Elsevier

Bioresource Technology

Volume 71, Issue 3, February 2000, Pages 253-259
Bioresource Technology

Effects of compost produced from town wastes and sewage sludge on the physical properties of a loamy and a clay soil

https://doi.org/10.1016/S0960-8524(99)00074-7Get rights and content

Abstract

Organic fertilizer produced by composting 62% town wastes, 21% sewage sludge and 17% sawdust by volume, was applied at the rates of 0 (control), 75, 150 and 300 m3 ha−1 to loamy and clay soils, in order to investigate its potential for soil improvement. The experiments were conducted in areas characterised by a semi-arid climate. The chemical properties of the soils were affected directly by the amendment compost. The physical properties of the amended soils were improved in all cases as far as the saturated and unsaturated hydraulic conductivity, water retention capacity, bulk density, total porosity, pore size distribution, soil resistance to penetration, aggregation and aggregate stability, were concerned. In most of the cases the improvements were proportional to the application rates of the compost and they were greater in the loamy soil than in the clay soil.

Introduction

The continuous decomposition of organic matter in cultivated soils of arid and semiarid regions may lead to soil degradation with a consequence of inability to ensure a sustainable production. The application of organic wastes, and particularly composted municipal refuse and sewage sludge, could be a way of solving two problems, the waste disposal and the correction of the low organic matter content of many agricultural soils. Using wastes in agriculture is an economical disposal of these materials, and it is interesting from an ecological point of view as it reduces negative effects on the environment. However, it could lead to phytotoxic levels of heavy metals in soils.

Among the publications related to waste application on land only a small percentage deals with the improvement of soil physical properties. There are references to improving soil water content (Epstein, 1975, Epstein et al., 1976, Kelling et al., 1977), soil water retention capacity (Gupta et al., 1977, Morel et al., 1978, Kladivko and Nelson, 1979, Kumar et al., 1985), saturated hydraulic conductivity (Epstein, 1975, Kumar et al., 1985), compactibility (Ohu et al., 1985, Ekwue, 1990, Stone and Ekwue, 1993), aggregation (Pagliai et al., 1981), total porosity and pore size distribution (Walter, 1977, Kladivko and Nelson, 1979; Pagliai et al., 1981; Mathan, 1994), soil crusting (Pagliai et al., 1983) and penetration resistance of the soil (Kumar et al., 1985).

The (partial) reference by several authors to improving only some of the physical properties at any one time gave the reason for the present work to be conducted. Therefore, in this work, an attempt was made to investigate the potential soil improvement related to the waste application and taking into consideration almost all physical properties.

Section snippets

Methods

The compost used was produced from a mixture of 17% sawdust, 21% sewage sludge and 62% town wastes by volume, following the Beltsville Aerated Pile Method (Wilson et al., 1980). The cured compost was passed through a 5 mm mesh screen before soil incorporation. The contents of cadmium, zinc, copper, lead, nickel and chromium were, respectively, 2.3, 1100, 450, 60.6, 104 and 798 ppm. These were below the safe levels for plant growth. The germination of seeds (Lepidium sativum L.) test was done

Results and discussion

Chemical properties of the soils were affected directly by the compost amendment (Table 1). Organic matter, pH and CEC were increased with the compost rates. Physical properties should be affected indirectly through the improvement of soil structure.

The effects of the treatments on the bulk density of the two soils are shown in Table 2. Compost significantly reduced the bulk density of the soils (P=0.05). The highest reduction was 19.7% and 16.7% for the 300 m3 ha−1 compost addition rate in the

Conclusions

The amendment compost improved all physical properties under consideration in the two soils. The improvement was proportional to the compost rate. The results supported the following conclusions:

Bulk density and penetration resistance were reduced. The reduction was greater in the loamy soil than in the clay soil.

Total porosity and saturated hydraulic conductivity were increased. The increase of total porosity was greater in the loamy soil than in the clay soil, and saturated hydraulic

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