SECTION II Utilization of Compost in Horticultural Cropping Systems © 2001 by CRC Press LLC CHAPTER Compost Effects on Crop Growth and Yield in Commercial Vegetable Cropping Systems Nancy E Roe CONTENTS I II Introduction Compost Research for Vegetable Cropping Systems A Corn B Cruciferous Crops C Cucurbits D Legumes E Solanaceous Crops F Other Crops III Conclusions References I INTRODUCTION Harvested acreage for 25 selected fresh vegetables and melons was 748,677 in the United States in 1997 (USDA, 1998) Acreage of 10 processing vegetables added an additional 574,660 The value of production for these 25 fresh market vegetables and 10 processing crops totaled $9.27 billion in 1997 (USDA, 1998) Vegetable production should constitute an ideal use for compost since most crops are grown in annual systems that have a high profit potential Impediments to the utilization of compost in these intensive production systems include compost costs; transportation costs; lack of adequate application equipment; and lack of clear and consistent demonstration of compost benefits to plant growth, yield, and profits © 2001 by CRC Press LLC Research projects in the U.S and other countries have focused on the use of composts from materials that are readily available in large quantities in the local area Due to the high bulk density of most composts, local availability is critical for practical and economical usage In many U.S vegetable crop production areas, such as south Florida, the proximity of large human populations provides an opportunity for production of composts from municipal wastes In others, such as parts of North Carolina and the high plains of Texas, large numbers of confined animal feeding operations produce animal manures that can be composted Feedstocks for composts evaluated on vegetable crops include mixed municipal solid waste (MSW), sewage sludge (biosolids), yard trimmings, wood chips, animal manures, food processing byproducts, and other agricultural wastes Each of these composts has its own properties and may affect soil characteristics, crop growth and, ultimately, yield in distinct ways Research projects also generally center on crops that are grown and consumed in the local area or country where the work is being performed Therefore, research results are difficult to categorize Nevertheless, worldwide compost quantities are increasing, compost quality is improving, and more commercial vegetable growers are evaluating compost or integrating it into their production systems II COMPOST RESEARCH FOR VEGETABLE CROPPING SYSTEMS A summary of recent research reporting effects of compost on vegetable crop growth and yield is provided in Table 5.1 The following section provides some details (arranged by crop or crop group) of these studies A Corn A biosolids/yard trimming compost was applied in 1979 and 1980 on land previously mined for sand and gravel in a study by Hornick (1988) Compost rates were 40, 80, or 160 Mg·ha–1 in each year Control plots were fertilized with 179N122P-112K (kg·ha–1) Sweet corn (Zea mays var rugosa Bonaf.) was grown in 1979, 1980, and 1981 as a test crop In all three years, corn grain yields were not significantly different between compost rates and the control, and there were few differences in grain nutrient concentrations Residual N from the 80 and 160 Mg·ha–1 compost rates was sufficient to keep grain N concentrations similar to those from control plants in the third year Hue et al (1994) conducted a pot study using a highly weathered Ultisol, for which it had been determined that P availability was the main plant nutritional limitation Rates of yard trimming compost at 75% (by volume) or higher mixed with the soil increased corn growth, but lower rates did not have an effect as compared to corn grown in unamended pots Pots filled with mixtures of three tropical soils (an Inceptisol, a Mollisol, and an Oxisol) and an MSW compost at rates from to 25% (by volume) were seeded with corn, and placed in a greenhouse (Paino et al., 1996) Plants were grown for 85 days, followed by two additional corn crops in the same soil mixes Although there were some differences in the effects of the compost on the three soil types, © 2001 by CRC Press LLC biomass produced was generally higher in mixtures which contained higher rates of compost B Cruciferous Crops Municipal waste compost at 0, 7, 14, and 27 Mg·ha–1 did not affect head yields of broccoli (Brassica oleracea L Italica group) fertilized with 84 or 168 kg·ha–1 of N on a fine sand in a study by Roe et al (1990) Low rates of a vegetable waste and manure compost (3 Mg·ha–1) with fertilizer N at 75 kg·ha–1 significantly improved broccoli crop response and N use efficiency when compared to a fertilizer-only treatment of 150 kg·ha–1 N plus 50 kg·ha–1 P (Buchanan and Gliessman, 1991) Increasing applications of compost alone (3, 7.5, and 30 Mg·ha-1) tended to increase broccoli yield and N accumulation, but decreased N use efficiency Smith et al (1992) reported no detrimental effects on cabbage (Brassica oleracea L Capitata group) yields from a biosolids/straw compost used at rates up to 100% of the N requirement At any given rate of applied N, optimal cabbage yields were obtained when half the N was supplied from an organic source (compost) and half from ammonium nitrate Compost application improved the efficiency of mineral fertilizer use The beneficial effects of compost were attributed to favorable effects on soil physical conditions and to the gradual release of essential phytonutrients Chinese cabbage (probably Brassica rapa L Chinensis group) yields were increased by the addition of swine waste compost at 25 Mg·ha–1, with or without sawdust, compared to no-compost plots with an acid field soil (pH ≤ 5.0), but not with a neutral soil (Kao, 1993) All plots also received fertilizer at a rate of 80N9P-33K (kg·ha–1) With the acid soil, Zn and Cu concentrations in the leaves from plots with sawdust/swine waste compost were higher than in leaves from no-compost plots Maynard (1994) reported that yields of broccoli and cauliflower (Brassica oleracea L Botrytis group) from unfertilized plots amended with a mixed compost (poultry manure, horse manure, spent mushroom compost, and sawdust) at 56 or 112 Mg·ha–1 were similar to or greater than yields from plots fertilized with 150 N66P-125K (kg·ha–1) C Cucurbits Winter (butternut) squash (Cucurbita moschata Duch ex Poir.) seedlings emerged slightly faster from plots mulched with MSW compost than from polyethylene mulched plots, but fruit yields were unaffected (Roe et al., 1993) A summer squash (Cucurbita pepo L.) crop was grown following a tomato (Lycopersicon esculentum Mill.) crop in a field where two MSW composts had been applied at 0, 33, or 67 Mg·ha–1 and a third MSW compost at 0, 67, and 135 Mg·ha–1, before tomato planting Total squash yields and mean fruit size were increased by all rates of two of the composts and not affected by the other, compared to plots without compost (Bryan et al., 1994) © 2001 by CRC Press LLC Table 5.1 Summary of Recent Research Reporting Effects of Compost on Vegetable Crop Growth and Yields Crop Alliaceae Onion Asteraceae Lettuce Brassicaceae Broccoli Cabbage Cauliflower Chinese cabbage Chenopodiaceae Spinach Cucurbitaceae Cucumber Summer squash Winter squash Fabaceae Cowpea Snap bean Soybean Malvaceae Okra Poaceae Corn Solanaceae Eggplant Pepper Tomato © 2001 by CRC Press LLC Growth Compost Responsez Yield Effectsz Reference BS/AW BS/WC NA NA +, = + Smith et al., 1992 Bevacqua and Mellano, 1993 BS/WC NA + Bevacqua and Mellano, 1993 MSW AM, AW NA NA = + AM BS/AW AM AM/AW NA NA NA NA +, = + +, = +, – Roe et al., 1990 Buchanan and Gliessman, 1991 Maynard, 1994 Smith et al., 1992 Maynard, 1994 Kao, 1993 BS NA +, = Mellano and Bevacqua, 1992 AW MSW MSW + NA NA + +, = = Kostov et al., 1995 Bryan et al., 1994 Roe et al., 1993 MSW MSW NA NA + +, = AM YT wood NA + + +, = +, = NA Bryan and Lance, 1991 Ozores-Hampton and Bryan, 1993a Allen and Preer, 1995 Gray and Tahwid, 1995 Lawson et al., 1995 MSW + + BS/YT YT MSW NA + + – NA NA MSW NA + MSW MSW NA NA = – MSW MSW BS/YT leaf BS/YT MSW MSW MSW MSW AW MSW MSW NA NA NA NA +, = NA NA NA NA NA NA NA – – = = + + + –, = + +, =, – +,– +, – Bryan and Lance, 1991 Hornick, 1988 Hue et al., 1994 Paino et al., 1996 Ozores-Hampton and Bryan, 1993b Roe et al., 1992 Ozores-Hampton and Bryan, 1993b Clark et al 1994 Roe et al., 1994 Roe and Stoffella, 1994b Maynard, 1996 Roe et al., 1997 Bryan and Lance, 1991 Manios and Kapetanios, 1992 Bryan et al., 1994 Clark et al., 1994 Maynard, 1994 Obreza and Reeder, 1994 Ozores-Hampton et al., 1994 Table 5.1 Summary of Recent Research Reporting Effects of Compost on Vegetable Crop Growth and Yields (Continued) Crop Growth Compost Responsez BS/YT BS Various MSW MSW AW NA NA NA NA NA + Yield Effectsz = + +, – + + + Reference Roe and Stoffella, 1994a Allen and Preer, 1995 Alvarez et al., 1995 Bryan et al., 1995 Maynard, 1995 Stoffella and Graetz, 1997 Note: BS, biosolids; AW, agricultural wastes; WC, wood chips; MSW, municipal solid waste; AM, animal manures; YT, yard trimmings z NA, +, –, = represent: information not available, increased, decreased, or equal, respectively Kostov et al (1995) reported that greenhouse cucumbers (Cucumis sativus L.) grown on a medium containing composting vegetable wastes with the addition of synthetic nutrients produced fruit 10 to 12 days earlier and had a yield 48 to 79% higher than those grown in soil mixed with cattle manure at a 2:1 ratio (dry weight basis) The composting wastes raised soil temperatures, increased CO2 production and microbial biomass, and released nutrients for plant utilization D Legumes Recognition of the need for more research into the relationship between soil microbiological populations and organic matter may result in more studies of compost effects on legume nodulation and N fixation Lawson et al (1995) reported that soybeans (Glycine max L.) grown in acid or saline soil amended with 4% wood waste compost had improved nodulation and shoot growth when compared with those in unamended soil Other studies of vegetable legume crop responses to composts have focused on yields With N added at 84 kg·ha–1 , 13 and 20 Mg·ha–1 of MSW compost gave higher cowpea (Vigna unguiculata [L.] Walp.) pod yields than Mg·ha–1 of compost or no compost With 168 kg·ha–1 N, yields were higher with 7, 13, and 20 Mg·ha–1 compost than with no compost (Bryan and Lance, 1991) An MSW compost incorporated at 90 and 135 Mg·ha–1 into a calcareous limestone soil resulted in snap bean (Phaseolus vulgaris L.) yields that were similar to beans grown without compost in the first crop, but quadratic yield increases with compost rate increases (starting from the zero-rate control) in the subsequent crop (Ozores-Hampton and Bryan, 1993a) Composts from biosolids, horse manure, and yard trimmings were applied for years to identical plots of a silt loam soil at rates of 53 Mg·ha–1 (Allen and Preer, 1995) Snap beans from the manure compost plots produced yields equal to those from fertilized control plots in the first year In the second year, the manure and yard trimmings compost plots produced the highest yields © 2001 by CRC Press LLC Gray and Tawhid (1995) reported that snap bean seedling emergence and plant survival in unmulched plots were increased by the addition of 2.5 cm of leaf compost as a mulch over rows after seeding E Solanaceous Crops Many of the studies involving compost utilization for solanaceous crop production have been conducted in Florida The combination of a large vegetable industry on soils low in organic matter, plus high urban populations producing large quantities of organic wastes has supported extensive compost research in Florida When 10 Mg·ha–1 of MSW compost was applied in trenches in combination with 6.7 to 13.4 Mg·ha–1 of MSW compost incorporated into beds on a gravelly soil, tomato yields were higher than with no compost (Bryan and Lance, 1991) Manios and Kapetanios (1992) studied MSW compost use in greenhouse tomato production Although all treatments were supplied with equal amounts of fertilizer through irrigation, yields of greenhouse tomatoes grown in soil were highest with the highest MSW compost application rates (10 m3 compost per 1000 m2 soil), compared to m3 compost per 1000 m2 soil or no-compost They also reported that compost stored outside and exposed to natural conditions for one winter affected yields similarly to compost that was stored under cover, despite a lower electrical conductivity (EC) in the former compost Roe et al (1992) evaluated MSW compost as a mulch, compared with a standard polyethylene mulch, on bell pepper (Capsicum annuum L.) production systems They reported that biosolids/yard trimmings compost used as a mulch at 112 and 224 Mg·ha–1 on bell peppers grown on raised beds increased total fruit yields when compared with no mulch, but yields were similar to or lower than with polyethylene mulches Municipal solid waste compost used as mulches at 13, 40, or 121 Mg·ha–1 decreased bell pepper yields as compared with polyethylene mulches, even though all plots were fertilized with a total of 269N-45P-192K (kg·ha–1) However, yields increased linearly with increasing compost mulch rates In another experiment, total bell pepper fruit yields from plots mulched with MSW compost at 224 Mg·ha–1 were less than half of those from polyethylene-mulched plots (Roe et al., 1994) Ozores-Hampton and Bryan (1993b) reported increased total marketable and large fruit from eggplant (Solanum melongena L.) and higher yield of large bell pepper fruit grown in plots amended with MSW compost at 90 and 134 Mg·ha–1 than from unamended plots In another experiment, one MSW compost was applied at 0, 33, or 67 Mg·ha–1 and another at 0, 67, and 135 Mg·ha–1, and tomatoes were planted, followed by squash (Bryan et al., 1994) Additional compost was applied at identical rates prior to planting a subsequent tomato crop In both tomato crops, growth and yields were reduced by one of the composts, but not affected by the other In a four-season experiment, MSW compost applied at 67 and 135 Mg·ha–1 on drip- irrigated plots, with fertilizer at 215, 309, or 403 kg·ha–1 of N, 44 kg·ha–1 of P, and 248, 356, or 464 kg·ha–1 of K, reduced yields in the initial crop of bell peppers in compost plots A subsequent tomato crop had more extra large and total marketable © 2001 by CRC Press LLC fruit, when compared with no-compost plots (Clark et al, 1994) This compost may have been initially immature, since another pepper crop grown on the identical plots resulted in increased yields Fertilizer applied to compost plots for that crop did not affect yields, but increased yields in no-compost plots Yields from early and final harvests and extra large fruit in an additional tomato crop also were higher in compost plots than in no-compost plots Maynard (1994) reported that tomato and bell pepper fruit yields from plots amended with compost produced from poultry manure with other agricultural wastes were similar to or greater than yields from fertilized plots, except in one crop of tomatoes where they were lower Obreza and Reeder (1994) reported that immature MSW composts at 13, 27, 75, and 112 Mg·ha–1 generally did not change or decreased yields of tomatoes for years, when compared with plants grown without compost and fertilized at the same rate (56N-49P-93K kg·ha–1 preplant and 172N-57P-230K kg·ha–1 applied through the drip system) With N at rates of 240 kg.ha–1, fruit yields from tomatoes grown in soil amended with one MSW compost at 48 Mg·ha–1 or another at 24 Mg·ha–1 were similar to those from plants grown in plots without composts (Ozores-Hampton et al., 1994) Transplanting tomato and pepper plants into a field containing an uncured (immature) and newly incorporated biosolids/yard trimming compost at 135 Mg·ha–1 (fresh weight) immediately or up to weeks after compost application did not result in yield differences in pepper or tomato fruit when compared with unamended plots (Roe and Stoffella, 1994a, 1994b) Tomatoes produced higher yields when grown with amendments of horse manure or biosolids compost at 53 Mg·ha–1 than with the same rate of yard trimmings compost, biosolids/yard trimmings compost, or fertilizer at 220N-97P-183K (kg·ha–1) in one year, but in the second year, highest yields were from the fertilized or biosolids compost-amended plots (Allen and Preer, 1995) Alvarez et al (1995) reported that three of four commercial composts incorporated into a soil increased growth of tomato plants, while one compost depressed tomato growth Compost amendments caused only small variations in the total numbers of bacteria, actinomycetes, and fungi in the rhizosphere of tomato plants However, the addition of some composts increased the incidence of certain rhizobacteria antagonistic to soilborne pathogens such as Pythium ultimum and Rhizoctonia solani Auclair et al (1995) compared organic growing media for greenhouse tomato production When tomatoes were grown on peat moss and shrimp compost, fruit contents of Ca, Cu, Fe, P, and Zn increased and fruit ripened later than when tomatoes were grown on composted cattle manure Marketable yield of tomatoes grown in calcareous soils was increased by additions of two MSW composts, one at 37 and 74 and the other at 74 and 148 Mg·ha–1, compared with similarly fertilized plots without compost (Bryan et al., 1995) Rates were selected so that the total N added would be 370 and 740 kg·ha–1 for the two rates of each of the composts Fruit size from compost plots was similar in the first year and larger in the second year when compared with fruit from unamended plots © 2001 by CRC Press LLC An MSW compost applied just before planting each spring at 56 and 112 Mg·ha–1 with fertilizer at 146N-64P-121K (kg·ha–1 ) resulted in tomato fruit yield increases in three consecutive years, compared with fertilizer only (Maynard, 1995) Undecomposed leaves (15.2 cm depth) tilled into plots in spring or fall or leaf compost (112 Mg·ha–1) incorporated in spring for three years with fertilizer at 146N64P-121K (kg·ha–1) resulted in similar bell pepper yields in the control and compost plots while yields were lowest from both treatments with undecomposed leaves in the first year (Maynard, 1996) In the second year, plants in compost-amended plots produced higher yields than plants in control plots or in plots with a fall application of leaves, but similar yields to plants in plots with a spring application of leaves In the third year, yields were similar among all treatments When biosolids/yard trimming compost at 134 Mg·ha–1 or no-compost was combined in a factorial arrangement with 0, 50, and 100% of a grower’s standard fertilizer (71N-39P-44K kg·ha–1 broadcast and 283N-278K kg·ha–1 banded in bed centers), highest bell pepper fruit yields occurred in the plots with compost and 50% fertilizer (Roe et al., 1997) In other studies, compost made from filtercake, a sugarcane (Saccharum officinarum L.) processing waste, was used (Stoffella and Graetz, 1997) Tomatoes were transplanted into pots filled with a 1:1 (v:v) mixture of the compost and a sandy field soil, the field soil only, or the compost only Plants from pots with compost or compost mixtures had higher shoot weights, thicker stems, and larger shoot to root ratios than plants grown in unamended field soil In a field experiment, plants from plots with the filtercake compost at 224 Mg·ha–1 were larger and produced higher yields than plants grown without compost, regardless of fertilizer rates (Stoffella and Graetz, 1997) F Other crops Okra (Abelmoschus esculentus [L.] Moench) grown in pots with MSW compost mixed at 10 to 30% (v:v) with a very gravelly loam soil had increased lateral root development and early fruit yields compared to plants grown in unamended soil (Bryan and Lance, 1991) Onion (Allium cepa L.) yield on a sandy loam soil increased with increasing rate of organic matter application, when the organic matter was biosolids/straw compost, or digested or raw biosolids (Smith et al., 1992) Biosolids compost at 12 and 25 dry Mg·ha–1 increased onion and spinach (Spinacia oleracea L.) yields when incorporated to a soil depth of 10 cm, but not to a 30 cm soil depth (Mellano and Bevacqua, 1992) Onion and lettuce (Lactuca sativa L.) plants grown in plots of sandy loam soil with biosolids/wood chips compost applied over a 2-year period, at cumulative totals of 37 and 74 Mg·ha–1, produced higher yields than the unamended control (Bevacqua and Mellano, 1993) © 2001 by CRC Press LLC III CONCLUSIONS Generalizing from numerous projects that examine the use of different composts at varying rates with or without additional fertilizers on various vegetable crops in diverse soils and assorted climates is extremely hazardous However, if we cannot find enough similarities to develop guidelines for compost utilization, then this research is unproductive from a practical standpoint Responses to composts are often more pronounced when crops are grown less intensively or are under an environmental stress In their review, Gallardo-Lara and Nogales (1987) summarized vegetable and agronomic crop responses to MSW compost as being more positive in poorer soils, and reported that mixtures of synthetic fertilizers and composts are usually more efficient than either alone in meeting crop nutritional requirements Gray and Tawhid (1995) reported that pod yields of bush snap beans were increased in a dry season, but not in a wetter one, by a leaf compost mulch Buchanan and Gliessman (1991) reported that broccoli N use efficiency was highest in treatments that combined N from a synthetic source with compost Another consideration is that nutrient levels in composts are not always in the correct proportions for plant growth There is a potential for buildup of some nutrient concentrations in the soil if composts are applied at high enough rates to supply the most limiting nutrients, usually N Excessive concentrations of plant nutrient elements raise the potential for environmental damage and may threaten the safety of those consuming the vegetables With increased interest in food safety and nutrition, researchers are beginning to report the concentrations of elements and compounds in plants that have the potential to be beneficial or to cause harm to humans who are consuming the vegetables Kao (1993) stated that annual applications of sawdust/swine waste compost at high rates (25 or 50 Mg·ha–1) to acid soils would eventually raise soil Zn and Cu to toxic levels In another study, a compost and a vermicompost decreased the nitrate concentration, but increased the K concentration of lettuce leaf tissue, when compared with synthetic fertilizers (Ricci et al., 1995) Although much evidence points toward soil and environmental improvements with compost use, as well as crop yield increases in many instances, the use of compost must increase profits in order for it to become an accepted practice among vegetable growers Kostov et al (1995) reported that it was more economical to use composting vegetable residues for greenhouse cucumber production than a manured soil Roe and Cornforth (1997) reported that uncomposted dairy manure and dairy manure compost both increased growth, yield, and net income from melons (Cucumis melo L.) and broccoli in a low-input growing system, but it was less expensive to use the uncomposted manure However, food safety concerns prevent the use of uncomposted manures directly on vegetable crops Although compost is organic matter, it can contain potentially harmful pollutants, such as heavy metals and human pathogens, which must be prevented from entering © 2001 by CRC Press LLC would likely impact handling, monitoring, and perhaps permitting, and any nonbiodegradable plastic from the diapers would need to be removed for some compost applications A Market Trends for Compost Compost has a variety of uses, ranging from its traditional use by gardeners as a soil enhancement to more innovative uses for wetland restoration, landfill cover, and industrial pollution control A report by the U.S EPA lists eight separate market segments for compost and the potential demand for each segment (Table 11.3) In all, the potential demand for compost far outweighs the supply of compost that could be available if the entire applicable waste stream were composted By far, the largest potential demand is agricultural It is estimated that the agricultural market for compost could reach 684 million m3 (895 million yd3) per year If the entire organic portion of the U.S waste stream were composted it would generate approximately 20 million m3 (26 million yd3) per year By contrast, the potential market demand by nurseries is less than 0.8 million m3 (1 million yd3) per year Table 11.3 Potential Market Size for Compost Products and Current Market Penetration Market Segment Potential Market Size m3 (millions) Estimated Market Penetration (%) Agriculture Silviculture Sod production Residential retail Nurseries Delivered topsoil Landscapers Landfill cover 684.3 79.5 15.3 6.1 0.7 2.8 1.5 0.5