Potassium & Phosphorus Management in Orchards

Franz Niederholzer, UCCE Advisor Colusa and Sutter/Yuba Counties

California Plant and Soil Conference

February 6, 2019

University of California Cooperative Extension

Agriculture & Natural Resources

There is a need to assess the value of P fertilization to tree crop yield.

I am unaware of any replicated trials w/ P in CA tree crops showing yield response, (although a lot is used in trees).

--------------per ton of crop---------------

Crop Nitrogen K2O P2O5 Almond 136 193 41

Pistachio 56 58 14 Walnut 29 40 9 Peach 4-12 10 3 Prune 13 23 --

Valencia 3.7 4.3 0.8 Cherry 9-12 9 3

On a per ton basis, crop export of K exceeds N for all major nut crops, stone fruit and oranges.

Nutrient Nutrient removed in 1000 lb kernel crop

Nutrient/acre removed in average crop

Potassium 80.0 lbs 195.2 lbs Nitrogen 68.0 lbs 165.9 lbs Phosphorus 8.96 lbs 21.86 lbs

Calcium 6.68 lbs 16.30 lbs Magnesium 4.64 lbs 11.32 lbs

Sulfur 2.62 lbs 6.39 lbs Boron 0.31 lbs 0.76 lbs Iron 0.19 lbs 0.46 lbs Zinc 1.12 oz 2.72 oz

Manganese 0.68 oz 1.66 oz Copper 0.34 oz 0.83 oz

P. Brown, U

C Davis

Potassium is the most expensive nutrient in a “crop swap”* plan.

Removal/acre* Replacement cost $/acre*

Nitrogen 166 96 Potassium as K2O 231 168 Phosphorus as P2O5

50 35 *harvested crop replacement nutrient management plan.

Potassium is the most expensive nutrient in a “crop swap”* plan.

Removal/acre* Replacement cost $/acre*

Nitrogen 166 96 Potassium as K2O 231 312 Phosphorus as P2O5

50 15 *harvested crop replacement nutrient management plan.

Potassium fertilizer is more expensive & the results less dramatic compared

to nitrogen.

N

K

Treatment (K2O/acre/

year)

1998 Kernel yield

(lb/acre)

1999 Kernel yield

(lb/acre)

2000 Kernel yield

(lb/acre)

ROI (income$:

fertK$)

0 lb 780 a 3930 a 2410 a 240 lb 890 a 3840 a 2860 b

600 lb 830 a 4380 a 2860 b

960 lb 1070 a 4020 a 2770 b

Reidel, Weinbaum, Brown and Duncan, UC Davis

Potassium fertilization provides a return on investment, especially after heavy crop year.

1.2 2.4 6.1

120 240 360 Meat lbs/a

2008 -61 51 145 3000 2009 -196 38 226 3000

2010 -294 -74 134 3100 2011 -360 -197 40 3950 2012 -158 29 274 700

---lbs K2O applied/acre/year---

Orchard K use is driven by cropload. Net loss of K from orchard can occur even with fertilization.

1.1

1.3

1.4

1.5

1.2

1.7

2.3

2.3

1.2

1.8

1.8

2.0

P. Brown, U

C Davis

Most of the K in an almond at harvest is in the hull.

--------------------mg K per nut------------------

Hull shell kernel

High K 33 8.2 6.7

Low K 23 7.0 6.3

Reidel, Weinbaum, Brown and Duncan, UC Davis

Topics discussed in this presentation.

Understanding K+ use by different tree crops

K+ in soils

4R’s of K

Soil pH affects availability of certain nutrients, particularly phosphorus.

http://www.depi.vic.gov.au

Potassium in the soil

Cation is a positively charged ion (for example, K+)

https://online.science.psu.edu/chem101

http://www.extension.umn.edu/distribution/cropsystems/DC6437.html

K+ is held on the CEC and in the soil solution.

Potassium and nitrogen reach roots by two processes: mass flow and diffusion. Generally, N is more soil mobile than K.

Nutrient Root interception Mass Flow Diffusion

Nitrogen 1 99 0

Potassium 2 20 78 At the root surface, plants expend energy to absorb the nutrients.

Factors that limit K mobility/plant availability in soil.

• Texture. Finer texture means longer route to root for K+ = slower diffusion rate. Finer textured soils = more CEC, hold more K +.

• Parent material. Soils formed from granitic parent material (eastside of the San Joaquin Valley) fix K+. Biotite (mica) weathering to vermiculite releases K, but those sites can be “refilled” with fertilizer K and that K is not plant available in the time you expect it to be.

• Irrigation. Low soil moisture levels limit diffusion (and mass flow).

Because K availability is influenced by soil type, know your soil!

Topics discussed in this presentation.

Understanding K+ use by cropping almonds.

K+ in soils

= 70-90 acres of K, removed in a crop

Maintaining adequate K+ in orchards.

Keep an eye on leaves in the spring for symptoms of K deficiency.

--------------per ton of crop---------------

Crop Nitrogen K2O P2O5 Almond 136 193 41

Pistachio 56 58 14 Walnut 29 40 9 Peach 4-12 10 3 Prune 13 23 --

Valencia 3.7 4.3 0.8 Cherry 9-12 9 3

On a per ton basis, crop export of K exceeds N for all major nut crops, stone fruit and oranges.

K deficiency reduces the yield potential of an almond tree.

• Nut size and crop set are not affected by deficient K, but…

• % crop grown on previous year’s shoots off 21%

• Shoot growth reduced 18% • News spurs per tree off 41%

•Yield off 10% Weinbaum, Brown, DeJong, Duncan, 2001

Why pay attention to Potassium nutrition?

–The per acre annual K fertilizer bill is double that of N

–Not keeping up could cost you, but over fertilizing could eat up most of the return on investment.

–K is highly variable across the landscape and a good candidate, whenever the map generating technology catches up to delivery, for site specific application.

Target leaf K and P levels.

-------------% July leaf levels-------------- Almond Pistachio Walnut

Deficient K 1.0 1.6 0.9 Adequate K 1.40 1.8-2.2 1.2-1.5 Deficient P 0.14 0.14-0.17 <0.09

Topics discussed in this presentation.

Understanding K+ use by different tree crops

K+ in soils

4R’s of K

Traditional winter banding of potassium sulfate (SOP), 2 bands/tree.

Now, there are more liquid K fertilizers, as well as…

Equipment to facilitate use of dry materials in fertigation.

Use the 4-R’s to guide K and P fertilization (as well as N).

• Right Rate • Right Time • Right Location • Right Material

Use the 4-R’s to guide K and P fertilization (as well as N).

• Right Rate • Right Time • Right Location • Right Material

Annual K at maintenance rate beat occasional “big slugs”in walnut.

B. Olson, Walnut research reports, 1995

400 lbs/a MOP every year

1600 lbs/a MOP every

4 years

CONTROL

--------------per ton of crop---------------

Crop Nitrogen K2O P2O5 Almond 136 193 41

Pistachio 56 58 14 Walnut 29 40 9 Peach 4-12 10 3 Prune 13 23 --

Valencia 3.7 4.3 0.8 Cherry 9-12 9 3

On a per ton basis, crop export of K exceeds N for all major nut crops, stone fruit and oranges.

Data sources: See next slide

Data sources for values on previous slide: • Almond, Pistachio: Data from Brown et al. 2008-2013

Final report to CDFA • Walnut: Data from Pope et al. 2015

(https://ucanr.edu/sites/cawalnut/category/Nitrogen/ • Peach, Cherry: Data from

http://treefruit.wsu.edu/orchard-management/soils-nutrition/fruit-tree-nutrition/

• Prune: Data from Weinbaum et al. 1994 Values are for dried fruit.

• Valencia: Data from Labanauskas and Hardy, Cal Ag, 1972

Irrigation systems can be designed to treat varieties separately.

Use the 4-R’s to guide K and P fertilization (as well as N).

• Right Rate • Right Time • Right Location • Right Material

Walnut July leaf K levels, Chico area. 260 lbs K2O banded in each winter.

00.20.40.60.8

11.21.41.61.8

1986 1988 1990 1992 1994 1996

Sum

mer

leaf

K

Leaf K

Data from B. Olson, Walnut research reports, 1995

Annual rainfall totals help explain low K in some years despite high input.

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

1986 1988 1990 1992 1994 19960

5

10

15

20

25

Rainfall Dec-Mar

Leaf K

Data from B. Olson, Walnut research reports, 1995

K and P (and N) accumulation in walnuts is linear from May – August.

0

20

40

60

80

100

May June July August Harvest

Lb n

utrie

nt /

ton

of c

rop Nitrogen

Potassium

Phosphorus

Data from K. Pope, et al., Walnut research reports, 2015

Almond nut K accumulation is steady thru the season, N accumulation slows after May.

Days after full bloom Days after full bloom

Nitrogen storage in woody tissue = ̴40 lbs N/acre Potassium storage in woody tissue = ̴25 lbs K/acre

P. Brown, UC Davis

N K

Use the 4-R’s to guide K and P fertilization (as well as N).

• Right Rate • Right Time • Right Location • Right Material

Right Place: Irrigation Rapidly Moves N into Soil Surface applied N Followed by Irrigation (90 minutes)

Broadbent, 1958, graph from www.IPNI.org

Traditional winter banding of SOP, 2 bands/tree.

Growers on low CEC soils use targeted spreading of dry SOP fertilizer in orchards with micro-sprinklers.

Photos: Wes Asai Consulting, Turlock, CA

Band K where the irrigation water reaches so its available through the summer.

Use the 4-R’s to guide K and P fertilization (as well as N).

• Right Rate • Right Time • Right Location • Right Material

All K fertilizers deliver K, but the anion can be an issue. • Sulfate of Potash (potassium sulfate) is safest, but

least soluble. Can go on dry or injected. • Potassium carbonate (Pot carb) increases pH. • Potassium thiosulfate (KTS) is a soil acidifier, and has

label limits to keep trees safe. • Muriate of potash (potassium chloride) is

inexpensive, but packs Cl-. Be careful… • Potassium nitrate is expensive, but delivers N and K at

1:3 ratio. • The majority of compost K and P are rapidly plant

available. • N:K in fruit/nuts is close to 1:1. What about N+K

liquid blends? 7-0-7, 10-0-12, etc….

Use the 4-R’s to guide K and P fertilization (as well as N).

• Right Rate. Target replacing crop use. Annual program is best.

• Right Time. Fall or in-season (linear crop K use through the season).

• Right Location. In the tree row where irrigation water reaches.

• Right Material. Work with your CCA to select the best for your situation.

Thank you!