b. Enhancement of Soil Fertility and Plant Nutrition

of organic N in composts allows them to be considered as environmentally sound

alternatives to controlled-release chemical fertilizers that have been used widely in

turfgrass management, particularly with respect to conservation of N that could be

lost by nitrate leaching from rapidly mineralizing or soluble fertilizers.

The slow mineralization rates of composts can be a drawback in providing N to

crops, thus requiring that large applications be made to provide adequate N. Sufficient quantities of compost may not be available at one time. Also, applications may

have to be made in several passes over the field. Consideration must be given to the

total amount of compost that is applied in one or multiple applications. Gouin (1993)

recommended that compost applications to landscapes not exceed 300 m3·ha–1 (about

10 Mg·ha–1) to avoid salinity and nutrient imbalances. Landshoot (1995) recommended that compost applications of between 250 and 500 m3·ha–1 (2.5 to 5 cm

layers) be incorporated into soil to improve stand development and growth of

turfgrass. This range of amounts was sufficient to provide nutrients and to increase

organic matter in soil and yet to avoid problems associated with large applications

of compost to land.

Composts, as with many organic byproducts with fixed ratios of nutrients, may

have an unfavorable ratio of N to other macronutrients so that applications to meet

N requirements may give too high additions of other nutrients, such as P (Jacobs,

1998). Blending of low rates of compost application with chemical N fertilizers is

an alternative to massive applications of compost to supply all of the N (Sikora,

1996). Blending helps to adjust the ratio of N to other nutrients to closely match

crop requirements, aids in adjustment of wide C:N ratios, and facilitates N release

from composts. Cisar (1994) and Cisar and Snyder (1992) noted that an initially

high C:N ratio in some composts restricted release of N, caused a low-N status of

foliage of several turfgrass species, and slowed establishment of sods grown directly

in compost on plastic sheeting. Frequent fertilization quickly overcame these restrictions. With time, which allowed for mineralization of N from the composts and

narrowing of C:N ratio, quality of sod improved with composts thereby lessening

the need of further fertilization. Cisar (1994) reported additional benefits of soil

amendment with composts. For example, his research demonstrated that pesticide

leaching through sand amended with MSW compost was less than that through sand

alone. He noted further that salinity of compost did not seem to affect turfgrass

growth in pots and that electrical conductivity dropped from 2.65 dS·m–1 to 0.65

dS·m–1 with rainfall and irrigation. Landshoot (1995) reported that composts with

salinities ranging from electrical conductivities of 4 to 8 dS·m–1 did not hinder

Kentucky bluegrass growth in soil amended with compost (250 or 500 m3·ha–1),

since dilution of the compost with soil seemed to alleviate any deleterious effects

due to salinity.

Landshoot (1995) reported that incorporation of compost at 250 or 500 m3·ha–1

with a starter fertilizer [40N-20P-20K (kg·ha–1)] increased the rate of bluegrass

establishment in land (clay loam) relative to the rate in unamended land or in topsoilamended land. Biosolids compost, brewery byproduct compost, farm manure-yard

trimmings compost, and paper mill byproduct compost gave best results due to their

effects in improving soil physical conditions, such as water-infiltration rates, and

their relatively high amounts of available N and P. Composts of yard trimmings and

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spent mushroom substrate improved soil physical conditions but were not as effective

as the other composts for supplying nutrients. Use of starter fertilizers increased the

rate of sod establishment with all composts except those made from biosolids or

brewery byproducts, which contained enough readily available plant nutrients to

mask any effects from the starter fertilizers.

Landshoot (1995) noted that one poultry manure compost and another yardtrimmings compost in his evaluations were unsatisfactory for use in turfgrass establishment. A 30% seedling death rate with the poultry manure compost was attributed

to its high NH4 concentration. High NH4 concentrations are toxic and are characteristic of immature composts (O’Brien and Barker, 1995a, 1995b, 1996a, 1996b,

1997). The yard-trimmings compost was deemed unsatisfactory because of its high

weed seed population, which imparted a 50% weed cover to plots. Weed seeds can

be introduced with immature compost of seed-containing feedstocks or with composts in which weeds were allowed to grow and to produce seeds (Landshoot, 1995).

Landshoot (1995) reported that the improved soil structure with respect to waterinfiltration rate and improved plant nutrient supply lasted for at least 3 years. After

3 years, compost-amended soils had water-infiltration rates of 25 cm or more per

hour compared to less than 2.5 cm per hour with unamended or topsoil-amended

soil. Turfgrass growing in unamended soil or in topsoil-amended soil showed symptoms of P deficiency. Landshoot (1995) estimated that composts supplied N for 3

years, but in decreasing amounts with time, and suggested using monitoring of turf

color and soil testing to recommend amounts of N fertilization.

Landshoot (1995) suggested also that composts can be used as surface applications to established turfgrass areas. With surface applications, compost should be

applied in about 0.65-cm thick layers and then incorporated into soils with aeration

tillage with a hollow-tine soil aerator implement and a drag mat to break up the

cores and to mix the compost into the soil. Successive surface applications without

incorporation should be avoided since the unincorporated compost leads to a dry

surface layer that appears to restrict turfgrass rooting in the surface zones. However,

incorporation by aeration can be stressful to turfgrass in hot, dry periods; hence,

surface applications should be restricted to cool, moist seasons when grass is growing

actively (Landshoot, 1995).

In production of ryegrass (Lolium multiflorum L.) in fine sands (Myakka fine

sand) of south Florida, supplemental fertilization with ammonium nitrate (50 kg·ha–1

of N) improved stand establishment and forage yields with compost applications

supplying N at amounts ranging from 168 to 672 kg·ha–1 (Stratton and Rechcigl,

1998). Over a 2 year period, yields of compost-amended areas were twice those of

areas receiving only ammonium nitrate applied at equivalent N rates. Sullivan et al.

(1998) reported similar results with forage tall fescue (Festuca arundinacea Schreb.)

with compost applications enhancing yields for 3 years after an initial application.

Land applications (155 Mg·ha–1) of yard trimmings-food residues compost with an

average N concentration of 17 g·kg–1 gave twice the dry matter yields of grass

produced with wood chips-sawdust-food residues compost with an average N concentration of 8 g·kg–1 (Sullivan et al., 1998).

Compost applications in addition to supplying nutrients to land can increase

availabilities of soil-borne nutrients or add nutrients other than N to soil. Yard waste

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compost amendments increased the soil solution P of an acid soil (Ultisol, pH 4.85)

with high P-fixing capacity (Hue et al., 1994). However, Wen et al. (1997) noted no

increases in P accumulation by several non-turf crops and no increase in sodium

bicarbonate extractable soil P following applications of biosolids compost, livestock

manure compost, or uncomposted biosolids. Wen et al. (1996/1997) noted, however,

that K availability from the composts or uncomposted biosolids was equal to that

from KCl if enough organic materials were added. Incremental additions of compost

also increased the pH and extractable Ca of media. On the other hand, some composts

may lead to nutrient immobilization in soil (Barker, 1997), but simultaneous applications of N with composts can alleviate immobilization of N and later facilitate

release of N from composts (Stratton and Rechcigl, 1998).

Barker (1997) suggested that composts with less than 1% N (10 g·kg–1) are more

suitable as mulches than as sources of nutrients. Hartz et al. (1996) with pepper

(Capsicum annuum L.) production noted no net release of N from field-incubated

composted green plant residue and noted N immobilization with the compost incubated in containers in studies of growth of tomato (Lycopersicon esculentum Mill.)

or marigold (Tagetes erecta L.). Supplemental N fertilization was required to sustain

growth and to obtain optimum yields with use of the compost, which was 1.1% N

(11 g·kg–1).

Peacock and Daniel (1992) noted that initial release of N from organic fertilizers

may be slow due to the need for microbial degradation. However, microbial inoculation of an organic fertilizer (mixture of soybean [Glycine max Merr.] meal, blood

meal, bone meal, and potassium sulfate) did not enhance tall fescue or hybrid

bermudagrass (Cynodon dactylon [L.] Pers. x Cynodon transvaalensis Davy.) growth

or N absorption relative to use of the uninoculated fertilizer, which released less

than 20% of the N relative to an equivalent application of urea. These results suggest

that the release of N from composts with inherently low N may be insufficient for

turfgrass fertilization and that supplemental N applied with the compost would

increase the benefits achieved from compost.

c. Preparation of Seedbeds for Turf or Sod Production

Composts have been used successfully in soil preparation for turfgrass establishment, sod production, and landscape operations. Angle et al. (1981) reported that

the hazards of direct application of biosolids to land were lessened by composting.

Composting of biosolids reduced the number of pathogenic organisms, lessened the

availability of heavy metals, reduced odors, and gave a granular material that was

easier to handle relative to uncomposted biosolids. Furthermore, applications of

biosolids compost (Angle et al., 1981) improved establishment rate from seed and

general appearance of turfgrass of mixed species even with compost applications of

260 Mg·ha–1 or larger. The effects were attributed to improved physical conditions

such as higher water-holding capacity and chemical properties such as higher pH

of acid soils and higher nutrient availabilities. Also, Giusquiani et al. (1995) noted

that, following incorporation of MSW compost in land, total pore volume in soils

increased and that enzymatic activities indicative of increased microbial activity

were enhanced. Applications of MSW compost to a clay loam stabilized aggregated

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soil structure, prevented crusting, and aided in the reclamation of saline-sodic soils

(Avnimelech et al., 1992).

Bevacqua and Mellano (1994) reported higher fresh clipping-weight yields of

tall fescue grown in sandy loam amended with biosolids compost in field or in

greenhouse culture relative to those obtained with equal applications of dried,

uncomposted biosolids. No statistical differences in accumulations of copper (Cu),

Zn, nickel (Ni), or cadmium (Cd) in leaf tissues were noted, but with the exception

of Cd, measurable increases in these metals were detected in soil. Relative to

unamended soil, soil treated with a cumulative application of compost (74 Mg·ha–1)

over a 2-year period had slightly more acidic pH (7.4 vs. 7.7), higher organic matter

concentrations (1.50 vs. 0.77%), higher primary nutrients (N, P, K), and increased

salinity (EC 2.44 vs. 1.52 dS·m–1) .

O’Brien and Barker (1995a) evaluated composts, made from MSW-biosolids,

biosolids-woodchips, farm manures-crops residues, and autumn leaves, in the preparation of seed beds for perennial ryegrass or wildflower (mixed annual and perennial

species) establishment. Composts were applied in thin layers (2.5-cm thick) on the

soil surface or the same amount was incorporated shallowly (5-cm deep) into soil.

Mature composts with low ammoniacal concentrations (<150 mg·kg–1 of N) were

essential for establishment of ground cover by turfgrass or by wildflowers. Bare

spots and weeds dominated the areas where the sod crops were not established due

to high NH4 (>2000 mg·kg–1 of N) in immature composts. The areas of suppressed

crop growth persisted into the second and several ensuing growing seasons. To avoid

the phytotoxicity of immature composts, a delay of 7 to 21 days between application

of composts and seeding of perennial ryegrass was necessary to reduce NH4 contents

(O’Brien and Barker, 1996a, 1996b). Composts that were aged for 1 year by storage

in piles after they were first considered suitable for land application were more

suitable for production of perennial ryegrass or wildflower sods on plastic sheeting

than were composts used without the additional curing (O’Brien and Barker, 1995b).

Another problem noted by O’Brien and Barker (1995a) was the proliferation of

weeds following surface-applied or soil-incorporated composts. Nutrients from composts stimulated weed growth during the summer season of the first year following

spring application of composts so that the areas even without kill from the immature

composts were dominated with annual broadleaf and grassy weeds (O’Brien and

Barker, 1995a). Establishment of annual wildflower species was unsuccessful

because of weed competition. However, early in the second growing season following a winter, turfgrass or perennial wildflower populations dominated weeds in the

stands so that the appearance of the turf and wildflower meadows was excellent.

Weeds that grew during the first year arose from germination of soil-borne seeds

(O’Brien and Barker, 1995a). Weed control was accomplished if a barrier mulch

(newspaper, plastic fabric, or sawdust) was placed under a thin layer (1-cm to 2.5cm thick) of compost mulch to impede emergence of weeds above the soil surface

(Barker and O’Brien, 1995). A application of pre-emergence herbicide to the soil

surface immediately before compost application also essentially eliminated problems

with weed establishment in compost-mulched soil (Barker and O’Brien, 1995). Weed

control in the first year allowed for establishment of an abundance of annual wildflowers, which were lost without weed control. No N fertilization was needed for

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