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K Injected Irrigation

Potassium Fertilizers Injected through Three Drip/Micro-Irrigation Systems on Almonds

Roland D. Meyer
Extension Soils Specialist, UC Davis

 High yielding almond orchards with declining leaf potassium levels which are often irrigated with drip or micro-sprinkler systems present a challenge as to the most efficient method of applying potassium. An experiment was established to compare surface banded potassium sulfate with injected potassium sources: sulfate, chloride, thiosulfate and mono-potassium phosphate through three irrigation systems: single line drip, double line drip and micro-sprinkler to evaluate there effect on almond yields and leaf K concentrations. There were significant differences between the 1998 meat yields for treatments in all three irrigation systems with one or several of the mono-potassium phosphate (MKP) treatments resulting in the highest yields and the banded K2SO4 treatments having among the lowest yields (Table 1). There was no clear trend for all of the potassium treatments to have a higher almond yield than the control. The control (no potassium applied) treatment yields for each of the three irrigation systems were slightly above (single and double line drip) or below (micro-sprinkler) the average yields for all plots under each system. As was the case in 1997, yields in 1998 did not show a consistent trend as rates of applied potassium were increased. April 1998 leaf potassium concentrations were somewhat inconsistent with respect to rates and sources of applied potassium under the three irrigation systems (Table 2). The July samples indicated a significant increase in leaf potassium concentrations for all sources and rates under all three-irrigation systems over the controls. This was most evident under the micro-sprinkler system where 9 out 12 treatments had leaf potassium levels greater than 2.00%. The average leaf potassium concentrations for the three irrigation systems were 1.68% for the single line drip, 1.73% for the double line drip, and 2.12% for the micro-sprinkler. Leaf potassium levels were consistently increased as the rate of applied potassium for each source was increased under all three irrigation systems. The October samples indicated a significant increase in leaf potassium concentrations for all sources and rates under all three irrigation systems over the controls. Leaf potassium levels were consistently increased as the rate of applied potassium for each source was increased under all three irrigation systems except for the K2SO4 treatments (#2, 3, 7 and 8) for the single line drip irrigation system (Table 2). It is interesting to note that the fall banded potassium sulfate (K2SO4) treatments under the micro-sprinkler and double line drip systems resulted in relatively high leaf potassium levels compared to other sources and rates whereas the banded treatments did not have nearly as high leaf potassium levels under the single line drip system. This would be expected since the irrigation water was not wetting the area where the potassium had been applied. Only winter rains would have wetted the soil and provided for some uptake of potassium early in the spring. July leaf phosphorus concentrations ranged from 0.12 to 0.155% but there were not significant differences between any of the treatments for the three irrigation systems.

  

Table 1

Almond meat yields for 1996, 1997, and 1998 for the fall banded versus source and rate of potassium injected through three irrigation systems experiment at Nickels Soil Laboratory.

 

Irrigation and Potassium Fertilizer Treatments

1996 Yield

(lbs meats/A)

1997 Yield

(lbs meats/A)

1998 Yield

(lbs meats/A)
Single line drip (4 replications)
* 1. Control (No K) 1993 2132 2449 ab
* 2. 1 lb. K2O/tree K2SO4 1954 2526 2469 ab
* 3. 2 lbs. K2O/tree K2SO4 1809 2170 2494 ab
* 4. 1 lb. K2O/tree MKP 1985 2398 2786 a
5. 2 lbs. K2O/tree MKP 1819 2301 2355 ab
* 6. 1 lb. K2O/tree KTS 1999 2520 2307 ab
* 7. 2 lbs. K2O/tree K2SO4 1754 2386 2102 b
8. 4 lbs. K2O/tree band K2SO4 2009 2191 2257 b
9. 1 lb. K2O/tree KCl 1765 2783 2170 b
LSD 0.05 407 664 524
 NS NS
 Double line drip (2 replications)
* 1. Control (No K) 1827 2455 2628 ab
* 2. 1 lb. K2O/tree K2SO4 1997 2285 2347 ab
* 3. 2 lbs. K2O/tree K2SO4 1748 2529 2335 ab
* 4. 1 lb. K2O/tree MKP 1899 2289 2729 a
* 5. 1 lb. K2O/tree KTS 1664 2745 2079 b
* 6. 2 lbs. K2O/tree band K2SO4 1984 2368 2358 ab
LSD 0.05 391 732 631
 NS NS
 Micro-sprinkler (2 replications)
* 1. Control (No K) 2023 2223 c 2645 abc
* 2. 1 lb. K2O/tree K2SO4 2437 2418 bc 2916 abc
* 3. 2 lbs. K2O/tree K2SO4 2312 2844 ab 2698 abc
4. 4 lbs. K2O/tree K2SO4 2196 2686 abc 2685 abc
* 5. 1 lb. K2O/tree MKP 2192 2962 a 2952 ab
6. 2 lb. K2O/tree MKP 1925 2692 abc 2843 abc
7. 4 lb. K2O/tree MKP 2182 2882 ab 3140 a
* 8. 1 lb. K2O/tree KTS 2422 2378 bc 3207 a
9. 2 lbs. K2O/tree KTS 2277 2657 abc 2663 abc
10. 2 lbs. K2O/tree KCl 2300 2762 abc 2628 abc
*11. 2 lbs. K2O/tree band K2SO4 2312 2887 ab 2325 c
12. 4 lbs. K2O/tree band K2SO4 2220 2542 abc 2428 bc
LSD 0.05 549 542 619
 NS   

 *Potassium fertilizer treatments common to all three irrigation systems.

 

Table 2

Almond leaf potassium concentration in 1998 for the fall banded versus source and rate of potassium injected through three irrigation systems experiment at Nickels Soil Laboratory.

 

Irrigation and Potassium Fertilizer Treatments

Leaf Potassium

April 2(%)

July 7(%)

October 8(%)
Single line drip (4 replications)
* 1. Control (No K) 1.54 b 1.18 d 1.19 c
* 2. 1 lb. K2O/tree K2SO4 1.78 ab 1.78 b 1.90 b
* 3. 2 lbs. K2O/tree K2SO4 1.85 a 1.87 ab 1.91 b
* 4. 1 lb. K2O/tree MKP 1.80 ab 1.77 b 1.91 b
5. 2 lbs. K2O/tree MKP 2.03 a 2.10 a 2.28 a
* 6. 1 lb. K2O/tree KTS 1.78 ab 1.73 bc 1.77 b
* 7. 2 lbs. K2O/tree K2SO4 1.74 ab 1.48 c 1.42 c
8. 4 lbs. K2O/tree band K2SO4 1.86 a 1.47 c 1.38 c
9. 1 lb. K2O/tree KCl 1.82 ab 1.71 bc 1.77 b
LSD 0.05 0.306 0.281 0.281
        
Double line drip (2 replications)
* 1. Control (No K) 1.94 1.41 1.44 b
* 2. 1 lb. K2O/tree K2SO4 2.02 1.78 1.85 ab
* 3. 2 lbs. K2O/tree K2SO4 1.58 1.88 1.99 a
* 4. 1 lb. K2O/tree MKP 1.87 1.72 1.78 ab
* 5. 1 lb. K2O/tree KTS 2.14 1.77 1.85 ab
* 6. 2 lbs. K2O/tree band K2SO4 1.95 1.82 1.81 ab
LSD 0.05 NS NS 0.481
        
 Micro-sprinkler (2 replications)
* 1. Control (No K) 1.81 b 1.26 f 1.27 g
* 2. 1 lb. K2O/tree K2SO4 1.81 b 1.71 e 1.79 f
* 3. 2 lbs. K2O/tree K2SO4 1.79 b 2.33 bc 2.25 cd
4. 4 lbs. K2O/tree K2SO4 1.78 b 2.59 ab 2.70 a
* 5. 1 lb. K2O/tree MKP 2.16 ab 2.06 cde 2.01 def
6. 2 lb. K2O/tree MKP 1.92 b 2.39 abc 2.36 bc
7. 4 lb. K2O/tree MKP 2.54 a 2.77 a 2.56 ab
* 8. 1 lb. K2O/tree KTS 1.85 b 1.81 de 1.86 ef
9. 2 lbs. K2O/tree KTS 2.13 ab 2.06 cde 2.11 de
10. 2 lbs. K2O/tree KCl 2.23 ab 2.15 cd 2.08 de
*11. 2 lbs. K2O/tree band K2SO4 1.88 b 2.11 cd 2.14 cd
12. 4 lbs. K2O/tree band K2SO4 2.04 ab 2.20 bcd 2.22 cd
LSD 0.05 0.526 0.394 0.251

*Potassium fertilizer treatments common to all three irrigation systems.

 

 

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Copyright © 1999 Colusa County Cooperative Extension, Univ. of California
Last modified: September 01, 2000