Source-separated municipal solid waste compost application to Swiss chard and basil

A growth room experiment was conducted to evaluate the bioavailability of Cu, Mn, Zn, Ca, Fe, K, Mg, P, S, As, B, Cd, Co, Cr, Hg, Mo, Na, Ni, Pb, and Se from a sandy loam soil amended with source-separated municipal solid waste (SSMSW) compost. Basil (Ocimum basilicum L.) and Swiss chard (Beta vulgaris L.) were amended with 0, 20, 40, and 60% SSMSW compost to soil (by volume) mixture. Soils and compost were sequentially extracted to fractionate Cu, Pb, and Zn into exchangeable (EXCH), iron- and manganese-oxide-bound (FeMnOX), organic-matter (OM), and structurally bound (SB) forms. Overall, in both species, the proportion of Cu, Pb, and Zn levels in different fractions followed the sequence: SB > OM > FeMnOX > EXCH for Cu; FeMnOX = SB > OM > EXCH for Pb; and FeMnOX > SB = EXCH > OM for Zn. Application of SSMSW compost increased soil pH and electrical conductivity (EC), and increased the concentration of Cu, Pb, and Zn in all fractions, but not EXCH Pb. Basil yields were greatest in the 20% treatment, but Swiss chard yields were greater in all compost-amended soils relative to the unamended soil. Basil plants in 20 or 40% compost treatments reached flowering earlier than plants from other treatments. Additions of SSMSW compost to soil altered basil essential oil, but basil oil was free of metals. The results from this study suggest that mature SSMSW compost with concentrations of Cu, Pb, Mo, and Zn of 311, 223, 17, and 767 mg/kg, respectively, could be used as a soil conditioner without phytotoxic effects on agricultural crops and without increasing the normal range of Cu, Pb, and Zn in crop tissue. However, the long-term effect of the accumulation of heavy metals in soils needs to be carefully considered.     

Phytoavailability and fractionation of copper, manganese, and zinc in soil following application of two composts to four crops

Two experiments were conducted to evaluate the effect of compost addition to soil on fractionation and bioavailability of Cu, Mn, and Zn to four crops. Soils growing Swiss chard (Beta vulgaris var. cicla L.) and basil (Ocimum basilicum L.) were amended (by volume) with 0, 20, 40, and 60% Source-Separated Municipal Solid Waste (SS-MSW) compost, and dill (Anethum graveolens L.) and peppermint (Mentha X piperita L.) were amended with 0, 20, 40, and 60% of high-Cu manure compost (by volume). The SS-MSW compost applications increased the concentration of Cu and Zn in all fractions, increased Mn in acid extractable (ACID), iron and manganese oxides (FeMnOX), and organic matter (OM) fractions, but decreased slightly exchangeable-Mn. Addition of 60% high-Cu manure compost to the soil increased Cu EXCH, ACID, FeMnOX, and OM fractions, but decreased EXCH-Mn, and did not change EXCH-Zn. Addition of both composts to soil reduced bioavailability and transfer factors for Cu and Zn. Our results suggest that mature SS-MSW and manure composts with excess Cu and Zn could be safely used as soil conditioners for agricultural crops.     

Wool-waste as organic nutrient source for container-grown plants

A container experiment was conducted to test the hypothesis that uncomposted wool wastes could be used as nutrient source and growth medium constituent for container-grown plants. The treatments were: (1) rate of wool-waste application (0 or unamended control, 20, 40, 80, and 120 g of wool per 8-in. pot), (2) growth medium constituents [(2.1) wool plus perlite, (2.2) wool plus peat, and (2.3) wool plus peat plus perlite], and (3) plant species (basil and Swiss chard). A single addition of 20, 40, 80, or 120 g of wool-waste to Swiss chard (Beta vulgaris L.) and basil (Ocimum basilicum L.) in pots with growth medium provided four harvests of Swiss chard and five harvests of basil. Total basil yield from the five harvests was 1.6–5 times greater than the total yield from the unamended control, while total Swiss chard yield from the four harvests was 2–5 times greater relative to the respective unamended control. The addition of wool-waste to the growth medium increased Swiss chard and basil tissue N, and NO₃–N and NH₄–N in growth medium relative to the unamended control. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) microanalysis of wool fibers sampled at the end of the experiments indicated various levels of decomposition, with some fibers retaining their original surface structure. Furthermore, most of the wool fibers’ surfaces contained significant concentrations of S and much less N, P, or K. SEM/EDX revealed that some plant roots grow directly on wool-waste fibers suggesting either (1) root directional growth towards sites with greater nutrient concentration and/or (2) a possible role for roots or root exudates in wool decomposition. Results from this study suggest that uncomposted wool wastes can be used as soil amendment, growth medium constituent, and nutrient source for container-grown plants.     

Assessment of wool waste and hair waste as soil amendment and nutrient source

A field and two container experiments were conducted to assess uncomposted wool and hair wastes as a nutrient source for crops and to evaluate their potential to improve soil biological and chemical properties. Overall, addition of wool or hair waste to soil increased yields of basil (Ocimum basilicum L. 'Trakia'), thorn apple (Datura innoxia Mill. 'Inka'), peppermint (Mentha x piperita L. 'Black Mitchum'), and garden sage (Salvia officinalis L. 'Desislava'), increased NH(4)-N and NO(3)-N in soil, increased total N (and protein) content in plant tissue, stimulated soil microbial biomass, and decreased mycorrhizae colonization of plant roots of thorn apple but not in basil. Wool and hair waste additions to soil altered slightly the content and composition of plant secondary metabolites (essential oils or alkaloids); however, overall the constituents remained within the "typical" range for the respective crops. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis demonstrated that wool and hair wastes decompose slowly under field or greenhouse conditions, and act as a slow release S, N, P, and K fertilizer. These results, along with the measured concentrations of NO(3)-N in soil at harvest, suggest that the addition of wool or hair waste of only 3.3 g kg(-1) of soil may support two to five harvests or crops under greenhouse conditions and two to four field seasons in field production systems, and would improve soil biological and chemical characteristics. Further research is needed to optimize the rate of application of these waste materials to the nutrient requirements of specific crops to avoid nitrate leaching into the ground water. In addition, the effect of wool and hair waste on other environmental end points should also be further investigated before specific recommendations for growers are provided.     

Compost, manure, and gypsum application to timothy/red clover forage

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 NO(3)-N and NH(4)-N in the soil profile. All fertility treatments increased dry matter yields from the two cuts each year relative to the control. Residual soil NO(3)-N and NH(4)-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.