Citrus Growers Forum

hoosierquilt · Posted: Sat 04 Feb, 2012 1:18 pm

I know I've read some on the forum about the 5-1-3 NPK ratio for citrus fertilizer, but not sure if this is for container citrus or for in ground citrus? Also, where are folks getting this information? Can someone point me to the research on this? I was told by the folks at UCR Extension Citrus services that young citrus are fine with a triple formulation (i.e., 15-15-15). Plus micronutrients of course. Any links to the research behind this would be helpful!
Smile

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Patty S.

Millet · Posted: Sat 04 Feb, 2012 2:39 pm

For in ground trees, the University of Florida recommends 6-6-6 or 8-8-8 for young trees 1 to 3 years old. For trees 4 years old and up, either 8-8-8 or 10-10-10. The Universities book titled "Florida - Your Dooryard Citrus Guide" by Jim Ferguson states---"Do not use a fertilizer with higher than an 8-8-8 analysis on young trees during years 1 - 3". You can read about the research concerning the 5-1-3 ratio that citrus absorb nutrients through their roots in the text book titled " The Genus Citrus" by Dugo and Di Giacomo. - Millet (352 ABO-)

jcaldeira · Posted: Sat 04 Feb, 2012 5:05 pm

Millet wrote:

For in ground trees, the University of Florida recommends 6-6-6 or 8-8-8 for young trees 1 to 3 years old. For trees 4 years old and up, either 8-8-8 or 10-10-10. The Universities book titled "Florida - Your Dooryard Citrus Guide" by Jim Ferguson states---"Do not use a fertilizer with higher than an 8-8-8 analysis on young trees during years 1 - 3". You can read about the research concerning the 5-1-3 ratio that citrus absorb nutrients through their roots in the text book titled " The Genus Citrus" by Dugo and Di Giacomo. - Millet (352 ABO-)

It is my understanding that nitrogen leaches out of the soil much more than phosphorus or potassium. It would seem to me that after the first few years of fertilizing with a general NPK formulation, we would want to go higher on the nitrogen relative to the other major nutrients. Millet, what is your thinking on this?

hoosierquilt · Posted: Sat 04 Feb, 2012 6:08 pm

Thanks Millet, exactly the info I was after. And, as far as more N with mature citrus trees, it is the opposite theory. You want to promote blossoms and fruit, not more vegetative growth. At least, that's what was shared in my class and during the UCR Citrus Collection tour by Dr. Kahn.

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Patty S.

jcaldeira · Posted: Sat 04 Feb, 2012 6:56 pm

hoosierquilt wrote:

. . . And, as far as more N with mature citrus trees, it is the opposite theory. You want to promote blossoms and fruit, not more vegetative growth. At least, that's what was shared in my class and during the UCR Citrus Collection tour by Dr. Kahn.

During a quick web search, I came upon some reports that suggest nitrogen and potassium fertilizers are often more needed by citrus than phosphorus. From U. of Florida:
http://edis.ifas.ufl.edu/ss418

Quote:

Nutrient Accumulation and Loss

As a young citrus grove gets older, some nutrients applied in fertilizers and soil amendments will tend to accumulate in the soil, while others will mostly leach out of the root zone with rain or irrigation water if not taken up by the trees. The extent to which soil nutrient accumulation takes place will depend on the nutrient, its application rate, and the characteristics of the soil. For sandy Florida soils, the following are rules of thumb regarding nutrient accumulation or leaching:

Cu, Zn, and Mn will accumulate in the root zone as a result of fertilizers applied to the soil or tree foliage. Soil accumulation of Cu resulting from frequent Cu-based fungicide applications can be particularly high.

Ca and Mg will accumulate in the root zone as a result of calcitic or dolomitic limestone applications, or soil-applied fertilizers.

As the amount of organic matter or clay in the soil increases, the accumulation of S applied as a component of many fertilizers will increase.

P will normally accumulate in the root zone unless the soil is extremely sandy and low in organic matter.

N, K, and B are nutrients that are poorly held by sandy soils and will be leached by rainfall or excessive irrigation. Thus, they usually must be applied as fertilizer every year.

Quote:

What about N and K2O fertilizer rates? In citrus fertilization research conducted on southwest Florida flatwoods soils, maximum yield has been obtained using N rates within the currently recommended range of 160 to 240 lbs N per acre per year. When coated, controlled-release fertilizers were applied in place of standard, water-soluble materials, rates could be lowered because nutrient use efficiency increased. Additional work with P and K fertilizer rates suggests that K influences citrus yield on the same order of magnitude as N. However, citrus is not very sensitive to P fertilization on flatwoods soils, especially if P has accumulated in the soil from previous fertilizer applications.

Further, an Australian government report is also recommending more nitrogen: http://www.dpi.nsw.gov.au/agriculture/horticulture/citrus/management/nutrition/nutrition#Tables See Table 2.

John

Millet · Posted: Sat 04 Feb, 2012 7:52 pm

The actual fertilizer formulation used will depend on the tree's location. For example, in the state of Florida, the soil already naturally contains plenty of the element phosphorous. Therefore, in Florida a fertilizer containing phosphorous is not needed, so something like 10-0-10, 12-0-12 or even a 15-0-14 would be use on mature 5+ year old trees.

1 year old in ground citrus tree should be fertilized 6 times per year, using a fertilizer such as 6-6-6 or 8-8-8. Do not use a fertilizer with a higher analysis than 8-8-8 on young trees during years 1 - 3.

2 year old tree - fertilize 5 times per year.

3 year old tree - fertilize 4 times per year.

4+ year old tree - fertilize 3 times per year.
Millet (351 ABO-)

hoosierquilt · Posted: Sat 04 Feb, 2012 8:00 pm

jcaldeira, it was Tom Shea, who is UC Riverside's Staff Research Associate- Subtropical Horticulture, that shared this piece of information during our class on Citrus in the Garden this weekend. Tom serves growers, managers, and allied agri business people in growing and managing subtropical tree crops such as citrus, avocado, and dates in the state of California. He stated that mature trees do not need as heavy an application of Nitrogen as young, less mature trees, and that you want to promote the production of blossoms and flowers, instead of promoting a lot of vegetative growth. Yes, it is true N leaves the soil at a higher rate than either Phosphorus or Potassium, but for us in S. California, where we only experience a few inches of rain a year (as opposed to Florida, which probably gets 5 to 10 times the amount of annual rainfall), just don't see the leaching from rainfalls on a consistent basis as many other citrus-growing areas of the country. So, maybe that's why Tom shared that advice with us during our class.

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Patty S.