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TECHNICAL REPORTS

Waste Management

Compost, Manure, and Gypsum Application to Timothy/Red Clover Forage

^a Mississippi State Univ., North Mississippi Research and Extension Center, 5421 Hwy. 145 South, P.O. Box 1690, Verona, MS 38879
^b Dep. of Engineering, Nova Scotia Agricultural College, 50 Pictou Rd., Cox Institute R-151, P.O. Box 550, Truro, Nova Scotia, Canada B2N 5E3
^c Dep. of Plant and Animal Sciences, Nova Scotia Agricultural College, 50 Pictou Rd., Cox Institute R-151, P.O. Box 550, Truro, Nova Scotia, Canada B2N 5E3
^d Agric. and Agrifood Canada, Crops and Livestock Research Centre, 440 University Ave., Charlottetown PEI, Canada C1A 4N6

^* Corresponding author (vj40{at}pss.msstate.edu)

Received for publication August 23, 2005.

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Some of the most fertile agricultural land in Atlantic Canada includes dykelands, which were developed from rich salt marshes along the Bay of Fundy through the construction of dykes. A 2-yr field experiment was conducted on dykeland soil to evaluate the effect of fertility treatments: source-separated municipal solid waste (SS-MSW) compost, solid manure, commercial fertilizer, and gypsum on (1) timothy/red clover forage productivity, (2) N, S, and other nutrients uptake, and (3) residual NO₃–N and NH₄–N in the soil profile. All fertility treatments increased dry matter yields from the two cuts each year relative to the control. Residual soil NO₃–N and NH₄–N concentrations in the fall of the second year decreased with depth, and beyond 20-cm depth were lower than 1 mg kg^–1. Gypsum application equivalent to 40 kg S ha^–1 increased dry matter yields and N uptake by forage, and increased soil Mehlich 3-extractable S, tissue S, and uptake of S, Ca, P, Cu, Fe, and Mn relative to the control. High rates of compost can provide sufficient N, S, and perhaps other nutrients to a perennial forage system under the cool wet climate of Atlantic Canada with no heavy metal enrichment of forage. However, the chemical N provided greater total N uptake than organic sources, except the high rate of compost, suggesting that the N availability from organic sources was not well synchronized with forage N demand. Municipal solid waste compost may also increase soil and forage tissue Na, which might be of concern.

Abbreviations: MSW, municipal solid waste • SS-MSW, source-separated municipal solid waste

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
IMPROVING SOIL FERTILITY and nutrient efficiency and reducing negative impacts of agricultural practices on the environment are now among the top priorities of the agricultural industry in North America. In recent decades, there has been an increased interest in recycling of nutrients through the use of waste products as alternative plant nutrient sources (Pierzynski and Gehl, 2005). In recent years the production and the use of municipal solid waste (MSW) compost in crop production systems in Atlantic Canada has increased. However, the use of industrial composts as crop nutrient sources and soil conditioners brings the concern of possible contamination of crops and soil with heavy metals (Epstein, 1997). There have been no studies conducted on the use of source-separated municipal solid waste (SS-MSW) compost as a nutrient source for hay production on dykelands, which represent some of the most fertile agricultural land in Atlantic Canada. Also, there are no comparative studies on nutrient availability from this type of compost and solid manure, which are typically applied to dykelands (Papadopoulos et al., 1991).

There are over 33 000 ha of dykelands protected from the salt water in Nova Scotia and New Brunswick. Some of the dykelands were developed for agriculture around 300 years ago; others were developed quite recently from rich salt marshes along the coast of Bay of Fundy of Nova Scotia and New Brunswick. The dykelands, relatively flat, rock-free silty clay loams, play an increasingly important role for crop production in the region and for wildlife conservation. Generally, dykelands have a shorter cropping season compared to other agricultural lands because they hold water late in the spring and are not well suited for fall plowing. Another common issue of dykeland soils is their high salt content that gives these soils properties of sodic or saline soils (Rodd et al., 1993). Crop diversity on dykeland soils has therefore been limited by the shorter cropping season, excess water, and excess salts.

Dykeland soil characteristics can be improved through the application of animal manures and composts to increase organic matter (Papadopoulos et al., 1991) and gypsum to alter the Ca/Na ratio (Carter and Pearen, 1989). In addition to Ca, gypsum provides S, which may alleviate hidden S deficiencies and improve N uptake. Recently, one of the nutrient deficiencies identified in Atlantic Canada and in Europe was S deficiency due to the use of high purity fertilizers, continuous cropping with high-yielding varieties, and the reduction of anthropogenic SO₂ emission (MacGrath et al., 1996; Riley et al., 2002). Sulfur may be easily washed from the surface soil, especially in regions with high precipitation. According to the USEPA (USEPA, 2006), SO₂ emissions in Atlantic Canada have been reduced by 50% for the period between 1980 and 1998 (from around 3.7 millions t y^–1 to around 1.8 millions t y^–1). Sulfur deficiency may result in reduced N uptake, yield, and quality of plants. Research has demonstrated that S addition increased yields in alfalfa, wheat, corn, canola, oilseed rape, and potato (Stewart and Porter, 1969; Millins and Mitchell, 1989; Weil and Mughogho, 2000; Pavlista, 2005; Rehm, 2005). Agricultural crops vary widely with respect to their tolerance to low external solution S and different crops may have different critical tissue S concentration (Hitsuda et al., 2005). The effects of S on timothy have been studied in container experiments (Warman and Sampson, 1994a, 1994b); however, results cannot be easily extrapolated to dykeland field systems. Gypsum is an inexpensive source of S and Ca with large deposits available in Nova Scotia.

The objective of this study was to test the hypothesis that organic and commercial fertilizer sources provide comparable available N and S and produce comparable forage yields. The hypothesis was tested by determining the effect of MSW compost, manure, and mineral nutrient sources on timothy/clover forage yields, forage N and S concentration and uptake, distribution of NO₃–N and NH₄–N in the soil profile, and heavy metal enrichment of the forage.

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Site Description and Experimental Design
The field experiments were conducted in 2001 and 2002 on a dykeland soil in a site near Truro, Nova Scotia (45°22' N; 63°16' W). The site was seeded in 1988 with a mix of timothy (Phleum pratense L.) and red clover (Trifolium pratense L.) and maintained continuously for hay production by harvesting twice every season. Analyses of botanical composition of this perennial forage site demonstrated that the grass component was more than 85% of the stand. The field is 4.9 ha, with <1% slope and is approximately 11 m above sea level. Dykeland ditches separate this field from the adjacent dykeland fields. The soil type is a Bridgeville coarse loam (Orthic Humo-Ferric Podzol). According to the Nova Scotia Soil Testing Laboratory Services, the soil is considered high in Mg, medium to high in P, and medium in K and Ca (using the Mehlich 3 extraction method [Mehlich, 1984], a standard procedure in Atlantic Canada for the estimation of phyto-available soil nutrients) (Table 1). The Mehlich 3 (phyto-available) concentration of other elements was within the normal range for Nova Scotia agricultural soils.

Forage Harvesting, Tissue and Soil Sampling, and Analysis
The crop was harvested twice in each of the production years (2001 and 2002). In both years, the first harvest was done from 20–22 June; the second harvest was done at the beginning of September. Fresh yield was determined by harvesting a 9.0 m² swath across the middle of each plot using a Haldrup 1500 (Logstor, Denmark) small plot forage harvester. This harvester also gathers a representative subsample from each swath. The tissue subsamples were dried at 65°C for 72 h to determine dry matter yields and for mineral and trace element analyses. After drying, the tissue samples were ground in a Wiley Mill to pass a 1.0-mm screen. Soil samples (0 to 15 cm depth) for nutrient and trace element analysis were taken twice during the growing season: immediately after the two harvests in June and in September. The soil samples were air-dried at 20°C and ground with a mortar and pestle to pass through a 2.0-mm screen.

Aqua Regia and Mehlich 3 Extraction Procedures
Plant tissues samples were dissolved for total elemental analyses using an aqua regia decomposition procedure (International Organization for Standardization, 1995; Sastre et al., 2002). The amount of available nutrients in soil was determined with Mehlich 3 extraction (Mehlich, 1984). The concentration of macro and micronutrients in tissue and soil samples was measured by an inductively coupled argon plasma spectrometer (ICAP) model 61 (Thermo Jarrell Ash, Franklin, MA).

Deep Soil Coring, Nitrate Nitrogen, and Ammonium Nitrogen Extraction
The amounts of residual soil NO₃–N and NH₄–N were determined to a depth of 80 cm following the procedure of Bremmer (1965). Soil cores (0 to 80 cm) were taken in the fall of 2002 using a tractor fitted with a hydraulic soil sampler, which contained acetate sleeves of 3.8-cm diameter. The fresh soil cores (two from each plot) were sectioned into 10-cm increments. Fresh soil subsamples of 10.0 g from each of the 10-cm increments were extracted in 50 mL of 2 M KCl by shaking for 1 h, and then filtered through Whatman 934AH paper. Nitrate nitrogen and NH₄–N were measured colormetrically by segmented flow analysis on a TRAACS 800 AutoAnalyzer (Technicon Industrial Systems, Tarrytown, NY).

Acid-Detergent Fiber, Neutral-Detergent Fiber, and Energies
Dry forage samples from the first cut of the second cropping season were analyzed in triplicate for acid-detergent fiber (ADF), neutral-detergent fiber (NDF), and energies using the procedure described in Goering and Van Soest (1970) and in Van Soest et al. (1991).

Statistical Analyses
For % total N, N uptake, dry matter yield, and concentration and uptake of tissue S data from the 2 yr (2001 and 2002) of field experiments were analyzed together as a 7 x 3 factorial in six blocks and the responses measured repeatedly in June and in September. The 21 treatment combinations were completely randomized within each block. Since the exact growing conditions in 2001 and 2002 cannot be repeated in future years, and since year was not a factor of interest, the six blocks were generated as the combinations of the 2 yr and the three locations in the field. However, the variance components for year and blocks (locations in the field) within year are computed separately to indicate the magnitude of variability due to these factors. In the model, the six blocks were used as random blocks; fertility with 7 levels (high chemical N, low chemical N, high compost, low compost, high manure, low manure, and unamended control), and gypsum with 3 levels (S0: zero S, S1: 20 kg S ha^–1, and S2: 40 kg S ha^–1) were used as fixed factors of interest. Nitrate nitrogen and NH₄–N, measured repeatedly at 8 depths in 2002, were analyzed as repeated measures in space. The phyto-available concentration of soil nutrients that were measured only once in September of each year were analyzed as a 7 x 3 factorial in 6 yr by location blocks. Because total soil concentrations of these nutrients were measured in September of 2002 only, they were analyzed as a 7 x 3 factorial in 3 location blocks. For each response, the validity of model assumptions was verified by examining the residuals as described in Montgomery (2001). For most of the response variables a square root transformation was needed to meet the normal distribution of the error terms assumption. The analyses were completed using Proc Mixed (SAS Institute, 1999) which overcomes several shortcomings of Proc GLM for analyzing repeatedly measured data and designs with mixed effects (Littell et al., 1996). The most appropriate covariance structure for the repeated measures analysis was determined based on the Akaike's information criterion (AIC) and Schwarz's bayesian criterion (SBC) values. When either the main or the interaction effects of the fixed factors (fertility, gypsum, and cut or depth) were significant (p values < 0.05) or marginally significant (0.05 < p value < 0.1), orthogonal contrasts were constructed and tested. For fertility, the orthogonal contrasts were: (1) unamended control vs. fertilized, (2) chemical N vs. compost and manure, (3) compost vs. manure, (4) high vs. low compost, (5) high vs. low manure, and (6) high vs. low chemical N. For gypsum, the orthogonal contrasts were: (1) 0 vs. gypsum and (2) 1 vs. 2 gypsum. For depth, the orthogonal contrasts were: (1) 0 to 10 cm vs. 10 to 80 cm, (2) 10 to 20 cm vs. 20 to 80 cm, (3) 20 to 30 cm vs. 30 to 80 cm, (4) 30 to 40 cm vs. 40 to 80 cm, (5) 40 to 50 cm vs. 50 to 80 cm, (6) 50 to 60 cm vs. 60 to 80 cm, and (7) 60 to 70 cm vs. 70 to 80 cm. These contrasts were run within the levels of the interacting factor whenever an interaction effect was significant. Letter groupings, using a 5% level of significance, were also generated for concentration and uptake of tissue S and dry matter yield responses. To show a complete picture of the performance of the treatments, the means (back-transformed to the original scale) for the significant effects are also shown in the tables.

	RESULTS AND DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
The two harvests were significantly different for dry matter yields (Table 3 and Table 4). Generally, dry matter yields were greater from the first cut than from the second cut, an observation that is typical for forages grown in Atlantic Canada (Lynch et al., 2004). The yield differences between the two harvests in this region are due to the moist spring and the subsequent drought periods in July and August. The significance of the differences between the yield from the two harvests depended on the type of fertility for total N concentration and N uptake (Table 3). The significant interaction between gypsum and depth with respect to NO₃–N and the lack of fertility effect on NO₃–N (Table 5) demonstrated that gypsum may have a greater effect on the distribution of NO₃–N in the soil profile than fertility in perennial forage on dykeland. To our knowledge, this finding has not been previously reported.

The higher forage yields in the compost treatments vs. the manure may be due to (1) higher available and mineralizable N in compost, and/or (2) the presence and availability of all plant nutrients in compost. Based on our previous studies with the same type of compost and manure, first year N availability was assumed to be 22% from compost and 40% from the solid manure. However, N availability from the surface-applied compost and manure may have been different, and most probably lower than assumed. The high rate vs. low rate of compost application increased forage yields and N uptake with the first cut but had no effect on forage tissue N, tissue S, or S uptake. This result suggests that (1) forage is able to utilize the additional N with the higher compost rate in the early wet spring conditions of Atlantic Canada and (2) perhaps N availability from compost is lower than the assumed 22% and hence the response to the high compost rate. High and low manure rates provided the same forage tissue N, N uptake, forage yields, tissue S, and S uptake. Since manure yields were close to the yields in the control and the N uptake in the manure treatments was lower than in the chemical N treatment, this result may be an indication that N availability from manure was less than the assumed 40%. Hence, the higher manure rates were not able to provide sufficient N for maximum yields or for yields different from the low manure rates. High rates of chemical fertilizer compared with low rates increased tissue N and N uptake in the second cut only, and had no effect on forage yields, tissue S, and S uptake. This result seems to suggest that timothy/red clover mix may not respond positively to N above 95 kg ha^–1.

Overall, a higher rate (S2 as opposed to S1) of gypsum application increased forage yields and N and S uptake (Table 4) confirming our hypothesis that S addition (as gypsum) may improve N uptake and forage yields. Gypsum provides both S and Ca. However, gypsum solubility is not high enough to elevate soil solution Ca concentration sufficiently to produce a significant effect on N compared with other more soluble compounds like calcium nitrate and calcium chloride. Indeed, in this experiment, gypsum had no effect on soil Mehlich 3-extractable Ca or tissue Ca, most probably due to its slow solubility and the relatively small amount of Ca input with gypsum compared with overall soil Ca. It is well known that in time the high rate of gypsum supplies easily available Ca that can co-migrate with sulfate ions, increase exchangeable Ca and reduce exchangeable Al with no effect on pH (Oates and Caldwell, 1985; Sumner et al., 1986). The indicated positive effects of surface-applied gypsum improve root-growing conditions and subsequently gypsum may have indirect but positive effects on crop yields (Toma et al., 1999; Ritchey and Snuffer, 2002). Hence, we can assume that several direct and indirect effects of gypsum contributed to the increased N uptake and forage yields on the dykeland system. High rates of compost increased soil Mehlich 3-extractable Ca relative to the control and to the N treatments, but had no effect on tissue Ca. Tissue Ca was decreased in the high N treatment, probably due to the dilution effect. This result may also indicate that Ca accumulation in timothy/red clover forage is stable in spite of Ca supply, confirming previous research on similar forage systems (Lynch et al., 2004). Although tissue S in the second cut was greater, the overall S uptake with the first forage cut was greater than with the second cut (Table 4).

Soil Nitrate Nitrogen and Ammonium Nitrogen in the 0- to 80-Centimeter Soil Depth
There was also a significant interaction between fertility and S (gypsum) on residual soil NH₄–N and between gypsum and depth on residual soil NO₃–N (Table 5). Surprisingly, fertility did not have an effect on residual NO₃–N. Overall, the highest NO₃–N and NH₄–N concentrations were found in the top 10 cm, less in the 10- to 20-cm depth, and least in the 20- to 80-cm depth (Table 8 and Table 9). Lynch et al. (2004) in a study with organic amendments on timothy/red clover reported the effect of fertility on soil residual inorganic N, but only in the surface layer 0 to 5 cm. Contrasts of different depths indicated that generally, residual soil NO₃–N after 20 cm, and NH₄–N after 40 cm did not vary much (Table 8).

Biosolids and chemical fertilizer treatments did not increase available S (but increased marginally total S) relative to the unamended control (Table 11). Application of biosolids (compost or manure) increased the concentration of phyto-available S compared with the chemical fertilizers. Also, compost application increased the concentration of both total and phyto-available S compared with manure. High rate of compost increased phyto-available S compared with the low rate. However, high rate of manure application did not increase the concentration of total or phyto-available S compared with the low rate of manure. On the other hand, while a high rate of chemical fertilizer increased total S marginally, it did not increase phyto-available S (Table 11). The highest mean values for soil total and available S (10.2 and 515 mg kg^–1, respectively) were obtained from high compost. Increased rates of gypsum application tended to increase phyto-available S (Table 11). Although fertility increased total and phyto-available S, tissue S concentration in all treatments except in the manure (Table 7) was not different. This observation along with other reports (Warman and Sampson, 1994a, 1994b) suggest that Mehlich 3 extractant may not be suitable for assessment of plant-available S in Atlantic Canada soils. Our results agree with the findings of Gaskin et al. (2003) that application of biosolids might not necessarily increase tissue S of forage grass.

Our exploration of the presence of relationships between tissue concentration and available (Mehlich 3-extractable) nutrients in the soil within each treatment combination using nonparametric regression did not reveal any pattern. If there were any relationship, it would have been revealed by the nonparametric regression, which is capable of showing the prevailing linear or nonlinear relationship. Treatments did not significantly change laboratory estimates of forage quality (ADF, NDF, and energies) (data not shown).

Heavy Metals
The application of industrial composts to agricultural land and crops could increase heavy metals in harvestable crop parts (Deportes et al., 1995; Epstein, 1997). To quantify the effect of SS-MSW compost on soil and crops with respect to heavy metals, measurements included total and extractable amounts of Pb, Cu, Zn, Cd, Ni, and Cr in soil and in compost (data not shown). Cadmium, Pb, Cr, and Ni concentrations in forage tissue from all treatments were below the detection limit of ICAP (0.005 mg L^–1 for Cd, and 0.05 mg L^–1 in solution for Pb, Cr, and Ni, respectively). Fertility treatments did not alter Cu concentration in forage tissue. The high compost rate decreased Zn concentration in the second cut relative to the control and N treatments, while manure and low rate of composts decreased tissue Zn relative to the high N treatment only. The observed decrease in tissue Zn is possibly due to Zn binding by organic matter making it unavailable to plants.

	CONCLUSIONS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
The results from this study demonstrated that MSW compost could provide the same yields of timothy/red clover on dykelands as chemical sources of N, and higher yields than solid manure. If an inorganic N fertilizer is to be used, 95 kg of N ha^–1 yr^–1 is sufficient to provide optimal forage yields on dykelands in Atlantic Canada. There is no yield advantage for using 190 kg vs. 95 kg N ha^–1 yr^–1 from inorganic fertilizer. Our results and other reports suggest that in permanent forage on dykelands systems residual NO₃–N may be concentrated in the top 0 to 20 cm which lowers the probability for NO₃–N leaching into the groundwater. Overall, the highest NO₃–N and NH₄–N concentrations were found in the top 20-cm depth, and least in the 20- to 80-cm depth. In this experiment, fertility did not have an effect on residual NO₃–N or on forage quality (ADF, NDF, and energies). We found that gypsum may have a greater effect on the distribution of NO₃–N in the soil profile than fertility in forage cropping systems on dykelands. Gypsum application calculated to provide 40 kg total S ha^–1 increased forage yields and N and S uptake, and did not induce soil or tissue Mg deficiency. Our results demonstrated that MSW compost can be used as a source of N and can provide sufficient S and other nutrients to timothy/red clover mix on dykelands. Compost (at high application rates) might have the potential to replace inorganic N fertilizers in these cropping systems; however, further research is needed to evaluate availability of P, K, and other nutrients from compost vs. commercial fertilizers before a recommendation is made. Municipal solid waste compost may also increase soil and forage tissue Na, which might be of concern.

	ACKNOWLEDGMENTS

 
This work was partially supported by Agriculture and AgriFood Canada, AgriFutures Nova Scotia grant #190 awarded to Dr. V.D. Zheljazkov (Jeliazkov) et al., and by Nova Scotia Department of Agriculture and Fisheries AgriFocus 2000 Technology Development grant DEV21-022 awarded to Dr. V.D. Zheljazkov. The work on heavy metals in compost was supported by NSERC Discovery Individual Grant awarded to Dr. V.D. Zheljazkov. We thank Ms. Lindsay Hainstock, Mr. Cory Murphy, Mr. Scott Veitch, Mr. Scott Savoy, Mr. Paul McNeil, Ms. Stephanie Butler, Mr. Dan Tully, and Ms. Drucie Janes for their assistance in the field and in the laboratory. We thank Dr. Nancy McLean from the Nova Scotia Agricultural College for critically reviewing the manuscripts and suggesting improvements. We also thank the anonymous reviewers for their comments and suggestions, which resulted in more focused and much improved paper.

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