THE EFFECT OF SOIL MOISTURE ON RESIDUAL FLUID AND GRANULAR PHOSPHORUS AVAILABILITY

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1 THE EFFECT OF SOIL MOISTURE ON RESIDUAL FLUID AND GRANULAR PHOSPHORUS AVAILABILITY Therese MBeth 1, Mike MLughlin 1,2, Json Kiry 2, Dvi Chittleorough 3 n Roger Armstrong 4 1 Shool of Agriulture, Foo n Wine, University of Aelie, PMB 1, Glen Osmon, SA 564, Austrli. (therese.meth@elie.eu.u, mihel.mlughlin@elie.eu.u) 2 CSIRO Ln n Wter, PMB 2, Glen Osmon, SA 564, Austrli (json.kiry@siro.u). 3 Shool of Erth n Environmentl Sienes, University of Aelie, Aelie, SA 55, Austrli. (vi.hittleorough@elie.eu.u). 4 Deprtment of Primry Inustries, PMB 26, Horshm Vitori 341 Austrli (roger.rmstrong@pi.vi.gov.u). Arevitions; monommonium phosphte (MAP), tehnil gre monommonium phosphte (TGMAP), zin (Zn), phosphorus (P). ABSTRACT Flui n grnulr fertilizer ontining zin n phosphorus were inute for four weeks ir ry n t optiml moisture in six soils from the erel growing regions of Southern Austrli n Knss. Following the inution, mesurements were me of fertilizer iffusion, solule nutrient onentrtion n lile nutrient onentrtion. The results emonstrte tht ry inution inhiits the iffusion of phosphorus n zin fertilizer n nees to e onsiere when ry sowing fertilizer n see simultneously. The ry inution lso erese the lility of zin t the point of fertilizer pplition initing tht espite the presene of high onentrtions of zin, this zin hs lrey rete with the ry soil n the mount of potentilly ville zin hs reue. INTRODUCTION Lortory experiments hve inite tht fixtion retions for phosphorus (P) slow own in ry soil (Brmley et l. 1992), n resiul effetiveness of superphosphte erese s soil wter ontent inrese (Bolln n Bker 1987). However, these experiments e P to soil s liquis or powers n uniformly mixe the fertilizer with the soil. Inee, muh of the erly glsshouse work on intertions etween soil moisture n nutrient vilility hve use soils with fertilizer P n mironutrients uniformly mixe throughout the plnt growth meium rther thn ne s flui or grnulr fertilizer whih is the norml metho of pplition in the fiel. As result of these lortory stuies, the ommon pereption is tht ry soil mens tht fertilizers o not ret with the soil, n resiul fertilizer effiieny in the yer following rought is high. Our reent reserh hs shown tht movement of soil wter in n roun grnules n hve mrke influene on hemil retions whih ontrol fertilizer effetiveness (Hettirhhi et l. 26; Lomi et l. 26). When fertilizer grnule is ple in moist soil, it rws soil wter towrs it n lso rws solutes in the soil wter into the grnule. In lreous soil this enhnes preipittion of lium phosphte ompouns in n roun the grnule (Lomi et l. 24), whih reues grnulr fertilizer effetiveness mrkely (Bertrn et l. 26; Hollowy et l. 21). We hve isovere this is one of the resons why elivery (into soil) of extly the sme fertilizer formultion in flui form n enhne fertilizer effiieny mrkely ompre to grnulr prouts, espeilly in lreous soil (Lomi et l. 24). It is therefore evient tht hnges in soil wter sttus oul

2 mrkely ffet the retions ourring in n roun fertilizer grnules in soil, phenomenon not well reproue in most lortory experiments when nutrients re uniformly mixe throughout the soil. The ims of this experiment were to investigte the effet of soil moisture n fertilizer form on the iffusion n lility of P n zin (Zn) in six ifferent griulturl soils from Southern Austrli n the US. MATERIALS AND METHODS Six soils were hosen from erel proution res of Southern Austrli n Knss, USA. The Austrlin soils were Lnghorne Creek (lrosol), Wrrmoo (hyperli lrosol), Kngroo Isln (ironstone), n Wlpeup (sn). The US soils were Osge ounty n Wry of Weir, Cherokee ounty, Knss (Btes silt lom). Some si soil properties re shown in Tle 1. We hve exlue Kngroo Isln n Wlpeup from the full t presenttion ue to spe onstrints. Tle 1. Soil Chrteristis Test Units Lnghorne Creek Kngroo Isln Wlpeup Wrrmoo Osge Wry ph H 2 O EC 1:5 S/m CCO 3 % w/w 2.8 n n 6 * * Cly % w/w * * TOC % w/w Totl C mg/kg Totl Fe mg/kg Totl Al mg/kg Totl P mg/kg DGT CE P μg/l Totl Zn mg/kg EC-eletril onutivity, Al-luminium, Fe-iron, C-lium, CCO 3 - lium ronte, TOCtotl orgni ron, DGT PCE- iffusive grient in thin film effetive onentrtion phosphorus.*t not ville, n -not etete. The two soil moisture tretments were ir ry (to simulte ry fertilizer pplition) n 8% of fiel pity (to simulte optiml moisture onitions for sowing n fertilizer pplition). The two fertilizer tretments were grnulr unote monommonium phosphte (MAP, 1:22:) mnully ote with zin hlorie solution, n flui tehnil gre monommonium phosphte (TGMAP, 12:26:) with zin hlorie in solution. For the grnulr tretment, fertilizer grnules were selete se on their weight in orer to 8.8 mg P per petri ish n ote with 3μL of zin hlorie solution to.6 mg Zn per petri ish. For the flui tretment liquots ontining 8.8 mg P were ilute to 2 μl with istille wter. Soils were pke to n pproximte ulk ensity of 1.3 g/m 3 in 15m imeter petri ishes, wet to the pproprite moisture ontent n llowe to equilirte for 24 hrs. Following this equilirtion, Zn ote MAP grnule or 2μL of Zn-TGMAP len ws pplie to the very entre of the petri ish, n the petri ishes were inute t 2 C for four weeks, t the two ifferent moisture potentils. At the en of the inution onentri rings of soil with inresing rius were remove from the ish t the moisture t whih they were inute. The soils were then rie own t 35 C n susmples were use to mesure the ph, iffusion n lility of Zn n P. The perentge of P (or Zn) from fertilizer in the soil setions ollete from the

3 P (% of e) P (% of e) P (% of e) P (% of e) point of fertilizer pplition ws lulte s follows %Pe = [Pse x Wse]/ sum of [Pse 1-4 x Wse1-4] where se is the soil setion, Pse n Wse re the onentrtion of fertilizer P n the soil weight of eh setion respetively. Pse is lulte y sutrting the P onentrtion of untrete soil from the onentrtion of the fertilize soil. A suset of ll t will e presente in this pper. Gentstt 1 th Eition ws use for ll sttistil nlyses. Phosphorus Diffusion n Soluility RESULTS AND DISCUSSION The most importnt effets of the tretment regime on phosphorus iffusion ws the effet of inution moisture on P iffusion. A ry inution resulte in little or no iffusion of fertilizer P (isplye s P % of e) wy from the first setion (-7.5mm) of the petri ish where the fertilizer ws e (Figure 1.1,1.3 n 1.4.). A moist inution resulte in improve iffusion with the seon petri ish setion (7.5-13mm) hving greter mount of P thn the first setion for the non-lreous soils (Lnghorne Creek, Osge n Wry). In ontrst there ws not the sme ifferene etween inution moistures for the lreous Wrrmoo soil suggesting tht fertilizer iffusion is severely restrite even when this soil is inute wet (Figure 1.2). There ws smll iffusion vntge in the seon setion (7.5-13mm from pplition point) for the flui P soure when inute wet in the Wrrmoo soil. We suspet tht we hve not oserve the lrge ifferenes etween flui n grnulr forms in the Wrrmoo soil euse we use unote fertilizer in orer to lyer Zn on the fertilizer grnule in the lortory efore ing it to the petri ish Lnghorne Creek grnulr ry grnulr wet flui ry flui wet Wrrmoo grnulr ry grnulr wet flui ry flui wet Tretment Tretment Wry grnulr ry grnulr wet flui ry flui wet Osge -7.5mm mm mm mm grnulr ry grnulr wet flui ry flui wet Tretment Tretment Figure 1.1 Lnghorne Creek, 1.2 Wrrmoo, 1.3 Wry n 1.4 Osge. Perentge of P erive from fertilizer in petri ish soil setions. Within fertilizer n setion, olumn ppene with ifferent letter represents ifferent P % of e (i.e. Fig 1.1. setion -7.5mm ry is greter thn wet n setion mm wet is greter thn ry). P<.1 LSD setion -7.5mm=7.4, setion mm=3.52, setion 13-33mm=2.8 setion mm not signifint.

4 Wter Solule P (mg/kg) Wter Solule P (mg/kg) Wter Solule P (mg/kg) Wter Solule P (mg/kg) The issue with the restrition of iffusion is the inrese proility of exessive P onentrtions t the point of ition whih then prtiipte in preipittion retions reuing the lility of fertilizer (Lomi et l. 24). This reue iffusion effet, regrless of fertilizer form, nees to e onsiere when mking eisions out ry sowing, espeilly in soils with high levels of lium, iron or luminium. The wter solule P t losely follows the iffusion t (Figure ). The highest onentrtion of wter solule P is in the first (-7.5mm) setion n iminishes wy from the point of pplition. The wet inution h the effet of inresing the mount of wter solule P in the seon (7.4-13mm) setion in ll ses exept for the lreous Wrrmoo soil where there is no ifferene etween tretments in this setion. In this seon setion, the Lnghorne Creek n Wry soil h more wter solule P for the flui tretment thn the grnulr, ut the opposite ws true for the Osge soil. The implitions of the solule P t will e etter efine with the lile P t whih is urrently eing nlyse n will e provie uring the orl presenttion Lnghorne Creek 2.2. Wrrmoo grnulr ry grnulr wet flui ry flui wet grnulr ry grnulr wet flui ry flui wet Tretment Tretment 2.3. Wry 2.4. Osge -7.5mm grnulr ry grnulr wet flui ry flui wet mm mm mm grnulr ry grnulr wet flui ry flui wet Tretment Tretment Figure 2.1 Lnghorne Creek, 2.2 Wrrmoo, 2.3 Wry n 2.4 Osge Wter solule P (mg/kg). Within setion, olumn ppene with ifferent letter represents ifferent Wter solule P. (i.e. Fig 2.1. setion -7.5mm grnulr ry > flui ry >grnulr wet> flui wet). Wter x fertilizer intertion P<.1 LSD setion -7.5mm=14.4, setion mm=15.14, setion 13-33mm= not signifint setion mm not signifint. Zin Diffusion n Lility When the Osge n Wry soil ws inute ry, there ws virtully no iffusion of Zn wy from the point of pplition. In omprison there ws some iffusion of Zn when inute wet n therefore greter % of Zn e ws lote in the seon (7.5-15mm) n thir (13-33mm) setions. In ontrst, in the highly lreous Wrrmoo soil, the wet n ry inute Zn fertilizer ehve in the sme wy with smll mount of Zn mesure

5 Zn (% of e) Zn (% of e) Zn (% of e) Zn (% of e) in the seon n thir setions in oth ses. The Lnghorne Creek t is iffiult to interpret s the grnulr wet tretment t is not ville Lnghorne Creek * * * grnulr ry grnulr wet flui ry flui wet Wrrmoo grnulr ry grnulr wet flui ry flui wet Tretment Tretment Wry grnulr ry grnulr wet flui ry flui wet Osge -7.5mm mm mm mm grnulr ry grnulr wet flui ry flui wet Tretment Tretment Figure 3.1 Lnghorne Creek, 3.2 Wrrmoo, 3.3 Wry n 3.4 Osge. Perentge of Zn erive from fertilizer in petri ish soil setions. Within fertilizer n setion, olumn ppene with ifferent letter represents ifferent % Zn e (i.e. Fig 3.3. setion -7.5mm ry is greter wet n setion mm wet is greter thn ry). P<.1 LSD setion -7.5mm=13.7, setion mm=5.12, setion 13-33mm=4.14 setion 33-43mm not signifint.* t not ville. The lile Zn in the first -7.5mm petri ish setion is presente in Figure 4 (the lility of Zn in the remining setions is so low tht it is not presente). The effet of fertilizer ws not signifint therefore t is ompre on wet inution vs. ry inution sis. The t show tht for two of the non-lreous soils (Lnghorne Creek n Osge) the mount of lile Zn t the point of fertilizer pplition is higher when fertilizer is inute moist while there ws no effet of soil moisture in the Wry soil. In the lreous Wrrmoo soil the mount of lile Zn is higher when the soil ws inute ry suggesting rpi fixtion n/or preipittion retions in the presene of moisture. Detetion of Zn is n issue, espeilly for the Wrrmoo whih hs very high fixtion pity for Zn. The higher level of lile Zn when wet suggests tht while there my e high onentrtions of Zn when inute ry, the lility of this nutrient is iminishe n must e ssume to e reting with the soil.

6 -7.5mm setion Lile Zn (mg/kg) Lnghorne Creek wet Lnghorne Creek ry Osge Wet Osge Dry Wrrmoo Wrrmoo Wry Wet Wet Dry Wry Dry Tretment Figure 4.Lile Zin (mg/kg) in the first setion (-7.5mm from point of pplition) of the petri ish. Different letters inite signifintly ifferent lile Zn within soil type (P=.3, LSD=.526). CONCLUSIONS The mjor fining of this stuy is tht the iffusion of oth flui n grnulr forms of P n Zn re inhiite when inute ry. In the highly lreous soil, the iffusion of Zn n P were inhiite regrless of whether the soil ws wet or ry. Lile Zn ws foun to e higher t the point of pplition when inute wet suggesting tht while there my e high onentrtions of Zn t the point of fertilizer pplition when inute ry, the lility of this nutrient hs een restrite. The purpose of this experiment ws to simulte the onitions of wet vs. ry sowing (where fertilizer is ssume to e provie t the time of sowing). Given the effet of soil moisture, filling in the ontinuum etween wet n ry sowing with testing of senrios suh s flse strts where there is wet sowing followe y n rupt ry spell n ry sowing ut with optimum moisture onitions ensuing will mke signifint ontriution to our ility to mnge fertilizer itions for optiml vilility. This work suggests to us tht there re three importnt res requiring further lrifition whih re; 1. The effet of o-loting vs. physilly seprte pplition of Zn n P on fertilizer iffusion n lility; 2. The effet of using unote vs. ote fertilizer grnules on iffusion n soluility; n 3. The effet of wet-ry yles on iffusion n soluility. REFERENCES Bertrn I, MLughlin MJ, Hollowy RE, Armstrong RD, MBeth TM (26) Chnges in P iovilility inue y the pplition of liqui n power soures of P, N n Zn in lkline soils. Nutrient Cyling in Agroeosystems 74, Bolln MDA, Bker MJ (1987) Inreses in soil wter ontent erese the resiul vlue of superphosphte. Austrlin Journl of Experimentl Agriulture 27,

7 Brmley RGV, Brrow NJ, Shw TC (1992) The Retion etween Phosphte n Dry Soil I. The Effet of Time, Temperture n Dryness. Journl of Soil Siene 43, Hettirhhi GM, Lomi E, MLughlin MJ, Chittleorough DJ, Self P (26) Density Chnges Aroun Phosphorus Grnules n Flui Bns in Clreous Soil. Soil Siene Soiety of Ameri Journl 7, Hollowy RE, Bertrn I, Frishke AJ, Bre DM, MLughlin MJ, Shepper W (21) Improving fertiliser effiieny on lreous n lkline soils with flui soures of P, N n Zn. Plnt n Soil 236, Lomi E, MLughlin MJ, Johnston C, Armstrong RA, Hollowy RE (24) Moility, soluility n lility of flui n grnulr forms of P Fertiliser in lreous n nonlreous soils uner lortory onitions. Plnt n Soil 269, Lomi E, MLughlin MJ, Johnston C, Armstrong RD, Hollowy RE (24) Moility n lility of phosphorus from grnulr n flui monommonium phosphte iffers in lreous soil. Soil Siene Soiety of Ameri Journl 68, Lomi E, Shekel KG, Armstrong R, Forrester S, Cutler JN, Pterson D (26) Speition n istriution of phosphorus in fertilize soil: synhrotron-se investigtion. Soil Siene Soiety of Ameri Journl 7, ACKNOWLEDGEMENTS The uthors woul like to thnk the Flui fertilizer Fountion for their ontinue finnil support n enourgement. Our thnks to the Austrlin Reserh Counil n the South Austrlin Grins Inustry Trust for the provision of funing (Projet no. LP882492). Further knowlegement to the Deprtment of Primry Inustries, Vitori n the Grins Reserh n Development Corportion, for ongoing ollortion (Projets CMI n DAV95). Thnks to Gng Hettirhhi for the provision of US soils.