## 1 Introduction  
The alarming increase in the world population requires the development of new farmlands to grow sufficient food, which, in turn, necessitates greater use of fertilizers in order to achieve the required food production. In developing countries, the rising prices of chemical fertilizers, coupled with the growing concerns for sustainable soil productivity, have led to a renewed interest in the application of organic manure in soil fertility restoration [1]. Organic manure is a vital resource not only for supplying plant nutrients, but also for replenishing the organic matter content of the agricultural soils [2]. Biosludge is a by-product obtained predominantly from secondary wastewater treatment plants. The organic nature of biosludge, which contains plant nutrients and several other useful trace elements, makes it a valuable organic fertilizer for use in farming applications [3; 4; 5]. In view of its richness in terms of organic biomass and soil nutrient content, the best management option might be to utilize dried biosludge for agricultural purposes [6]. Owing to its attractive properties, the application of biosludge as a fertilizer has increased from 20% in 1972 to 55% in 1997 in USA [7]. Boron is an essential trace element in plants, which plays a key role in controlling calcium metabolism. In case of boron deficiency, the pectin to lipid ratio in plants is shifted in favor of pectin. A disruption of the nucleic acid metabolism, which results in growth disturbances, has also been observed in plants deficient in boron [8]. Moreover, boron is critical for both cell elasticity and the prevention of excessive conversion of sugar to starch. Phosphorus is another essential micronutrient, which mainly affects energy transfer pattern in plants. Its adequate availability stimulates early plant growth. In particular, phosphorus is required for the manufacture of phosphate-containing nucleic acids, adenosine triphosphate (ATP), and membrane lipids. Soils that have been used heavily for agricultural crops are very often deficient in phosphorus. Alkaline and calcareous soils have phosphorus deficiency because of the formation of poorly soluble calcium phosphate minerals. Such phosphorus deficiency in soils can cause shortened plant stem internodes, poor root systems, darkening of leaf tissue, and crop reduction. Similarly, molybdenum is a trace element with a key role in the biochemical processes related to the conversion of atmospheric nitrogen into useful ammonia by bacteria [9]. Its deficiency can eventually result in a diminished number of flowers, severely affecting the development of pollen in the plants [10]. In addition, molybdenum is necessary for the correct functioning of several essential metalloenzymes such as xanthine oxydase, aldehyde oxidase, and sulfite oxidase. Common methods of chemical analysis of soils and fertilizers for mineral micronutrients include atomic absorption spectrometry (AAS), inductively coupled plasma optical emission spectrometry (ICP-OES), and inductively coupled plasma mass spectrometry (ICP-MS) [11; 12; 13]. In addition to the AOAC (Association of Analytical Communities) official method 965.09, AAS has been widely utilized for the quantification of various elements in plant nutrient sources [14]. The limitations of AAS with regard to sensitivity, accuracy, simplicity, and freedom from interferences have resulted in the increased use of emission-based techniques such as ICP-OES for the determination of elements in the soils and related materials [15]. Commonly employed excitation sources for emission techniques include flames, electric arcs, and plasmas. In particular, argon plasma-based systems have been utilized extensively for both qualitative and quantitative analyses over the last 40 years [16]. In this context, the microwave plasma atomic emission spectrometry (MP-AES) introduced recently by [PERSON] represents a very important and useful addition to the existing array of analytical techniques [17].