Effects of Fresh and Composted Dairy Manure Applications on Alfalfa Yield and theEnvironment in Arizona

E. C. Martin,* D. C. Slack, K. A. Tanksley, and B. Basso

ABSTRACTThe Unified Animal Feeding Operation Strategy requires that field

application of animal waste, a common fertilization and disposal prac-tice, may not exceed crop nutrient needs. Additional guidelines setforth by the Arizona Department of Environmental Quality state thatanimal waste applications on agricultural fields in designated ConfinedAnimal Feeding Operations (CAFOs) must be made in a mannersuch that the total N applied to the field cannot exceed the uptakefrom the crop grown. Because alfalfa is grown year round and cantake up large quantities of N, many operators of CAFOs apply animalwaste to their production alfalfa fields as method of waste disposal.In this research, fresh and composted dairy manure was applied toplots in a production alfalfa (Medicago sativa L.) field to determinethe impact on alfalfa yield, soil nitrogen (N), phosphorus (P), andelectrical conductivity (EC) levels and the potential for nitrate (NO3)and phosphate (PO4) leaching. Unfertilized plots were maintained ascontrols. Fresh and composted manure was applied to fertilized plotsafter each harvest at a rate intended to replace N removed from theprevious cutting. After 1.5 yr and 13 cuttings, soil analysis down to150 cm depth showed no significant difference in soil N betweentreatments. At study end, NO3N made up 1.1% of total N in thefertilized plots but only 0.6% in control plots. Changes in soil N werenot significant. Soil P content increased in fertilized plots but remainedstable in control plots. Final soil PO4 measurements were 16, 99, and116 kg ha21 in the control, manure-treated, and compost-treated plots,respectively. Leachate from three drainage lysimeters contained nodetectable NO3 or PO4 from any of the treatments. LSD showed nodifference in EC between the beginning and the end of study, andalfalfa yield did not vary among treatments.

NEW RULINGS from the Arizona Department of En-vironmental Quality state that animal waste ap-plications to agricultural fields in designated ConfinedAnimal FeedingOperations (CAFOs)must bemade in amanner such that the total N applied to the field doesnot exceed the uptake from the crop grown. One cropcommonly grown on CAFOs is alfalfa (Medicago sativaL.) for animal feed. Alfalfa does not require N fertilizerbecause it forms a symbiotic relationship with microor-ganisms that convert atmospheric N into amino acids,but it uses soil N when it is available in high concentra-tions (Phillips and DeJong, 1984). Because of its deeprooting pattern, it is often recommended to help reducenitrate (NO3) pollution (Peterson and Russelle, 1991).In Arizona, where alfalfa is grown year round, its poten-

tial as a manure N disposal crop is high. The practice ofapplying animal waste to crops as a method of disposal iscommon (James et al., 1996, Jokela, 1992; Miller andDonahue, 1995). However, improper applications maypose a threat to environmental quality if the soil isoverloaded with nutrients (Andraski et al., 2000). Nitro-gen applied in excess of crop needs may leach intogroundwater (Jemison and Fox, 1994), contributing tononpoint-source pollution (Lanyon, 1994; Daliparthy etal., 1994, Daliparthy et al., 1995; Matson et al., 1997;Basso and Ritchie, 2005).The effects of the application of raw and composted

animal manures on nitrate leaching have been evaluatedby several researchers, but published results are incon-sistent. Leclerc et al. (1995) found lower nitrate leachingfrom applications of composted manure than from inor-ganic fertilizer supplying the same amount of N over a5-yr rotation. Several studies report a higher risk ofnitrate leaching if manure is applied to soils high inorganic matter or if applications are made in autumn-winter (Chambers et al., 2000; Chalmers, 2001; Yan-Wang et al., 2002). Daliparthy et al. (1994) found thatmanure had no effect on alfalfa yield when applied at112 kg N ha21 and had decreased yields at 336 kg Nha21, probably due to a smothering effect. Schmitt etal. (1993, 1994) conducted a 2-yr study of manure appli-cations (28, 56, and 112 m3 ha21) to alfalfa in Minnesotaand reported a positive or neutral effect on yield andno change in soil and plant N levels. A recent study byLloveras et al. (2004) found that swine slurry manureapplied at 187.4 and 374.8 kg N ha21 had no effecton alfalfa yield relative to a control. The N balance(estimated amount of N fixed by the crop) differedsignificantly between the high N application rate andthe control in one of two research sites. Basso and Rit-chie (2005) found that NO3N leached from manure-,compost-, and inorganic fertilizer-treated plots at 681,390, and 311 kg N ha21, respectively, over 6 yr of amaize-alfalfa rotation in Michigan. Yields did not differamong treatments or between treatments and unfertil-ized controls.To qualify and quantify chemical and water move-

ment through the soil profile in situ, many researchershave used lysimeters. During the past few decades, ly-simeters have been used for a variety of purposes, in-cluding evapotranspiration measurements (Ritchie andBurnett, 1968; Ritchie, 1972), nitrate leaching quantifi-cation (Reeder, 1986; Owens, 2000; Martin et al., 1994;Basso et al., 1995), and management impacts on nitrate

E.C. Martin and D.C. Slack, Dep. of Agric. and Biosyst. Eng., Univ.of Arizona, Tucson, AZ 85721; K.A. Tanksley, Pima CommunityCollege, Tucson, AZ 85709; and B. Basso, Dep. of Cropping Syst.,For. and Environ. Sci., Univ. of Basilicata, Potenza, Italy. Received2 Feb. 2005. *Corresponding author (edmartin@cals.arizona.edu).

Published in Agron. J. 98:8084 (2006).Manuredoi:10.2134/agronj2005.0039 American Society of Agronomy677 S. Segoe Rd., Madison, WI 53711 USA

Abbreviations: AZSCHED, Arizona irrigation scheduling computerprogram; CAFO, confined animal feeding operation; DM, dry matter;EC, electrical conductivity; LSD0.05, Fishers least significant differ-ence; MAC, University of Arizonas Maricopa Agricultural Center;RFA, rapid flow analyzer; TKN, total Kjeldahl nitrogen.

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leaching (Rasse et al., 2000). Pakrou and Dillon (2000)showed that deep monolith lysimeters provide betterresults for estimating drainage and N fluxes to ground-water than the use of shallow or repacked lysimeters.In this research, the effects of the application of fresh

and composted dairy manure on a production alfalfafield were examined to determine the impact on alfalfayield; soil N, P, and electrical conductivity (EC) levels;and the potential for NO3 leaching in the arid southwest.

MATERIALS AND METHODS

Site Description

Alfalfa was planted on 17 Nov. 2000 at the University ofArizonas Maricopa Agricultural Center (MAC) in Maricopa,Arizona (1128109 N, 338059 E). The sites rainfall averagesslightly more than 177 mm per year, but only 210 mm ofrainfall were received during the 20-mo study period. Thevariety planted wasMecca II seeded at a rate of 28 kg ha21. Thesoil type was a Casa Grande fine-loam (mixed, hyperthermicTypic Natrargid). The research field was split into 12 plots,each 6 m wide and 137 m long. Fresh and composted manurewas applied to the surface of the treatment plots after eachalfalfa cutting at a rate intended to replace the total N removedby the harvest. There were three treatments: no N added(Control), composted manure (Compost), and fresh manure(Manure). The field was divided into four replicate blockswith three plots per block in a modified, randomized, com-plete-block design. Three lysimeters previously existed in thefieldone located in each of the first three blocks. One Con-trol (no N), one Compost, and one Manure treatment plotwas randomly assigned to each lysimeter. Other treatmentswere randomly assigned so that each block consisted of onereplicate of each treatment.

Irrigation and Fertilizer Applications

The field had a near zero slope and was surface irrigatedwith siphon tubes. Irrigations were scheduled using the Ari-Zona irrigation SCHEDuling (AZSCHED) computer pro-gram (Martin et al., 2003). AZSCHED is a computer modeldeveloped at theUniversity ofArizona that integrates weather,soil data, and crop factors to provide irrigation recommenda-tions. Weather data, including rainfall, were obtained fromthe Arizona Meteorological Network (Brown, 2004) stationapproximately 805 m north of the field location. AZSCHEDcomputes crop water usage using the Modified-Penman equa-tion to determine reference crop evapotranspiration combinedwith a heat unit-based crop coefficient (Martin et al., 2003).Irrigation amounts and dates were calculated by AZSCHEDusing a maximum allowed depletion of 50% of plant availablewater in the crop rootzone and an irrigation efficiency of 75%(Martin, 2000).

The fresh and composted manure were from a large (,2500head) dairy, located about 100 km northwest of MAC. Thefresh manure was scrapped from the yard within 10 d of analy-sis and application. The composted manure was made by fre-quent watering and turning of a 2:1 mixture of dry manureand landscape nursery cuttings. Its age was unknown becausethe dairyman was constantly adding, moving, and selling thecomposted manure. All fresh and composted manure sampleswere analyzed for N content (NO3, NH4, and total N), andfive samples were analyzed for phosphate (PO4) and EC levelsover the course of the study.

Total Kjeldahl nitrogen (TKN) was determined using thestandard digestion of Schumann et al. (1973) in conjunction

with the indophenol blue procedure and the Alpkem RapidFlow Analyzer (RFA) II (Bremner and Mulvaney, 1982). SoilNO3 was extracted with deionized water and analyzed forNO3N via Cd reduction by a modified GriessIlsovay methodusing the Alpkem RFA II. Analysis of NH4 was done onundigested samples using a 2 M potassium chloride (KCl)extraction (Keeney and Nelson, 1982) and the Alpkem RFAII. The TKN minus the original NH4 in the sample yieldedthe organic N originally present in the sample. The TKN plusthe NO3 equaled the total N in the sample, which was usedto calculate the amount of material needed to replace the Nremoved in each harvest. Soluble P (Olsen P) was determinedby sodium bicarbonate (NaHCO3) extraction and subsequentcolorimetric analysis (Olsen et al., 1954). Electrical conductiv-ity levels were determined using an electrical conductivityelectrode (Bremner and Mulvaney, 1982) and a 1:1 ratio offresh/composted manure to water.

All fresh and composted manure was applied with a manurespreader (Lakeside All Purpose Spreader, V-style) in one ortwo applications. Weights of the spreader and tractor weretaken before and after applications to determine the amountof material applied. An initial application of 43 and 35 kg Nha21 was applied to the Compost and Manure plots, respec-tively (differences reflect normal spreader variation), to in-duce the alfalfa to use soil N instead of forming N-fixingnodules.

Plant Harvest and Analysis

The alfalfa was harvested when ,10% of the field was atflowering. After mowing, the alfalfa was raked into a singlewindrow per plot. Forage yield was determined by collectingand weighing a random 2-m length of windrow from each plot.Subsamples were collected from the yield sample, weighed,and dried for 24 h at 658C to determine dry matter (DM)yield. Dried samples were ground using a Wiley Mill Model4 grinder with a 0.5-mm sieve before N content determinationby the Kjeldahl digestion method previously described. Weassumed that organic N removed by the Kjeldahl digestionsapproximated the total N content of the alfalfa because prelim-inary assays showed that harvested alfalfa contained ,0.5 mgkg21 of NO3 or NH4. Nitrogen concentrations were used withyield data to determine the total amount of N removed ineach harvest.

Soil Analysis

Soil samples were taken from the field on three separatedates using a Giddings Probe and a 50.8-mm hollow coresampler. Samples were taken in October 2000, before treat-ment initiation; January 2002, when the crop was partiallydormant; and August 2002, at the conclusion of the study.Each time, three soil cores were taken from each plot in 15-cmincrements down to 45 cm, then 30-cm increments to a depthof 150 cm. All samples were analyzed for TKN, NH4, NO3,P, and EC in the same manner as the fresh and compostedmanure. A bulk density of 1.5 g cm23 was assumed for thesoil based on data from Post et al. (1988). For more detailson extractions and analyses, see Tanksley (2003).

Lysimeters

Stainless steel drainage lysimeters (2.0 by 1.5 m by 1.8 mdeep) were installed in 1994 and filled with soil to simulate theactual soil profile (Martin et al., 1999). The tops of the lysime-ters were ,0.5 m below the soil surface, allowing leachate

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81MARTIN ET AL.: DAIRY MANURE APPLICATIONS ON ALFALFA IN ARIZONA

collection from ,2.3 m below the soil surface (Fig. 1). Leach-ate was collected in a stainless steel container below groundand measured and sampled at the surface using a vacuumpump and a 20-L plastic carboy. Although suction was used tosample the drainage water, the lysimeters were not under anysuction. The lysimeters were checked weekly for leachate thatwas analyzed for NO3 and PO4 content using the AlpkemRFA II.

Statistical Analysis

Statistical analysis was conducted using the general linearmodel of SAS (PROCGLMprocedures) (SAS Institute, 1996).Field replicated measurements were analyzed using Fishersleast significant difference (LSD0.05) in the analysis of variance.

RESULTS AND DISCUSSIONYield and Plant Analysis

Alfalfa was cut and analyzed 13 times throughout thestudy, yielding approximately 40 t ha21 DM and 1.2 tha21 N (Table 1). Yields did not differ among treat-ments, except in February 2002, when manure may haveprotected some plants from frost damage. Yields forthat cutting were 1408, 1770, and 2550 kg ha21 DM forthe Control, Compost, and Manure plots, respectively.Nitrogen removal mirrored yields (Table 1), althoughthe difference in N removed in February 2002 was notsignificant.

Irrigation and Cultural PracticesIrrigations were scheduled according to the recom-

mendations of AZSCHED, with the condition that no

irrigation could be scheduled within a week of harvest.This was done so that the harvest equipment could ma-neuver in the field. The total irrigation depth appliedover the study period was 3943 mm. The total rainfallover the study period was 210 mm. There were no addi-tional fertilizers or chemicals added to any of the plotsthroughout the study period. No herbicides or insecti-cides were required.

Fresh and Composted Manure AnalysisTotal N applications exceeded removal by 61 and 53%

in the Compost and Manure treatments, respectively(Table 1). Slightly more N was applied as compostedmanure than as fresh manure (Table 1) due to the diffi-culty in applying the correct amount of material with amanure spreader. The freshmanure had a higher NH4Ncontent and lower NO3N content than the composted

manure (Table 1). This was expected because the com-posted manure had some time to mineralize the NH4into NO3 during the composting operation. Phosphateconcentration and EC was higher for the fresh manurethan for the composted manure (Table 2).

Soil Sample AnalysisSoil analysis showed no differences between plots at

the beginning of the study (Table 3). Soil NH4 levelswere higher at the end of the study than at the beginningbut did not differ between treatments (Table 3). Nitratelevels were higher in fertilized plots than in control plotsby the end of the study (Table 3). At least 98% of soil Nwas in the organic form for all treatments and samplingdates. Neither total N nor organic N contents differedbetween treatments or sampling dates (Table 3). Electri-cal conductivity did not differ by treatment but fell froman average of 1.1 to 0.4 dS m21 over the course of thestudy (Table 3). Soil PO4P increased over the courseof the study in fertilized plots but not in unfertilizedcontrols (Table 3).

LysimetersLysimeters did not collect sufficient leachate to in-

duce drainage over the course of the study, reflectingproper irrigation, efficient plant water uptake, and alack of significant rainfall. At the end of the study, thefield was heavily irrigated to induce leaching. NeitherNO3N nor soluble P were detected in leachate at therespective detection limits of 0.5 and 0.25 mg kg21 (datanot shown).

Fig. 1. Drainage lysimeter system used to collect leachate from alfalfaplots (Martin et al., 1999).

Table 1. Summary data for dry matter alfalfa yield, N removed in harvest, and N added through fertilization for the 13 cuttings duringthe study period at Maricopa, AZ, 20012002.

Total applied

TreatmentDry alfalfa

yieldTotal Nremoved Material NO3N NH4N Organic N Total N

kg ha21 kg N ha21 kg ha21

Control 40 815 1222Compost 39 312 1222 156 403 172 13 1789 1975Manure 39 008 1215 123 673 3 33 1821 1856LSD (0.05) NS NS

NS, nonsignificant.

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Nitrogen Mass BalanceANmass balance calculation was performed to assess

N flux between the atmosphere and field. The N re-maining in the soil at the end of the study was estimatedby adding the N applied as fresh and composted manureto the pre-study N and subtracting the N removed bythe alfalfa cutting. Table 4 shows the mean N balance,suggesting that the addition of the N to alfalfa inhibitedfixation. Alfalfa in control plots fixed approximately1152 kg N ha21. There was no net N fixation in Compostand Manure plots, where alfalfa consumed 383 and 354kg N ha21, respectively. This compares with a recentreport that alfalfa fixed 1098 kg N ha21 without added

fertilizer but only 427 kg N ha21 when fertilized with50 m3 swine slurry ha21 (Lloveras et al., 2004).

CONCLUSIONSIn this research, fresh and composted dairy manure

was applied to plots in a production alfalfa field follow-ing recently released CAFO guidelines to minimize thepotential for nutrient contamination of the environ-ment. This study suggests that with proper application,fresh and composted manure can be applied to alfalfa inthe arid southwest with minimal risk of nitrate leaching.However, the lack of significant rainfall during the study

Table 3. Nitrogen, phosphorus, and electrical conductivity values of the soil taken at the beginning, midpoint, and end of the studyat a depth of 0150 cm.

Date

Parameter Treatment Oct. 2000 Jan. 2002 Aug. 2002 LSD (a 5 0.05)

kg ha21

NH4N Control 4.7 2.8 9.8 3.1Compost 2.4 2.7 10.3 3.3Manure 5.0 3.8 10.2 3.8LSD (a 5 0.05) NS NS NS

NO3N Control 48.3 0.8 18.1 12.4Compost 53.0 1.8 35.0 24.8Manure 54.3 3.4 33.9 13.4LSD (a 5 0.05) NS NS 14.0

Organic N Control 2838 3189 2793 NSCompost 2711 3176 3092 NSManure 2810 2665 3108 NSLSD (a 5 0.05) NS NS NS

Total N Control 2891 3193 2821 NSCompost 2767 3181 3136 NSManure 2869 2673 3152 NSLSD (a 5 0.05) NS NS NS

Phosphate P Control 20.4 12.0 16.3 NSCompost 29.1 94.4 115.6 83.6Manure 31.9 63.6 98.6 NSLSD (a 5 0.05) NS 77.7 76.1

dS/mEC (avg.) Control 1.05 0.59 0.41 NS

Compost 1.09 0.55 0.46 NSManure 1.11 0.52 0.46 NSLSD (a 5 0.05) NS NS NS

EC, electrical conductivity; NS, nonsignificant.

Table 4. Mean N balance values for the three treatments.

Nitrogen

Treatment

(A)Initial soilOct. 2000

(B)Applied

(C)Harvested

(D)Calculated soilAug. 2002

(A 1 B) 2 C

(E)Actual soilAug. 2002

(F)Balance(E 2 D)

kg ha21

Control 2891 0 1222 1669 2821 11152Compost 2767 1975 1222 3520 3137 2383Manure 2869 1856 1214 3511 3152 2359LSD (a 5 0.05) NS NS NS

NS, nonsignificant.

Table 2. Phosphorus concentration and electrical conductivity values for selected samples of fresh and composted manure.

PO4P EC

TreatmentNov.2000

May2001

Aug.2001

Oct.2001

July2002

Nov.2000

May2001

Aug.2001

Oct.2001

July2002

mg kg21 dS m21

Compost 424 409 309 326 359 14 33 26 26 41Manure 1246 1504 1188 1572 864 68 92 77 68 75

EC, electrical conductivity.

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83MARTIN ET AL.: DAIRY MANURE APPLICATIONS ON ALFALFA IN ARIZONA

period may have helped to mask potential leaching risks.The N mass balance analysis showed that the Controltreatment fixed more N (1152 kg N ha21) than the Ma-nure (2359 kg N ha21) and Compost (2383 kg N ha21)treatments, demonstrating inhibition of biologic N-fixa-tion by N application through organic compounds. Theaccumulation of P in the soil may be of concern in areaswhere surface water is near. Levels of 115 kg ha21 and99 kg ha21 of PO4P were found in the soil of the Com-post and Manure plots, respectively, at the end of thestudy.

ACKNOWLEDGMENTS

The authors wish to acknowledge the contribution of Dr.Jay Subramani for his assistance in the statistical analysis of thedata presented in this paper.

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