26 plus micronutrients) has been used in the Arbuckle area with some
reported success.
Objectives
(1) To evaluate the effect of fall, fall plus spring and spring foliar
applications of several nitrogen, phosphorus, potassium and boron treatments on growth,
nutrient concentrations in leaves and nut yields, and (2) To evaluate the effect of
several timings of foliar treatments on yields and leaf nutrient levels.
Experimental Procedures
The experiment was established on a March 1989 planting of Butte
variety with a 15 feet by 20 feet "diamond" tree spacing arrangement. The foliar
nutrient treatments listed (Table 1) were applied from 1995 to 1997 beginning with the
prebloom (A timing) application when the tip of the bloom was pink. The second (B timing)
foliar nutrient treatments are applied 30 days after the prebloom treatments and the third
(C timing) foliar nutrient treatments are applied 60 days after prebloom. Beginning the
fall of 1997, several new treatments were initiated with PHT and others having fall
applications along with spring applications.
Results for the first three years (1995-1997)
The foliar nutrient treatments listed in Table 1 were applied as
indicated for the 1997 season. The trees were observed for any leaf burn or phytotoxicity
but none was found until after the last application and only the treatments with the
highest nitrogen rate (20-0-0 and 20-12-8) resulted in brown spots or dead tissue on the
leaves. Perhaps as much as 5% of the total leaf area was brown indicating dead tissue. The
foliar sprays applied in the two previous years had shown no leaf burn.
Table 1 gives the almond meat yields for the three years the experiment
has been conducted. Several significant points can be noted from the data:
(1). The boron treatment gave the highest yield in 1996 (2166 meat
lbs/A), the second highest in 1997 (2667 meat lbs/A), and the third highest yield in 1995
(2144 meat lbs/A).
(2). The control treatment resulted in the lowest yield in 1997 (2233
meat lbs/A. In 1996, there were 11 treatments with higher yields than the control and 10
treatments with lower yields. In 1995, there were 10 treatments with higher yields than
the control and 11 treatments with lower yields. Control treatment yields were similar for
the two years, 1985 meat lbs/A in 1995 and 1827 meat lbs/A in 1996.
(3). There were no consistent trends in any of the three years for
yields to improve with either one, two or three foliar nutrient applications.
(4). There were no consistent trends in the three years for yields to
improve with nitrogen alone, nitrogen plus phosphorus plus potassium, nitrogen plus
potassium, slow release nitrogen alone (CoRoN) or nitrogen plus phosphorus plus potassium
plus sucrose (Fulcrum) foliar nutrient applications.
(5). The CoRoN treatments had the greatest shift in ranking of yield,
from 2 above and 3 below the control in 1995 to having all 5 treatments below the control
yield in 1996 and then in 1997 having the ranking of 4th, 5th, 13th, 18th and 19th.
(6). The Fulcrum treatments as a group had the more consistently
highest ranking yields for the three year period.
The results of leaf analysis indicate no differences in nutrient
concentrations (N, P, K, Ca, S, Zn, Mn, B) between the foliar treatments applied.
Potassium concentrations were all somewhat low in 1997 (average 1.07%). Applied rates of
potassium had no consistent influence on leaf potassium concentrations for any of the
three years. There were no treatment differences in the number of double meats per nut,
blanks, wormy meats, weights of wormy meats, average meat weight or the percentage of
meats, shells, and hulls of the kernel in 1997.
Results for the first year-1998 of the new study
The foliar nutrient treatments listed in Table 2 were applied
beginning in the fall of 1997. Almond tree leaves were observed for any leaf burn but none
was found until after the last application and only the treatments with the highest
nitrogen rate (20-0-0 and 20-12-8) resulted in brown spots or dead tissue on the leaves.
Perhaps as much as 1-2% (compared to the 5% observed in 1997) of the total leaf area was
brown indicating dead tissue. The foliar sprays applied in 1995 and 1996 had shown no leaf
burn.
Table 2 gives the almond meat yields for the first year the experiment
has been conducted. Several significant points can be noted from the data:
(1). The boron treatment had the sixth highest yield in 1998 as
compared to the highest yield in 1996 (2166 meat lbs/A), second highest in 1997 (2667 meat
lbs/A), and the third highest yield in 1995 (2144 meat lbs/A).
(2). The highest yielding treatment was #18 (2677 meat lbs/A) which
received one application of Fulcrum and the second highest treatment was # 22 (2610 meat
lbs/A) which received three applications of Fulcrum. This is somewhat difficult to explain
because the other four treatments which received Fulcrum had a trend for having lower
yields.
(3). The PHT treatments receiving one application and two applications
gave the 3rd and 5th highest ranking yields but other treatment
yields were somewhat lower (10th, 11th, and 22nd highest
ranking yields).
(4). The control treatment resulted in the thirteenth highest yield in
1998 (2340 meat lbs/A) while it had the lowest in 1997 (2233 meat lbs/A). In 1996, there
were 11 treatments with higher yields than the control and 10 treatments with lower
yields. In 1995, there were 10 treatments with higher yields than the control and 11
treatments with lower yields. Control treatment yields were similar for the two years,
1985 meat lbs/A in 1995 and 1827 meat lbs/A in 1996.
(5). There was no consistent trend for yields to improve with
either one, two or three foliar nutrient applications.
(6). There was no consistent trend for yields to improve with nitrogen
alone, nitrogen plus phosphorus plus potassium, nitrogen plus potassium, slow release
nitrogen alone (CoRoN) or nitrogen plus phosphorus plus potassium plus sucrose (Fulcrum)
foliar nutrient applications.
(7). The two CoRoN treatments had yields below the control (14th
and 18th ranking yields).
Leaf samples taken on June 29 and October 12, 1998 will be analyzed for
total nitrogen, phosphorus, potassium, manganese, and boron. Leaf samples taken on June 29
will also be analyzed for zinc. The results have not been received from the laboratory.
Table 1
Almond meat yields for three years as influenced by foliar nutrient
applications (Nickels Soil Laboratory).
| Treatments |
Application
Rate,
lbs N, P2O5, K2O/A |
Yield,
meat lbs/A |
| No. Fertilizer |
A* |
B* |
C* |
1995** |
1996** |
1997** |
|
|
|
|
|
|
|
|
|
| 1. Control |
0-0-0 |
0 |
0-0-0 |
0 |
0-0-0 |
(11) 1985abc |
(12) 1827 bcd |
(22) 2233 c |
| 2. Urea (LB)†† |
5-0-0 |
|
|
|
|
(1) 2259a |
(8) 1871abcd |
(11) 2420abc |
| 3. Urea (LB) plus MKP† |
5-3-2 |
|
|
|
|
(15) 1879abc |
(15) 1799 bcde |
(3) 2560abc |
| 4. Urea (LB) |
5-0-0 |
0 |
10-0-0 |
|
|
(6) 2089abc |
(10) 1851abcd |
(17) 2346abc |
| 5. Urea (LB) plus MKP† |
5-3-2 |
0 |
10-6-4 |
|
|
(18) 1813abc |
(9) 1868abcd |
(14) 2404abc |
| 6. Urea (LB) |
5-0-0 |
0 |
10-0-0 |
0 |
10-0-0 |
(20) 1777abc |
(20) 1694 cde |
(21) 2269 bc |
| 7. Urea (LB) plus MKP† |
5-3-2 |
0 |
10-6-4 |
0 |
10-6-4 |
(14) 1886abc |
(16) 1784 cde |
(1) 2734a |
| 8. Urea (LB) plus MKP† |
5-3-2 |
0 |
10-6-4 |
0 |
20-12-8 |
(7) 2063abc |
(3) 1943abc |
(16) 2378abc |
| 9. CoRoN |
5-0-0 |
|
|
|
|
(19) 1777abc |
(21) 1602 de |
(5) 2507abc |
| 10. CoRoN |
5-0-0 |
0 |
5-0-0 |
|
|
(8) 2054abc |
(14) 1810 bcd |
(18) 2329 bc |
| 11. CoRoN |
5-0-0 |
0 |
10-0-0 |
|
|
(21) 1691 bc |
(19) 1751 cde |
(13) 2411abc |
| 12. CoRoN |
5-0-0 |
0 |
10-0-0 |
|
10-0-0 |
(4) 2131ab |
(13) 1820 bcd |
(4) 2523abc |
| 13. CoRoN |
5-0-0 |
0 |
10-0-0 |
0 |
20-0-0 |
(22) 1597 c |
(22) 1487 e |
(19) 2300 bc |
| 14. Boron-Solubor 20%
B (3 lbs/A) 0.6 lb B/A |
|
|
(3) 2144ab |
(1) 2166a |
(2) 2667ab |
| 15. Urea (LB) plus KNO3 |
5-0-2 |
|
|
|
|
(16) 1868abc |
(18) 1754 cde |
(15) 2387abc |
| 16. Urea (LB) plus KNO3 |
5-0-2 |
0 |
10-0-4 |
0 |
|
(5) 2099ab |
(4) 1925abc |
(20) 2273 bc |
| 17. Urea (LB) plus KNO3 |
5-0-2 |
0 |
10-0-4 |
0 |
10-0-4 |
(13) 1887abc |
(11) 1845 bcd |
(10) 2424abc |
| 18. Fulcrum |
5-3-2 |
|
|
|
|
(2) 2239a |
(6) 1909abcd |
(7) 2465abc |
| 19. Fulcrum |
5-3-2 |
0 |
5-3-2 |
|
|
(9) 2043abc |
(7) 1886abcd |
(8) 2432abc |
| 20. Fulcrum |
5-3-2 |
0 |
10-6-4 |
|
|
(10) 2013abc |
(17) 1780 cde |
(12) 2411abc |
| 21. Fulcrum |
5-3-2 |
0 |
10-6-4 |
0 |
10-6-4 |
(17) 1823abc |
(5) 1924abc |
(6) 2478abc |
| 22. Fulcrum |
5-3-2 |
0 |
10-6-4 |
0 |
20-12-8 |
(12) 1952abc |
(2) 2106ab |
(9) 2426abc |
|
|
|
|
|
|
|
|
|
| LSD0.05 |
|
|
|
|
|
496 |
321 |
400 |
* Timing of treatment applications: (A) Prebloom – 2/3-4/95;
2/13/96-trts #2-8 and 2/14/96-trts #9-13 & 15-22; 2/17/97-trts #2-13 & 15 and
2/18/97-trts #16-22. (B) 30 days after prebloom application – 3/6/95-trts #4-8 and
3/30/95-trts #10-13,16-17,19-22; 3/19/96; 3/17/97; and (C) 60 days after prebloom
application – 4/4/95-trts #6-8 and 5/2/95-trts #12-13, 17, 21-22; 4/30/96; 4/17/97.
The fall application of treatment #14 was made on 11/10/95 and 10/23/96. All materials
were applied in spray volume of 3 gal/tree on individual plots having 5 trees each.
Unfortunately the entire trial received a foliar boron application of 0.82 lb B/A on
10/30/96.
** Rank of yield for each year is given in parenthesis.
† MKP=Mono Potassium Phosphate (0-51.5-34).
†† LB= low biuret urea.
Table 2
Almond meat yields for 1998 as influenced by foliar nutrient
applications (Nickels Soil Laboratory).
| Treatments |
Application
Rate
lbs N, P2O5, K2O/A |
Yield** |
| No. Fertilizer |
Fall |
A* |
B* |
C* |
(meat lbs/A) |
|
|
|
|
|
|
|
|
|
| 1. Control |
0-0-0 |
0 |
0-0-0 |
0 |
0-0-0 |
0 |
0-0-0 |
(13) 2340ab |
| 2. Urea (LB)† |
|
|
5-0-0 |
|
|
|
|
(17) 2259ab |
| 3. Urea (LB) plus MKP†† |
|
|
5-3-2 |
0 |
10-6-4 |
0 |
10-6-4 |
(4) 2543ab |
| 4. Urea (LB) plus MKP |
|
|
5-3-2 |
0 |
10-6-4 |
0 |
20-12-8 |
(7) 2486ab |
| 5. Boron plus MKP |
B+5-12-8 |
0 |
5-0-0 |
0 |
5-12-8 |
0 |
5-12-8 |
(19) 2230ab |
| 6. Boron plus MKP |
5-12-8 |
0 |
B |
0 |
5-12-8 |
0 |
5-12-8 |
(9) 2393ab |
| 7. PHT |
|
|
1.5-3-3 |
|
|
|
|
(3) 2584ab |
| 8. PHT |
|
|
1.5-3-3 |
0 |
1.5-3-3 |
|
|
(5) 2534ab |
| 9. PHT |
|
|
1.5-3-3 |
0 |
3-6-6 |
|
|
(22) 2197 b |
| 10. PHT |
|
|
1.5-3-3 |
0 |
3-6-6 |
0 |
3-6-6 |
(11) 2384ab |
| 11. PHT |
|
|
1.5-3-3 |
0 |
3-6-6 |
0 |
6-12-12 |
(10) 2391ab |
| 12. CoRoN |
|
|
5-0-0 |
0 |
10-0-0 |
0 |
10-0-0 |
(14) 2297ab |
| 13. CoRoN |
20-0-0 |
0 |
5-0-0 |
0 |
10-0-0 |
0 |
10-0-0 |
(18) 2238ab |
| 14. Boron-Solubor 20%
B (3 lbs/A) 0.6 lb B/A |
|
|
|
(6) 2516ab |
| 15. Urea (LB) plus KNO3 |
|
|
5-0-2 |
0 |
10-6-4 |
|
|
(21) 2204 b |
| 16. Fulcrum |
10-6-4 |
|
|
|
|
|
|
(15) 2286ab |
| 17. Fulcrum |
10-6-4 |
0 |
5- 3- 2 |
|
|
|
|
(20) 2221ab |
| 18. Fulcrum |
|
|
5- 3- 2 |
|
|
|
|
(1) 2677a |
| 19. Fulcrum |
|
|
5- 3- 2 |
0 |
5-3-2 |
|
|
(8) 2448ab |
| 20. Fulcrum |
|
|
5- 3- 2 |
0 |
10-6-4 |
|
|
(16) 2264ab |
| 21. Fulcrum |
|
|
5- 3- 2 |
0 |
10-6-4 |
0 |
10-6-4 |
(12) 2352ab |
| 22. Fulcrum |
|
|
5- 3- 2 |
0 |
10-6-4 |
0 |
20-12-8 |
(2) 2610ab |
|
|
|
|
|
|
|
|
|
| LSD0.05 |
|
|
|
|
|
|
|
463 |
* Timing of treatment applications: Fall applications were made on
11/21/97 (Treatments # 5, 6, 13, 16, 17); (A) Prebloom-pink tip treatments # 2-15 and #
17-22 were applied on 2/26/98; (B) 30 days after prebloom application –
4/15/98-treatments # 3-6, 8-13, 15, and 19-22; and (C) 60 days after prebloom application
– 5/22/98-treatments # 3-6, 10-13 and 21-22. All materials were applied in a spray
volume of 3 gal/tree on individual plots having 5 trees each. All boron treatments (# 5, 6
and 14) received the same rate of boron—0.6 lb B/A.
** Rank of yield for each year is given in parenthesis.
† LB= low biuret urea.
†† MKP=Mono Potassium Phosphate (0-51.5-34).
|
