Forage Yield and Nutrient Uptake as Influenced by …mrusan/Forage Yield and Nutrient...

JOURNAL OF PLANT NUTRITION

Vol. 27, No. 2, pp. 351-365, 2004

Forage Yield and Nutrient Uptake asInfluenced by Secondary Treated Wastewater

Munir J. Mohammad1,* and Mohammad Ayadi2

IDepartment of Natural Resources and the Environment,Faculty of Agriculture, Jordan University of Science and

Technology (JUST), Irbid, Jordan2Ramtha Regional Center for Agricultural Research and

Technology Transfer, Ramtha, Jordan

ABSTRACT

The effect of irrigation of forage crops with treated wastewater onthe yield and nutrient uptake was evaluated under field conditions.Three field experiments were conducted at a farmer's field nearRamtha Wastewater Treatment Plant, Jordan. Corn (Zea mays) wasplanted for two seasons as a summer crop while vetch (Vicia saliva)was planted for one season as a winter crop during 1994-1995. Plotswere irrigated with either potable water (PW) or wastewater (WW) in

*Correspondence: Munir J. Mohammad, DepartI;Ilent of Natural Resources andthe Environment, Faculty of Agriculture, Jordan University of Science andTechnology (JUST), P.O. Box 3030, Irbid, Jordan; Fax: 962-2-7095069; E-mail:[email protected].

351

DOl: 1O.1081jPLN-120027659Copyright @ 2004 by Marcel Dekker, Inc.

0190-4167 (Print); 1532-4087 (OnIine)www.dekker.com

352 Mohammad and Ayadi

amounts according to the following treatments: (i) PW equivalentto 100% class A pan reading (PW); (ii) WW equivalent to 100% classA pan reading (WW1); (iii) WW equivalent to 125% class A panreading (WW2), and (iv) PW with application fertilizer equivalent tonitrogen (N) and phosphorus (P) content of WWl (PWF).Treatments were replicated four times in randomized completeblock design. Plant samples were taken during the growing seasonsand were ana1yzed for dry weight, yield, yield components, andnutrient uptake. The results indicate that WW irrigation increasedthe yield of both corn and vetch. Both rates of WW application hadsimilar effect on crop production. Supplemental fertilization withthe potable water irrigation (PWF) enhanced vetch production andincreased grain weight for corn in the second season (1995). Theuptake of macronutrients and micro nutrients by corn increased withWW irrigation, while the uptake by vetch increased with both WWirrigation and PW supplemented with fertilization. It was concludedthat under the conditions of this study, secondary treated WW couldbe a source of plant nutrients and can be reused for irrigation toincrease forage crop production.

Key Words: Wastewater; Vetch; Corn; Nutrient uptake.

INTRODUCTION

One of the applications of wastewater is its reuse as irrigation waterin agriculture. In arid and semi-arid regions, wastewater is considered avaluable source of irrigation water and a fertilizing materia1.[1,2]Althoughwastewater reuse in irrigation is a common practice in these regions, thereis a widespread and growing concern about its adverse environmentalimpact on the environment and health hazards. [2-5]Therefore, inappro-priate handling and management of wastewater reuse for irrigationcan create serious environmental and health hazardsY] This encouragemost countries to continuously modify and update the standards andguidelines for reuse of wastewater for irrigation.[6,7]

When wastewater is used properly for irrigation it is consideredan environmentally sound disposal practice. [8] Such a proper use canrelatively minimize pollution of the ecosystem which otherwise would becontaminated by direct disposal of wastewater into surface or groundwater.[9,lO] Protection of environment and public health can be attainedthrough adoption of integrated management practices including waste-water treatment, soil and crop selection, method of application andhuman exposure contro1.[9]

Forage Yield and Nutrient Uptake 353

Wastewater contains essential nutrients for plant growth like N,P, and potassium (K), micronutrients such as iron (Fe), zinc (Zn),manganese (Mn), and copper (Cu) and a considerable amount oforganic matter. [10-12]This makes wastewater a good fertilizer and soilamendment that would increase crop yield and enhance soil fertility andproductivity. However, improper management of wastewater irrigationmay provide the crops with nutrients beyond their specific require-ment and subsequently accumulate them at undesirable high levelsin the crop. This would lead to reduction in the yield and itsquality.[4,10,13,14]Therefore, management of irrigation with wastewatershould consider the nutrient content in relation to the specific croprequirements and the rate of application of wastewater should be adjustedaccordingly.

Irrigation with wastewater has been studied for several crops andunder different climatic conditions,l1O-12,1S]Campbell et aIYS] stated thata weekly application of 25 mm of wastewater was enough to supply40-80% of the corn N requirements and all P needed. Other researchersreported similar results.[16] Ouazzani et aL[1?] found that meadowsirrigated with wastewater received Nand P in amount equivalent orsuperior to the recommended dose of fertilizers for meadows. Jamjoumand Khattari[18] found that corn yield was increased by irrigation withwastewater and they attributed this increase to the enhancement ofnutrient uptake and improvement of the physical properties of thesoil. Heavy metals were not affected by the addition of wastewater.Other researchers found that heavy metals and micro nutrients canbe accumulated in the soil and the plants after long term wastewaterapplication. [4]

Research on wastewater reuse in agriculture under arid landcondition of the Mediterranean region was aimed mainly on the direct

effect of irrigation with wastewater on the yield response of s<?mecrops.Less attention was given to nutrient uptake, nutrient cycling and relatedaspects of environmental pollution. The use of secondary treatedwastewater for irrigation is restricted for vegetable and uncookedcrops and can be used mainly for forage crops. In arid countries, theshortages of good quality water led to shortages of forage and feedingcrops. Animals feeding on forage crops irrigated with wastewater, canbe affected by the levels of nutrients and heavy metals of the crops,therefore, research activities should periodically address these param-eters. The main objective of this study was to evaluate wastewater as asource of irrigation water and of nutrients for forage crops and determinethe yield and the uptake of nutrients and heavy metals by forage cropsirrigated with wastewater.


MATERIALS AND METHODS

The study was conducted at a farmer's field located near the RamthaTreatment Plant, Jordan in a soil which had never been previouslyirrigated.The following (wo sources of irrigation water were used toirrigate vetch (Vicia saliva) and corn (Zea mars) forage crops: potablewell water and secondary treated municipal wastewater, from theRamtha Wastewater Treatment Plant in Ramtha, Jordan. Plots were

irrigated with either potable water (PW) or wastewater (WW) accordingto the following treatments: (i) PW equivalent to 100% class A panevaporation reading (PW), class A pan is a standard field tool to measurewater evaportion over time, evaporation readings were taken periodicallyfrom the nearest Meteorological Weather Station and were used toestimate the water requirement of the crops; (ii) WW equivalent to 100%class A pan reading (WW1); (iii) WW equivalent to 125% class A panreading (WW2) and (iv) PW plus an application of fertilizer equivalent toNand P contents of WW1 (PWF). Irrigation in the WW2 was sufficientto ensure that soil leach ate percolated beneath the root zone to leach outany possible accumulation of salts contained in the WW. A leachingfraction of approximately 25% was maintained through out the studyfor the WW2 treatment. All treatments were replicated four times in arandomized complete block design (RCBD). For the PWF treatment, Nas ammonium suIfate and P as triple superphosphate were broadcastedinto the soil surface before each irrigation.

Three field experiments were conducted during the study periodwhere corn was planted as a summer crop for two seasons and vetch as awinter crop for one season. In the first season the corn was planted inMay 1994 and harvested in August, 1994 followed by vetch planted inFebruary 1995 and harvested in May 1995. Then corn was planted againin the same plots in May 1995 and harvested in August 1995. Plotdimensions were 3.75 x 3 m in which corn was planted in rows at a depthof 6 cm. The distance between rows was 75 cm and that within rows was

25cm. Vetch was planted at a rate of 120kgha-l.The crops were irrigated through a closed irrigation pipes to the

experimental plots where the water was distributed uniformly. Corn wasirrigated twice a week and vetch once a week except during rainy periods.The amount of irrigation water was monitored by a water meter installedin the irrigation system. In 1994 season, corn was irrigated with 540 mmand 675 mm for the WW and WW1 treatments and with 540 mm for each

of the PW and PWF treatments, respectively. In 1995 season, corn wasirrigated with 615mm for each of the PW, PWF, and WW1 treatmentsand 769 mm for the WW2 treatment. The winter vetch crop grown after

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corn in 1994 was irrigated with 74mm for each of the PW, PWF, andWWl treatments and with 93 mm for the WW2 treatments, respectively.

The soil of the experimental site was calcareous and fine texturedwith pH of 7.8; electrical conductivity (EC) of 0.8 dS m-I; cationexchange capacity (CEC) of 32.1 cmol kg-I and total N of 0.09% andsodium bicarbonate extractable P of 5.2mgkg-l. The WW used for

irrigation had a pH of 7.56 and total dissolved solids (TDS) of1225 mg kg-I. The concentration of phosphate, ammonium, and nitratewere 49,118, and 2.9mgkg-l, respectively. The concneration of Fe, Mn,and Zn in the WW were 0.14, 0.07, and 0.3 mg L -I, respectively. On theother hand, the values of the pH, TDS, and nitrate for the PW were 7.9,650, and 59 mg kg -I, respectively. Other parameters of the PW were verylow or nondetectable. Detailed analysis of the soil and irrigation water

used are reported in Mohammad and MazahrehY9]

Shoot Sampling and Analysis

At harvest four corn plants were sampled from each of the middlethree rows in each plot. A total of 12 plants were sampled from each plotrepresenting a sampling area of 2.25 m2. The stover and grain dry weightsof corn were determined in each sample. The number of ears per plantwas counted and the weight of air dried 250 seeds was determined. Atflowering stage, the above ground (shoot) portion of the vetch plants washarvested from the middle third of the main plot and the dry shoot weight(at 68°C) was determined. The oven dry weights of corn and vetch wereused to calculate nutrient uptake. Oven-dried plant and grain sampleswere ground to a through 2-mm sieve. Milled samples were anaJyzed fortotal N using a modified micro-Kjeldahl digestion procedure,[2O]and fortotal P after dry ashing with the ascorbic acid molybdate blue methodYI]Total K was also determined in the dry ashed samples digestion usingflame emission photometry. Micronutrients and heavy metals in the dryashed samples were determined using the atomic absorption spectro-photometer. The recovery of potable water and wastewater applied to thecorn and as supplemental irrigation to the vetch was calculated as kg ofthe dry weight production per mm of irrigation water applied. Analysis ofvariance (ANOVA) was used to determine the effect of each treatment.When the F ratio was significant means were tested using Fisher'sLeast Significance Test (0.05 probability level). Statistical analyses wereperformed with Systat statistical program. [22]


RESULTS AND DISCUSSION

Yield and Yield Components

The grain and stover weights of corn were increased significantly byWW irrigation compared to PW irrigation (Fig. 1). The higher rate ofWW (WW2) gave higher stover weight than the lower rate (WW1) in1995 season but had similar effect on both stover and grain weights as the

Figure 1. Corn grain and stover and vetch shoot weights (T/ha) as affected bypotable and wastewater irrigation. PW = potable water; PWF =water potable

with fertilizer added; WWl and WW2 = low and high wastewater rates,respectively. Columns with different letters are significantly different (p < .05).

5.

4.

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I.

O.

PW PWF WWI WW2

Treatments

6

5

4=

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0

PW PWF WWI WW2

Treatments

...r3 J 1995

....

g 2..coE!Eo-<

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0PW PWF WWI WW2

Treatments


lower rate in 1994corn season. The weights of grains and stover increasedsignificantly by application of Nand P along with the PW (PWF). Thiscould be attributed to the lower level of soil fertility that was probablypartially compensated by the Nand P application. However, WWirrigation caused a further increase in the yield indicating that WWprovided factors other than Nand P that can enhance soil productivity.Similar trend was observed on the weight of one ear, however the weightof one ear was affected similarly by the treatments in both seasons(Fig. 2). The weight of (250) seeds were increased by WW irrigationregardless of the application rate compared to PW water irrigation inboth season. However, PWF treatment had a significant positive effecton the seed weight only in the 1995 season. However, the number of ears

--a--

c

a a

PWF WWl WW2Treatments

I Elg/ear l1lig/250seeds11Ears #/pll

Figure 2. Corn yield components (wt per ear or 250 seeds and number of earsper plant). PW =potable water; PWF = water potable with fertilizer added; WWIand WW2 =low and high wastewater rates, respectively. Columns with differentletters are significantly different (p < .05).

140 1199410 120'"'8 100 d='

80 1 w:J=100

60......cQJ)

40.

20

0

PW

160 1 1995 a140

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§ 100=10 800

;: 60QJ).

40

20

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PW PWF WWl WW2

Treatments

I Elglear l1lig/250seeds11Ears #/pll


per plant was not different among treatments. This indicates that theincrease in the yield was attributed mainly to the size of the ears or seedrather than to the number of ears per plant.

Since the vetch is a winter crop, the amount of irrigation waterapplied during the growing season was much lower than that applied tocorn. The shoot weight of vetch at the flowering stage was increased byWW irrigation regardless of the application rate compared to the PWirrigation (Fig. 1). However, supplying the potable water with Nand P(PWF) increased shoot weight as much as the WW2, but lower than theWWl. It is not clear why the vetch growth was reduced with higher rateof the WW (WW2). A possible explanation is that the vetch, as a nitrogenfixing legume crop, may have been over-fertilized with excess N providedby the higher rate of WW.l4,IO]Another explanation is the possiblegrowth inhibitors and toxic substances applied by the higher rate ofWW.[4,13,14]

The positive effect of WW application was reported by otherresearchersyo,Z3] Moreover, such positive effect was observed comparedto that obtained when even Nand P was supplied with the PW. Thisemphasizes the possibility that WW provided factors other than Nand Pthat enhances crop production such as possible improvement of soilphysical conditions and soil organic matter content. [23]Therefore, thisincrease in the yield of both corn and vetch by irrigation with WW ismainly attributed to the high original nutrient content in the WW[S,Z4]and to the improvement of soil physical conditions and possible additionof organic compounds that enhances soil fertility and plant uptake ofindigenous soil nutrients.[4,IO,Z3]

Nutrient Contents

Nitrogen uptake by corn grain and stover was significantly increasedby WW application in both 1994 and 1995 seasons (Tables I and 2).Nitrogen uptake by corn did not increase by supplemental Nand Pfertilization (PWF). Nitrogen uptake by vetch was increased by bothWW and PWF irrigation treatments (Table 2). The effects of both ratesof WW irrigation on N uptake were similar but higher than PWF. Theenhanced N uptake by forage crops with WW irrigation would enhancedtheir protein content, thus improving nutritional value of these foragesfor animal feed. Other researchers found that nitrogen and proteincontents were increased with WW irrigation in corn[14]and in mead-OWS,[17]which enhanced nutritional value of the forage crops andconsequently meat and milk productionY7]


Table 1. Macronutrient uptake (kg ha-I) by corn grain and stover as affected bypotable and wastewater irrigation in 1994.

*PW =potable water; PWF = potable water with fertilizer added; WWl andWW2 =lowest and highest wastewater application rates respectively.**Means of different letters within rows are significantly different (p < .05).

*PW =potable water; PWF =potable water with fert.ilizer added; WWl andWW2 = lowest and highest wastewater application rates respectively.**Means of different letters within rows are significantly different (p < .05).

Phosphorus uptake by corn in both seasons had generally similartrend as N uptake (Tables 1 and 2). Phosphorus uptake by vetch wasincreased by both rates of WW irrigation and supplemental Nand Pfertilization of PW (PWF) (Table 2). Both Nand P were accumulated in

Treatments

Parameters PW PWF WWl WW2

N: Stover 20.6 b 20.6 b 30.5 a 38.5 aGrain 37.6 b 36.3 b 56.7 a 64.3 a

P: Stover 2.72 b 4.21 b 7.63 a 8.90 aGrain 5.38 b 6.73 b 12.12 a 13.44 a

K: Stover 25.1 b 28.3 b 88.4 a 108.4 aGrain 4.61 b 5.11 b 9.78 a 11.76 a

Table 2. Macronutrient uptake (kg ha-I) by corn grain and stover and vetchshoot as affected by potable and wastewater irrigation in 1995.

Treatments

Parameters PW PWF WWl WW2

Corn, 1995N: Stover 19.8 c 20.2 c 35.3 b 46.0 a

Grain 41.9 b 43.3 b 69.3 a 76.9 aP: Stover 3.30 b 4.92 b 10.85 a 14.39 a

Grain 6.07 b 6.10 b 14.23 a 15.78 aK: Stover 25.5 b 30.0 b 110.9 a 143.8 a

Grain 4.97 b 6.10 b 11.93 a 15.28 a

Vetch, 1995N: Shoot 39.5 b 65.9 a 103.5 a 89.5 aP: Shoot 3.53 c 5.51 b 11.66 a 9.25 bK: Shoot 17.3 c 32.7 b 73.3 a 79.7 a


higher amount in the grain than in the stover of corn which suggest thegrain has higher nutritional value for animal feeding (Table 2).

The uptake of Nand P by corn with higher rate of WW applicationin 1995season was greater than in 1994season. This was attributed to thehigher dry weight of grain and stover and possibly due to the residual Nand P in the soil' accumulated during land application of WW in theprevious 1994 season. These additions of Nand P from WW applica-tion beyond the crop removal may be required to compensate for thelow initial soil Nand P availability in most arid lands.[25]However,continuous application of WW may lead to accumulation of thesenutrients in the soil to levels high enough to cause nutrient imba1ance,[4]therefore, one should take this into consideration before determining therate of application.

Compared to the PW irrigation, K uptake by grain and stover ofcorn was significantly increased by both rates ofWW applications in bothseasons. However, unlike for Nand P, the stover of corn accumulatedmore K than the grain. Both WW irrigation rates and PW supplementedwith Nand P (PWF) increased K uptake by vetch (Table 2). This increasewas significantly lower for the PWF than for both rates ofWW. The WWirrigation increased the K uptake by about 4.5 fold compared to the PWirrigation. Luxury consumption of K by the crops is well documented[26]and such consumption could be beneficial for enhancing crop toleranceto salinity when irrigated with WW. Compared to the PW irrigationtreatments, both rates of WW irrigation increased the uptake of Fe, Mn,Zn, and Cu by corn grain and stover in both 1994 and 1995 seasons(Tables 3 and 4). No significant differences were observed between thetwo rates ofWW application. The stover accumulated higher levels of Fe,Mn, and Zn, but relatively lower levels of Cu compared to th~ grains. Forvetch crops, WW irrigation and PW irrigation supplemented with NandP gave similarly higher Fe, Mn, Zn, and Cu uptake than the PWirrigation (Table 4). However, WW treatments enhanced their uptakemore than the PWF did. Although the micronutrient content in the WWrelatively low, their accumulation in the soil and their subsequent uptakeby the crops are possible because of the continuous seasonal WWapplication. This was evident from the higher uptake of micronutrientsby both rates of WW. The chelation and solubilization effects of theorganic compound on the bioavailability of micronutrients[27] providedby the WW application to the soil[4] could be responsible for theenhancement of their uptake by the plants. Long term application of WWtherefore, may lead to accumulation of these micronutrients and heavymetals in the soil to levels beyond crop uptake creating health andenvironmental hazards. [26]


*PW =potable water; PWF = potable water with fertilizer added; WW 1 andWW2 = lowest and highest wastewater application rates respectively.**Means of different letters within rows are significantly different (p < .05).

*PW =potable water; PWF =potable water with fertilizer added; WW 1 andWW2 =lowest and highest wastewater application rates respectively.**Means of different letters within rows are significantly different (p < .05).

Table 3. Micronutrient uptake (gha-l) by corn grain and stover as affected bypotable and wastewater irrigation in 1994.

Treatments

Parameters PW PWF WWI WW2

Corn, 1994Fe: Stover 386 b 470 b 1009 a 1081 a

Grain 136b 156 b 245 a 254 aMn: Stover 259.1 b 283.1 b 422.2 a 451.5 a

Grain 18.18 b 18.29 b 32.82 a 35.70 aZn: Stover 211.1 b 250.3 b 329.4 a 324.3 a

Grain 67.58 b 73.17 b 99.70 a 110.0 aCu: Stover 21.32 b 25.27 b 31.11 a 31.48 a

Grain 24.32 b 27.17 b 38.32 a 40.74 a

Table4. Micronutrient uptake (gha-I) by corn grain and stover and vetch shootas affected by potable and wastewater irrigation in 1995.

Treatments

Parameters PW PWF WW1 WW2

Corn, 1995Fe: Stover 429 b 489 b 1011 a 1302 a

Grain 168 b 191 b 291 a 294 aMn: Stover 250 b 295 b 518 a 587 a

Grain 18.8 b 23.1 b 37.6 a 40.9 aZn: Stover 255 b 268 b 395 a 472 a

Grain 66.8 b 74.8 b 97.8 a 114 aCu: Stover 21.78 c 27.55 c 43.40 b 48.09 a

Grain 28.15 b 34.67 b 52.33 a 53.24 aVetch, 1995

Fe: Shoot 235.4 c 480.0 b 919.1 a 791.5 bMn: Shoot 194.5 b 388.3 a 482.8 a 405.2 aZn: Shoot 150.8 b 293.7 a 409.5 a 396.4 aCu: Shoot 11.56 b 21.25 a 30.97 a 23.94 a


Table 5. Recovery of potable and wastewater applied (kg mm-I) by corn grainand stover and vetch shoot in 1994 and 1995 seasons.

*PW=potable water; PWF =potable water with fertilizer added; WWl andWW2 = lowest and highest wastewater application rates respectively.**Means of different letters within rows are significantly different (p < .05).

Recovery of Irrigation Water Applied

The recovery of the irrigation water applied is shown in Table 5. Forboth seasons the recovery of the WW irrigation by corn was significantlyhigher than PW treatments. The recovery for the higher rate of WW wassmaller than for the lower rate, suggesting that excessive use of WWcaused leaching and deep percolation rather than for crop evapotran-spiration.[2S]Despite this lower recovery with the higher rate of WW, itmay be necessary to apply water in excess to ensure leaching of saltscontained in the WW below the root zonePS] The recovery of irrigationwater applied to the vetch had similar trend as that observed for corn(Table 5). However, the absolute values were relatively higher for vetchthan for corn mainly because vetch is a winter crop and therefore,received much less irrigation water.

CONCLUSIONS

It can be concluded that secondary treated WW can be successfullyused to irrigate and enhance growth of forage crops. High yields of foragecrops such as corn and vetch can be obtained by WW irrigation.Moreover, WW provided factors other than Nand P for improving cropproduction such as improving soil fertility and soil organic matterthat were measured and reported in an earlier articleY9] Continuous

Treatments

PW PWF WWl WW2

Corn, 1994Stover 3.87 c 4.33 b 5.65 a 4.71 bGrain 4.74 c 4.98 c 7.24 a 6.22 b

Corn, 1995Stover 3.58 b 4.00 b 5.69 a 5.34 aGrain 4.49 c 5.22 c 7.46 a 6.41 b

Vetch shoot, 1995 20.13 c 35.13 b 45.00 a 29.25 b


application of WW may lead to accumulation of plant nutrients andheavy metals to undesirable high levels in the crops and thereby reducingtheir quality and nutritional value as forage crops for animal feeding.Therefore, crop selection and rate of application should be carefullymanaged to minimize any possible adverse effect on crop quality. Aperiodic monitoring of crop quality parameters is required when usingWW for irrigation.

ACKNOWLEDGMENTS

This study was funded partially by the National Center forAgricultural Research and Technology Transfer and by the ResearchDeanship of Jordan University of Science and Technology.

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