b'InteractiveEffectsofNitrogen overall objectives of this study are to 1) some varieties are more responsive thanandBiostimulantsonPotato Evaluatetheeffectivenessofturkey others due to a shallower and less exten-Yield and Nitrogen Use Efficiency manure as an amendment for full sea- sive root system.The overall objectiveAttentiontobiostimulantscontaining sonpotatoesand2)Determinethe ofthisresearchistoimprovepre-biologicals and nitrogen-fixing microor- effects of four biostimulants at two N dictability of potato response to P fertil-ganisms has increased in recent years. rates + a control and two N sources on izer.To accomplish this objective, twoWhile there is no legal definition of a potato yield and quality. The study is fieldstudies,onefumigatedandthecropbiostimulant,acurrentworking being conducted with Russet Burbank at othernotfumigatedareproposedtodefinition is as follows: a plant bios- the Sand Plain Research Farm in Becker, evaluate the effect of P rate, mycorrhizaltimulant is a substance or microorgan- MN.Five N treatments are being evalu- inoculation,andPplacementonPism that, when applied to seeds, plants ated: a three N rates (0, 120 and 240 lb responsebytwopotatovarietiesoftherhizosphere,stimulatesnatural N/A).The N is applied as ESN or a com- Russet Burbank and Ivory Russet.Thisprocesses to enhance or benefit nutrient binationofESNandturkeymanure. research will also evaluate the use of theuptake, nutrient efficiency tolerance to Fourbiostimulants(BSure,BSure+ Mehlich-3 extractant to assess whetherabiotic stress or crop quality and yield. Invigorate,Radiate,andRadiate+ aPsaturationindex(extractableClaims have been made that using these Accomplish)willbetestedateachN P/extractable Al) can predict P responseproducts will improve sustainability of rateintworowsalongwithtwo better than a P soil test alone.Based oncropping systems, including the cultiva- untreatedrows.Biostimulantswillbe results from the first year Ivory Russet istionofpotatovarietiesusedforfresh appliedaccordingtolabelrecommen- highly responsive to P fertilizer rate onmarket or processing.However, most of dations.Totaltuberyield,finaltuber high P testing soils and on soils with athe results available have been obtained set, tuber quality, and graded yield will high P saturation index. There was nofromgreenhousestudiesandthefew be recorded at harvest.difference due to mycorrhizae inocula-field studies that have been conducted tion or to P placement.Russet Burbankareofteninconsistent.Therefore,a ReevaluationofPhosphorusRe- was less responsive to P, suggesting themore systematic approach to determin- quirements for Irrigated Potatoes P response by Ivory Russet is more plantingtheefficacyofbiostimulantsis This is the second year of the three-year related than soil related. needed.This approach should be vali- study to evaluate Potato P response ondatedthroughreplicatedfieldstudies high P testing soils. Potatoes are often Evaluation of Management Prac-with variable fertilizer application rates highly responsive to phosphorus (P) fer- ticestoImproveSoilHealthfortodetermineiftheseproductscan tilizer application. Phosphorus fertilizer Potato Production reduce fertilizer inputs and/or increase recommendations for this crop are cur- This study is the third year of a largeyields or fertilizer use efficiency.Turkey rentlybasedonsoiltestPandyield multistateresearchprojectentitledmanure is an amendment that can sup- goal, but previous studies have shown Enhancing Soil Health in U.S. Potatoply a slow release from of N and at the that economic responses can sometimes Production Systems funded in 2018 bysametimeaddorganicmattertothe occur even on high P testing soils.theUSDA-NIFASpecialtyCropssoil.As long as manure is applied at Research Initiative.Updates about thisleast 120 days before harvest, it is con- Because of this response, some P fertiliz- project can be found at the followingsideredanacceptableamendmentfor er is usually recommended for this crop website:http://potatosoilhealth.cfans.potatoproduction.Becausemanure evenwhenthePsoiltestishigh. umn.edu/.For one of the four projectstimulates microbial activity in the soil, Reasons why potato responds to P on objectives, each participating state hasit is considered a beneficial amendment highPtestingsoilsarenotclear,but set up replicated plots evaluating howfor improving soil health and may be an mightbeduetouseoffumigation, variousmanagementpracticesaffectinteresting nutrient source to compare which would eliminate or reduce myc- soil health indicators and potato yieldwithbiostimulantapplication.The orrhizal associations.Alternatively, the andquality.OurstudyattheSandresponse might be variety related where Plain Research farm evaluates the effects16 POTATO GROWER JULY/AUGUST 2021'