GAFSA ROCK PHOSPHATE AND TRIPLE SUPERPHOSPHATE FOR DRY MATTER PRODUCTION AND P UPTAKE BY CORN

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1 Efficiency of phosphte fertilizers 9 GFS ROCK PHOSPHTE ND TRIPLE SUPERPHOSPHTE FOR DR MTTER PRODUCTION ND P UPTKE B CORN Rossini Mttos Corrê; Clístenes Willims rújo do Nscimento*; Silvn Keely de Sá Souz; Fernndo José Freire; Gleibson Brbos d Silv UFRPE - Depto. de gronomi, Ru Dom Mnoel de Medeiros s/n - Dois Irmãos Recife, PE - Brsil. *Corresponding uthor <cwnscimento@yhoo.com> BSTRCT: Crops in generl mke poor use of phosphorous fertilizer nd, s result, recommended rtes nd production costs re very high. Phosphorus cn be mde more redily vilble to plnts by proper mngement of phosphte fertiliztion, selecting both, type of fertilizer nd ppliction method. This study ws crried out to evlute the efficiency of the nturl Gfs rock phosphte nd the triple superphosphte on dry mtter production nd P uptke by corn plnts cultivted in greenhouse. Fertilizers were pplied loclized nd brodcst/incorported on to two soils with contrsting phosphorus cpcity fctors (PCF). Rock phosphte brodcst ppliction ws s efficient s triple superphosphte in incresing corn plnt dry mtter in the Tropudult, with lower PCF. This effect ws not observed on the Hplustox, owing to the lower P solubility due to the higher C concentrtion in this soil. Triple superphosphte rtes incresed plnt P uptke in both soils nd for both ppliction forms. Rock phosphte resulted in higher P-content in plnts, but only for brodcst ppliction on the. Key words: rock phosphte, phosphte fertiliztion, phosphorus fixtion FOSFTO DE GFS E SUPERFOSFTO TRIPLO N PRODUÇÃO DE MTÉRI SEC E BSORÇÃO DE FÓSFORO PELO MILHO RESUMO: Os fertilizntes fosftdos, de modo gerl, presentm bix eficiênci de utilizção pels culturs. Ess relidde fz com que s doses plicds sejm lts, elevndo o custo de produção. O umento d disponibilidde de fósforo pr s plnts pode ser obtido medinte o mnejo correto d dubção fosftd, com ênfse n fonte utilizd e no modo de plicção mis dequdo pr solos com diferentes cpciddes de dsorção do elemento. vliou-se eficiênci do fosfto nturl de Gfs e do superfosfto triplo, em mostrs de dois solos (rgissolo mrelo e Ltossolo mrelo) com diferentes ftores cpcidde de fósforo (FCP), em diferentes doses plicds de form incorpord e loclizd, sobre produção de mtéri sec e bsorção de fósforo por plnts de milho cultivds em cs de vegetção. No rgissolo mrelo (menor FCP) o fosfto nturl de Gfs incorpordo foi tão eficiente qunto o superfosfto triplo no umento d produção de mtéri sec d prte ére ds plnts de milho. Pr o Ltossolo mrelo (mior FCP) esse efeito não foi obtido, provvelmente, devido à diminuição d solubilizção do fosfto nturl cusd pelos miores teores de C no solo. s doses de superfosfto triplo umentrm bsorção de P pels plnts de milho em mbos os solos e modos de plicção. s doses de fosfto nturl de Gfs umentrm o conteúdo de P ns plnts de milho pens pr plicção incorpord no rgissolo. Plvrs-chve: fosfto nturl, dubção fosftd, fixção de fósforo INTRODUCTION Highly wethered tropicl soils hve high phosphorus (P) fixing chrcteristics. In this environment, incresing P vilbility to plnts cn be chieved by proper mngement of phosphte fertiliztion, s well s by choosing the most suitble fertilizer for ech soil type (Novis & Smyth, 999). Fertilizers of higher phosphte solubility, such s triple superphosphte, re obtined from phosphte rock tht is treted nd concentrted by chemicl mens, nd hve high concentrtion of P redily vilble to plnts (vn Rij et l., 982). Nturl phosphtes, on the other hnd, cn be divided in two ctegories: nturl phosphtes of low rectivity (igneous nd metmorphic origin), nd nturl rective phosphtes (sedimentry origin). In Brzil, nturl phosphtes hve shown low initil efficiency in reltion to superphosphtes, improving fter some yers of ppliction. Imported nturl phosphtes, such s the Gfs, re usully more efficient thn Brzilin ones. Gfs phosphte cn be s efficient s superphosphte when brodcst nd incorported into the soil, but loclized ppliction is much less efficient (vn Rij et l., 982). Sci. gric. (Pircicb, Brz.), v.62, n.2, p.9-64, Mr./pr. 200

2 60 Corrê et l. Loclized ppliction of phosphorus hs the dvntge of temporrily decresing soil fixtion, but the disdvntge of reducing the number of roots in contct with the element. The higher the volume of soil in contct with the pplied rte of P, the less P will be vilble to the plnt, given the higher proportion of formed non-lbile P. This trde-off between rte nd locliztion is ggrvted s the phosphorus cpcity fctor of the soil increses. Lower rtes of phosphorus should be more efficient in supplying this nutrient to the plnt when pplied loclly, but this does not men tht the supply is stisfctory, s it would be if lrge rte of P is pplied throughout the volume of soil vilble to the root system. However, lower volume of roots in restricted spce, even if it is rich in phosphorus, my not be sufficient to supply the plnt with ll the required P. For stisfctory phosphorus uptke by the plnt, P rtes should be vrible depending on the type of fertilizer nd method of ppliction (Novis & Smyth, 999). Considering tht minerl fertilizers, especilly phosphtes, re essentil for incresing or mintining crop productivity, it is obvious tht there is need to improve ppliction methods to void wstge so tht frmers gin mximum benefit from such tretments. The im of this study is to ssess the efficiency of both Gfs phosphte nd triple superphosphte on smples of two soils with different phosphorus cpcity fctors, using different rtes nd ppliction methods, in reltion to the production of dry mtter nd uptke of phosphorus by corn plnts. MTERIL ND METHODS Smples of two soils from the Pernmbuco Forest Zone, Brzil were collected from the 0 to 2 m lyer: Tropudult from the municiplity of Goin (7 '8'' S, 00'09'' W), nd n Hplustox from Sirinhém (8 '27'' S, 06'8'' W). The soils were selected on the bsis of two criteri: low concentrtion of vilble phosphorus nd different mximum phosphte dsorption cpcities (MPC). Soil smples were ir-dried, broken up nd pssed through 2 mm sieve. fter homogenistion, sub-smples were tken for chemicl nd physicl chrcteriztion of the soil smples (Tble ). Soil cidity ws ltered by dosing with clcium crbonte nd mgnesium crbonte with 4: molr rtio, determined beforehnd by n incubtion test. fter cidity correction (ph in H 2 O: 6.7 for the nd 6.4 for the ), phosphorus rtes were pplied to smples nd incubted for thirty dys (Gonçlves et l., 989), with wter content kept t 80% of field cpcity. The pplied phosphorus rtes to ech soil were determined ccording to the respective P-remining vlue (lvrez V. et l., 2000). They corresponded to 0, 7, 0, 22 nd 00 mg dm - for the nd 0, 20, 240, 60 nd Sci. gric. (Pircicb, Brz.), v.62, n.2, p.9-64, Mr./pr. 200 mg dm - for the, using triple superphosphte nd Gfs phosphte. These rtes were pplied in two wys: incorportion throughout the soil volume to simulte brodcst ppliction nd incorportion t the centre of the pot. The experiment ws crried out in greenhouse using pots filled with. dm of soil. Ten dys fter sowing, the mize (São José cultivr) ws thinned, leving two plnts per pot. Nutrients were supplied to the plnts, except for the phosphorus, bsed on lvrez V. (974), t the following concentrtions: 0 mg dm - of N (KNO nd (NH4)2SO4), 0 mg dm - of K (KNO e K 2 SO 4 ), 40 mg dm - of S (K 2 SO 4 nd (NH 4 ) 2 SO 4 ), 8 mg dm - of B (H BO ),.664 mg dm - of Mn (MnCl 2 4 H 2 O), 4 mg dm - of Zn (ZnSO 4 7 H 2 O),.29 mg dm - of Cu (CuSO 4 ),.6 mg dm - of Fe (FeSO 4 7 H 2 O) nd 0, mg dm - of Mo (N 2 MoO 4 2 H 2 O). Pots were weighed to provide reference for dily irrigtion with distilled wter to increse soil wter content to 80% of field cpcity. On the fortieth dy fter germintion, the eril plnt prts were collected nd oven-dried t 6ºC until constnt weight. The dry mtter ws ssessed nd the mteril ground up to crry out nitric-perchloric digestion nd determine P levels in the extrcts ccording to Brg & Defelipo (974). Tble - Chemicl nd physicl chrcteriztion of soil smples used in the experiment. Chrcteristic Tropudult Hplustox ph (H O) C - ) c M g - ) c. 6. K + - ) c 2 2 H l - ) c l - ) c Potentil CTC (mmol dm - ) c vilble P ( Mehlich- ) (mg dm - ) Remining- P (mg L - ) MPC (mg dm - ) dsorption energy (mg L - - ) k- Freundlich Snd (g kg - ) 880 Silt (g kg - ) 0 40 Cly (g kg - ) 90 Bulk density (g cm - ).47. Prticle density (g cm - ) Field cpcity (g g - ) 0 24 Permnent wilting point (g g - ) Porosity (%) EMBRP (997), 2 lvrez V. et l., (2000), lvrez V. (987), 4 Equilibrium constnts of Freundlich isotherm (Novis & Smyth, 999). MPC: Mximum phosphte dsorption cpcity.

3 Efficiency of phosphte fertilizers 6 The experiment ws set up s rndomized block design in fctoril scheme, with two types of soil, two phosphorus sources, two ppliction methods for the sources nd five rtes, with three replictes, totlling 20 plots. The dt were submitted to vrince nd regression nlysis. The degrees of freedom for the tretments were broken down to ssess the min effects of the fctors nd interction mong them. RESULTS ND DISCUSSION significnt difference ws observed by the F- test (P < 0) for production of dry mtter in the eril plnt prts s function of sources, for both soils (Tble 2). In tretments with triple superphosphte, which on verge produced higher proportion of dry mtter s compred to nturl phosphte, the greter mount of P vilble probbly offset the smller volume of root in contct with the fertilizer, since no interction (P < 0) ws observed between ppliction methods nd rtes of fertilizer. In line with this observtion, other uthors (Cstilhos & nghinoni, 988; lves et l., 999) hve lso observed tht the ppliction of soluble P to only prt of corn root systems does not influence the production of dry mtter the plnts. On the other hnd, Brreto & Fernndes (2002) confirmed tht brodcst ppliction with incorportion into the soil of triple superphosphte incresed corn production in the, by comprison with the loclized ppliction of this fertilizer. This pprently conflicting result is relted to the low P bsorption cpcity of the soil studied by these uthors, llowing higher P uptke owing to the incresed root contct with the fertilizer, with no significnt increse in P-fixtion. In our study, the lower rte of triple superphosphte used in the (7 mg dm - ) supplied the P required for plnt growth since there ws n incresed P-content in the plnts receiving higher rtes (Tble ) without proportionl increse in the production of dry mtter (Tble 2), s observed by the squre-root behviour of production s function of P rtes (Tble 4). In the cse of the lomy soil, despite the fct tht the verges for different locliztions of triple superphosphte did not differ by the F-test, the rte x distribution interction ws significnt (P < 0), indicting higher increse in the production of dry mtter when rtes of up to 240 mg dm - triple superphosphte were pplied loclly (Tble 2). Silv et l. (99) nd Prdo et l. (200) observed tht sources of soluble P pplied on loclized bsis incresed the production of corn dry Tble 2 - Production of dry mtter by corn shoot s function of rtes, sources nd distribution of P in the smples of two soils with different phosphorus cpcity fctors. Rte Triple Incorported Superphosphte Loclize d mg dm g per pot (Locl) b B (Locl) b B rges followed by the sme letter, lower cse between distributions nd upper cse between sources, did not differ in the F-test (P < 0). Sci. gric. (Pircicb, Brz.), v.62, n.2, p.9-64, Mr./pr. 200 Source of phosphorus Incorported Gfs phosphte Loclize d

4 62 Corrê et l. Tble - Phosphorus content of corn shoot dry mtter s function of rtes, sources nd distribution of P in smples of two soils with different phosphorus cpcity fctors. Rte Triple Incorported superphosphte Loclize d Incorported Gfs phosphte Loclize d mg dm g per pot (Locl) b 2.47 b B (Locl) b 06.7 B rges followed by the sme letter, lower cse between distributions nd upper cse between sources, did not differ in the F-test. - - Tble 4 - Regression equtions nd determintion coefficients between P rtes (mg dm - ) nd production of dry mtter (g per pot) for corn plnts submitted to triple superphosphte () nd nturl phosphte () in two soils nd using two ppliction methods. Distribution incorported loclized incorported loclized incorported loclized incorported loclized **, * significnt to nd %. Eqution R 2 = ** X - 4* X 98 = * X - 4* X 96 = ** X - 07* X 99 = * X - 006* X 90 = * X - 02* X 99 = * X - 08* X 97 = ** X 99 2 = *X * X 92 mtter in two s. bove the rte of 60 mg dm -, however, the production of dry mtter ws the sme for both methods of pplying the fertilizer, indicting tht the fvourble effect of loclized ppliction of P regrding dry mtter depends on the rte. Despite the high mximum phosphte dsorption cpcity (MPC) of this soil (Tble ), high rtes distributed throughout the volume of the soil were cpble of supplying the P-contents required for plnt growth, probbly becuse higher quntities of the element were vilble in reltion to the higher quntities dsorbed s result of this type of ppliction. The production of dry mtter of Gfs phosphte treted corn ws influenced by the method of ppliction for the two soils, lthough this effect ws much more pronounced for (Tble 2), for which the effect of Sci. gric. (Pircicb, Brz.), v.62, n.2, p.9-64, Mr./pr. 200

5 Efficiency of phosphte fertilizers 6 the dose depended on the wy in which the fertilizer (P < 0) ws pplied. For this soil, the brodcst ppliction of nturl phosphte with incorportion resulted in shoot dry mtter production equl to tht obtined with soluble source, s suggested by vn Rij et l. (982) nd Korndörfer et l. (999). The recommended brodcst distribution with incorportion of nturl phosphtes, suggested by vn Rij et l. (982), did not hve stisfctory effect in reltion to loclized ppliction, lthough significnt in the production of dry mtter for the (higher P cpcity fctor, Tble 2). Shoot dry mtter production obtined with Gfs phosphte in both distributions on ws very low nd lower thn tht obtined with triple superphosphte. Similr results were obtined by Coutinho et l. (99), Oliveir et l. (996), Smbtti et l. (998) nd Gtiboni et l. (2000), who compred the effect of Gfs phosphte with soluble phosphorus fertilizers on the production of green mtter. Clcium tretment cn reduce the solubiliztion of nturl phosphtes due to the elevtion of the ph nd C content (Kminski & Peruzzo, 997; Novis & Smyth, 999). However, elevtion of the ph ws not the min reson for the lower efficiency of the nturl phosphte in the, since the ph of the two soils fter clcium tretment ws similr, wheres the P-contents of the plnts for brodcst ppliction on the were very much higher thn those observed under the sme conditions for (Tble ). Exchngeble C contents in the soil fter ppliction of clcium, however, were much higher in the (66.7 mmol c dm - ) thn in the (9.8 mmol c dm - ). Korndörfer et l. (999) observed tht the efficiency of Gfs phosphte ws prcticlly equl to tht of triple superphosphte in supplying P to corn plnts in n (ph in wter:.8), with C contents (9 mmol c dm - ) very similr to those observed in the. Therefore, the high content of exchngeble C ws probbly the min cuse of lower solubiliztion of Gfs phosphte in the nd, consequently, the lower efficiency of this source in reltion to triple superphosphte. In ddition, the inverse reltionship between the P cpcity fctor nd uptke (Gonçlves et l., 989; Crvlho et l., 99; Novis & Smyth, 999) my hve contributed to this result. In this cse, the lower quntity of P relesed by solubiliztion of the nturl phosphte my hve been dsorbed in the t rte higher thn the plnt cpcity to tke up the element. For the, thnks to its lower P cpcity fctor, competition between fixtion by the soil nd uptke by the plnt ws not significnt, resulting in higher contents vilble to the plnts. s result of the nturl scrcity of P in the soils, there ws strong increse in the production of plnt dry mtter fter the ddition of the first dose of the element, with lower increse in production for subsequent doses, s chrcterized by the squre-root djustment obtined for the mjority of regressions (Tble 4). Compring the two triple superphosphte ppliction methods, there is higher P-content in shoot dry mtter using brodcst ppliction with incorportion for the, which is not the cse for the (Tble ). However, the interction (P < 0) between distribution nd rte tht occurred in the reinforced tht the loclized ppliction of the fertilizer promoted higher ccumultion of P for rtes of 20, 240 nd 60 mg dm -, confirming the results for dry mtter production (Tble 2). This soil with higher MPC (Tble ) cted s phosphorus drin nd competed with the plnt for phosphorus (Novis & Smyth, 999) owing to the higher re of contct resulting from ppliction with incorportion; t the highest rte ( mg dm - ) this effect ws not observed, probbly owing to the higher vilbility of P to the plnts t this high concentrtion, which could hve hstened the fixtion nd incresed the P-content in soil solution. Loclized ppliction of triple superphosphte to soils with high mximum phosphte dsorption cpcity provides wy of reducing contct between the phosphte fertilizer nd the soil, thus reducing P dsorption, llowing the fertilizer to hve more prolonged residul effect, s observed by Fernández et l. (2000) in experiments with Euclyptus cmldulensis ssessed nine yers fter instlltion. Tble - Regression equtions nd determintion coefficients between P rtes (mg dm - ) nd P-contents (mg per pot) in corn plnts receiving triple superphosphte () in two soils nd using two different distribution methods, nd rtes of Gfs phosphte (GP) brodcst on. Soil () () (GP) **, * significnt to % nd %. Distributio n Incorported Loclized Incorported Loclized Incorported Eqution R 2 = ** x 99 2 = **x - 00* x 94 = ** x 92 = ** x 99 = * x 92 Sci. gric. (Pircicb, Brz.), v.62, n.2, p.9-64, Mr./pr. 200

6 64 Corrê et l. On the bsis of the P-content in plnt shoot, regression equtions were djusted s function of the rtes of triple superphosphte nd nturl phosphte. The responses were liner, with exception to loclized triple superphosphte ppliction to the, which hd highly significnt squre djustment (Tble ). Significnt models for P-content s function of Gfs phosphte were not obtined, with exception to brodcst ppliction with incorportion in, corroborting to lower P solubiliztion of this source nd its lower efficiency when pplied loclly. CONCLUSION For the, the incorported Gfs phosphte ws s efficient s the triple superphosphte in incresing the production of shoot dry mtter of corn plnts. For the, this did not hppen owing to the reduced solubiliztion of the nturl phosphte, probbly due to the higher C-content of the soil. Triple superphosphte rtes incresed corn plnt phosphorus uptke in both soils nd ppliction methods. 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Revist Brsileir de Ciênci do Solo, v.7, p , 99. Received October 2, 200 ccepted Februry, 200 Sci. gric. (Pircicb, Brz.), v.62, n.2, p.9-64, Mr./pr. 200