P.R. Warman, Nova Scotia Agricultural College, Truro,
N.S., B2N 5B3
& V. Rodd, Agriculture & Agri-Food Canada, Nappan, N.S. BOL 1CO
Field experiments have been in progress in a Pugwash sandy loam near Truro, N.S. since 1996. The experimental objectives have been to evaluate the effect of MSW compost upon the yield, plant nutrient and trace metal content of three vegetable crops ( potatoes, squash, sweet corn) grown in a three-year rotation, and to measure changes in soil chemical properties throughout the rotation period. This study is part of the National Agricultural Compost Trials. It is one of the few studies in existence where all the macro- and trace elements (as listed in the CCME Compost Quality Guidelines) are being evaluated, both in plant tissue and the soil.
The experimental design is a randomized complete block factorial involving the three crops each year. The fertility treatments are a) NPK fertilizer based on the crop's soil test requirements; b) MSW compost at Rate 1; c) MSW compost at Rate 2; d) MSW compost at Rate 3; e) 1/2 MSW compost at Rate 1 + 1/2 NPK (treatment a). Compost applications to the potatoes and sweet corn are based on total P analysis , while compost applications to the squash are based on total N analysis assuming 100% N availability (the MSW1 rate) from the compost. MSW compost Rates 2 and 3 are two and three times as high as Rate 1, respectively.
The paper will highlight the yield and plant tissue results of the 1998 cropping year, results related to plant nutrient uptake and the effect of treatments on soil pH.
Introduction
Composting of source-separated municipal solid waste (SSMSW) has gained popularity with municipalities in North America as a mechanism to divert refuse from landfills. In Nova Scotia alone, there are two major facilities producing compost from SSMSW as opposed to mixed solid waste.
All users of MSW compost require knowledge of its value in order to determine its nutrient availability, its effect on soil physical properties, and its influence on heavy metal uptake and the nutrient content of crops. Further, potential human pathogens which may be associated with composted crops must be evaluated as to their virality. Since MSW compost is a relatively new soil amendment, there are relatively few studies which provide a compost user with the necessary information to determine its effectiveness. As newer facilities 'come on stream', using combinations of ash, yard waste, biosolids, food waste, etc., MSW compost will be used for both high and low value crops. The landscape trade will continue to be an important user of commercial compost, but given the volumes of material which will be produced in the future, more and more compost will be applied to cropland, if only for its value as a stablilized organic amendment.
Field grown tomatoes seem to be the most popular vegetable crop grown with MSW compost amendments. Ozores-Hampton et al. (1994) grew tomatoes and followed them with squash, one of the three crops used in our study. A survey of the literature on the production of sweet corn and potatoes using compost as a fertilizer showed that MSW compost was very infrequently used (Warman and Havard, 1998). Recently, however, Macleod et al. and Simard et al. with Agriculture and Agri-Food Canada (AAFC) have evaluated other sources of MSW for potato production and soil fertility (their work is published in previous additions of the CCC proceedings).
The compost produced at the Lunenburg Regional Recycling and Composting Facility is being evaluated by a team of researchers from AAFC and NSAC as part of the Canada-wide effort to evaluate soil and crop productivity from MSW compost. The research is in its third year of field and greenhouse evaluation and involves common vegetable crops, small grains, small fruit or ornamentals and the bioavailability of 11 trace elements. Some of the results from 1996 and 1997 were presented the past two years in Warman et al. (1996) and Warman and Mkhabela (1997); the following results from the vegetable crop study are from the third year of this project.
The three crops are representative of different vegetable groups with different nutrient demands, growth requirements, and impacts on the soil from relatively low (squash) to high (potatoes) impact. This experiment differs from our previous studies (Warman and Havard, 1996, 1998) and the long-term organic-conventional study (Warman, 1998) in that a specific rotation is being used and different rates of a specific source of compost (MSW), with and without fertilizer, is being evaluated.
Materials and Methods
The experiment has been conducted in Lower Onslow, N.S. in a Pugwash sandy loam (Humo-Ferric Podzol, CLI Class 2). The MSW compost was from the Municipality of Lunenburg's source-separated composting plant. Three I crops were each planted into 20 plots (24 plots in 1997) of 16 m2, equivalent to 4 replicates of 5 treatments randomly assigned to each block. Amendment rates for 1998 are shown in Table 1; the treatments were as follows:
(a) NPK Fertilizer
(b) MSW Compost Rate 1
(c) MSW Compost Rate 2 (Rate 1 x 2)
(d) MSW Compost Rate 3 (Rate 1 x 3)
(e) 1/2 NPK Fertilizer + 1/2 MSW Compost Rate 1
The NPK rate for each crop was based upon the soil test recQmmendations
for Nova Scotia using the Mehlich-3 extract levels found in fall soil samples.
MSW additions for the corn and potatoes were based on P requirements assuming
100% P availability; while MSW additions to the squash plots were based
on its N requirement assuming 100% N availability (MSW1).
Soil and compost samples were extracted or digested with H20, Mehlich 3 or HNO3 and analysed using a pH meter, a LECO CNS Analyser, AAS, ICP (Warman et al. 1995) or colorimetry. Table 2 shows the elemental analysis of the MSW compost used in 1998 (note, the results differ from the analyses reported in 1996 and 1997). Plant populations counts were conducted after emergence, at flowering and at harvest. Weeds, insects and diseases were controlled with the use of registered pest-control products applied as recommended. At flowering or tasseling, eight whole potato or corn plants (roots & above ground parts) were taken from each plot, oven dried & weighed for total dry matter yield. The most recently mature squash leaf from each hill (4-6/plot) was sampled Sept.1. All plant parts were ground and analyzed for 13 essential and 8 trace elements. Crops were hand-harvested at maturity and potato tuber, corn ear and squash fruit weights were recorded.
Results and Discussion
The fresh weight yields from the plots are shown in Table 3. The treatments influenced marketable cob weight and total potato tuber yield but not marketable tuber yield or squash fruit weight/plant. Although not always significant at p<0.05, the order of treatment plot yield always produced the highest yield from the NPK treatment and the lowest yield from the MSW1. The MSW treatments were always in the order of MSW3> MSW2> MSW1. The half NPK+MSW1 treatment produced the equivalent yield to that of the MSW3. Fresh weight yields of the eight potato plants followed the same order as indicated for tuber yields; dry weight yields of the eight plants/plot/treatment, however, were not significantly different because the % dry matter followed the opposite trend of MSW1> MSW2> MSW3> NPK +MSW1 /2> NPK. For the sweet corn, fresh weight, % dry matter and dry weight of the 8 plants/plot were not affected by treatments. Furthermore, the average fresh cob weight of the five treatments were similar at 218 g/cob. Therefore, vegetable crop yields following three years of compost application have not really changed much, the NPK treatments still provide a nutrient boost in wet (1996), dry (1997) and above-average (1998) cropping years.
Tables 4a and 4b show the significant treatment effects. on essential nutrient content or nutrient uptake for the three crops. Six elements were influenced by treatments for the whole potato crop samples but only three elements for the whole corn samples and one for the squash tissue were so affected. The fertilizer or fertilizer-compost treatments produced the highest N, Ca and Mg content in the total plant samples. Tissue Mn was highest in the NPK plots for potatoes and squash and was likely associated with the lowest soil pH (Table 5), a relationship which has been previously cited by the senior author and others. MSW compost treatments produced higher plant Cu levels, as related to the increased Cu applications associated with the compost. Cu concentrations in the plants, however, were not near toxicity levels.
To date (November 13, 1998), only soil pH of all the soil tests to be conducted has been evaluated. Table 5 clearly indicates the liming effect associated with the compost applications and the linear response of compost rates to soil pH. Mehlich 3 extractable nutrients will be determined and correlated with the nutrient content and/or uptake of the whole plant samples or tissue (squash). Also, soil physical and biochemical properties will be evaluated and possibly a carry-over crop will be seeded in 1999.
Acknowledgements
We wish to thank I. Walsh and R. Ring for their exemplary work in the lab and the field. Compost and financial assistance was provided by the Municipality of Lunenburg, the Halifax Regional Municipality, NSDOE, Miller Waste Ltd and the MII Matching Fund Initiative of AAFC; infrastructure support was furnished by Coastal BioAgresearch Ltd.
References
Ozores-Hampton, M., Schaffer, B, and Bryan, H.H. 1994. Nutrient concentrations, growth, and yield of tomato and squash in municipal solid- waste-amended soil. HortScience 29:785-788.
Warman, P.R. 1998. Results of the long-term vegetable crop production trials: conventional vs compost-amended soils. Acta Horticulturae 469:333-341.
Warman, P.R. and Havard, K.A. 1996. Yield, vitamin and mineral content of four vegetables amended with either composted manure or conventional fertilizer. J. of Vegetable Crop Production 2(1 ):1 3-25.
Warman, P.R. and Mkhabela, M. 1 997. Influence of MSW compost on vegetable crop growth and soil properties: Year 2. Proceedings of the 7th Annual Meeting of the Comnposting Council of Canada, Montreal, P.Q., Nov. 5-7, 1997, pp.89-97.
Warman, P.R. and Havard, K.A. 1997b. Yield, vitamin and mineral contents of organically and conventionally grown potatoes and sweet corn. Agriculture, Ecosystems and the Environment 68:207-216.
Warman, P.R., Muizelaar,T., and Termeer, W.C. 1995. Bioavailability of As, Cd, Co, Cr, Hg, Mo, Ni, Pb, Se, and Zn from biosolids amended compost. Compost Sci. & Utilization 3(4):40-50
Warman, P.R., Mkhabela,
M. and McLaughlin, N. 1996. The effect of composts and commercial fertilizers
on vegetable crop production and soil properties. Proceedings of the 6th
Annual Meeting of The Composting Council of Canada, Toronto, Ont., Nov.
6-8,1996, pp.298-307.
Table 1. Amounts of MSW and Fertilizer Applied to the Experimental Plots in 1998
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| (tons/ha) |
(kg/plot) |
(kg/ha) |
(g/plot) |
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(34-0-0) |
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(0-46-0) |
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(0-0-60) |
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(34-0-0) |
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(0-46-0) |
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(0-0-60) |
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(34-0-0) |
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(0-46-0) |
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Table 2. MSW Compost Analysis for 1998 (mean + sd)
C N P K Ca Mg S Na Fe Mn pH= 7.93 ±0.08 EC= 1.93 mhos/cm
| Crop | NPK | MSW1 | MSW2 | MSW3 | NPK+MSW/2 |
| CORN | |||||
| (cob wt- kg/plot) | 13.3b | 9.9a | 10.7ab | 11.6ab | 11.1ab |
| treatments * at p= 0.023 | |||||
| POTATOES | |||||
| marketable (treatments NS at p 0.05) | |||||
| 52.1 | 42.7 | 42.9 | 49.1 | 50.3 | |
| (tuber wt- kg/plot) | Total = Grade A + B (treatments * at p= 0.012) | ||||
| 56.0b | 43.6a | 45.3a | 50.8ab | 52.8ab | |
| SQUASH | treatments NS at p= 0.05 | ||||
| (fruit wt- kg/plant) | 5.2 | 3.8 | 3.2 | 4.4 | 3.3 |
* treatment means in a row followed by different letters are significantly different at p<0.05.
Table 4a. Significant treatment effects on vegetable nutrient content (p = <0.05)
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g/kg |
g/kg |
g/kg |
mg/kg |
mg/kg |
mg/kg |
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| NPK | 29.5b | 7.57b | 4.59b | 30.5b | 7.90a | 111ab |
| MSW1 | 18.8a | 5.52a | 2.97a | 13.6a | 8.74ab | 94a |
| MSW2 | 19.5a | 5.85a | 2.82 | 15.1a | 8.98ab | 129b |
| MSW3 | 20.0a | 6.13ab | 2.77a | 16.7a | 10.32b | 136b |
| NPK+ MSW/2 |
25.5b | 7.00ab | 4.88b | 17.2a | 9.71b | 115ab |
* treatment means in a row followed by different letters are significantly different at p<0.05.
Note: the N, Mg, Mn and Na uptake by potatoes was similarly affected by the treatments
Table 4b. Significant treatment effects on vegetable
nutrient content or uptake
(p = <0.05)
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| Treatment | g/8 plants |
g/kg |
mg/kg |
mg/kg |
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| MSW/2 |
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* treatment means in a row followed by different letters are significantly different at p<0.05.
Table 5. Effect of Treatments on September 1998 Soil pH
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Corn | Potato | Squash |
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5.87a | 5.95a | |
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6.31ab | 6.49bc | |
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6.42bc | 6.61bc | |
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6.77c | 6.73c | |
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6.05ab | 6.38b | |
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* treatment means in a row followed bg different letters are significantly different at p<0.05.
