Soil fertility management for pepper production

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Soil fertility management for pepper productionlbs per acre20 - 3040 - 60 P2O5120 - 18080 - 110fruit content240 - 320 200 - 260total plant contentK2ONTypical nutrient uptake by a bell pepper cropproducing 50,000 lb of fruit/acre :Common soil tests for P availability :Olsen (bicarbonate) test - extraction in sodium bicarbonate at pH 8.5best method if soil pH > 6.5Bray test - extraction in dilute aciduseful in acidic soil (pH < 6.5) Represents available P, not total P Bray values higher than Olsen in most casesPhosphorus requirement for pepper :Does the Olsen test measure plant-available P ?Bio-available P (anion membrane) technique0.02.04.06.08.00 50 100 150 200Olsen P (PPM)Anion resin P (ug/cm2)r = 0.89Bio-available P vs. Olsen P :30 California soils in vegetable rotationsTemperature affects soil P bioavailability :01234567829 76 85 142 177Soil Olsen P level (PPM)Anion resin extractable P(ug/cm2)5 C = 41 F15 C = 59 F25 C = 77 FOn average, each 10 oF increase in soil temperature increases bioavailable P by 20%High LowLettucePotatoPepper?TomatoSoil P availability requirement :Is P application always necessary ?What application rate is reasonable ?Soil P availability requirement :Is P application always necessary ?What application rate is reasonable ?Agronomic threshold(Olsen test)High LowLettucePotatoPepper?Tomato60 PPM 20 PPMpositive crop response unlikely> 40 PPMpositive response likely, especiallyin cold soil20 - 40 PPMpositive response guaranteed < 20 PPMPepper response to applied POlsen P levelpositive crop response unlikely> 40 PPMpositive response possible, especiallyin cold soil20 - 40 PPMpositive response guaranteed < 20 PPMPepper response to applied POlsen P levelApplication rate ? limit application to crop removal rate in fields with high soil P rates > 120-150 lb P2O5/acre questionable, regardless of soil test levelNitrogen management : Crop N uptake is predictable by growth stagelb N per acre per day:< 1 4 - 5 < 3Nitrogen management : Crop N uptake is predictable by growth stagelb N per acre per day: Not all N needs to come from fertilizer application:- residual soil NO3-N can be substantial- soil N mineralization can be up to 1 lb / acre / day< 1 4 - 5 < 3Irrigation efficiency and N management : at common soil NO3-N levels during the season, one inch ofleaching may carry 20-30 lb NO3-N/acre out of the root zonePotassium management : Crop K uptake is predictable by growth stagelb N per acre per day:< 1 4 - 7 < 4Potassium management : Crop K uptake is predictable by growth stagelb N per acre per day:< 1 4 - 7 < 4 pepper has a moderately high K requirement (240 - 320 lb K2O/acre) majority of K ends up in fruitleaf K declines to feed the fruit; thats why deficiency shows lateEvaluating soil K supply : exchangeable K, usually expressed as PPM K as a % of base exchange[milliequivalent of K / (meq Ca + Mg + Na + K)] x 100Soil test K interpretation : fields > 200 PPM exchangeable K, and > 3% of base exchange, do not require K fertilization soils < 150 PPM, or < 2% of base exchange, should be fertilized K fertilization is most effective during fruit set and early fruit developmenthttp://vric.ucdavis.edu/veg_info_topic/fertilization.htmCrop monitoring options In-season soil nitrate testing : high root zone soil NO3-N concentration (> 20 PPM) indicatethat additional N application can be postponedSoil nitrate testing most useful early in the seasonPetiole testing as a management tool ? high NO3-N or PO4-P concentration guarantees current sufficiency,but does not project far into the futurePetiole testing as a management tool ? high NO3-N or PO4-P concentration guarantees current sufficiency,but does not project far into the future lower NO3-N or PO4-P concentration does not prove deficiency2004-05 survey of 75 coastal lettuce fields0.01.02.03.04.05.06.07.02 4 6 8 10 12 14 16 18 20Field% leaf N Currentsufficiencythresholdat early heading stage :Leaf total N of the 20 highest yielding fields03,0006,0009,00012,00015,0002 4 6 8 10 12 14 16 18 20FieldMidrib NO3-N (PPM)CurrentsufficiencythresholdMidrib NO3-N of the 20 highest yielding fieldsat early heading stage :Tissue sampling in processing tomato : 4 high yield commercial fields UCD fertilizer trialTissue sampling in processing tomato : 4 high yield commercial fields UCD fertilizer trial102030405060200 400 600 800 1000 1200Growing degree daysLeaf N (g kg-1)field 1field 2field 3field 4UCD deficientUCD adequateUCD excessiveTissue sampling in processing tomato : 4 high yield commercial fields UCD fertilizer trial102030405060200 400 600 800 1000 1200Growing degree daysLeaf N (g kg-1)field 1field 2field 3field 4UCD deficientUCD adequateUCD excessive03,0006,0009,00012,00015,000200 400 600 800 1000 1200Growing degree daysPetiole NO3-N (PPM) field 1field 2field 3field 4UCD deficientUCD adequateUCD excessiveDoes petiole testing indicate recent nutrient uptake ?2007 UC Davis processing tomato trialConclusion :Most petiole NO3-N is already in cell vacuoles, and therefore theconcentration is affected by the rate at which the plant convertsnitrate to organic N; factors other than soil nitrate supplygovern that rate02004006008001,0001,2001,4001,6004 6 8 10 12 14Weeks after transplantingNO3-N(mg liter-1)sapxylemCalcium disorders : symptoms develop because insufficient Ca is moved into actively growing cells during fruit development Calcium disorders : symptoms develop because insufficient Ca is moved into actively growing cells during fruit development origin of the problem is the inefficient way plants move Ca into fruit;soil Ca limitation seldom the primary problemCalcium disorders : symptoms develop because insufficient Ca is moved into actively growing cells during fruit development origin of the problem is the inefficient way plants move Ca into fruit;soil Ca limitation seldom the primary problem control by soil or foliar Ca application is minimally effectiveHow much plant-available calciumdo California soils have ?15 representative California soils testedy = 0.20xr = 0.720501001502002503000 200 400 600 800 1000 1200Soil solution Ca (PPM)Saturated paste Ca (PPM) most California soils have 100 - 200 lb/acre Ca in solution in thetop foot; as plants remove it, more becomes available at normal application rates, fertilizer Ca only marginally increasessoil Ca supply0.000.100.200.300.400 2 4 6Leaf Ca (%)Fruit Ca (%)Processing tomato fruit quality survey, 140 fields :Calcium doesnt move into fruit easily : Ca moves in transpirational flow in xylem, so leaf Ca is high Ca does not move in phloem, so fruit Ca is low; surface waxon fruit makes foliar application questionableWhat can be done to minimize calcium disorders ? prevent water stress choose adapted varieties avoid high ammonium levels during early fruit development

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