Establishing a PourThru Sampling Program for Geraniums

Transcription

1 N.C. Flower Growers' Bulletin - Februry, 2000 Volume 45, Number Estblishing PourThru Smpling Progrm for Gerniums Bn E. Whipker, Willim C. Fonteno, Todd J. Cvins, Jmes L. Gibson Deprtment of Horticulturl Science North Crolin Stte University Providing proper nuttionl progrm is essentil for growing top qulity plnts. Smpling the root substrte for ph nd electcl conductivity (EC) with the PourThru extrction method is quick nd simple check of the nuttionl sttus of the crop nd cn provide clues bout crop's performnce before deficiency or toxicity symptoms pper. Gerniums mke lrge contbutionto the bottom line of most greenhouse opertions nd should be included in PourThru monitong progrm. Gerniums re prticulrly sensitive to low ph, which cn result in iron nd /or mngnese toxicity. Routine PourThru smpling will enble growers to detect unfvorble trends before they become nuttionl problems. Smpling Procedures Smpling results re only good if they represent the whole crop. How to set up smpling progrm, which crops to smple, nd the numberof smples to collect re ll fctors to consider. Below re instructions for tking representtive PourThru smples for in-house testing. Crop Fctors Consider tking seprte smples within crop if there re lrge vtions in the substrte type used (differentmnufcturersor ingredients), the fertilizer type or rtes used (cidic or bsic types), or plnting dtes. Frequency The PourThru extrction method is quick nd simple wy to monitor your crop's nuttionl sttus. The speed of this method mkes weekly smpling possible. Idelly smpling should be done weekly, but in prctice it my not be possible. If time vilbility is concern, consider selecting the "Top 0 Crops ofconcern", bsed on theireconomic vlue or if they tend to hve nuttionl problems. Then divide the crops you pln to smple into 2 groups of 5 nd lterntely smple ech group every other week. The frequency of testing depends on the size of the continer used for production, s smller volumes of substrte re more susceptible to rpid chnges in ph thn lrger, more buffered volumes of substrte. For plugs, test ph twice ech week (some growers test every three dys). Weekly testing should be sufficient for crops such s flts of bedding plnts nd 4" pots. Forlong-term cropsgrowninlrgercontiners (suchs 6" pots), monitongevery two weeksmy be sufficient to void out-of-rnge substrte ph. Number of Smples to Collect For routine nlysis, one should collect nd nlyze minimum of 5 individul pots (or for bedding plnts minimum of 5 cell pcks) from plnts treted the sme. As generl rule, smple 5 potsper,000pots of similrlytreted plnts. Results from ech of the 5 smples cn then be verged for single "interprettion vlue". (Do not combine the 5 smples for single test.) (A smpling form is provided.) Ifthe5 vlues vrywidely inphor EC you my need to increse your smple size. Other Tips If you hve tken steps to correct n EC or ph problem, then one should resmple those plnts t lest weekly. If needed, one cn smple s frequently s every other dy. If results seem typicl, consider resmpling before mking drstic chnges, especilly to the substrte ph. For more informtion on PourThru techniques, extr chrts, grphs nd generl guidelines check out our WEB sites: 0

2 N.C. Flower Growers' Bulletin - Februry, 2000 Volume 45. Number I How to Collect the Lechte. Irgte yourcroponehourbefore testing (Figure l). Mke sure the pots re wtered to continer cpcity. If your utomtic irgtion system is vble, wter the pots/flts you pln to smple by hnd. If you rc using constnt liquid feed, irgte with fertilizer solution s usul. If you use peodic feeding (weekly, etc.): ) irgte with cler wter, b) test dy or two before you re to fertilize, nd c) test on the sme dy in the fertilizing cycle ech time. Figure l. Irgte continers thoroughly. 2. Plce sucer under continer. After the continer hs drined for n hour, plce plstic sucer under the continers to be smpled (Figure lb). If you re testing seedling gerniums in bedding plnt flts, pull out one cell pck nd plce it in the sucer (Figure lc). Figure lb. Sucerfor pots. Figure lc. Sucersfor cell pcks.. Pour enough distilled wter on the surfce ofthe continer to get 50 mloflechte (Figure Id). The mount of wter needed will vry with continersize, crop nd environmentl conditions. Use the vlues in Tble s guides. Figure Id. Applying wter for extrction. II

3 N.C. Flower Growers' Bulletin - Februry, 2000 Volume 45, Number I 4. Collect lechte for ph nd EC (Figure e). Mke sure you get bout 50 ml oflechte ech time you test (Figure If)- Lechte volumes over 60 ml will begin to dilute the smple nd give you lower EC redings. 5. Clibrte your ph nd EC meters por to testing (Figure lg). Your test results re only s good s your lst clibrtions. You should clibrte your instruments every dy tht you use them. Alwys use fresh stndrd solutions. Never pour used solution bck in the oginl bottle. HHHHRHHflfl Figure Je. Collected lechte for testing. f0fccomoucm,t',.. "'HDAIID 0UT«- ^^ S'f J W F Jf"SollionpH«* -^W *' ' fl Figure If Collect 50 ml (2.5 ounces) for testing. Figure Ig. Clibrtion stndrds for testing. ' 6. Mesure ph nd EC of your smples (Figure lh). Test your extrcts s soon s possible. EC will not vry much over time provided there is no evportion of the smple. The ph will chnge within 2 hours. Record your vlues on the chrts specific to ech crop. Figure Ih. Jesting lechte smples. 2

4 N.C. Flower Growers' Bulletin - Februry, 2000 Volume 45, Number Testing, Interpreting, nd Mnging Substrte ph The ph of the substrte, is very importnt to plnt nuttion. The ph directly ffects the vilbility of mny plnt nutents, especilly micronutents. Too low of ph (below 5.8) cn result in incresed micronutent vilbility tht cn led to phytotoxic responses in gerniums. For exmple, low ph my increse the vilbility ofiron nd mngnese nd result in iron nd / or mngnese toxicity. At the other end of the spectrum, ph bove 6.8 cn led to micronutentdeficiency problems, especilly with iron. Both excessively low nd high ph's should be voided with gernium production. Figure 2 lists the optiml ph rnge for gerniums. Testing nd Interpreting Substrte ph You should test your crop substrte ph on routine bsis. Growers should test the ph of substrte por to use, to ssure the ph hs been properly djusted. We hve developed ph recording chrts for your use (Figure ). The trget ph rnge, upper decision rnge, nd the lower decision rnge hve been estblished. Ifthe substrte ph climbs into or bove the upper ph decision rnge, ction should be tken to lower ph. If the substrte ph drops into or below the lower ph decision rnge, ction should be tken to rise ph. Adjusting Substrte ph Substrte ph does chnge over time due to mny fctors. The four min fctors ffecting substrte ph re O the initil components nd mendments used in developing the substrte, including the liming chrge; the lklinity content of your irgtion wter; the fertilizer(s) pplied to the crop; nd 0 the species being grown. Obviously, once into prodiction you Tble. Amount of wter to pply to vous continers to obtin 50 ml (2.5 ounces) of extrct*. Continer Size 4 inch 5 inch 6 inch 6.5 inch zle milliliters Wter to dd** ounces qurt qurt qurt Flts 606 (6 plnts) 20 (6 plnts) 204 (48 plnts) *Continers should he brought to full continer cpcity 0 to 60 minutes before pplying these mounts. **These mounts re estimtes. Actul mounts will vry depending on crop, substrte type, nd environmentl conditions. cnnot chnge the species being grown or chnge the substrte composition, but you cn mke djustments to your wteng nd fertiliztion progrms. Loweng Substrte ph. Listed below (in preferred order) re immedite steps to tke to lower substrte ph if it climbs into or bove the upper decision rnge: O Acidify the irgtion wter to n endpoint phof5.8. Switch from bsic (nitrte-bsed) fertilizer to cidic (mmonium-bsed) fertilizer. Apply n iron sulfte (FeS04-7H20) drench using lb per 00 gllons of wter. Lightly mist off ny solution on the folige fter ppliction. Acidify the irgtion wter to n endpoint phof5..

5 - - - *- ~ - ~ "". N.C. Flower Growers' Bulletin - Februry Volume 45, Number I If you frequently encounter n increse in your substrte ph, you should consider employing the following long-term steps (listed in preferred order) to keep the ph from sing: Reduce the initil lime chrge of your substrte before plnting. Acidify your irgtion wter down to ph 5. por to use. Try using n cidic (mmoniumbsed) fertilizer throughout the cropping peod. Incresing Substrte ph. Listed below (in preferred order) re immedite steps to tke to rise substrte ph if it drops into or below the lower decision rnge: Stop neutrlizing the lklinity of your irgtion wter (if you re currently cidifying your wter). Switch from cidic (mmoniumbsed) fertilizers to bsic (nitrtebsed) fertilizers. Apply flowble limestone products s substrte drench. Strt with qurt per 00 gllons rte. Lightly mist off ny solution on the folige fter ppliction. If you frequently encounter decrese in your substrte ph, you should consider employing the following long-term steps (listed in preferred order) to keep the ph from dropping: Increse the initil lime chrge ofyour substrte before plnting. Try using bsic (nitrte-bsed) «* "O -^ ir. in C S "I t^ -r -r "i e -T t _M H^ t & K -r - -. "i ^ *s * r -^ H "! = r-' -^ «z tj? >. ^ k. : V rl n i- S r- * <; ^~ r^? ^ - t/! C z r~? l-s JS r- -T - -T 2* S * J* s- 8 5? = s S- -5 X 2 "5 u to Si r- - I-;? t.- ;- -c i*l r*\ ~^ "^ ^< c i. &* <0 JS S. g 2». k] r,.,. >c l*j ^ == =f? ; c u -T T -t feif? 5 *C rf. r^ ttsr - _= 5 f. f, -*-..2? = <e ". r*j QS^S 99 rl H o * * S c u,5 " _ M c ^ f*s o i»i *i. 5 M ;.?! '5 -^ fc~ on 00 X 'f, 00 > 0 00 <r, <r. 4> 5 "i 0 -i I -T X if. r; u E X U e ^M j2 I " &?l I r) ^^JH r. j. Q l '- -f M - " S -f 00 -T - M O c x. E > -' _= ": 'S -T "i ": e "t -T n -T c ": " fj B -f q rl rj rj '- -T ~ S oe r; f<; -T f*j ;_ S ^; * i" *. v 2 ^ J 5 5 v- P N't CI) 5S. sc = = ^_^B o B n l -T - 2 o ; u ff. * i u xf 5 T 00 *>. x.? = * e o SJ -* "o r; EC O. 5- s 8j B c J5 = * - "! * "i ^M ^m "i r. v SI u M M S JS s 5 ^ CA s 5 B SP =< o u!s 5 5 I- ^ O - i-i o ^ u & U f«. S " e c c >. c N -t s _ 8 '5 2 O -? Im 5 4

6 N. C Flower Growers' Bulletin - Februry, 2000 Volume 45, Number I fertilizer throughout the cropping peod. Inject potssium bicrbonte (KHC0) into your irgtion wter to rise the lklinity. Strt with.4 oz per 00 gllons. This will supply meq/loflklinity nd lso supplies 9 ppm K with every wteng (so reduce potssium feed ccordingly). Testing, Interpreting, nd Mnging Substrte EC Soluble slts re the totl dissolved slts in the root substrte (root medium) t ny given time nd re mesured in terms of electcl conductivity (EC). A conductivity meter mesuresthe pssgeofelectclcurrentthrough solution. The higher the EC content, the esier it is for electc current to move through the solution nd the higher the EC vlue. The EC of the substrte provides n insight to the nutent sttus ofthe crop. One needs to keep in mind tht not ll of the slts mesured by n EC meter re fertilizer slts. An EC meter mesures the sum of ll slts in solution, but does not provide detils on the type or mount of ech slt present. High EC. Growers need to be wre ofsubstrte EC levels becuse excess slts cn ccumulte when: lechingdung irgtion is insufficient; the mount offertilizer pplied is greter thn wht is required by the plnt; or when the irgtion wter contins high mount of dissolved elements. Excessively high EC redings re ssocited with poor plnt shoot nd root growth. Plnt symptoms often begin on the lower leves s lef chlorosis nd progress to necrotic lef tip mrgins. If the root substrte is llowed to dry down, plnts my lso exhibit wilting symptoms becuse of diebck of the root tips, which further inhibit wter nd fertilizer uptke. High EC hs lso been linked with the incresed incidence of Pythium root rot. Low EC. At the opposite end of the spectrum, when the EC content of the substrte is too low, plnt growth cn be stunted or lower lef discolortion cn resultfrom the lckoffertilizer. Usully nitrogen is the most typicl nutent deficiency symptom, mnifesting itself s lower lef yellowing. Fctors Affecting EC Fertilizers. Floculture crops re usully fertilized with constntliquidfertiliztion (CLF) or weekly bsis, so EC levels of the root substrte cn be used to mesure the nutent sttus of the crop. Substrte EC levels re more consistent with the CLF irgtion method thn with single weekly fertiliztion. Substrte EC levels with the weekly fertiliztion regime cn vry gretly due to: the timing fter fertiliztion tht the smple ws tken nd the number of cler irgtions tht were pplied between the fertilizer pplictions. The nutent contbution of slow relese fertilizers cn lso be monitored with regulrsubstrte testing. Most fertilizer mtels, except ure, contbute to the EC contentofthe substrte, nd the mostcommon ones re nitrtes (N0), potssium (K), clcium (C), mgnesium (Mg), sulftes (S04), nd bicrbonte (HC0). Orgnic mtels lso contbute to the EC content fter they hve been chnged from n insoluble to soluble form. One cn lso monitor the ccurcy of their fertilizer injector to ensure the fertilizer ppliction rte is on trget. Irgtion Wter. In some res, elevted substrte EC levels cn be cused by high concentrtionsofclcium(c), mgnesium (Mg), sulftes (S04), sodium (N), or bicrbonte (HC0) in the irgtion wter. Irgtion Method. Pst irgtion recommendtions hve specified tht sufficient mount of wter be pplied so the entire volume of root substrte is moistened nd 0 to 20% leching ofwter out the bottom ofthe continer 5

7 N.C. Flower Growers' Bulletin - Februry, 2000 Volume 45, Number occurs. Leching prevents excess soluble slts from building up in the root substrte. This is still the esiest nd most efficient irgtion method. However, with incresed concern ofrun-offnd wter conservtion, irgtion nd fertiliztion prctices re chnging to reduce or eliminte leching. The fertiliztion rte cn often be decresed by 25% to 50% nd still mintin dequte EC levels if using reduced leching irgtion system or flood irgtion system. The negtive effects of high EC re more pronounced for growers who grow on the dry side. Ifthe root substrte is llowed to dry down, plnts my lso exhibitwilting symptoms becuse of diebck of the root tips, which further inhibit wter nd fertilizer uptke. It is especilly importnt for dry growers to monitor their EC levels to ensure they re within the cceptble rnge to void root dmge. Ifone suspects tht their EC levels re too high, be sure to mintin dequte moisture levels within the substrte. SubstrteType. Somesubstrtes hve fertilizer strterchrgedded which increses the substrte EC. These mixes re generlly used for growing estblished plnts. The type of substrte in your mix cn lso influence the substrte EC level. Sphgnum pet hs very low chemicl content, while composted pine brk nd coir usully hve slight EC chrge. It is good ide to test ny new substrte mix por to use to ensure it meets your specifictions. Crop Fctors. When estblishing n EC monitong nd mngement progrm one needs to mtch the fertilizer ppliction rte with the fertilizer demnds of the crop. There re two min prmeters which need to be considered: the crop's nutent demnds nd the stge of development. Ech re discussed below. Nutent Demnds. Crops vry in their fertility requirements for optiml growth. Gerniums re moderte feeders nd grow best when the PourThru EC levels for ctively growing plnts re between 2.0 to. ms/cm (Figure 2). Stge of Crop Development. The nutent demnds of crop vry by development stge. Plugs nd cuttingwhich re rootingrequirelower levels offertility nd fertilizer demnds increse s they become estblished. Actively growing plnts hve the highestnutentdemnds. Finlly, nutent demnds decrese s plnt sets buds nd flowers. In fct, extensive reserch hs shown tht flower longevity is incresed when fertilizer rtes re decresed or terminted t visible bud or just por to floweng. An EC monitong pln for gerniums should be fine-tuned to ccount for the crop's nutent demnds nd stge of development. Figure 2 contins the trget EC levels for estblishment, ctive growth, nd bloom stges of growth for plnts using the PourThru extrction method. Tble 2 contins interprettive EC vlues for the :5, :2, sturted medi extrct (SME), nd PourThru extrction procedures. Testing nd Interpreting Substrte EC You should test your crop substrte EC on routine bsis to detect trends over time. Smples cn be nlyzed either within the opertion or sent to commercil lb. Growers should test their substrteec por to use, to ssure the EC is within the proper rnge. We hve developed EC recording chrts for your use with the PourThru extrction method (Figure 4). The trget EC rnge for the ctive growth phse of the crop hs been filled in. Dung the first 2 weeks fter trnsplnting, growers should grdully increse the substrte EC to the trget level. Use the EC vlues listed in Figure 2 dung the plnt estblishment phse s guideline. Also s the crop blooms, growers should grdully decrese the EC levels. EC vlues for the finishing stge re lso listed in Figure 2. If the substrte EC climbs into or bove the upper EC decision rnge, ction should be tken to lower EC. If the substrte EC drops into or 6

8 N.C Flower Growers' Bulletin - Februry, 2000 Volume 45, Number below the lowerec decision rnge, ction should be tken to rise EC. Adjusting Substrte EC The substrte EC chnges over time due to mny fctors. The four min fctors ffecting substrte EC re: the initil components nd mendments used in developing the substrte, including the substrte type nd initil nutent chrge; fertility regime; the plnt's nutent demnds; nd the crop's development stge. Obviously, fter the crop hs been plnted one cnnot chnge the species being grown or the substrte composition, but you cn mke djustments to your fertiliztion progrm s the plnt grows. Steps to Lower EC. Listed below (in preferred order) re immedite steps to tke to lower substrte EC if it climbs into or bove the upper decision rnge: Decrese the fertiliztion rte or decrese the frequency offertiliztion (irgte with cler wter). Lech to reduce the slts level. The root substrte should be irgted normlly llowing for 20% leching, then followed immeditely with nother irgtion. After this, the root substrte should be llowed to dry to the usul stge, nd if further leching is required, the double-irgtion tretment cn be repeted. Recheck the EC level to mke sure it is within the cceptble rnge. Stepsto IncreseEC. Listedbelow (in preferred order) re immeditesteps to tke to rise substrte EC if it drops into or below the lower decision rnge: color within to 2 weeks. Do not overpply. It is importnt to correct nutent deficiency when symptoms first pper becuse lower lef drop or necrosis cnnot be reversed. Increse the fertiliztion frequency. Use constnt fertiliztion rte of 200 to 250 ppm N nd discontinue ny cler wter irgtions until the EC levels re within the cceptble rnge. Points to Remember. Ifusing clcium nitrte (C(N0)2)+potssium nitrte (KN0), remember to supply P, Mg, nd micro-nutents to the plnts. If using or , remember to supply C nd Mg to the plnts. Conclusion This PourThru progrm is designed for growers to Monitor nd Mintin their crops, It is simple progrm for rpidly determining crop's ph nd EC. It is progrm tht llows growers to chngetheir focus to prevention insted ofcure, nd ction insted ofrection. Ifgrowers dopt this proctive progrm nd follow it crefully, nuttionl problems cn be virtully eliminted. We wouldlike to thnk the Fred C. Gloeckner Foundtionforfunding support ofthis reserch project. See North Crolin Stte University Horticulture Informtion Leflet 558 for more detils. Avilble t: Increse the fertiliztion rte. Apply fertilizer like clcium nitrte (C(N0)2) + potssium nitrte (KN0), , or Excel Cl-Mg t the rte of00 to 400 ppm N. A corrective N fertiliztion will return the lower leves to the norml green 7

9 Figure. PourThru ph chrt for gerniums. PH 7.4 Crop: Gernium (zonl) Strting Dte (week 0) Ending Dte Trget ph Rnge: 6.0 to 6.6 Upper ph Decision Rnge: 6.6 to 6.8 Lower ph Decision Rnge: 5.8 to 6.0 PoiirThlU 7. III II II III II I. J 4. - J J- _ i lli II II Week

10 I I Figure 4. PourThru EC chrt for gerniums. PourThru EC (ms/cm) Crop: Gernium (zonl) Strting Dte (week 0) Ending Dte Trget EC Rnge: 2.2 to. ms/cm Upper EC Decision Rnge:. to.5 ms/cm Lower EC Decision Rnge: 2.0 to 2.2 ms/cm I I IllfllJIIjIfljjl BHii i i i i i i i i i i i i i i i i i i i i i i i i i Week

11 N.C. Flower Growers' Bulletin - Februry, 2000 Volume 45, Number PourThru Smpling Form Crop: Dte: Smples ml dded ml out ph EC Comments Loction: Averge Crop: Dte: Smples ml dded ml out ph EC Comments Loction: Averge Crop: Dte: Smples ml dded ml out ph EC Comments Loction: Averge 20

12 N.C. Flower Growers' Bulletin - Februry, 2000 Volume 45, Number I Tble 2. EC interprettion vlues (ms/cm) for vous extrction methods'. :5 : 2 SME PourThru2 Indiction 0 to to to to to to to to 2.6 Very Low. Nutent levels my not be sufficient to sustin rpid growth. Low. Suitble for seedlings, bedding plnts nd slt sensitive plnts. 0.6 to to to to to to.75.5 to to to.0.76 to to to 7.8 >. > 2.25 >6.0 > 7.8 Norml. Stndrd root zone rnge for most estblished plnts. Upper rnge for slt sensitive plnts. High. Reduced vigor nd growth my result, prticulrly dung hot wether. Very High. My result in slt injury due to reduced wter uptke. Reduced growth rtes likely. Symptoms include mrginl lef burn nd wilting. Extreme. Most crops will suffer slt injury t these levels. Immedite leching required. Adpted from: On-site testing of growing medi nd irgtion wter Btish Columbi Ministry of Agculture. : Due to the vbility of the PourThru technique results, growers should lwys compre their results to the SME method to estblish cceptble rnges.