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Home , Leaching (agriculture), Soil, Soil chemistry

OF AND FROM THE PROFILE D. V. Calvert1

Great concern has been expressed in recent years source of as the principal contributor in view of on the possible of our waterways with the constancy of seasonal outputs from and pesticides originally applied in agricultural treatment . endeavours. Ecologists have charged that fertilizers are It has been speculated that enrichment of serious polluters of the environment (8). Considerable waterways would be greatest in areas composed mainly anguish was brought to the agricultural community by a of sandy and intensively sprayed and fertilized cash proposal made by the Illinois Control Board (22) to limit such as exist in Florida (19). This speculation appears the amount of nitrogen that can be applied to Illinois to be at least partly right when we turn our attention to the cornfields. Data to substantiate these charges and proposals results of research studies conducted in Florida. For of legislation were not available in many cases. Many example, Calvert and Phung (4) reported lossesof nitrogen immediate investigations of our management practices from a newly developed grove near Fort Pierce, Florida of will be necessary to find what production practices have approximately 35% of the applied nitrogen. Forbes et a/. to be modified in order to assure that from (12) reported NO3-N concentration in soil from agricultural sources is kept at a minimum if the nation both cultivated and uncultivated deep sandy soils of Florida is to meet the 1985 goal of "the concept of zero - to range from 1 to 17 ppm at the 12O-cm depth. The discharge" as conceived by the Environmental Protection concentrations are similar to the 0.3 to 8 ppm NO3-N Agency (9). rangepreviously reported (4). Graetzet a/. (13) in Florida It appears that fertilization practices have affected found that approximately 45% of the nitrogen applied to the nutrient content of some waterways, based on a millet planted on Eustis fine leached below the number of recent research reports. For example, Bingham zone. This soil is -drained and has little biodegradable et al. (2) found that both water and nitrate- in the lower horizons, hence it was speculated that nitrogen (NO3-N) losses from a 389 hectare (960 acre) microbial did not occur. Studies conducted citrus watershed near Riverside, California were substantial, by the Central and Southern Florida Control District representing 40 to 50% of the water entering the watershed (7) have shown that average concentrations and about 45% of the nitrogen applied each year as ferti- tend to increase with increasing "drainage ". This lizer. Harmeson and larson (14) and Harmeson et al. (15) "drainage density" index is simply the total length of reported that the nitrate content of surface in defined waterways (both natural and manmade) within Illinois sampled prior to 1956 did not exceed the USPS the watershed divided by the watershed area. Drainage Standard of 45 rng per liter. This standard has since been density consequently provides a valid general indicator equalled or exceeded in at least 9 major streams. High of phosphorus concentrations since the type of agricultural nitrate concentrations were associated with areas of land used is basically the same. intensive agricultural production where soils were Soil residue studies conducted by Tucker well-drained, fertile, rich in organic nitrogen and where and Phillips (24) indicate that used in groves high levels of nitrogen were applied. Increased on Florida's deep at recommended rates are nitrate concentrations were correlated with increased dissipated to a large extent before reaching ground water stream flow, both reaching maximums during late winter levels. Similar studies are in progress on bedded groves in and early spring with minimums attained in late summer Florida's flatwoods. Wheeler et aI. (26) found that neither and early fall. This pattern would suggest an agricultural acarol nor chlorobenzilate miticides had significant long- lasting effects on soil microbiological populations and that both chemicals had rapid rates of disappearance from the 1Associate Professor of Soil , AgricultUral Research 2 flatwood soils studied. Center, IFAS, University of Florida, Fort Pierce. The main purpose of my talk today is to review 78 the nutrient and movement studies conducted designs, open and submerged drains, had little, if any, effect in conjunction with the SWAP drainage investigation near on nutrient and pesticide movements (4, 25). Nitrate-N Fort Pierce, Florida. It will be my pleasure to personally concen~rations were only slightly lower in submerged lines show you our facilities for conducting the SWAP related than in the open drains. concentrations and research for those accompanying us on the Short Course orthophosphate-phosphorus (PO4-P) discharge were Tour. I would like to briefly explain the SWAP drainage essentially the same from both types of drains. research study in relation to the pesticide and nutrient Our greatest differences and probably most movement studies for those not remaining for the tour. meaningful results from the study have come as a result of The SWAP project is,a cooperative research effort the treatments imposed in the SWAP drainage area. of the Agricultural Research'Service of the United States Briefly, we have found the nutrient movement resulting Department of and the University of Florida from the 3 tillage treatments to be as follows: Greatest Institute of and Agricultural Sciences. Its primary leaching losses through the soil profile for both PO4-P and objectives were to evaluate systems of water management NO3-N have occurred from the ST plots. Concentrations and tile drain sludge control on Florida flatwood soils of PO4-P appearing in the drainage water from ST plots (spodosols). The research project is entitled Soil-Water- were higher than expected and may indicate fixation - relationships (SWAP) and was established mechanisms occur to a lesser degree in the A horizons of by the U. S. Congressin January, 1968. The SWAP drainage Oldsmar fine sand than other associated soils (3). Both DT study at the ARC Fort Pierce basically is a 25-acre and DTL plots leached very little PO4-P into drains, Iysimeter study on production and management of citrus apparently due to the greater surface and chemical groves on tile-drained flatwoods soils. for retention of PO4-P provided by the deep tillage. The We took advantage of the highly organized and DTL treatment did give significantly more NO3-N developed cooperative drainage study to intensify our movement into the drains than the DT treatments which efforts to investigate the possible losses of pesticides and wa~ probably due to the higher rate found for fertilizer from citrus groves on these types of soils, aided the DTL soil (20). by a research grant sponsored by the Environmental Not only have concentrations of nutrients in the tile Protection Agency. The SWAP field study was designed to out-flow water varied considerably with tillage treatments, investigate the effect of 3 types of land preparation and 2 but they have also varied with amount of discharge water, drain line designs on the growth of 12 different citrus scion- rate and time of fertilization (3) (Table 1) and season combinations. We have a total of 9 plots made up (Tables 2 and 3). Monthly NO3-N concentrations in the of 3 replications of each of 3 tillage or land preparation drainage water from the SWAP tillage treatments did not treatments. Tillage treatments are DT (deep tillage), DTL exceed 8 ppm in the period May, 1971 through April, (deep tillage plus ) and ST (surface tillage). Deep tillage 1972. The United States Public Health Service has selected was accomplished with a tile trencher to a depth of 106 cm 10 ppm NO3-N as the critical limit above which water is (42 inches) continuously across the for each considered unsafe for drinking purposes (6). Concentrations hectare plot (2.5 acres). Deep-limed plots received 55 tons of PO4-P in the waters from DT and DTL were very low per ha (25 tons per acre) of dolomitic agricultural limestone (0.4 ppm) while concentrations ranged from 0.2 to 0.9 ppm before deep mixing. in ST water (3). There was a trend for both NO3-N and The objectives of this study are multiple and I will PO4-P to increase in concentration with increase in deal today with only those allied to nutrient and pesticide rainfall, particularly in the summer months. Nutrient monitoring. Three research objectives along these lines were concentrations in drainage water sampled from the to 1) monitor the loss of surface-applied fertilizers and surrounding perimeter ditch system and from the drains of pesticides through and drainage from a citrus a non-tilled non-agricultural (check treatment) area nearby grove located on Florida flatwood soils, 2) establish and in the water at the discharge outfall for the overall -line (background) data for concentration levels of project generally were much lower than that found in the agricultural chemicals for the area under investigation drainage water from the tilled and cropped areas. The and 3) evaluate the effect of selected carefully defined outfall sump water did not exceed 2.5 ppm NO3-N in the agricultural management systems upon pollution of soil peak period of August, 1971 (unpublished data, Florida water. Agricultural Experiment Station). Now I would like to briefly review with you some of The lower concentration of in the ditch the results we have obtained toward meeting these and outfall can probably be explained by phosphorus objectives. fixation with materials in the ditch banks and by its by plants in and near the water. There is also a NUTRIENT MONITORING (LONG TERM STUDY) dilution effect caused by water coming from unfertilized areas. are probably assimilated by absorption by First, we found that our 2 different types of drain plants and by denitrification in the near-anaerobic con- 79 ditions of the ditd1 bottom. The. results are similar to TIbI. 2. Me.n concentretlon and drain dilCh.~ per month of N. those obtained in e cooperativestudy betweenthe u. S. P end K under 3 ~ of soil m8\8g8ment during Mev thr~ Geological Survey end the Centrel end Southern Floride Octob.- 1971.XV Flood Control District of the Chandler Slough (7, 17) Meen whid1 indicated thet a segment of undistu~ mersh Soil Concentration dildta9 8t the lower end of the wetershedis effective in reducing EI8Inent tr881ment Meenz R8IgB /monthz the phosphorusconc»ntretions. Phosphorus concentrations were reduced 25% to 55% in the water after flowing me/llter qn.. N~-N ST 5.02 . 0.68-7- 4.84 . through the marsharee. DT 2.04 b 0.32-3.15 1.19 b Totel disd1..ge of nutrients is a function of both DTL 4.07 . 0.75-7.34 2.28 b nutrient concentrationand volume of water flow in a given period. I am indebted to E. H. Stewart, USDA-ARS PO4-P IT 0.83 a OA7-{}.90 0.68 . Hydrologist at the SWAP drain. site, for supplying us DT 0.27 b 0.10-0.38 0.16 b DTL 0.17 c o.OO-4-~ 0.10 b with a continuous record of weter flow from e8d\ drain line and for surface runoff values for each tillage plot, K ST 7.66 a 4.0-12.4 7:'- . as well as a reco'rdof the total flow from the overallSWAP DT 8.15 . 4.5- 8.80 3.17 b area during the periods when the nutrients and pesticides DTL 4.46 . 2.2- 6.Y 2.»b were monitored. Results of the hydrologic studi" conducted et the SWAP site have been Sl.Hnmarizedel.- XRep"oduced from the Journal of Envlronment8i Ouellty, 412): where (1, 23). Mean monthly disd1argesof NO3-N and 186, 1976, by penn_Ion of the Amerlc8n SocIetY of AeronCMnY PO4-P in the drainagewater ~re generallygreater from 13). the ST treatment than either DT or DTL treetrnents (3) (Table 1), Peak disd1argesof both nutrients were obtain.t YHigh reinfe" period. during August, 1971, es shown in Figs. 1 and 2; this coin- ZMeen, follo~ by dlff8r8ftt 1ett8n are ,i~lflcently different cided with a large epplication of fertilizer prior to (P-o.06),. Irldic818dbv Duncen',multipte ~ test. est~lishing a covercrop for erosioncontrol. Meenmonthly

T~e ,. Fertilizer N. Pend K eppliedlheend -ter dilctlarved T.~. 3. Me.n concentr8tionand dr8/n dischargeper month of N. from 3 . tr881menu.K P and K under 3 ~ of soil managementduring Novemt»r -w;u~~~ - 1971thr~ ApiJ 1972.xy F8ftiIiZ8r -'P'ied Det8 N P K ST DT DTL Mean -- Soil Concentmion dilCh~ kg/ha m3Jha Elen.nt u.tment Meetlz R8ng8 lmondtz 1971 M8Y 3.87 1.~ 3.21 222 247 126 malll- kglha June 7.90 3.45 8.66 1,398 790 879 N~-N IT 1.51 a 0.40-2.81 0.62 a July 7.90 3.45 8.66 768 ~ 513 OT 0.72 b 0.43-1.00 0.23 b Aupt 41.60 18.11 34.45 1,385 818 70S OTL 1.20 a 0.8-2.00 0.29 b Sept8mber 10.32 1.13 8.67 804 431 339 October 10.32 1.13 8.57 883 572 541 PO4-P IT 0.428 0.19-0.70 0.18 . M.n 876 677 484 DT 0.07 b 0.02-0.30 0.02 b DTL O.OO7c 0.00-0.01 0.01 b 1972 F8bru8Y 10.32 1.13 8.57 787 628 432 K IT 2.76. 1.01-4.10 1.48 8 April 10.32 1.13 8.57 886 523 391 DT 3.73 . 2.0 -5.20 1.38 . Mev 10.32 1.13 8.57 836 672 468 DTL 3.12 . 1.6 -5.20 0.92 b Jun. 16.68 1.73 13.03 3.325 1.889 1,369 July 15.68 1.73 13.03 677 486 388 ~ 1,278 769 em XReproduced from the Journal of Environmental Quality, 4(2): 185, 1975, by permiliion of the AmericM SocIety of Aeronomy (3). XReproduced from the Joumel of Envlronment8 Quel/ty.4(2):184. 1975. by perm_Ion of the ~rlcan SocIety of A,onomy (3) y Low r8inf81 period.

ZFr~ ~ supplied by E. H. S~rt. USDA-ARS.Aer. R8. ZM... fotlo_d by different Ien.n are li~iflC81tly different c-n." FortPIerce, Fl. (P-o.05), . Indic8t8d by Duncan', multiple range teat. 80

NO3-N discharges for May through October, 1971 (wet period) amounted to 4.8 kg/ha for ST, 1.2 kg/ha for DT and 2.3 kg/ha for DTL treatments (Table 2); while mean monthly discharges for the low rainfall period of Nov- ember, 1971 through April, 1972 amounted to 0.6 kg/ha for ST, 0.2 kg/ha for DT and 0.3 kg/ha for DTL (Table 3). Mean monthly PO4-P discharges were in the order of 0.6 kg/ha for ST, 0.2 kg/ha for DT and 0.1 kg/ha for DTL in the high rainfall period and 0.2 kg/ha for ST, and 0.02 kg/ha for DT and 0.01 kg/ha for DTL in the low rainfall period. Nitrate-nitrogen losses in the subsurface drainage water from the ST, DT, and DTL plots were to 31.9, 8.3 and 15% respectively, of the nitrogen applied in the fertilizer (3) (Table 4). Orthophosphate-P losses from the DT and DTL plots were considerably less than MONTHS from the ST plots. Those losses were equivalent to 14.2. Fig. 1. The effect of 3 soil preparation treatments on N~-N 3.4 and 2.0% of the phosphorus applied to the ST, DT. discharged in drainage water during May, 1971 through July, DTLpiots, respectively. 1972. [Reproduced from the Journal of Environmental Quality, 4(2):184, 1975, by permission of the American Society of INTENSIVE STUDIES OF NUTRIENT LEACHING (3)].

Several short-term intensive studies on NO3-N, PO4-P and pesticidelosses in both surfaceand subsurface drainagewater from the 3 SWAPtillage systemshave been conducted in the past 2 years (5). The pesticide portion of these studies will be summarizedseparately. These studies were conducted during the drier portions of the years so that we cou1d control the water () variable more preciselY- Losses were examined after applying irrigat.ionsamounting to 12.9,7.6,5.6 and 3.&cm of water and fertilizations amounting to 530 kg per ha of an 8-2-8 (42 kg/ha nitrogen as amR1oniumnitrate and 50 kg/ha PO4-P as superphosphate)fe~tilizer and nominal applications of 2,4-D, chlorobenzilate and terbacil. An ex~ption was the 5.6-cm irrigation period when plots MONTHS were not treated with fertilizer and pesticidesprior to irrigation. The preceding fertilization had been made 2 Fig. 2. The effect of 3 soil prep.-. treatments on PO4-P (ortho- months prior to the 5.6-cm irrigation. Each intensive phosphates) discharged in dr.~ ~er during May, 1.971 through July, 1972. [Reproduced from the Journef of study period lasted 14 days, commencingwith fertilization Environmental Quality, 4(2):184, 1975, by permitSion of the and immediatelyfollowed by irrigation. American Society of Agronomy (3)]. A series of smooth nutrient concentration and dischargecurves with well-defined peaks were obtained Table 4. Estimated loa of nutrienU In drainage ~er from ploU from these studies (5). Examplesof the type of curve under 3 systems of expreaed as % of total obtained by intensive sampling are presentedin Figs. 3 nutrientS applied.z and 4 for NO3-N and PO4-P dischargesin the subsurface drainagewater during parts of May and June, 1974 (12.9 Soil treatment cm of irrigation was applied on May 21). We are hopeful NO3-N PO4.p K that these curves will be useful in the formulation of mathematical models having predictive value for future leachingevents. ST 31.9 '..2 62.3 DT 8.3 3.4 35.5 Surface-tilled plots .gave greater NO3-N dis~ari8s DTL 15.0 2.0 23.2 (Table 5), 14.4 kg/ha NO3-N, in the 14-day period after the 12.9-cmirrigation than either DT or DTL, which were ZReproduced from the Journel of Environmental auelity, 4(21:185, 0.6 and 4.8 kg/he NO3-N, respectively.Discharges from 1976, by permillion of the American-Society of Agronomy (31. 81 DTL were higher, however, than from DT, probably becausethis mixed and limed soiJhas a higher nitrification

rate, as Phung showed (20). ST plots dischargedup to _I 00 0.38 kg/ha PO4-P in the 14-day period following the .. . ~ 12.9-cm irrigation, but phosphatedischarges from DT and .. 80 DTL were only 0.07 and up to 0.11 kg/ha PO4-P in the ~... ~ 60 14-dayperiod, respectively(5). E The contribution of surface runoff water to the ~ z overall nutrient enrichmentof the ditch water was low for ." 40 0 ...\ the DT plots, less than 0.65 kg/ha NO3-N for DTL and Z r D~~&~ less than 0.44 kg/ha for DT after the 12.9-cm irrigation, 20 IT and was zero for ST since there was no runoff from the ST areaduring any of the irrigation studies(5). 21 -22-~ .." i6 21 L" 30 31 MAY JUNE It was especially interesting to find that drainage 1974 from the 5.6-cm irrigation without fertilization did not Fig. 3. leaching r8P0nte of NO3-N to r.lar grCNe fertili~8tion initiate significant dischargeof nutrients from the profiles. ~d 12.9 cm of irrigation. [Reproduced from the Journal of This tends to indicate that time of fertilization definitely is Environmental Quality, 512):lln press), 1976, by permission of one of the factors causingenrichment of the tire outflow. the American Society of Agronomy 15)). Estimatedpercentage losses of NO3-N were sizable from the 12.9- and 7.6-cmirrigations for both ST and DTL treatments (5). ST lost nitrogen equivalent to 34.0% and 12.6%, respectively,of the nitrogen appJiedin fertilizer While DTL losses were equivalent to 12.9 and 8.3%, respectively,of the appliednitrogen after the 12.9-and 7.6- cm . Loss of PO4-P from ST was 3.7 and 1.3% of applied phosphorousand 1.3 and 0.1% from DTL after the 2 irrigations, respectively. Losses of NO3-N and PO4-P generallywere insignificant for the 5.6- and 3.8.cm irrigations (5).

PESTICIDEMOVEMENT

Water samptes collected during each of the intensive study periods were divided into 2 parts, one for nutrient analysis and the other frozen and delivered to Willis Wheeler. Associate Professor in the Food Science Department in Gainesville. Dr. Wheeler was responsible for the determination of pesticide content of the water through - chromatography. Pesticides used for Table 5. To~ dischwge of NO3-N and PO4-P in subsurl- this study were chlorobenzilate, a miticide applied to citrus drainage ~er in respon. to 4 irrigation arnounts.z trees and used at a rate of 1.4 kg/ha; 2,4-0 applied at a rate - of 3.7 kg/ha in a 1-m swath over the "pop up" sprinkler Amount of i~on""e"'"' Soil - .,.,Ji8d (cm.""~~: ' irrigation system at the SWAP site; and terbaciJ applied at treatment12.9 7.6 5.6 - 4.5 kg/ha applied as a 3-m band around the base of the trees. The pesticide-movement results selected for ka/haN93.-N discussion today were collected during and after the 12.9 IT ".4 5.3 2.2 0.9 cm irrigation previously discussed in the nutrient studies. OT O;8;c 0.4 0.001 0.01 DTL 4.8 3.2 0.1 0.01 The chemicals listed above were applied on March 5, 1974 g/haPO4-P and irrigation of the plots started several hours thereafter. ST 388 136 -64.0 42 Irrigation continued for 39 hours until a total of 12.9 cm DT 72 5 0.4 T~ of water was applied to the plots. Water samples were taken DTl 107 4 3.0 T~ when flow started in the drains and every 2 hours thereafter for a period of 60 hours; then one sample per day for 7 ZReproduced from the Journal of Environmental Quality, 5(2): more days and then 2 samples were collected per week (In p~), 1976, by permission of the Amef'ican Society of Agro- thereafter. nomy (5). 82

Data obtained during the first 26 hours of sample rapid in DTL and DT than in undisturbedsurface soil and collection illustrate some trends of how pesticides can undisturbed spodic (organic layer) horizon. Phung migrate downward through soil when applied to the surface (20) also found that the content of the drain of a sandy soil. Terbacil was found in highest concentration outflow water was considerablyhi~er in ST than in DT or in the DTl water initially, and it remained highest DTL and that submergedvs open drain outflows wereonly throughout the initial 26-hour period (25). ST was initially occasionally different. quite low in terbacil followed by rapid increase over the Fiskell and Calvert (10) made a comprehensive study sampling period, with a peak at 20 hours. The DT of the chemicalproperties of ST. DT and DTL profiles with treatment remained low and fairly constant in terbacil ~ple cores to 10 depths per treatment. Soil cores were throu~out the the 26-hour period studied. Maximum 15 cm long and weretaken to a depth of 150cm. They terbacil found in the drainage water in this study were noted that depth of dolomitic lime incorporation 124, 110 and 60 parts per billion for the ST. DTl and drastically affected nitrification and they attributed to DTl treatments, respectively. nitrate formation the pH changes found after The DT soil treatment drainage water exhibited a incubation. Only 14 tons/he of free dolomite higher 2,4-0 concentration than did the other 2 treat- remained after 2 years from the original 55 tons/ha applied ments (25). The DTl treatment drainage water showed hence they attributed this loss to denitrification and soil the lowest concentration; this being sharply divergent reaction which would explain the rather high levels from the terbacil situation. Maximum 2,4-D concentrations found in the drainage water over this period. in the drain. water during the 26-hour period were Fiskell and Calvert (10) further showed that approximately 110, 48 and 35 parts per billion for DT, redistribution of from the A (surface) and DTL and ST. respectively. Bh (organic hard pan) horizons by deep tillage hid 25% Chlorobenzilate has not been detected so far in any v..iability to the 105-cm depth end that the sum of of the water samples analyzed (25). Sampling and analysis exchangeable cations (field CEC) to the 75-cm depth was have been continuous for the last 2 years and this material in the order DTL > DT> ST. has been applied several times during this period. Studies conducted by Fiskell and Mansell (11) on Pesticide concentration data for the open drains phosphorous retention showed that deep tillage of the exhibited differences in some cases and similarities in spodosol increased Langmuir maximum from 6 others. The DTL treatment showed the lowest levels of to 96 ppm with a further increase of about 20 ppm for terbacil while the DT and ST treatments had comparable DTL soil. They also noted that phosphoroussorption levels. DTl was the highest, however, for submerged increased with contact time for the unmixed organic pan. drains. The open-drain data for 2,4.D was similar to that DT and DTL ~ples. bu~as most rapid for the unmixed presentedearlier for the submergeddrains (25). surface horizon and the top of the organic pan horizon. They did not show that incorporation of limestoneused in RELATED STUDIESCONDUCTED IN THE FIELD, DTL influenced the quality of phosphorous leached from GREENHOUSE, AND LABORATORY the soil over the DT treatment (without deeply placed limestone). Other studies, both on and off the drainage site but Kanchenasut(16) in her laboratory investigationsof supporting the pesticide and nutrient move~ent research the ST profile showed thet sorption of phosphorous by the at the site, have been conducted in several departments soil did limit the movement of phosphorous as the soil on the main campus in Gainesville. These studies are solution moves through weter-saturated cores from the designed to supply information to help explain the surface (A1) end spodic (B2h) horizons. Water desaturetion differences among treatments obtained at the field site. tended to decreese the mobility of phosphorous in these 2 I would now like to point out a few of the supporting horizons even further. Mobilities for phosphorousend studies that have been carried out. were similar and rapid during water flow through Phung and Fiskell (21) found that oxygen depletion cores from the subsurface (A2) horizon. in poorly-drained soil profiles is followed by denitrification Mansell et 8/- (18) observed in enother study using and ferrous and manganous-manganeseproduction soil from the SWAP site that water-soluble herbicides such prior to sulfide production. as terbacil were very mobile in the A2 horizon (white sendy Phung (20) found that factors involved in oxidation- layer directly under the surface layer). even for the low reduction changes in the 3 soil modifications were 1) source concentrations of herbicides applied to the soil. of organic matter as , 2) a rapid loss of nitrate in the These are only a few of the studies conducted in top 6 inches of soil compared to a slow loss in the black conjunction with the SWAP drainage site. There were many spodic horizon when the soil is flooded and 3) ferrous iron other studies conducted in the past few years that are not and sulfide dev,lopment was found to be more reported here, especially in relation to the study of water 83 flow through the 3 soil managementsystems (), low concentrations, nearly zero, observed in water from the check area during identical time periods. The higher SUMMARY overall nutrient content from the grove area would confirm that the agricultural practice of fertilization does increase Our results from the leaching studies show that nitrogen and phosphorous nutrient concentrations in the drainage of the 3 soil management systems are greatly water. However, the lower concentrations in the perimeter different. Drainage rates for tile in the ST plots are much ditch and at the outfall shpws that these nutrient higher than for DT and DTL plots. Deep tillage on these concentrations are reduced significantly before being soils tends to incorporate clay and organic materials from discharged into the drainage canals administered by the the layers into the sandy surface soil, thereby Central and Southern Florida Flood Control District. decreasing the of the soil in the Rate of water discharge through the drains had a root zone. Poorer drainage characteristics of DT and DTL considerable influence upon the discharge of flux for both plots provided improved soil- capacities. 2,4-0 and terbacil. Scatter in the data is significant, but the however. There were also increased cation exchange flux of either herbicide appeared to increase from zero up capacities which in turn resulted in larger growth rates for to a maximum or peak zone and decrease down to an young citrus trees than those planted in ST plots. insignificant value. The discharge of pesticide was almost Hydraulic response of the ST soil was particularly complete within approximately 2 days after irrigation rapid and of greater magnitude than for DT and DTL soils. and closely follo~d the disd\arge of drainage water. The Not only were peak flow rates approximately 2 to 3 times magnitude of peak disd\arge flux for 2,4-0 was less than greater for ST drains than for the other drains, but for terbacil. Chlorobenzilate molecules were not detected accumulative drainage of water from ST drains was also in the drain water. more than twice that for DT and DTL. Deep tillage of the Thus, a combination of subsurface drainage and deep tile-drained soil appeared to decrease the magnitude of tillage appeared to offer the advantages of 1) greater maximum drainage rates and prolong "temporary" soil- capacity to retain infiltrated water against drainage loss, water storage over very long periods of time. 2) providing a "buffering capacity" against very fast rates Deep tillage of the tile-drained soil appeared to of rise during rainy periods, but increasing decrease the quantity of NO3-N leached, and this decrease surface runoff over surface tilled and 3) permitting the may be partially due to the net influence of denitrification maintenance of an aerobic, unsaturated root zone which during of NO3-N throu~ the DT and DTL mils. has a large capacity to attenuate leaching lossesof nitrogen Peak loss rates of phosphorous from drain lines and phosphorous, and thus minimize pollution of nearby coincided with those for nitrogen. As expected, deep tillage drainage canals. drastically decreased leaching losses of phosphorous fertilizer. Unexpectedly however, deep of deep- LITERATURE CITED tilled soil did not appear to influence leaching of phosphorous. 1 Alberts, R. R., E. H. Stewart and J. S. Rogers.1971. These and other data suggest that the Ground water recession in modified profiles of of this spodosol provides rapid lateral water flow and tends Florida flatwood soils. Soil Sci. Soc. Fla. Proc. to circumvent flow vertically through the chemically 31:216-217. reactive but slowly permeable spodic horizon. The 2. Bingham,F. T., S. Davisand E. .1971. Water subsurface drainage of this layered spodosol tends to relations, balanceand nitrate leachinglo.s of a increase leaching lossesof fertilizer nutrients. 960-acrecitrus watershed.Soil Sci. 112:410-418. Deep tillage of the tile-drained soil tended, however, 3. Calvert, D. V. 1975. Nitrate, phosphateand potas" to decrease drainage, increase cation exchange capacity of sium movement into drainagelines under three soil the A2 layer and decreasenutrient leaching rates. managementsystems. J. Environ. Qual. 4: 183-186. Our data show that higher concentrations of nutrients 4. and H. T. Phung. 1971. Nitrate- in the drainage water usually followed fertilizations, nitrogen movement into ;:.rainagelines under differ- especially those followed by heavy rainfall. Irrigations of ent soil managementsystems. Soil Crop Sci. Soc. 2 to 3 cm, except where applied excessively for FI.. Pro. 31 :229-232. experimental purpose, and low rainfall apparently had 5. , E. H. Stewart, R. S. Mansell and little, if any, effect on nutrient concentrations in the df'ain J. G. A. Fiskell. 1976. Movementof nitrate and phos- water. Evidently, a quantity of water above the water phate throultt soil and drain tile outlets. J. Environ. holding capacity of the soil is needed, either from rainfall Qual. (In press). or irrigation to initiate significant nutrient movement. 6. Case,A. A., A. Gelperin,P. C. Ward and E. F. Win- The higher concentrations of nutrients observed in ton. 1970. The health effects of nitrates in w8ter" the drainage water after fertilization contrasts with the In: Nitrate and water supply: Source and control, 84 Proc. 12th Sanitary Eng. ConI. Univ. of Illinois, responses. Ph.D. Dissertation. University of Florida, Urbana p. 40-65. Gainesville, 209 p. 7. Central and Southern Florida Flood Control District. 21, and J. G. A. Fiskell. 1972.A review 1975. lake Okeechobee-Kissimmee basin water of redox reactions in soils. Soil Crop Sci. Soc. Fla. quality summary information. March 20, 1975. Proc.32:141-145. 8. Commoner, Barry. 1968. Threats to the integrity of 22. Stanford, George. 1973. Rationale for optimum the nitrogen cycle: Nitrogen compounds in soil, nitrogen fertilization in corn production. J. Environ. water, atmosphere and precipitation. Annual meeting, Qual. 2: 159-165. A mer. Assoc. Adv. Sci. Dallas, TX. 23. Stewart, E. H. and R. R. Alberts. 1971. Rate of 9. Environmental Protection Agency. 1974. Proposed subsurfacedrainage as influenced by criteria for . EPA Office of Water level in modified profiles of Florida flatwood soils. Planning and Standards, Vol. 1. Soil Crop Sci. Soc.Fla. Proc. 31 :214-215. 10. Fiskell, J. G. A. and D. V. Calvert. 1975. Effect of 24. Tucker, O. P. H. and W. F. Wardowski. 1973. The deep tillage, lime incorporation and drainage on Florida citrus industry's commitment to a better chemical properties of spodosol profiles. Soil Sci. environment.J. Environ. Qual. 2:70-74. 120: 132-139. 25. Wheeler,W. B. and R. W. Mansell.1974. Movement 11 and R. S. Mansell.1975. Effect of of chlorobenzilate.terbacil and 2,4-0 through soil P rate, time and profile modifications on P equili. into subsurface-drain line outflow water. J. Agr. bria in a spodosol. Soil Crop Sci. Soc. Fla. Proc. Food Chern.23: (In Press). 34:(ln Press). 26. , O. F. Rothwell and O. H. Hubbell. 12. Forbes, R. B., C. C. Hortenstineand E. W. Bistline. 1973. Persistenceand microbiological effects of 1974. Nitrogen, phosphorus, and soluble acarol and chlorobenzilate in two Florida soils. in solution in a Blanton fine sand. Soil Crop J. Environ. Qual. 2:115-117. Sci. Soc. FIB.Proc. 33: 202-205. 13. Graetz, D. A., l. C. Hammon and J. M. Davidson. QUESTIONS 1974. Nitrate movementin a Eustisfine sandplanted .to millet. Soil Crop Sci. Soc. Fla. Proc. 33:157-160. 0: When you were talking about 2.5 times the 14. Harmeson, R. H. and T. E. larson. 1970. Existing amount of nitrogen needed, you were referring to mature, 1eve1sof nitrates in water-the Illinois situation. bearing trees, weren't you? In: Nitrate and water supply: Source and control. Caillert: Yes, because I was speaking of trees Proc. 12th Sanitary Eng. Con'., Univ. of Illinois, producing 500 boxes per acre (50 tons per ha). Urbana.p. 27.39. 0: What are the standards for nutrient content in 15. , F. W. Sollo and T. E. Larson.1971. water going into drainage ditches and away from the field The nitrate situation in Illinois. J. Amer. Water where it was applied? Aren't some nutrients necessary in WorksAssoc. 63:303-310. the various bodies of water? 16. Kanchanasut.1974. Influence of soil, Calvert: I'm curious about that myself. The only and flow velocity upon miscible displacement of standards I've seen are those by the U. S. Public Health phosphate and chloride in undisturbed cores of a Service, in which 10 ppm is too high in water to be used for spodosol.M. S. Thesis.Soil Sci. Dept. Univ. of Fla. drinking. Beyond that there doesn't appear to be any 17. Lamonds, A. G. 1974. Chemical characteristics standard. of the lower Kissimmee River, Florida. United Regarding nutrients in the water, we actually fertilize StatesDepartment of the Interior, GeologicalSurvey, fish to increase fish size and numbers. The shellfish (USGS).(In Press). industry depends on nutrient-rich water. and the reason 18. Mansell,R. W., W. B. Wheeler,Uta Elliott and Mark it isn't so good around Ft. Pierce is because the drainage Shaurette. 1971. Movement of acarol and terbacil water is flushed out of the area by the inlet. So we may be pesticidesduring displacementthrough columns of trying to prevent something that may prove detrimental Wabassofine sand. Soil Crop Sci. Soc. Fla. Proc. in the long run. We do need to know what levels are 31:239-243. satisfactory or even necessary. 19. Nelson, L. B. 1972.Agricultural chemicalsin relation Ecologists are concerned about nitrates and to environmentalquality: Chemicalfertilizers, pres- phosphates in runoff water because of ent and future. J. Environ. Qual. 1: 1-6. or dying of lakes, due to of and other 20. Phung, H. T. 1972. Reduction processesin modified organic matter which grows profusely under conditions of spodosol systems and their effect on some plant high nutrient levels in the water. Whether man is doing 86 very much to accelerate this process remains to be seen. or so before it dried, while the dry fertilizer would still Certainly, man appears to have some influence on' it. be sitting in granular form on the soil surf~. Too, Q: In the application of fertilizer,. wou.ld there be a subsequent or irrigation would have to dissotve the greater loss of nutrients from liquid or dry formulatioos? nutrients in granular form before soil . Thus, Calvert: This is purely a guess, but I would think the liquid fertilizer would appear to be-better distributed there would be less loss from liquid fertilizer. The re~n and thus better utilized by the plant.. is that the liquid fertilizer could penetrate the soil 1 cm