It can be concluded that secondary treated WW can improve soil fertility parameters, however, more efficient treatment is recommended to reduce salt content.
COMMUNICATIONS IN SOIL SCIENCE AND PLANt'
ANALY:Sl;)
Vol. 34, Nos. 9 & 10, pp. 1281-1294,2003
Changes in Soil Fertility Parameters in Response to Irrigation of Forage Crops with Secondary Treated Waste,yater lVlunir J. lVlohammad1,*and N. I\tlazahreh2 [Department of Natural Resources and the Environment. Faculty of Agriculture, Jordan University of Science and Technology (JUST), Irbid, Jordan 2National Center for Agricultural Research and Technology Transfer, Baqa'a, Jordan
ABSTRA CT Field experiments were conducted to evaluate the effect of irrigation with treated wastewater on soil fertility and chemical characteristics. Three field experiments were conducted at a farmer's field near Ramtha Wastewater Treatment Plant. Corn (Zea mays) was planted for two seasons as a summer crop while vetch (Vicia saliva) for one season as a winter crop. Plots were irrigated with either potable water (PW) or wastewater (WW) in amount according to the following treatments: i) potable water
*Correspondence: Jvlunir 1. Mohammad, Department of Natural Resources and the Environment, Faculty of Agriculture, Jordan University of Science and Technology (JUST), P.O. Box 3030, Irbid, Jordan; Fax: 962-2-7095069; E-mail: mrusan@ just.edu.jo. 1281 DOl: 10.1081/CSS-120020444 Copyright @ 2003 by Marcel Dekker, Inc.
0010-3624 (Print); 1532-2416 (Online) www.dekker.com
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Mohammad and Mazahreh equivalent to 100% class A pan reading (P\V); ii) wastewater equivalent to 100% class A pan reading (WWI); iii) PW with application fertilizer equivalent to Nand P content of WW (PWF) and iv) wastewater equivalent to 125% class A pan reading (WW2). Treatments were replicated 4 times in a randomized complete block design. Soil samples were taken before and at the end of the growing season and were analyzed for soil parameters. WW samples were taken and analyzed periodically for major characteristics. WW analysis indicates inefficient treatment and high values of Biological Oxygen Demand, salt content and reduced form of nitrogen. The results of the field experiments indicate that WW irrigation decreased soil pH and increased soil salinity, soil phosphorus (P), potassium (K), iron (Fe), and manganese (Mn) levels. Soil organic matter increased only in the topsoil and by the highest rate of WW irrigation. This effect could be attributed either directly through the addition of the nutrients and organic compounds to the soil or indirectly through enhancing solubility of soil nutrients. Soil zinc (Zn) and copper (Cu) were not significantly affected by W\V irrigation. It can be concluded that secondary treated WW can improve soil fertility parameters, however, more efficient treatment is recommended to reduce salt content. In addition, proper irrigation management and periodic monitoring of soil quality parameters are required to minimize adverse effect on the soil. Key Words: \Vastewater; micronutrients.
Soil pH; Soil salinity;
Soil macro
and
INTR 0 DUCT! 0 N The demand for water is continuously increasing in arid and semi arid countriesJ1J Therefore, water of higher quality is preserved for drinking purposes while that of lower quality is recommended for irrigation. [2] Municipal wastewater is less expensive and considered an attractive source of irrigation water in these countries. [3] Therefore, the interest in reusing wastewater for irrigation is rapidly growing in most countries. Moreover, irrigation with municipal wastewater is considered an environmentally sound wastewater disposal practice that helps in minimizing the pollution of the ecosystem subjected to contamination by direct disposal of waste water into surface or '-ground waterJ4] In addition, wastewater is a valuable source for plant nutrients and organic matter needed for maintaining fertility and productivity of arid soils.fS]However reuse of waste water for irrigation may poten'tial1y create environmental prt)blems if not properly treated and managed.f6,71
Irrigation with Secondary Treated Wastewater
1283
When wastewater is used continuously as the sole source of irrigation water for field crops in arid regions, excessive amounts of nutrients were simultaneously applied where their accumulation in the soil may cause unfavorable effects on productivity and quality of crops and soil. [8,9] Therefore, management of irrigation with wastewater should consider the nutrient content in relation to the specific crop requirements and levels of plant nutrients in the soil and other soil fertility parameters. In Mediterranean countries such as Jordan, there is an increasing and urgent need to conserve and protect water resources. Water is a vital resource but a severely limited one in these countries. Consequently the reuse of wastewater for agriculture is highly encouraged. [1,10]In Jordan, for example, the available amount of wastewater is expected to reach up to 150 MCIvI in 2010[11] and most of this water has undergone secondary treatment. [12]This relatively large quantity of wastewater has a substantial fertilizer value and is a potential for useful irrigation water. [13-15] Secondary treated wastewater usually contains essential plant nutrients such as N, P, K and micronutrients. On the other hand, wastewater may also contain pathogens, toxic chemical substances above acceptable levels and plant nutrients in excess of crop requirements.[4] Consequently, reuse of wastewater for irrigation can lead to accumulation of these substances in the soils thus affecting their fertility and producti vi ty .
The majority of the research conducted on wastewater reuse in agricul ture focuses mainly on its effect on plant growth and development with little attention to the changes induced in the soil fertility and chemistry parameters. The objectives of this study were to evaluate the fertility and chemical soil characteristics and the possible accumulation of heavy metals in these soils, in response to irrigation of forage crops with treated wastewater.
lVIATERIALS AND METHODS Three field experiments were conducted at a farmer's field located near the Ramtha Treatment Plant in a soil that had never been previously irrigated. Two sources of irrigation water were used to irrigate vetch (Vicia sativa) and corn (Zea mays). Potable well water (PW) and secondary treated municipal wastewater (WW), from the Ramtha Waste water Treatment Plant in Ramtha, Jordan, were used. Plots were irrigated with either potable water (PW) or wastewater (WVV)in amount according to the following treatments: i) PW equivalent to 100% class A pan evaporation reading (as taken periodically from the nearest Meteorological Weather Station) that estimates the water requirement of the crops ii); PWF which is PW plus an application of fertilizer
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Mohammad and Mazahreh
equivalent to Nand P contents ofW\V1 iii); WW1 equivalent to 100% class A pan reading and iv) \VW2 equivalent to 125% class A pan reading. Irrigation in the WW2 was sufficient to ensure that soilleachate percolated beneath the root zone to leach out any possible accumulation of salts contained in the WW. A leaching fraction of approximately 25% was maintained for WW2 treatment through out the study. All treatments were replicated 4 times in a randomized complete block design (RCBD). Nitrogen and P were not applied to the soil except for one treatment (PWF) as designed by the experiment. For this treatment, N was added as ammonium sulfate and P as triple superphosphate. Both Nand P fertilizers were broadcasted into the soil surface before each irrigation at a rate equivalent to their content in the amount wastewater used for the same irrigation as estimated from the class A pan reading. The corn crop was planted as a summer crop for two seasons and vetch as a winter crop for one season. In the first season the corn was, planted in May 1994 and harvested,in August 1994 followed by vetch planted on February 1995 and harvested in May 1995. Then corn was planted again in the same plots in May, 1995 and harvested in August, 1995. Corn was planted in rows, 75 cm between rows and 25 cm between plants at a depth of 6 cm. The plot dimensions were 3.75 X 3111,with five rows of plants in each plot. Vetch was planted at a rate of 120 kg ha - 1 The irrigation \vater was delivered through a closed irrigation lines to the experimental plots where the water was distributed unifonnly. A water meter was installed in the irrigation system for monitoring the amount of irrigation water to be applied. The crops were irrigated twice a week for the summer corn crop and once a week (except during the rainy periods) for the winter vetch crop.
Soil Sampling and Analysis Before seeding, composite soil samples were taken to a depth of 1.2 m from each block. At the end of the growing seasons, composite soil samples were from a depth of 0.30 and 0.6 m from each plot. Samples were air dried, grounded to pass 2 mm sieve. Soil samples were then analyzed for pH and for electrical conductivity (EC) in the saturation paste;[J6] for total Kjeldahl:
nitrogen[I7]; for phosphorus by extraction with 0.5 M NaHCO3[18];for CaCO3 by acid neutralization method[J9]; for exchangeable K by extrac60n with 1M NH4Oac[20];for cation exchange capacity (CEC) by the method described by Polemio and Rhoades[2J] and for soil texture by hydrometer methodJ22] Soil
. .
;
organic matter was measured by rapid oxidation, [23]and Fe, Zn, Cu, and Mn .
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Irrigation with Secondary Treated Wastewater Table 1.
Soil depth (cm) 0-30 30-60 60-90 90-120 a
EC
Selected characteristics of soil at the experimental site.
K(mg
(%)
P (mg kg-I)
CEC (cmol
kg-I)
kg-I)
Texture
12.2 15.2 15.2 14.8
5.2 4.3 2.5 1.9
537.6 438.6 401.5 413.9
32.1 29.1 28.4 24.5
Clay Clay Clay Clay
aNI (%)
CaCO3
pH
ECa (dS m-I)
7.8 7.7 7.7 7.8
0.8 0.6 0.6 0.8
0.48 0.34 -
= electrical conducti'v'ity;OM =
by extractions Table 1.
organic matter.
with DTP A. [~41Selected soil characteristics
are presented
in
Water Sampling and Analysis Wastewater samples were analyzed weekly for physical and chemical variables. The average values over the study period are reported in Table 2. The potable well water samples were analyzed once per season and the average values of the study period are also shown in Table 2. Irrigation water samples were analyzed according to the American Public Health Association (APHA). [25] -
Statistical
Analysis
Analysis of variance (ANOV A) was used to determine the effect of each treatment. When the F ratio was significant a multiple mean comparison was performed using Fisher's Least Significance Test (0.05 probability level). Statistical analyses were performed with SYSTAT Statistical Program. [26]
RESUL TS AND DISCUSSION The amount of irrigation water applied to crops was as follows: 540 mm and 675 mm of treated wastewater for the W"VI and WW2 for the corn '-'grown in 1994 season. The potable water for each of the PW and PWF treatments was applied in amount of 540 which is equivalent to the amount applied to the WWl treatment. For the corn grown in the 1995 season, the amount of potable
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Mohammad and Mazahreh Table 2.
Characteristics of the potable and secondary treated wastewater used for irrigation (mean values over the study period). Parameters (m aka-I)
Secondary treated wastewater
Potable water
7.56 1225 290 49 118 2.9 586 0.14 0.07 ND 0.03 0.04 0.01 ND 0.02
7.9 650 ND 0.03 ND 59 262 ND ND ND ND ND ND ND ND
pH (unit)
TDS BOD5 PO4 NH4 NO3 Cl Fe Mn Cu Zn Cd Cr Ni Pb
'TDS
-
=
total
dissolved
oxv~en demand: ~
ND
solids;
BOD
= nondetectable.
= biological
water and treated.wastewater applied for the treatments P\V, PWF, WWl, and WW2 were 615 mm, 615 mm, 615 mm, and 769 mm, respectively. The vetch crop grown in the 1994 winter season received 74 mm, 74 mm, 74 mm, and 93 mm for the P\V, P\VF, WWl, and v.lW2 treatments, respectively. During the rainy periods irrigation water was not applied. Therefore, vetch as a winter crop received relatively less irrigation water as supplemental irrigation.
Irrigation '" ater Characteristics The wastewater used for irrigation is alkaline with pH value of 7.56 and saline with an average content of total dissolved solids (TDS) of 1225 mg L -] (Table 2). The wastewater contains much higher ammonium compared to nitrate concentration (Table 2) indicating inefficient effluent treatment and incomplete nitrification. [27.28]The inefficient and incomplete oxidation of effluent is also evidenced by high values of biological oxygen demand BaD (Table 2). On the other hand, the higher contents of ammonium, nitrate and
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Irrigation with Secondary Treated Wastewater
phosphate compared to potable water are considered a good source of plant nutrients for improving soil fertility and productivity. Concentrations of heavy metals in the wastewater are higher than in the potable water but remained lower than the recommendedinaximum levels in irri2ation water. However, " their danger is associated with: possible accumulation in soil and plants with continuous use of wastewater in irrigating the same fields. Therefore, they should be periodically monitored in the soil and plants. ~
Soil Characteristics Soil pH at the end of the growing season was significantly lower for both rates of wastewater application compared to both rates of potable water treatments (Table 3). The high content of ammonium in the wastewater resulted in its accumulation in the soil. Nitrification of this ammonium would serve as a source of hydrogen ions which may lead to the decrease in the soil pH. [9,29]Although this decrease in the soil pH might not persist longer due to the higher buffering capacity of this highly calcareous alkaline soil and the soil pH is expected to rise again/91 the crops would probably benefit from this
Table 3.
Soil characteristics of the soil irrigated with potable and wastewater at the end of the study period (% for Nand mg kg -1 for other nutrients). Treatmentsa Parameters
pH EC, dS m-I OM, % N P (NaHCO3-P) K (OAc-K)
..
Soil depth, cm
PW
PWF
WvVl
vVW2
0-30 30-60 0-30 30-60 0-30 30-60 0-30 30-60 0-30 30-60 0-30 30-60
7.71 a 7.80 a 0.81 a 0.95 a 0.51 a 0.50 a 0.07 a 0.05 a 4.3 a 3.5 a 541 a 502 a
7.73 a 7.82 a 0.82 a 0.94 a 0.55 a 0.49 a 0.06 a 0.05 a 4.9 a 4.0 a 533 a 540 a
7.56 b 7.70 a 1.8 b 1.6 a 0.6 a 0.54 a 0.06 a 0.06 a 9.3 b 9.1 b 581 a 638 b
7.51 b 7.80 b 1.6 b '2.0 b 0.73 b 0.56 a 0.07 a 0.06 a 9.9 b 9.2 b 583 a 653 b
Means with different letters within rows are significantly different (p < 0.05). a PW = potable water; PWF potable water with fertilizer added; WW 1and WW2 = lowest and highest wastewater application rates respectively.
Mohammad and Mazahreh
1288
temporal decrease in soil pH during the growing season. Such decrease in the soil pH would enhance solubility and availability of certain nutrients in c:t1careous soils such as phosphorus, Fe~ Mn, Zn, and CU.[30,31]Soil pH was also reported to increase following long term wastewater application[32] where the authors attributed this increase to the chemistry and high content of basic cations such as Na, Ca, and Mg in the wastewater applied for a long period. Wastewater irrigation resulted in significantly higher values for electrical conductivity (EC) of the soil saturation extract compared to soil irrigated with potable water (Table 3). The increase in EC is mainly attributed to the original high level of TDS of the wastewater that would accumulate in the soil with continuous wastewater application. Potable water, unlike wastewater, did not increase the original EC of the soil. Other researchers reported similar increase in the soil EC by wastewater irrigation, [9,33]but contrary to our results they observed an increase in the soil EC even by irrigation with potable water which caused a less increase in the soil EC compared to the wastewater irrigated soil.[34]Both potable water and potable water with the addition of fertilizer had similar effect on soil salinity. The lower rate of wastewater application (W\VI) increased salinity more in the topsoil while the higher rate (\VV.,r2)in the subsoil. The accumulation of salts in the topsoil more than in the subsoil ilTigated with the lower wastewater rate is probably related to evaporation effect and absence of the leaching fraction. The subsoil on the other hand, contained higher salt concentration when soil was irrigated by the higher rate of water application which was probably caused by moving salts deeper into the subsoil by the leaching fraction. [35]The continuous bund up of salts in the soil surface may adversely affect seed germination, seedling establishment and plant growth and may also deteriorate soil productivhy.[4] Increased salinity may also negatively affect activity of the phosphatase enzyme and soil microorganismsl33] which will be negatively reflected on soil productivity. Therefore, addition of the leaching fraction to the irrigation requirement should be considered when wastewater is used for irrigation. .
Soil organic matter was not affected by potable water treatments nor by
wastewater irrigation treatments (Table 3) except by the higher rate of wastewater application which resulted in higher soil organic matter in the top soil, but not in the subsoil (Table 3). Vazquezmontiel et al.[9]found no positive effect on change in soil organic matter with wastewater irrigation, while other researchers reported an increase in the soil organic matter following wastewater irrigationJ34] The soil organic matter in this study was not increased by lower rate of wastewater irrigation which can be partially attributed to the possible decomposition and oxidation of the soil carbon toward the end of the growing season by the introduced microorganisIlls by wastewater.
.
Irrigation with Secondary Treated \Vastewater
l.l(s~
Soil Nitrogen, Phosphorus, and lVlicronutrients Both rates of wastewater increased levels of N, P, K, Fe and Mn in the soil, but not Cu and Zn (Tables 3 and 4). Neither potable water treatment significantly increased any of these plant nutrients. The increase in soil N, P, and K contents with waste water application can be attributed to their high content in the wastewater used (Table 2). On the other hand, although the wastewater contained very small amount of micronutrients, the DTP A extractable Fe and Mn significantly increased in the soil. This could be attributed to the chelation reactions of Fe and Mn with the organic compounds provided by wastewater application, which is considered one of the main mechanisms for enhancing solubility and availability of Fe and Nln in alkaline and highly calcareous soils. [30]In addition, both Fe and NIn are transitional metals that can easily change their oxidation states. The possible reducing conditions created during irrigation periods with wastewater can facilitate reduction of both Fe and Mn into the more soluble and available reduced forms. An evidence of reducing condition created by wastewater application can be considered through the enhanced denitrification with wastewater application observed by~.Schipper et al.[32] Both rates of wastewater application had similar effect on these soil parameters indicating that Table 4. DTPA extractable mlcronutrients and heavy metals in the soil (top 30 cm) irrigated with potable and wastewater at the end of the growing season (mgkg-I). Treatmentsa Parameters Fe Mn Cu Zn Cd Cr Ni Pb
PW
PWF
WWl
WW2
4.5 a 5.8 a 1.6 a 1.8 a 0.12 a 0.01 a 0.52 a 0.82 a
4.3 a 5.9 a 1.5 a 1.8 a 0.11 a 0.03 a 0.55 a 0.79 a
5.9 b 7.8 b 1.5 a 1.9 a 0.09 a 0.03 a 0.44 a 0.89 a
6.4 b 8.1 b 1.6 a 2.0 a 0.23 a 0.02 a 0.48 a 0.91 a
:Nleans with different letters within rows are significantly different (p < 0.05). a PW = potable water; PWF = potable water with fertilizer added; WW 1and WW2 = lowest and highest wastewater application rates, respectively.
Mohammad and Mazahreh
1290
the threshold rate necessary to change these soil paran1eters would be lower than or equal to the lowest rate. [32] Other researchers found that application of wastewater irrigation resulted in additions of N, P, K at about 4, 10, and 8 times, respectively, the recomn1ended fertilizer rates for forage crops. [36]Monnett et al.[37]found that nitrogen and phosphorus removal by wastewater-irrigated crops were 90% and 96%, respectively. On the contrary, Schipper et al.[32]found that total Nand total C were not affected by irrigation with either wastewater or potable water. The variation in these results is mainly attributed to the different chemical characteristics of wastewater used, type of soil, and crops involved and irrigation management adopted. Therefore, it is highly recommended that all these factors be considered when the rate of wastewater application is determined. The concentrations of the DTPA extractable heavy metals such as cadmium (Cd), chromium (Cr), nickel (Ni), and lead (Pb) in the soil after crop harvest were not affected significantly by the irrigation water source. This could be attributed to their very low concentrations in the irrigation water. In addition, fine textured soils have the capacity to treat waste water and retain considerable amount of heavy metals rendering them not bioavailable that commonly measured by DTPA extraction. It has been reported that the treatment capacity of the soil is somewhat fixed and is determined by the physical chemical properties of soil and by cropping system. [38]The soil of our experimental site has a fine texture and a high CEC, therefore, high retention capacity for elements and microorganisms delivered by wastewater irrigation is expected. However, improper (such as overirrigation) application and/or long term application of wastewater may lead to nutrient imbalance, toxicity problems by heavy metals, and soil deterioration or reduction on the soil productivity. Therefore, periodic monitoring of their concentrations in the soil is highly recommended because of the possible accumulation in the soil after continuous wastewater application. In addition, the possible increase in the solubility of the indigenous insoluble heavy metals ia the soil as a result of the chelation or acidification action of the applied wastewater irrigation has also been reported. [4]
CONCLUSIONS vV'astewater application has significant impact on chemical and fertility parameters of the soil. Therefore, characteristics of wastewater and soil should be considered, in management of wastewater irrigation projects. Based on the results of this study, it can also be concluded that continuous application of
Irrigation with Secondary Treated Wastewater
1291
waste water may lead to soil accumulation of plant nutrients and heavy metals beyond crop removal causing a nutrient imbalance in the soil. In addition, seasonal irrigation with wastewater leads to the accumulation of salts in the soil and leaching fraction should be considered to leach out the salts beneath the root zone. On the other hand, wastewater irrigation if properly managed can enhance soil fertility and productivity of the soil through increadng levels of plant nutrients and soil organic matter. Finally, proper management of wastewater irrigation and periodic monitoring of soil fertility and quality parameters are required to ensure successful, safe and long term reuse of waste water for irrigation.
ACKNOWLEDGJ\tIENTS This study was funded partially by the National Center for Agricultural Research and Technology Transfer and by the Research Deanship of Jordan University of Science and Technology.
REFERENCES 1. 2. 3.
4.
5.
6. 7.
Al-Salem, S.S. Environmental considerations for wastewater reuse in agriculture. Water Sci. Technol. 1996, 33 (10-11), 345-353. AI-Rashed, lVI.F.;Sherif, M.NI. Water resources in the GCC countries: an overview. Water Resour. Manag. 2000, 14 (1), 59-73. Arar, A. Water management and conservation measures under semi-arid and arid conditions. In Optimization of vVater in Agriculture, Proceedings of the Regional Seminar, Amman, Jordan, Nov 21-24, 1994; 177. Papadopoulos, I. Wastewater LVIanagementfor Agriculture Protection in the Near East Region; FAO Regional Office for the Near East: Cairo, Egypt, 1995; Tech. Bull. Weber, B.; Avnimelech, Y.; Juanico, M. Salt enrichment of municipal sewage: new prevention approaches in Israel. Environ. NIanag. 1996, 20 (4), 487 -495. Bahri, A.; Brissaud, F. Wastewater reuse in Tunisia: assessing a national policy. Water Sci. Technol. 1996,33 (10-11),87-94. Scott, C.A.; Geohring, L.D.; WaIter, M.P. Water quality impacts of tile drains in shallow, sloping, structured soils as affected by manure application. Appl. Eng. Agric. 1998, 14 (6), 599-603.
1292
8.
9.
10.
11.
12.
13. 14.
15.
16.
17. 18.
19.
Mohammad and Mazahreh
Fuller, W.H.; Tucker, T.C. Land utilization and disposal of organic wastes in arid regions. In Soil for Management of Organic Wastes and Waste"waters: Elliott, E.A., Ed.; SSSA: Madison, WI, 1977; 473. Vazquezmontiel, 0.; Roran, N.l.; Mara, D.D. Management of domestic waste-water for reuse in irrigation. Water Sci. Technol. 1996, 33 (l0-11),355-362. Udluft, P.: EI-Naser, H. Some aspects of 1110dernalternatives and principles of water resources use. Proceedings of Jordan's Water Resources and Their Future Potential Symposium: Garber, A.: Salameh, E., Eds., October 27-28, 1991; Amman, Jordan, 1992; 37. Garber, A.: Salameh, E. Proceedings of Jordan's Water Resources and Their Future Potential Symposium, October 27-28, 1991; Amman, Jordan, 1992. Jiries, A.: Hussain, H.: Lintelnlann, l. Deternlination of polycyclic aromatic hydrocarbons in wastewater: sediments, sludge and plants in Karak Province, Jordan. Water Air Soil Pollut. 2000, 121 (1-4), 121-228. Elliott, L.F.: Stevenson, F.J. Soils for lvfanagelnent of Organic Wastes arLdWastewaters; SSSA: Madison, WI, 1977. Bole, J.B.: Gould, \V.D. Irrigation of forages with rendering plant , wastewater: forage yield and nitrogen dynamics. J. Environ. Qual. 1985, 14 (1),119-126. Bilbeisi, M. Jordan's water resources and the expected domestic dell1and by the years 2000 and 2010: detailed according to area. Proceedings (~f Jordan's VVater Resources and Their Future Potential Symposium; Garber, A.: Salameh. E., Eds., October 27 -28, 1991: Amman, Jordan, 1992; 7. Rhoades, J.D. Soluble salts. In Methods of Soil ArLalysis,Part II, 2nd Ed.; Page, R.H., 1\1iller, R.H., Keeney, D.R., Eds.: American Society of Agronomy: 1\1adison,\VI, 1982. Nelson, D.\V.: Sommers, L.E. Total nitrogen analysis for soil and plant tissues. J. Assoc. Off. Anal. Chem. 1980, 63, 770-778. Olsen, C.R.: Cole, C.Y.; Watanabe, F.S.: Dean, L.A. Estimation of available phosphorus in soils by extraction lvith sodium bicarbonate; U.S. Government Printing Office: Washington, DC, 1954; USDA Circ. 939. Richards, L.A. Diagnosis and Improvenwnt of Saline and Alkaline Soils; U.S. Government Printing Office: \Vashington, DC, 1954; USDA Agric. Handbook No. 60.
Irrigation with Secondary Treated \Vastewater
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20. Thomas, G.W. Exchangeablecations. In Methods of Soil Analysis, Part H, 2nd Ed.; Page, A.L., Miller, R.H., Keeney, D.R., Eds.; American Society of Agronomy: Madison, WI, 1982; Agron. Nlonogr. 9. 21. Pol~mio, M.; Rhoades, J.D. Determining cation exchange capacity: a new procedure for calcareous and gypsiferous soils. Soil Sci. Am. J. 1977, 41, 524-528. 22. Gee, G.W.; Bauder, J.W. Particle-size analysis. In lVlethods of Soil Analysis, Part 1, 2nd Ed.; Klute, A., Ed.; American Society of Agronomy: Nladison, WI, 1986. 23. Nelson, D.W.; Sonlmers, L.E. Total carbon, organic carbon, and organic matter. In iVlethods of Soil Analysis. Part 2, 2nd Ed.; Page, A.L., Ed.; American Society of Agronomy: lVladison, WI. 1982: Agron. Nlonogr. No. 9; 539-580. 24. 25.
Lindsay, vV.L.;Norvell, vV.A.Development of a DTPA soil test for zinc. iron, manganese. Soil Sci. Soc. Am. J. 1978. 42, 421-'+28. APHA, Standard lvlethods for the Exmnination of \tVater and Wastewater.. 18th Ed.; American Public Health Association: WashinQton, DC, 1992. Wilkinson, L. SYSTAT: The System for Statistics: SYSTAT, Inc.: Evanston, IL, 1990. Shatanawi, NLR.; AI-Schrouf, A.NI. Information system for irrigation management in the Jordan Valley. Proceedings of the Regional Seminar Optimization of ~Vater in Agriculture, Nay 21-24. 1994; AlllmanJordan, 1994. Pescod, M.B. Wastewater Treatment and Use in Agriculture: Irrigation and Drainage; FAO: Rome, Italy, 1992; Paper #47. Hayes, A.R.; Mancino, C.P.; Pepper, LL. Irrigation of turfgrass with secondary sewage effluent. 1.Soil and leachate water quality. Agron. J. 1990, 82, 939-943. Nlohammad, M.J.A. The effect of Sand H:zSO4 application on the availability of Fe, Mn and Zn in calcareous soils, Washington State University, Pullman, WA, 1986; MS Thesis. Soon, Y.K.; Miller, H. Changes in rhizosphere due to ammonium and ~
26. 27.
28.
29.
30.
31.
nitrate fertilization and phosphorus uptake by corn seedlings. Soil Sci. 32.
33.
Soc. Am. Proc. 1977, 41, 77-80. Schipper, L.A.; Williamson, J.C.; Kettles, H.A.; Speir, T.W. Impact of land-applied tertiary-treated effluent on soil biochemical properties. J. Environ. Qual. 1996, 25 (5), 1073-1077. Garcia, C.; Hernandez, 1. Influence of salinity on the biological and biochemical activity of a calciorthird soil. Plant Soil 1996, 178 (2), 255-263.
1294
34. ,.,-
.)J.
36.
37.
38.
l\1ohanimad and Mazahreh
Mancino, C.F.; Pepper, LL. Irrigation of turfgrass with secondary sewage effluent: soil quality. Agron. J. 1992,84 (4), 650-654. Abu-A wwad, A.M. Irrigation water management for onion trickle irrigated with saline drainage water. Dirasat 1996, 23 (1), 46-55. Burns, J.C.; \Vesterman, P.; King, L.D.; Cummings, G.A.; Overcash, M.R.; Goode, L. Swine lagoon effluent applied to Coastal Bermudagrass. 1. Forage yield, quality, and element removal. J. Environ. Qual. 1985,140),9-14. Monnett, G.T.; Reneau, R.B.; Hagedorn, C. Evaluation of spray inigation for on-site waste-water treatment and 4isposal on marginal soils. Water Environ. Res. 1996,68 (1),11-18. Larry, K. Design and management considerations in applying minimally treated wastev.'ater to land. In Utilization, Treatment and Disposal of vVaste on Land: Brown, E.A., Ed.; SSSA: Madison, WI, 1986.
