The effects of biosolid application on soil chemical properties and Zea mays nutrition

The application of biosolid as a fertilizer in agricultural cultivation is a common practice in many countries. This study investigates the effects of sewage sludge and compost usage on soil chemical properties and Zea mays nutrition in comparison with those of iron and manganese sulfate solution. The experiment was carried out in a completely randomized block design with the following treatments: sewage sludge and compost with three levels (0, 25 and 50 t ha−1) and iron and manganese sulfate solution (1 g l−1 solution) with three replications. The application of sewage sludge (50 t ha−1) had highly significant (P < 0.01) positive effects on cation exchange capacity and organic matter, total nitrogen, phosphorus, iron and manganese diethylenetetramine-penta-aceticacid-extractable in soil, and nitrogen, phosphorus, iron and manganese in plant. Also, compost application (50 t ha−1) increased significantly (P < 0.01) the electrical conductivity in soil and potassium in soil and plant. Dry biomass increased significantly (P < 0.01) from 7.7 to 28.7 g per pot with sewage sludge application (50 t ha−1). Application of biosolid as fertilizer sources has become a common practice in Iran, especially in the agricultural lands. The reuse of these nutrients had some beneficial effects on soil fertility, such as increased cation exchange capacity, pH, organic matter, total nitrogen, phosphorous, iron and manganese. However, these benefits were limited by the presence of some potentially toxic trace metals in biosolid.

especially in the agricultural lands. The reuse of these nutrients had some beneficial effects on soil fertility, such as increased cation exchange capacity, pH, organic matter, total nitrogen, phosphorous, iron and manganese. However, these benefits were limited by the presence of some potential toxic trace metals in biosolids.

Background
Urbanization and industrialization processes always lead to increased production of waste, i.e.
wastewater and solid waste such as sewage sludge and urban waste (compost). The advantages of reusing waste are that it provides a convenient disposal of waste products and has the beneficial aspects of adding valuable plant nutrients and organic matters to soil (Horewell et al.2003). Sewage sludge and compost are beneficial soil amendment, especially for arable soils of inherently low organic matter content, as it may improve many soil properties, such as pH and the contents of organic matter and nutrients. The nutrients availability in soil depends on the nature of the chemical association between elements with the organic residual and soil matrix, the pH value of the soil, the concentration of the element in the compost and the sewage sludge, and the ability of the plant to regulate the uptake of a particular element (Stephen and Smith 2008). Soil organic matter content from compost and sewage sludge as has long been suggested as the single most important indicator of soil productivity (Haynes 2005 Organic matter usage can cause positive effect on physical, chemical and biological properties in the soil. Also the high attention to organic manure and replacement those with chemical fertilizer are necessary (During et al. 2003). In this respect, use all of the organic sources such as sewage sludge, compost and green fertilizer is necessary. The calcareous soil has more macro nutrients deficient than acid soils and low attention has to this subject. Therefore the use of biosolids could be benefit, because they have large amounts of organic matter that can improve the soil structure and water holding capacity (Giusquiani et al. 1995). As a resource, biosolids amendments present an attractive alternative for the improvement of agricultural land productivity due to its fertilizer value. Biosolids contain high proportions of nitrogen, phosphorus, and organic matter (as much as six times that found in manure). The objective of this research was to quantify the effects of biosolids as nutrient sources by investigating the effects of sewage sludge and compost application on ;(i) soil pH, EC, organic matter, total nitrogen, phosphorus, potassium , iron and manganese and Zea mays nutrition in comparison with iron and manganese sulfate solution Results and discussion

The effects of treatments on soil chemical properties
The application of biosolieds showed a tendency to increase of organic matter (OM %), cation exchange capacity (CEC) and soil pH, an effect that was significant (P < 0.01) at the higher application rates ( Table 2).
Also significant (P < 0.01) effect on electrical conductivity (EC) was found for the high compost application rates of 50 ton ha -1 . The reason of increasing soil pH and EC might is due to increased soil organic matter and alkali-metals at higher application rates of biosolids.

The effects of treatments on macro and micro nutrients concentrations in soil
The application of biosolids caused a significant (P < 0.01) increase of nitrogen, phosphorous and potassium contents at all treatments ( Fig. 1). The increase was related to the amount of biosolids applied. The highest N and P contents were obtained for the high sewage sludge application rates of 50 ton ha -1 . Nitrogen and phosphorous contents increased from 9.5 and 44.5 mg.kg -1 in control to 22 and 73 mg.kg -1 in sewage sludge usage respectively. Also the K content was increased significantly (P < 0.01) from 401 to 565 mg.kg -1 for the high compost application rates of 50 ton ha -1 . An increase in total organic matter and nitrogen through application of biosolids has also been found in the previous studies (Walter et al. 2000). However, Garrido et al. (2005) did not find a significant increase in organic matter and total nitrogen, possibly because a lower biosolids rate (4.5 t ha-1) was used in that study.
The concentrations of Fe and Mn DTPA-extractable in soils were increased significantly by application of sewage sludge (50 ton ha -1 ) from 7.4 and 41 mg.kg -1 in control to 10.7 and 52.2 mg.kg -1 respectively (Fig. 2).
This was probably due to the high concentrations of Fe and Mn in the biosolids. (Table 1).
The short-term nature (one time) of biosolids application in these experiments may have contributed to the lack of a significant effect on these elements. Trace metals in biosolids are generally strongly sorbed to the biosolids matrix. Thus, trace metals added to soil with biosolids are less phytoavailable than those added as simple inorganic salts.

The effects of treatments on macro and micro nutrients concentrations in plant
The application of biosolids caused a significant (P < 0.01) increase of nitrogen, phosphorous and potassium contents in plant shoot at all treatments (Fig. 3). The increase was related to the amount of biosolids applied. The highest N and P contents were obtained for the high sewage sludge application rates of 50 ton ha -1 .
Nitrogen and phosphorous contents increased from 32 and 69 mg.kg -1 in control to 74 and 102.6 mg.kg -1 respectively. Also the K content was increased significantly (P < 0.01) from 375 to 579.1 mg.kg -1 for the high compost application rates of 50 ton ha -1 . The concentrations of Fe and Mn in plant shoot were increased significantly by application of sewage sludge (50 ton ha -1 ) from 86.7and 60 mg.kg -1 in control to 125.4 and 81.7 mg.kg -1 respectively (Fig. 4). This was probably due to the high concentrations of Fe and Mn in the biosolids. (Table.1

The effect of treatments on dry biomass
Biosolids application increased the dry matter of Zea mays (Fig. 5). These growth parameters were obtained with increase as biosolids rates. The highest dry biomass was obtained for the high sewage sludge application rates of 50 ton ha -1 . Application of sewage sludge (50t.ha -1 ) significantly (P < 0.01) increased shoot dry matter from 7.7 to 28.7g pat -1 .

Canclusions
Application of biosolids as fertilizer sources has become a common practice in agricultural lands. The reuse of these materials had some beneficial effects on soil fertility, such as increased, organic matter, macro and micro nutrients. This study found that, cation exchange capacity pH, organic matter content, total nitrogen phosphorous, potassium Fe and Mn were improved in soils treated with sewage sludge and compost. However, these benefits were limited by the presence of some potential toxic trace metals in biosolids. The addition of biosolids, in the form of compost, also increased the soil EC. This was probably due to the short-term nature of

Greenhouse Study
Pot experiments were conducted in a randomized complete block design with three replication at the greenhouse of Islamic Azad University, Khorasgan branch. Experimental treatments were: sewage sludge and compost, with three levels (0, 25 and 50 ton ha -1 ), compound of iron and manganese sulfate, in clay loam soil.
Some chemical soil and biosolids properties were shown in Table 1.

Statistical analysis
Statistical analyses were performed using SPSS 16 software and comparison of means was done with Duncan test at 5% level.