Improving Fertilizer Use Efficiency for Horticultural Crops

University of Florida

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Increase fertilizer use efficiency: Low P fertilizer formula Soluble vs. Controlled-release fertilizers Fertigation Foliar fertilization Snake oils Other practices

Low P fertilizer formula

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Water-soluble fertilizer

>water-soluble. >plentiful. >lowest cost

materials. >leachable.

Typical water-soluble N and P fertilizers used in horticultural productionNitrogen Ammonium sulfate Ammonium nitrate Urea Potassium nitrate Calcium nitrate

Phosphorus Concentrated

superphosphate Mono-ammonium

phosphate Di-ammonium

phosphate Ammonium

polyphosphate

Nutrient release from CRF depends on temperature and moisture

Water-soluble Slow/controlled-Release

Ammonium nitrate

Non-coated

Urea formaldehyde

Coated

Osmocote

Dissolves allat once

Slowly decomposes to soluble N

Nutrients leakthrough coating

Examples of slow and controlled-release fertilizersNon-coated Nitroform Nutralene Nitamin IBDU(N sources only)

Coated Osmocote Polyon Nutricote Syncote Polymer/Sulfur-coated

fertilizers(N, P, K + others)

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Polymer coating layer

PLANT RESPONSE to CRF depends on how well the release curve matches plant need.

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Improved nitrogen use efficiency by10 50%

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8)%&/4!4!

Fewer applications needed.(Decreased application cost.)

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Percentage of full N rate25 50 75 1000 25 50 75 1004

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35Escote Meister Nutricote ProkoteSierraConventional

CR = 94% CR = 100%

CR = 100% CR = 100%CR = 84%

CR = 76%

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Environmentally advantageous;less fertilizer loss.(Decreased nitrate leachingbelow root zone.)

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Decrease salt damage?2

High-volume use of controlled-release fertilizer is limited to> >turfgrass >greenhouse >nursery >landscape

Cost of materials for citrus (3 yrs ago)!

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How does the relative COST OF FERTILIZER MATERIALS AND APPLICATION METHODSaffect fertilizer selection by producers?

Vegetables (3 yrs ago) Potato study: Cost of a water-soluble N fertilization

program D $38 to $63 per acre. Extra cost to use a CRF program cost D $8 to $79

more than the most expensive soluble N cost. Extra cost could be offset by reduced application rate

and/or providing cost-share to use CRF.

What do we know about CRF>>rates?>timing?>placement?>plant response?>leaching?>release rates as affected by

temperature and moisture?

Fertigation

Fertigation:What do we know about>

>nutrient use-efficiency?>application frequency?>plant response?>leaching potential?

Yield at four pre-plant/fertigation N fertilizer combinations.Fert. application method

Percent N applied

pre-plant

Percent N applied by fertigation

Total fancy pepper yield

Total marketable pepper yield

---------------- tons/acre ----------------0 100 4.2 9.1

30 70 4.4 9.570 30 3.8 8.3100 0 2.9 6.6

P-value 0.0531 0.0006

Fertigation improved N USE EFFICIENCY inbell pepper production.

355314Monthly286238Weekly424681Every irrigation2000

245611Monthly275836Weekly305176Every irrigation1999%%

N uptake efficiencyz

Relative amount of applied N that

leachedFertigations

per yearFertigation treatmentYear

6-year-old orange trees growing in lysimeters.

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With good water management, fertigationAPPLICATION FREQUENCY doesnt matter much.

Horticultural PLANT RESPONSE to fertigationis as good or better than the response observedwith well-managed dry soluble fertilization.In both cases, irrigation (and sometimesdrainage) water management is criticalfor success.

---31.319.0250---27.112.22007.121.511.81502.916.311.11000.8------50

---------------- lbs N/acre/year ----------------lbs/acre

CRFFertigationDry soluble fertilizerN rate

Estimated N leached below a ridge citrus grove root zone.

Why was there more leaching with fertigation comparedwith dry soluble fertilizer application?

Study authors: This occurred purely because ofunexpected prolonged irrigation or unexpected highrainfall following certain fertigation events in both years.

Foliar fertilization

Can FOLIAR FERTILIZER APPLICATIONimprove nutrient use efficiency?

Tree crops: Possibly Foliar uptake of urea can be 50% efficient; it

has enhanced flowering and yield. Phosphite is recognized as a P source; it has

increased flowering, fruiting, and lbs solids. Vegetables: No?

Leaves cannot absorb enough N/P to correct a deficiency.

Leaf burn is likely.

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Improve fertilizer use efficiency by: Develop a nutrient management plan Do a fertilizer trial by yourself Use appropriate application equipment. Use appropriate fertilizer sources and

formulations Add organic matter to the soil whenever

possible. Split fertilizer applications. Try to wet only the root zone when irrigating.

THANK YOU!

Questions?