Nutrient Content of Runoff Water From Rice Fields

Transcription

1 University of Arkansas, Fayetteville Tehnial Reports Arkansas Water Resoures Center Nutrient Content of Runoff Water From Rie Fields C. E. Wilson Jr. Southeast Researh and Extention Center P. A. Moore Jr. USA Agriultural Researh Servie R. J. Norman Rie Researh and Extention Center B. R. Wells University of Arkansas, Fayetteville Follow this and additional works at: Part of the Fresh Water Studies Commons, Hydrology Commons, Soil Siene Commons, and the Water Resoure Management Commons Reommended Citation Wilson, C. E. Jr.; Moore, P. A. Jr.; Norman, R. J.; and Wells, B. R Nutrient Content of Runoff Water From Rie Fields. Arkansas Water Resoures Center, Fayetteville, AR. PUB This Tehnial Report is brought to you for free and open aess by the Arkansas Water Resoures Center at It has been aepted for inlusion in Tehnial Reports by an authorized administrator of For more information, please ontat

2 llutribn'r COH'rENT OF RUWOFF WATl'tR FROM RICE FlELS.e. Wilson, Jr. SoutbE'dSt Res"trh and Extene.i..on CeJ"t er P.A. Moor :?, Jr. USA Agriultural Reaearh servie R.J. Norman Rie Reaearh dnd Extension Center ana B.R. Wella epartment of Agronomy Researh Projet Tehnial Completion Report Projet G he researh upon whih this r<>port is based w.aa f in&ned in part by the Unit ad States epartment of the rntorior as authorized by the Watnr Researh and evoloµnent At of 1984 P ). Arkansas Water Re oures Centor university of Arkanaao 113 Ozark Hall FayPtteville, AR 7271 Publiation No. 164 July l, June JO, 1993 ont.ante of thio publiation do not neesaarily refl<>t the views and poliies of the U.S. epart ment of the Interior, nor do<?s m<lntion of trade names or onwnerial produtu onetitut _ their ~ndoraemant or reommendation of or use by the U.S. Government. Thf" University of Arkansas, in ompliane with ted2ral and statf~ 1awa and regulations governing a!firmative ation and non-disrimination, doae not disriminate in the reruitment, admio&ion, and employment o: a~uoente, f~ulty, and staff in the oper~tion of any of ita aduational programo and ativitieo ~o defined by law. Aordingly, nothing in thio publiation should be viewed as diretly or indiretly "xpr<>using any 1 irnit3tion, spoifiation, or disrimination as to rae, r~li9ion, olor, or national origin; or to handiap, age, aex, or statue au a disablq;d Vi.etna.m--era veteran; exept as provided by law.!nquiriee onerning this po!y may be dire.ed to -he l\ffi~ma1 iv<> Ation oifier.

3 I TABLE OF CONTEHTS Abstrat 3 List of Figures 5 Aknowledgements... 6 Introdution. 7 A. Purpose and Objetives e. Related Researh and Ativities 7 Methods and Proedures Priniple Findings and Signifiane A. Inorgani N. B. Soluble P. Metals.. Comparison of Water Soures Conlusions Literature Cited ,

4 ABSTRACT HUTR.IENT CONTENT OF RUHOFF WATER FROM RICE FIELS Current pereption is that nutrient runoff from roplands is a signifiant ontributor to poor water quality in some areas. While extensive researh has been onduted to survey and ameliorate this problem for several upland rops, little work has been done to evaluate the problem with flooded rie Ory~a sat;iva, L.) soils. Sine rie prodution utilizes a major portion of the total irrigation water usage for ertain areas, it is important to understand the ontribution of rie prodution to non-point soure N and P in surfae water. Several prodution fields were seleted to evaluate the onentrations of nutrients in the floodwater at seleted distanes aross the field, inluding inlet and exit. The fields were evaluated in either 199, 1991, or 1992 and were managed by the individual rie produer. Water samples were olleted from several loations within eah field weekly following establishment of.the permanent flood and analyzed for inorgani N NH 4 -N, NC>J-N, and No2-N) and soluble P. The N onentrations in the floodwater normally peaked following N fertilizer appliation but rapidly delined r ~ and remained below 1 mg N L 1 Water management resulted in some variation among loations with respet to the timing and magnitude of these peaks. The P onentrations were usually highest near the well and delined to less than.5 mg P L- 1 as the water moved aross the field. This was attributed to plant uptake, uptake by algae, and sediment deposition. The data indiates that rie fields have the potential to be utilized as a 3

5 filtration system to redue the nutrient load of irrigation water similar to onstruted wetlands. use of atfish pondwater, in omparison to well water, resulted in only slightly higher total N and total P levels with higher amounts of the nutrients in the organi form. Although the. P levels were high enough to potentially ontribute to eutrophiation of surfae water, the water exiting the field was lower than at the entry point irrespetive of the soure. Also, the total P organi + inorgani) onentration was less than.5 mg P L- 1. g l

6 LIST OF FIGURES Fig. 1. Seasonal hanges in NH 4 -N onentration in rie irrigation water. Page 22 Fig. 2. Seasonal hanges in N~-N onentration in rie irrigation water. Page 23 Fig. 3. Changes in NH 4 -N onentration in rie irrigation water with respet to relative distane from the well. Page 24 Fig. 4. Changes in N~-N onentration in rie irrigation water with respet to relative distane from the well. Page 25 Fig. S. Changes in soluble reative phosphorus P4-P) onentration in rie irrigation water with respet to distane aross the field. Page 26 Fig. 6. seasonal hanges in soluble reative phosphorus P4-P) onentration in rie irrigation water. Page 27 Fig. 7. Conentrations of NH4-N, N~-N, and total N in rie irrigation water from a well A) or atfish pond B) with respet relative to distane from the soure. Page 28 Fig. 8. Conentrations of soluble reative phosphorus P4-P) and total l P in rie irrigation water from a well A).or atfish pond B) with respet to relative distane from the soure. Page 29 5

7 lj ACKNOWLEGEMENTS The authors would like to extend thanks to those who assisted with olletion and analysis of the many samples for this study inluding s. Castile,. Brooks, s. Fisher, and A. Weaver. We would also like to extend our thanks to the produers Fisher Farms, Summerford Farms, M&J Farms, Bradshaw Farms, and Reinhart Farms) for allowing us to ondut this researh on their farms. 6

8 :INTROUCTION A. Purpose and Obietives Reently the onern about environmental pollution resulting from appliation of ommerial fertilizers and pestiides in agriultural situations has inreased. Beause of this onern, it beomes inreasingly important to know how muh ontamination of surf ae water resulting from these appliations is atually present. Beause information onerning N and P runoff from rie fields is limited, this study was initiated to evaluate the seasonal variation in nutrient ontents in the rie floodwater with distane aross the field. B. Related Researh and Ativities Nitrogen and P in runoff from agriultural lands have been investigated extensively, partiularly for upland rop situations Stanford et al., 197; Water Resoures Committee, 197; Lin, 1972; Loehr, 1974; Chihester and Rihardson; 1992). some of the major topis of reent researh inlude N and P runoff as influened by tillage praties, irrigation, and various ropping situations e.g., Sharpley et al., 1992; Lowrane, 1992; Chihester and Rihardson, 1992). Most of the researh has foused on upland rops suh as orn Zea mays, L.), wheat ~ritiwn aestivwn, L.) and soybean Glyine maz, L.) Merr.). However, researh r evaluating the runoff from rie prodution is limited. The use of riparian forests for filtering nutrient runoff from rop prodution fields has demonstrated the ability to redue nutrients entering the surrounding watersheds Cooper et al., 1986; Jordon et al., 7

9 C 1993; Lowrane et al., 1984a,b; Peterjohn and Correll, 1984, 1986; Jaobs and Gilliam, 1985; Hayok and Pinay, 1993). The riparian forests take up N, P, and other nutrients, thus reduing the loads in the runoff water. Similarly, wetland eosystems at as a filter for nutrients ontained in water moving through the system, partiularly N and P Boyt et al., 1977; Lakshman, 1979; Reddy and ebusk, 1985; Tilton and Kadle, 1979). The mehanisms for filtration inlude plant uptake, inorporation into the soil, and gaseous losses resulting from the redued soil onditions assoiated with wetlands. Gaseous losses of N inlude nitrifiation - denitrifiation reations Patrik and Reddy, 1976; Reddy et al., 198; Reddy and Patrik, 1986) and NH 3 volatilization Mikkelsen and e atta, 1979; Brandon and Wells, 1986; Welle and Turner, 1984). It is believed that rie fields an at as a filtration system similar to the onstruted wetlands beause of the vegetation and flooded soils assoiated with rie prodution. Certain metals ontained in irrigation well water, partiularly Ca and Mg, are deposited due to the formation of arbonate preipitates when exposed to o 2 Gilmour et al., 1978). ue to this preipitation, the onentration in the floodwater usually dereases with inreasing distane from the well. The result is the aumulation of alium and magnesium arbonates in the soil whih leads to inreased soil ph. Subsequently, the potential for Zn defiieny exists during rie prodution. ata onerning the movement of other metals aross the field is limited. The majority of the irrigation water utilized in the rie-produing region of the Southern U.S. is used for the rie rop. onsequently, nutrient runoff from rie fields is a major onern in this region. 8

10 MATERIALS AN PROCEURES seven prodution rie fields were seleted to monitor the N and P onentrations of the floodwater during the 199, 1991, and 1992 growing seasons one field in 199, three fields in 1991, and three fields in 1992). The fields were loated in Ashley, rew, Linoln, and St. Franis ounties in Arkansas. Eah field was managed by the produer, inluding ultivar seletion. The rie was seeded on eah field and grown as an upland rop for 4-6 wk. At the four- to five-leaf growth stage, 6% of the reommended fertilizer N was applied as urea and a permanent flood was established and maintained until maturity. Fertilizer N was applied to eah field as urea at rates appropriate for the partiular ultivar. The N was applied in three appliations with 6\ of the N applied just prior to flooding, 2% applied at 1.3-m internode elongation IE), and 2% 1 d following IE. The fields are designated in the disussion aording to the produer's name and year. Water samples from eah field were taken weekly for the entire season at seven loations aross the field from entry point to exit inluding tailwater. Samples were olleted daily for the first wk following N fertilizer appliations. Water samples were olleted with a 6-ml syringe and filtered on loation through a.45-um membrane filter. The eletrial ondutivity EC), ph, and temperature of the floodwater was measured in situ at the time of sampling with a portable EC meter and a portable ph meter. The metal samples were aidified with one drop of onentrated HNO;s for preservation until analysis was performed. The water r r ~ { r samples were analyzed for soluble P Po 4 3 ) and inorgani N NH 4 + -N, NO;s -N, 9

11 u g C u and NOz" -N) with a Tehnion AutoAnalyzer II Tehnion Industrial Systems, 1973a,b, 1976a). Metals Ca, Mg, K, Na, Fe, Mn, Al, As, Cu, o, Cd, Cr, Zn, and Pb) were determined by indutively oupled atomi plasma spetrosopy Soltanpour et al., 1982). An additional study was onduted during 1991 and 1992 to ompare the nutrient ontent of runoff water from different irrigation water soures. Two fields were either irrigated with well water or with water pumped from a pond used for raising atfish. Samples were olleted from the field as desribed above. In addition to the analyses desribed for the other fields, unfiltered water samples were olleted to analyze for total dissolved P and total dissolved N. Total N and P were determined with a Tehnion AutoAnalyzer II Tehnion Industrial Systems, 1976b). PRINCIPLE FININGS AN SIGNIFICANCE A. Inorgani N The major peaks in the seasonal N onentrations in the floodwater were following N fertilizer appliations Fig. 1 and 2, respetively). As would be expeted this N peak was usually NH4-N Fig. l}. The N~-N r emained low throughout the season less than 1 mg N L" 1 ) exept for two loations Fig. 2). In 1991, the M&J farm site and the Reinhart farm site in 1992 had an initially high N~-N due to the time between N fertilization and appliation of the flood. The fields required 3 d to be ompletely flooded. Consequently, the lower end of the field resulted in greater nitrifiation and, thus, N~-N aumulation >2.5 mg L 1 ). The N~-N peak delined to less than.5 mg L" 1 for both of these loations within 1 d 1

12 following establishment of the flood. Most of the peaks observed during mid-season had fallen to below 1 mg NH4-N L 1 within 3 d. This is onsistent with previous researh indiating that mid-season N fertilizer appliations are utilized by the plant, inorporated into the soil biomass, or lost within 3 dafter appliation Wilson et al., 1989). The NH 4 -N onentration varied with flow distane and loation Fig. 3) The NH4-N onentration at the Summerford loation remained below. 5 mg L 1 during 1991 although the NH 4 -N onentration exiting the field was greater than the NH4-N onentration entering the field at the other two loations in 1991 and the Pine Tree loation in 199. The Bradshaw and Reinhart loations remained relatively onstant aross the field during The Fisher loation inreased aross the first 5% of the field from.2 to 1.8 mg N L" 1 but dereased to 1.1 mg NH 4 -N L" 1 at the outlet. Muh of the variation between loations an be attributed to differenes in water management by the individual produers. The produers ability to flood and/or drain the field differed primarily due to differenes in soil texture, field size, and well apaity. The N~-N onentration in the floodwater with respet to distane ~ from the inflow also varied among loations Fig. 4). At most of the loations, the N~-N onentration remained onstant at a level below.5 mg N~-N L" 1 However, at Reinhart in 1992 and M&J in 1991, the nitrate levels hanged with distane. At these two loations, N~-N inreased to levels of 1.5 mg N~-N L" 1 or more. This hange in N~-N onentration an be attributed to wetting and drying yles assoiated with the inability to apply the flood to the entire field rapidly or to maintain the flood permanently one it was established. 11

13 ~ The N onentrations reated muh as expeted. The onentrations were high immediately after N appliation but rapidly delined to levels below that whih is onsidered to pose a threat to surrounding watersheds. For most of the season, the N onentrations remained below l mg N L- 1 as previously reported for rie fields Moore et al., 1981). It is important to note the variability in the N onentration in the floodwater among the loations. These differenes are assoiated with water management whih is ruial for maximum effiieny of the fertilizer N Wells et al., 1988). If the early N appliation is made into the floodwater, the amount of NH4-N in the floodwater inreases, NH3 volatilization losses inrease Fillery et al., 1986), and, with an inrease in NH 4 -N or NOJ-N in the floodwater, the potential for inreased pollution exists Moore et al., 1993). The optimum N management tehniques are to apply the early N onto dry soil just prior to flooding and then establish a permanent flood as rapidly as possible Brandon and Wells, 1986; Moore et al., 1993; Wells and Turner, 1984). This tehnique utilizes the floodwater to inorporate the N into the soil Fillery et al., 1984; Wells and Turner, 1984) whih redues the buildup of Nin the floodwater. This method of applying the early N fertilizer has also shown to inrease yields and redue NH3 volatilization losses Wells et al., 1988). By utilizing good water management, N:5-N formation is redued, less N aumulates in the floodwater, and less potential for N in runoff water exists Fig. 2 and 4). However, when poor water management is used i.e. M&J farms , Reinhart farms ) more nitrifiation ours whih results in greater denitrifiation losses and potentially greater NOJ-N released into the surrounding surfae water. 12

14 B. Soluble P The soluble reative phosphorus SRP) dereased with inreased distane aross the field in all fields exept for Bradshaw-1992 Fig. 5). The SRP inreased initially at this site but dereased as the water moved aross the field Fig. Sa). The SRP in all of the fields was less than.5 mg P L" 1 at the end of the field, the level established as the minimum level upon whih eutrophiation of surfae water is possible Sharpley et al., 1992; Sharpley and Smith, 1993). The Summerford site ontained the highest initial SRP level at.5 mg P L" 1 However, this level dropped to approximately.15 mg P L" 1 and remained relatively onstant through the field. Although the level at this site was above the limits reognized as stimulating eutrophiation of surfae waters 1 ug L" 1 ) Sharpley and Smith, 1993), the irrigation water ontained less SRP at the outlet than the water entering the field from the well. Consequently, the water quality improved as a result of moving aross the field. For most loations, the SRP onentration in the well water was above that whih is onsidered to ause eutrophiation of surfae water Fig. 5). However, as the water progressed aross the field, the SRP onentration delined. For the Summerford loation, the SRP delined from.5 mg L" 1 to approximately.9 mg L" 1 within half the distane of the field Fig. Sa). The SRP measured at Reinhart-1992 delined from.15 mg L" 1 entering the field to as little as.2 mg L" 1 within 5% of the r flow distane Fig. Sb). Two onlusions an be obtained from these data. First, the inherent level of soluble P in irrigation entering rie fields is variable.1 to O.S mg L" 1 ). Seondly, rie fields an potentially at as a filter for P similar to the onstruted wetland eosystems Boyt 13

15 l n et al., 1977; Lakshman, 1979; Reddy and ebusk, 1985). The seasonal onentration of soluble P in the floodwater was variable Fig. 6). The peaks and valleys are a refletion of when the field was irrigated, partiularly for Sununerford farms in The well at this partiular field was inherently high in soluble P as denoted by the P onentration with distane aross the field Fig. Sb). When water was being applied to the field, the soluble P onentration was relatively high. After the field was flooded and the flood stabilized, the soluble P onentration delined. When water was added to the field beause of evaporation, transpiration, runoff, and plant utilization, the amount of P in the water inreased. The P onentrations were typially higher at the well than other loations aross the field. As the water flowed aross the field, the onentration of P generally dereased to less than a.as mg P L" 1 The ph of the inoming water was normally lose to 7 data not shown), due to a high C2 partial pressure. As the water moves aross the field, the o 2 degasses resulting in CaCO] preipitation and P 4 3 o-preipitation or alium phosphate preipitation Gilmour et al., 1978) onsequently, the P in the floodwater was redued. Also, P uptake and utilization by algae, rie plants, and any other vegetation ould also have ontributed to the redution in P onentrations as the water moved aross the field Sharpley et al., 1992; Sharpley and Smith, 1993). Although the soluble P onentrations were generally in exess of the limits reognized as stimulating aelerated eutrophiation of surfae waters.1 mg P L" 1 ), they were signifiantly redued from the onentration upon entering the field.

16 C. Metals As expeted, the a onentrations dereased or remained the same as the floodwater moved aross the field Table 1). The a onentrations ranged from 11 to 78 mg L. 1 entering the field and ranged from 11 to 54 mg L- 1 exiting the field. The summary presented in Table 1 also indiates the Mg was relatively low but did not hange appreiably between the inlet and exit points. As expeted the Fe and Mn onentrations were relatively high at some loations Table 1). Although most loations resulted in a derease in the onentration as the water moved aross the field, some loations atually inreased. The Fe onentrations ranged from 1 to 244 ug L- 1 entering the field and ranged from 9 to 41 ug L- 1 The Mn ranged from 3 to 195 ug L- 1 entering the field and ranged from 8 to 1745 ug L 1 exiting the field. ue to the hanges assoiated with soil redution following flooding, Fe and Mn generally beome more soluble. Consequently, it is feasible that an inrease in the Fe and Mn onentrations would result. If water management for the rie rop is not optimum, it is also possible that the redution neessary to solubilize an appreiable amount of Fe and Mn may not our. subsequently, Fe and Mn may be deposited in the fields l as the water moves aross the field beause of the oxidized soil onditions. At the Summerford site, the well water ontained a large amount of Fe 244 ug L- 1 ) relative to the other loations. Poor water management leads to redued N effiieny due to wetting and drying yles The wetting and drying yles at this site resulted in, in addition to the poor N effiieny Fig. 1), a signifiant amount of Fe preipitation due 15

17 to the oxidized soil onditions. Table 1. Comparison of inlet and outlet metal onentrations in the floodwater of four prodution rie fields. Bradshaw Reinhart Fisher Summerford Metal In Out In out In Out In Out mg L. 1 a K Mg Na s * * * * ug L 1 Al g As B Cd 4 3 o 9 6 er u 5 Fe Mn u Ni Pb * * * * Zn ph * = not determined 16

18 o. Comparison of Water soures Water from ponds is used to raise atfish is used in some areas of the rie produing region of the Southern U.S. In fat, rie is also grown in rotation with atfish on some farms. When the nutrient load of water from atfish ponds was ompared to irrigation from well water, the total N onentration was very similar between the two soures Fig. 7). The NO]-N onentration was very small for both soures. onentration was higher in the pondwater field than in the well water field. Thus, more of the N in the well water field onsisted of organi N. However, both sites had less than 3 mg N L" 1 of total N exiting the field in the runoff with less than.5 mg N L" 1 differene between the two sites. The total P ontent delined from as muh as.1 mg P L 1 to slightly more than.4 mg P L" 1 as the water moved aross the field from the atfish pond Fig. 8). However, the well water exiting the field ontained less than.4 mg P L" 1 More of the P in the atfish pond was in the organi form total - inorgani) than in the well water. However, as the water moved aross the field, the onentration of the water exiting the field was very similar for the two loations with about 5 \ of the total P in the P4-P form. r f This data onfirms the data from the other loations onerning the deline in P and N onentration as rie irrigation water flows aross the field. The total P and organi P in all of the fields was less than.5 mg P L" 1 at the end of the field but is higher than the ritial limits.1 and.2 mg P L" 1 of soluble and total P, respetively) established as ontributing to aelerated eutrophiation of surfae water Sharpley 17

19 r et al., 1992; Sharpley and Smith, 1993). The water exiting the field irrigated by pondwater ontained slightly higher onentrations of organi P than the field irrigated by well water, indiating that the ontribution Q L to surfae water eutrophiation is more likely used atfish pondwater for irrigation water. However, the amount of P in the water delined signifiantly by flowing aross the rie field. Had the water been released diretly from the atfish ponds, the level would have exeeded four times the ritial limit for total P. Consequently, the idea was onfirmed that rie fields an at similarly to onstruted wetlands Lakshman, 1979) and filter nutrients before entering surfae water. CONCLUSIONS Sine rie prodution utilizes a major portion of the irrigation water in the Southern Rie Belt, it is neessary to understand the potential for pollution resulting from field runoff. The results of this study emphasize the importane of water management with respet to N onentrations in the floodwater. The N~-N levels remained low when optimum water management was utilized. The soluble P onentrations were generally lower in the water exiting the field than in the water entering the field from the well. Although the P levels were suffiient at some loations to potentially ontribute to eutrophiation of surrounding surfae waters, the amount of P was generally higher entering the field than exiting the field. Removal of Fe and Mn apparently depends upon water management and the oxidation state of the soil. 18

20 LIRA~ CI Boyt, F.L., s.e. Bayley, and J. Zoltek Removal of nutrients from treatment muniipal wastewater by wetland vegetation. J. Water Pollut. Control Fed. 48: Brandon,.M., and B.R. Wells Improving nitrogen fertilizer in mehanized rie ulture. P In S.K. e atta and W.H. Patrik, Jr. ed.) Nitrogen eonomy of flooded rie soils. Martinus Nijhoff Publishing o., ordreht, The Netherlands. Chihester, F.w., and.w. Rihardson from lay soils as affeted by tillage. 59. Sediment and nutrient loss J. Envir. Qual. 21:587- ooper, J.R., J.W. Gilliam, and T.C. Jaobs Riparian areas as a ontrol of nonpoint pollutants. p In O.L. Correll ed.) Watershed researh perspetives. Smithsonian Institution Press, Washington, o.. Fillery, I.R.P., P.A. Roger, and S.K. e atta Ammonia volatilization from nitrogen soures applied to rie fields: II. Floodwater properties and submerged photosyntheti biomass. Soil Si. so. Am. J. 5: Fillery, I.R.P., J.R. Simpson, and S.K. e atta Influene of field environment and fertilizer management on ammonia loss from flooded rie. Soil Si. So. Am. J. 48: Gilmour, J.R., K.S. Shirk, J.A. Ferguson, and C.L. Griffis A kineti study of the CaC~ preipitation reation. Agri. Water Manage. 1: Hayok, N.E., and G. Pinay Groundwater nitrate dynamis in grass and poplar vegetated riparian buffer strips during the winter. J. Environ. Qual. 22: Jaobs, T.C., and J.W. Gilliam Riparian losses of nitrate from agriultural drainage waters. J. Environ. Qual. 14: Jordon, T.E.,.L. Correll, and.e. Weller Nutrient intereption by a riparian forest reeiving inputs from adjaent ropland. J. Environ. Qual. 22: Lakslunan, B An eosystem approah to the treatment of wastewaters. J. Environ. Qual. 8: Lin, s Nonpoint rural soures of water pollution. ep. Registration and Edu. Cir. III. p State water Survey, Urbana, Ill. r r { 19

21 Loehr, R.C Charateristis and omparative magnitude of nonpoint soures. J. Water Pollut. Control Fed. 45: Lowrane, R.R Nitrogen outputs from a field-size agriultural watershed. J. Environ. Qual. 21: Lowrane, R.R., R.L. Todd, and L.E. Asmussen. 1984a. Nutrient yling in an agriultural watershed: I. Phreati movement. J. Environ. Qual. 13 : Lowrane, R.R., R.L. Todd, J. Fail, Jr., o. Hendrikson, Jr., R. Leonard, and L. Asmussen. 1984b. Riparian forests as nutrient filters in agriultural watersheds. Biosiene 34: Mikkelsen,.S., and S.K. e atta Ammonia volatilization from wetland rie soils. p In Nitrogen in rie. IRRI, Los Banos, Laguana, Philippines. Moore, P.A., Jr., J.T. Gilmour, and B.R. Wells Seasonal patterns of growth and soil nitrogen uptake by rie. Soil Si. so. Am. J. 45: Moore, P.A., Jr., K.K. Baugh, R.J. Norman, B.R. Wells, and R.S. Helms Nutrient runoff from rie fields. p In B.R. Wells ed.) Arkansas Rie Researh Studies Ark. Agri. Exp. Stn. Res. Ser Patrik, W.H., Jr., and K.R. Reddy Fate of fertilizer nitrogen in a flooded rie soil. Soil Si. So. Am. J. 4: Peterjohn, W.T., and.l. Correll Nutrient dynamis in an agriultural watershed: Observations on the role of a riparian forest. Eology 65: Peterjohn, W.T., and.l. Correll The effet of riparian forest on the volume and hemial omposition of basef low in an agriultural watershed. p In.L. Correll ed.) Watershed researh perspetives. Smithsonian Institution Press, Washington, o.. Reddy, K.R., and W.F. ebusk seleted aquati marophytes. Nutrient removal potential of J. Environ. Qual. 14: Reddy, K.R., and W.H. Patrik, Jr enitrifiation losses in flooded rie fields. p In s.k. e atta and W.H. Patrik, Jr. ed.) Nitrogen eonomy of flooded rie soils. Martinus Nijhoff Publishing Co., ordreht, The Netherlands. Reddy, K.R., W.H. Patrik, Jr., and R.E. Phillipe Evaluation of seleted proesses ontrolling nitrogen loss in a flooded soil. Soil Si. so. Am. J. 44:

22 Sharpley, A.N., and S.J. Smith Predition of bioavailable phosphorus loss in agriultural runoff. J. Environ. Qual. 22: Sharpley, A.N., s.j. Smith, O.R. Jones, W.A. Berg, and G.A. Coleman The transport of bioavailable phosphorus in agriultural runoff. J. Environ. Qual. 21:3-35. Soltanpour, P.N., J.B. Jones, Jr., and S.M. Workman Optial emission spetrometry. In A.L. Page et al. ed.) Methods of soil analysis. Part 2. 2nd ed. Agronomy 9: Stanford, G.,.e. England, and A.W. Taylor Fertilizer use and water quality. ARS publ USA, Washington, o.. Tehnion Industrial Systems. Industrial method no. Tarrytown, NY. 1973a. Ammonia in water and waste water. 98-7w. Tehnion Instruments Corp., Tehnion Industrial Systems. 1973b. Nitrate and nitrite in water and waste water. Industrial method no. 1-7w. Tehnion Instruments Corp., Tarrytown, NY. Tehnion Industrial Systems. 1976a. Ortho-phosphate in water and waste water. Industrial method no. 94-7w/b. Tehnion Instruments Corp., Tarrytown, NY. Tehnion Industrial Systems. 1976b. Individual/simultaneous determination of nitrogen and/or phosphorus in B aid digests. Industrial method no a. Tehnion Instruments orp., Tarrytown, NY. Tilton,.L., and R.H. Kadle The utilization of a freshwater wetland for nutrient removal from seondarily treated wastewater effluent. J. Environ. Qual. 8: Water Resoures Committee Soil siene in relation to water resoures development: IV. Responsibility of soil siene in water quality improvement. Soil Si. So. Am. Pro. 34: Wells, B.R., R.J. Norman, and R.S. Helms Rie grain and dry matter response to nitrogen and water management. Ark. Farm Res. 372):13. Wells, B.R., and F.T. Turner Nitrogen use in flooded rie soils. p In R.. Hauk ed.) Nitrogen in rop prodution. ASA, CSSA, and SSSA, Madison, WI. Wilson, Jr., C.E., R.J. Norman, and B.R. Wells Seasonal uptake patterns of fertilizer nitrogen applied in split appliations to rie. Soil Si. So. Am. J. 53: r f 21

23 a lj l -- ~ Cl s..-~~~~~~~~~~--,-~~~,,.,,..~lfe..,--,m~. 1~"~1 4 A +F11t. t. t911 *M J ,...,,,.. 1llO E ~ e GI u 82 z... J: z -- :::.. g.2 i! 12 1 B Cl i u C.) ~ 4 J: z ays After Flooding - BralSl\aw, AoW\atl *Flsner;1992 Fig. 1. Seasonal hanges in NH4-N onentration in rie irrigation water during 1991 A) and 1992 B)

24 3.5, , ~. 3 ::;- 2.5 Cl g 2 ;:: jg Cll I.I z a" z ~ Cl 2.. 1ii E.5 QI I.I ~1 z.5 A ~"""-" 1M1' w&j, ,_,..Tl 1te O A O " - o ' I I.. o o O.,, o t o o <... t B -Reinhlllf Br dahaw, *Fisher. Tllll2 { ays After Flooding 52 Fig. 2. Seasonal hanges in N~-N onentration in rie irrigation water during 1991 A) and 1992 {B). 23

25 L..J..5 :::.i Cl.. : -e : 1 GI u z ~ 2.s ~~~~- -s.,,,..,,..,..,..,.., A Fiteh t, tllt *" &J. Ul1 ~,,.. '" s ~ F".en«,, ~ Cl g i! GI 8 1 ~ z z B Relative istane % * Aoirllwt. I " l Fig. 3. respet Changes in NH 4 -N onentration in rie irrigation water with to relative distane from the well during 1991 A) and 1992 B). 24

26 ,-..., 2 ~ -- en e i u 8 1 z., z -- ~ C'I. e o.a Cl> u 5 u o.s z... ~.4 A B ~"...,...,...,,... ~ Tr... '" Fi9llol.1'2 +1t11hNW. ton *Aoonhon. 1ooa I ~ ". ~ ' & s 25 so Relative istane %) Fig. 4. Changes in NOrN onentration in rie irrigation water with respet to relative distane from the well during 1991 A) and 1992 B). 25

27 LJ r.6 A -IUff'lfft... tm1 ~'1tM *N&J, :::.i g.4 -e.3 GI u u z..2 ~.1 Fig. rie 1991 o~~-'--~.. ---'~-...i...~-l----j r _...,fj,,...,~--. -, <1111~... tll.:r 8 *Reima j -e 'E.8 GI u : ).6 z ' ~.4.2 o. --..i..- ~---! : l Relative istane %) 5. Changes in soluble reative phosphorus P4-P) onentration in irrigation water with respet to distane aross the field during A) and ). 26

28 .25..-~~~~~~~~~~~-:::,_:..,...=::=.~ Cl E ~.15! Cll u : 8.1 z ; fl. A ,...,,...,,... *"'.J '"'. ~.. ;;i, FilChllr. 1' eHhaw 1"2 8 *Rei~ 1w.I.2 to,... I I Io I... I O O o,.a :::.i C) E -;;; ~ ~ i 'E Cll u : z ; fl ays After Flodfng Fig. 6. Seasonal hanges in soluble reative phosphorus Po 4 -P) onentration in rie irrigation water during 1991 A) and 1992 B). 27

29 A l r -:: Cl..5. i s... i u z o.s... -NH4-N..._N3 N *Total so S NH4-N N3-N Total N S... - ::.. Cl..1.S i 5i u z o.s so Relative istane%) Fig. 7. Conentrations of NH4-N, N~-N, and total N in rie irrigation water from a well A) or atfish pond B) with respet to relative distane from the soure. 28

30 :::~-= P4-P +Total P A - '.:J Cll _g> g ~ GI ~ ) O' ' ~.,,--~ P4-P +Total P B.1.. r f -'.:J. Cll.. =e.6... GI u ).4... ~. t t I O' l Relative istane %) Fig. 8. Conentrations of soluble reative phosphorus P4-P) and total P in rie irrigation water from a well A) or atfish pond B) with respet to relative distane from the soure. 29