PROCEEDINGS 2017 Crop Pest Management Short Course & Minnesota Crop Production Retailers Association Trade Show

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1 PROCEEDINGS 2017 Crop Pest Mngement Short Course & Minnesot Crop Prodution Retilers Assoition Trde Show Institute for Ag Professionls Do not reprodue or redistriute without the written onsent of uthor(s).

2 The Potssium Chllenge: How do we mnge K in our urrent prodution systems? Dniel Kiser Assoite Professor Deprtment of Soil, Wter nd Climte U of M Twin Cities dekiser@umn.edu

3 Potssium K in plnts Tken up in lrge quntities like nitrogen 5.2 l K 2 O//dy from V10 V14 (Bender et l., 2013) Critil for ell wll thikness nd stlk strength In inorgni (K + ) stte, not orgni K in soil STK is n index of exhngele K Influened y: wetting/drying, freezing/thwing, relese from rop residues nd ly minerlogy (relese vs fixtion) Vetsh, De. 2016

Potssium Avilility in MN K vilility inreses Loess Deep soils, medium to low in K, K soil test vlues do not drop drmtilly with depth Outwsh sndy, grvelly soils,

4 Potssium Avilility in MN K vilility inreses Loess Deep soils, medium to low in K, K soil test vlues do not drop drmtilly with depth Outwsh sndy, grvelly soils, low K, low CEC Till signifint strtifition of K in with mjority in surfe lyers, greter ntive K vilility in west. Lustrine high ly soils, typilly high K vilility

5 Why Reserh K Anlysis Methods? Courtesy of NRCS Des Moines Loe Till Lom nd Cly Lom soils Poorly Drined Brgelt nd Mllrino 2013 SSSAJ 77:

6 Wht Kind of grin yield responses n we expet when pplying K?

7 Corn nd soyen yield s ffeted y K rte during uild-up yers t Wse. Grin yield, u l K 2 O Initil STK= ppm Soyen

9 Corn nd soyen yield s ffeted y K rte during uild-up yers t Beker. Grin yield, u l K 2 O Soyen Initil STK=70 ppm

10 Phse I Summry Soil tests were uild into 3 rnges L-M-H t Wse nd Rohester VL-L-M-H t Beker 60 ls K2O eh yer ws le to mintin yield levels No K fertilizer did result in derese in yield The effet inresed over time There is no reson to let soil tests get low then not pply fertilizer

11 Soyen yield s ffeted y STK level nd fertilizer K rte in 2016 t Wse l K2O/ Soyen yield, u/ Low, 70 ppm Medium, Med-High, 120 Soil test K level

12 Soyen yield s ffeted y STK level nd fertilizer K rte in 2016 t Rohester l K2O/ Soyen yield, u/ Low-Med, 85 ppm Medium, Med-High, 125 Soil test K level

13 Soyen yield s ffeted y STK level nd fertilizer K rte in 2016 t Beker l K2O/ Soyen yield, u/ Very Low, 35 ppm Low, 70 ppm Med-High, 115 Soil test K level

14 Phse II Preliminry Summry Yield potentil ws still there for the Low testing plots if fertilized ordingly Amount of K needed to mximize yield for the given soil test lsses ws lose to wht is suggested No response to K in med-high soil tests Trgeting speifi rtes of K to uild to set soil test is diffiult

PKS Study Lotions Yer Bry P1-P NH 4 OAC-K SOM Lotion Est. YR 1 YR3 YR5 YR 1 YR 3 YR 5 --------ppm------- -%- Red Wing 2011 SiL 34 29 20 91 77 73 2.2 Rohester L 32 28 18 172 169 114 3.

15 PKS Study Lotions Yer Bry P1-P NH 4 OAC-K SOM Lotion Est. YR 1 YR3 YR5 YR 1 YR 3 YR ppm %- Red Wing 2011 SiL Rohester L Beker 2012 LS Lmerton L YR3 & YR5 dt represents the verge vlue for the ontrol (No P, K, or S) Colors represent expeted response to pplied fertilizer lue low, green moderte, red - high

16 Net Return over the Rottion Red Wing Rohester Nutrient Rte 2 yr 4 yr 6 yr Totl 2 yr 4 yr 6 yr Totl l/ $/re Phosphorus Potssium Sulfur P rtes re in l P 2 O 5 / /l K rtes re in l K 2 O/ $0.40.l S - $0.50/l Corn $4/u Bens $10/u Applied P nd K rte my not e the optimum rte for eh site Applition ost is not ftored into net return

17 Net Return over the Rottion Beker P rtes re in l P 2 O 5 / /l K rtes re in l K 2 O/ $0.40.l S - $0.50/l Corn $4/u Bens $10/u Applied P nd K rte my not e the optimum rte for eh site Applition ost is not ftored into net return Lmerton Nutrient Rte 2 yr 4 yr 6 yr Totl 2 yr 4 yr 6 yr Totl l/ $/re Phosphorus Potssium Sulfur

18 Questions Relted to Mngement K pplition n e eonomil in some situtions Wht rte is the est to use is still? Current suggested rtes should e lose to wht is required How do we est ssess when to pply K? Do urrent guidelines urtely predit K need?

19 Reltive Yield Response to K Strip Tril Dt: Yes/No Comprisons Corn Air Dry Corn Field Moist Reltive Corn Grin Yield (%) Big Mess!! Corse-Medium Textured Soils Medium-Fine Textured Soils Reltive Corn Grin Yield (%) Corse-Medium Textured Soils Medium-Fine Textured Soils Ammonium Aette K (ir dry) mg kg Ammonium Aette K (moist) mg kg -1 Dt does not look etter for K tested on moist smples Mg kg-1 = ppm

20 120 Field Moist Potssium Test - Corse Textured Soils 120 Air Dry Potssium Test - Corse Textured Soils Grin Yield (% of mximum) n=196 When STK < (STK) (STK) 2 R 2 =0.69 P< Grin Yield (% of mximum) When STK < (STK) (STK) 2 R 2 =0.40 P< Moist 0-15m Potssium (mg kg -1 ) Air Dry 0-15m Potssium (mg kg -1 ) Field Moist Potssium Test - Med/Fine Textured Soils Air Dry Potssium Test - Med/Fine Textured Soils Grin Yield (% of mximum) n=497 When STK < (STK) (STK) 2 R 2 =0.42 P< Moist 0-15m Potssium (mg kg -1 ) Grin Yield (% of mximum) Mg kg-1 = ppm When STK < (STK) (STK) 2 R 2 =0.14 P< Air Dry 0-15m Potssium (mg kg -1 )

21 Corse Textured Soils Critil Levels Using Qudrti Plteu Model Soil Texture Critil Level Soil Test t Plteu ppm Air Dry K Moist K Medium/Fine Textured Soils Soil Texture Critil Level Soil Test t Plteu ppm Air Dry K 200 Moist K Critil level is soil test vlue t 95% reltive yield

22 Summry If you wnt to limit the potentil for K defiieny then keeping soil test ove 200 ppm my e wrrnted (my not e eonomil) Soil test levels ner 150 ppm re likely oky for soils in the SE prt of the stte In SC nd SW MN it is more of? If you re elow ppm then there is enefits to pplying K in silt nd ly soils Critil level is likely lower for snds ut Where do we drw the line for this

23 Reommendtion Comprisons Iow Very Low Low Optimum High Very High Dry Moist Minnesot - Now Very Low Low Medium High Very High Dry Minnesot tenttive (numers re sujet to hnge-i.e. Dn s wild guess) Very Low Low Medium High Very High Dry M/F Dry - C Moist M/F Moist C

24 To Build or not to Build? Is it fesile to uild (nk) K in soils for future yers? When is the est time to soil smple fields for K? Wht is the est smple nlysis method? Does rop removl ensure soil test mintenne?

25 K Enrihment With Depth Red Wing, MN Rohester, MN Fll 2012 Fll 2013 Fll 2014 Fll 2015 Fll 2012 Fll 2013 Fll 2014 Fll " d 0-6" d 6-12" 6-12" 12-24" 12-24" Soil K (ppm) Soil K (ppm) Soil K (ppm) Soil K (ppm) 0 l K2O/ l K2O/ 200 l K2O/ 300 l K2O/ Soil K (ppm) Soil K (ppm) Soil K (ppm) Soil K (ppm) 0 l K2O/ l K2O/ 200 l K2O/ 300 l K2O/ Beker, MN Lmerton, MN Fll 2013 Fll 2014 Fll 2015 Fll 2016 Fll 2013 Fll 2014 Fll 2015 Fll " d d d 0-6" d 6-12" d 6-12" 12-24" 12-24" Soil K (ppm) Soil K (ppm) Soil K (ppm) Soil K (ppm) Soil K (ppm) Soil K (ppm) Soil K (ppm) Soil K (ppm) 0 l K2O/ l K2O/ 200 l K2O/ 300 l K2O/ 0 l K2O/ l K2O/ 200 l K2O/ 300 l K2O/

26 Corn nd soyen yield s ffeted y K rte during uild-up yers t Rohester. Grin yield, u l K 2 O Soyen Initil STK=130 ppm

27 Soil test K (dry) s ffeted y K 2 O fertilizer Soil test K, mg kg -1 rte nd smpling time t Wse l K 2 O Wse 0 J 11 O 11 J 12 O 12 J 13 O 13 J 14 O 14 J 15 O 15 Smpling (month yer)

28 Why Soil Test for K? Beuse it is etter thn plnt tissue test. Critil thresholds still tend to hold true Know where you re t in the stte Smple t the sme time eh yer Mye there is etter test option out there? Totl K uptke over ornsoyen rottion (ls K 2 O/) Red Wing Rohester K uptke = (K rte) R 2 =0.95 P=0.02 K uptke = (K rte) R 2 =0.97 P= K pplition rte (ls/k 2 O/)

29 Fll 2014 Moist vs. Dry K FAll Soil Test K (ppm) Air Dried Field Moist/Slurry STK = (K rte) R 2 =0.99 P<0.01 Red Wing % 17.2% STK = (K rte) R 2 =0.99 P<0.01 Fll Soil Test K (ppm) Air Dried Field Moist/Slurry STK = (K rte) R 2 =0.99 P<0.01 Rohester STK = (K rte) R 2 =0.99 P< K pplition rte (ls/k 2 O/) K pplition rte (ls/k 2 O/) 200 Air Dried Field Moist/Slurry Beker Air Dried Field Moist/Slurry Lmerton 8.5% FAll Soil Test K (ppm) STK = (K rte) R 2 =0.95 P=0.02 STK = (K rte) R 2 =0.97 P<0.01 FAll Soil Test K (ppm) STK = (K rte) R 2 =0.86 P=0.05 STK = (K rte) R 2 =0.91 P= % K pplition rte (ls/k 2 O/) K pplition rte (ls/k 2 O/)

30 Fll 2016 Moist vs. Dry K FAll Soil Test K (ppm) Air Dried Field Moist/Slurry STK = (K rte) R 2 =0.98 P<0.01 Red Wing STK = (K rte) R 2 =0.99 P=0.01 Fll Soil Test K (ppm) Air Dried Field Moist/Slurry STK = (K rte) R 2 =0.93 P=0.02 Rohester 21.1% 19.3% STK = (K rte) R 2 =0.97 P< K pplition rte (ls/k 2 O/) K pplition rte (ls/k 2 O/) 200 Air Dried Field Moist/Slurry Beker Air Dried Field Moist/Slurry Lmerton 12.1% FAll Soil Test K (ppm) STK = (K rte) R 2 =0.98 P<0.01 STK = (K rte) R 2 =0.99 P<0.01 FAll Soil Test K (ppm) STK = (K rte) R 2 =0.95 P=0.02 STK = (K rte) R 2 =0.96 P= % K pplition rte (ls/k 2 O/) K pplition rte (ls/k 2 O/)

31 Mintenne of Soil Test Vlues following 8 yers of P or K pplition Soil Test Chnge when pplying P or K sed on rop removl Annul P or K pplition required to Mintin Soil Test Study Lotion ppm yr l P 2 O 5-1 yr Phosphorus Lmerton Morris Sint Chrles l K 2 O -1 yr Potssium Delvn Lmerton Morris l K2O needed to uild K y 1 ppm Delvn Lmerton Morris l K 2 O/ppm Ammonium Aette

32 Overll Thoughts Soil texture ffets the ritil soil test K vlue for ir dry nd moist smples. Less for orse textured soils The moist K test hs less vlue for orse textured soils versus medium/fine No differene in the interprettion of the test for soyen versus orn Interprettion tegories for the ir dry test hve trditionlly een the sme

33 Thoughts on Plement More evidene to support nding of K for orn prodution Yield inreses in redued tillge systems (Ridge till, no-till, strip till?) Does nding inlude strter Dry strter possily In-furrow depends on the mount of K pplied Most liquids ontin smll mount of K Overll, still?? on nding nd rte redutions

34 Dniel Kiser University of Minnesot

Crop Rotations, Reduced Tillage and N Fertilization Effects on Corn Yields And Aflatoxin Levels

Crop Rotations, Reduced Tillage and N Fertilization Effects on Corn Yields And Aflatoxin Levels Crop Rottions, Redued Tillge nd N Fertiliztion Effets on Corn Yields And Afltoxin Levels J.E. Mtoh nd M. Rihrdson Texs AgriLife Reserh nd Extension Center Stte Hwy Corpus Christi, TX 78- jmtoh@g.tmu.edu