Meeting Nutrient Requirements of High Yielding Potato Crops

Potato Science Lecture 12Fertility ManagementIrrigated Potato Production

2Important NutrientsPrimary macronutrients

Nitrogen Phosphorus Potassium3Total potato plant N, P, and K Uptake

Days After EmergenceNutrient Uptake (lb/ac)4Total Potato Plant N, P, and K Uptake Rates at Aberdeen

Days After EmergenceNutrient Uptake Rates (lb/ac/day)KNPEarly-Season Soil Nutrient Placement

Fertilizer Placement

DryFertigationP, KNFoliarRelative Nutrient Mobility in SoilNitrogen Mobile (nitrate>urea>ammonium)Potassium moderately low mobilityPhosphorus low mobilityNitrogenNecessary for protein and chlorophyllUsed in large quantities by plantsQuantity available fluctuates rapidlyShortage associated with marked yield lossApplication important in all soils9

Soil N CycleLEACHING (NO3-)Nitrogen Deficiency Symptoms

General chlorosis (pale green color)

Younger leaves turn darker green, old leaves remain yellow

Upward cupping of deficient leaflets when severe11Potato Variety Nitrogen Response Trials Aberdeen, 2005

Soil AnalysisOne composite sample per 20-25 acres

0-12 inch sampling depth for potatoes

Combine 10-20 samples (zig-zag pattern)

Random but accurate samples13Total N Recommendations for Russet Burbank PotatoesPotential Yield (cwt/acre) Soil NO3-N (0-12 in depth)300400500600ppm---------------------------lb N/acre --------------------------0200240280320518022026030010160200240280151401802202602012016020024025100140180220Nitrogen Fertilizer Management Program

Apply up to 25-60% of N prior to planting

Apply remainder of N (40-75%) through the irrigation system during tuber development according to crop requirements

Slow release or controlled release N fertilizers applied preplant can be used to reduce N leaching

Preplant N applicationsNitrogen (partial application)25-30% on sandy soils30-40 % on sandy loam soils40-60 % on silt loams

Nitrogen fertilizers urea, mono-ammonium phosphate, ammonium sulfate, ammonium polyphosphate

16In-Season N ApplicationsBegin after tuber initiation and adjust according to tuber bulking rates and weekly petiole N concentrationsCut-off 3 to 4 weeks before vine killTarget = Total Seasonal N Requirement - preplant + sidedress applications 17Calculating In-Season N Application RatesBased on lb N/ac/day or week, which changes according to crop demand

Once tuber bulking begins, weekly crop N requirements can be estimated based on relationships between tuber growth rate and plant N uptake

Daily N uptake rates for different potato cultivars range from about 2 to 5 lb N/ac/day depending on the tuber-bulking rate

Can be applied as dry or liquid N fertilizersCalculating In-Season N Application RatesRusset Burbank requires about 3-4 lb N/ac/day (20-25 lb N/week) to prevent the loss of both N and dry matter from the tops and roots to the tubers during tuber bulking

Assuming 75-80% plant N uptake efficiency for injected N fertilizer, about 30 lb N/ac would satisfy crop N requirements for a week

Adjustments to projected rates to account for N mineralization should be based on weekly petiole nitrate tests

Total Yield Response to N for A03158-2TE and Russet Burbank at Aberdeen ID, 201346061050642320Tissue AnalysisPetiole analysis the most commonSample 4th petiole Sample under consistent conditionsDry the tissue immediatelyPrivate and public labsBase applications on sufficiency21A03158-2TE Petiole Nitrates, 2013Recommended petiole and soil (0-18 inches) NO3-N concentrations for Russet Burbank potatoes during different growth stages Tuber Tuber Sample Vegetative Initiation Bulking Maturation

------------- NO3-N (ppm) -------------

Petiole ----- 20,000-25,000 15,000-20,000 10,000-15,000

Soil > 20 20 15-20 < 1523

From Rowe, 199324Factors Affecting Petiole Nitrogen ConcentrationsPlant Factors:photosynthesisdry matter productionN metabolismtranspirationSoil Factors:temperaturemoisturemineralizationNH4+/NO3-physical conditionsRoot Factors:carbohydrate supplyroot healthroot length / depth

25Critical Time Period N builds up in (or is applied to) soil before plant uptake and may be lostImpact of Weather on Soil N Supply, Soil N Losses, and Crop N Demand Soil/Plant NSpringSummerFallPotato N UptakeSoil mineral N,Normal yearSoil mineral N,Wet springAmount of N fertilizer neededIn normalyearin year with wet springPotato Yield Response to N Fertilizer Following Fall or Spring Plowing of Alfalfa, Aberdeen 2002

Nitrogen Rate(lbs N/acre)Yield (cwt/acre)Spring plowFall plow

Potato Rotation StudyRexburg, ID 2003-2005Russet Burbank potato yields as influenced by N rates after alfalfa, wheat, or maize averaged across 2004 and 2005 seasons

83119164PhosphorusSecond most critical nutrientEssential for energy transferCritical for root growthGenerally low in soil availabilityRapidly tied up by soilManagement is long-termApplication important in all soils29

From Rowe, 199330Total Potato N, P, and K Uptake

Days After EmergenceNutrient Uptake (lb/ac)31Phosphorus and Dry Matter AccumulationDays After Emergence Accumulation/maximumdry matterP

33Soil P Buffering CapacityDepletion of solution P brings absorbed P into solution to maintain equilibriumRate of establishing new equilibrium depends on rate of desorption from absorbed forms and rate of diffusion (i.e., the withdrawal rate is proportional to the size of the bank)34Phosphorus Precipitation on CaCO3P adsorbed to CaCO3 surfaces forming ion clusters

Clusters allow for nucleation of Ca-P crystals

Common in calcareous soils of Southern Idaho35Calcite equilibrated for 10 days

0 ppm P

10 ppm P

25 ppm P

50 ppm P

100 ppm P

500 ppm P36Ammonium Phosphates

Reaction pHP Fertilizer GranuleCaHPO44H2OadsorptionprecipitationCa2+ H3PO4Recovery of Fertilizer PPlants recover 5 to 20%Remainder reacts with soil components

Residual fertilizer P builds up soil P to increase future availability

39Phosphorus Fertilizer ProgramAdequate P concentration in bulk soil to maintain optimal P concentration

Starter bands to enhance early season P availability

Maintenance / building of soil P levels40 Preplant Phosphorus Options Ammonium Phosphates - liquid and dry

Avail

Humic Acids

Controlled Release P

In-Season P Sources APP (10-34-0) and phosphoric acidBroadcast

Band42Preplant P Fertilizer Recommendations for Russet Burbank Potatoes

Apply an additional 40 to 80 lb of P2O5/acre as a starter at planting for soil test P levels below 30 ppm.Add 25 lb P2O5/acre as a starter for additional 100 cwt/acre above 400 cwt/acre.Soil Test P(0-12 inch depth)ppmPercent Free Lime------------ lb P2O5/acre ----------------0 4 812Dry Matter Balance

Dry Matter Balance (total / tubers) Average P in leaves (%)Y = 0.76X 0.7r2 = 0.67(0.22)Westermann and Kleinkopf, 19850.22% P = sufficiency levelPhosphorus FertigationMaintain petiole P concentration above 0.22% through tuber bulking30 to 40 lb P/A in late July can increase total P uptake 4 to 5 lb/ac

Typically use APP (10-34-0) or Phosphoric acid45PotassiumUsed in large quantities by plants

Important in translocation of nutrients

Easily leached in sandy soils

Some soils naturally low

Application important in all soils46Total Potato N, P, and K Uptake

Days After EmergenceNutrient Uptake (lb/ac)47

48Forms of Potassium in SoilMineral5,000 - 25,000 ppmNon-exchangeable50 - 750 ppmExchangeable40-600 ppmSolution1-10 ppm49K Absorption by Plants Primarily by diffusion and mass flow

Related to K intensity (solution K)

Diffusion : 85 - 95% of K uptake

Mass Flow : 5 - 10% of K uptake

K quantity (Q) = exchangeable KRelationship between STKC and K DiffusionSTKC, ppmK Diffusion ppm / day>

y = 0.0138x 0.30r2 = 0.64>Relationship between STKC and slow-release K from soil extractsSTKC, ppmSlow Release K, ppm / day>

175Soil K Recommendations Critical STKC for potatoes = 175 ppm

About 4.6 lb K2O/ac required to raise STKC 1 ppm per 1 foot of soil (without fixation)

Estimated K fixation 5% at 150 ppm STKC and 27% at 25 ppm STKCPotassium fertilizer recommendations

ppm ------------- lb K2O/ac ------------- (0-12 1nch) 300 400 500 600 Soil Test K Yield Goal (cwt/ac)Potassium Fertilization GuidelinesProbability of a K response: loamy sand > sandy loam > loam > silt loam Slight advantage for K2SO4 over KCl (@rates > 200 lb K2O/A) for:specific gravitiesNo. 1s55Potassium Fertilization GuidelinesBanded K not as effective as broadcast K K in starter band should be < 50 lb K2O/ac (salt effect)

Avoid high (>300 lb K2O/ac) spring applicationsyield reductions observed with spring applications of 400-600 lb K2O/ac

higher rates should be split fall/spring56Potassium Fertilization GuidelinesPreplant K more effective than applying most of the K in-season (fertigation)

Fertigation - no consistent difference between K sources (KCl, K2SO4, KTS)

Avoid large (>50 lb K2O/A) single fertigation applications57Potassium Fertilization GuidelinesUse petiole testing to determine K fertigation requirements

Maintain > 7.0 - 7.5 ppm K in fourth petiole

Cut off K fertigation 30 days before vine kill to avoid reducing specific gravity58N and P Fertilizer Effects on Specific Gravity of Russet Burbank Potatoes, Aberdeen (1985)N Applied (lb N/acre) P Applied (lb P2O5/acre)PotassiumDeficiency Symptoms

Symptoms appear on young, full-sized leaves

Leaflets become rugose (crinkled)

Leaves take on a scorched appearance with black pigmentation and necrotic (dead tissue) edges60

Potassium Deficiency Symptoms61

http://www.microessentials.com/62

Secondary Macronutrients

Sulfur Calcium Magnesium63SulfurImportant as a component of proteinsOften naturally availableMany sources Fertilizer by-product Water supply Organic matterSome soils inadequateIdeally, 15 ppm or greater 64SulfurDeficiency SymptomsGeneral chlorosisSimilar to nitrogen deficiency except young leaves remain yellow over timeLeaflet yellowing is uniform and general>0.20% S in petiole - sufficient65

Sulfur deficiency Symptoms66CalciumImportant for cell wall integrityAbundant in arid soilsIdeally, 300 ppm or greater Passive uptake - moderate solubilityPoor transport under cool conditionsFoliar applications not transported to tubersApplication necessary in acid soils for pH adjustment

67Calcium Deficiency SymptomsSymptoms appear on youngest leaves firstLeaflets cup upwardBrown spotting on leafletsLeaflets eventually dry up and become brown if symptoms are severe>0.60% Ca in petiole - sufficient

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Calcium Deficiency Symptoms

69MagnesiumComponent of chlorophyllDerived from native rocksSome soils deficientIdeally, 100 ppm or greater Application commonly necessary in acidic soils

70MagnesiumDeficiency Symptoms

Symptoms appear first on young mature leavesGeneral chlorosis with veins remaining greenLeaflets near growing point remain greenInterveinal necrosis causes scorched look>0.30% Mg in petiole - sufficient

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Mg Deficiency Symptoms72Micronutrients Boron Copper Iron Manganese Molybdenum Zinc73MicronutrientsEssential as activators and for enzyme systemsAvailability affected by pHBoron naturally low in some soilsCopper often deficient in muck soilsIron, manganese, and zinc unavailable in alkaline soils

74IronDeficiency Symptoms

Growing point and young leaves become yellow or in extreme cases, whiteUsually not accompanied by necrosisVeins and leaflet ends remain green> 50 ppm Fe in petiole sufficient> 4 ppm Fe in soil - sufficient

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Iron Deficiency Symptoms76

http://www.microessentials.com/77ManganeseDeficiency Symptoms

General yellowing of plantLeaves cup upwardBrown spotting occurs on leaflets, especially along larger veins and mid-ribs> 40 ppm Mn in petiole sufficient> 6-8 ppm Mn in soil - sufficient

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Manganese Deficiency Symptoms79ZincDeficiency Symptoms

Little leaf occurs, showing as small, narrow, chlorotic leafletsLeaflets cup upwardTip-burn on leafletsLower leaves bleach and fall from plant> 20 ppm Zn in petiole sufficient> 1.5 ppm Zn in soil - sufficient

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Zinc Deficiency Symptoms81Fertility Management PlanPrior to and at plantingSoil analysisPreplant fertilizer applicationsNitrogen (partial application)25-30% on sandy soils30-40 % on sandy loam soils40-60 % on silt loamsPhosphorus (broadcast and banded)Potassium (broadcast)Micronutrients, as needed82Fertility Management PlanDuring early tuber bulking

Continue petiole testingContinue seasonal applications of NCorrect deficiencies of P, K and microsFertigation for P (30-40 lbs P/ac) and K (