الفهرس 
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Abstract
The purpose of this research was to replace the term of “Agricultural Wastes” by the term “Agricultural By-products” since waste is a word indicates to a material useless that usually cannot be recycled or reused again. The usage of agricultural by-products become of important concern in the field of fertilization through composting such as agricultural by-products beside of reclamation of the desert soils which suffer from their low organic matter content. So, this investigation aimed to manufacture and develop compost after mixing regular compost fertilizer with agricultural by-products (plant sources) and evaluate these engineered organic manures after planting spinach plant. The results obtained could be summarized as follows:- 1. Quality Indices of the Engineered Organic Manures. C/N ratio. A clear increase was observed in the ratio of C/N in the case of addition of (Compost + FYM), where this value is18.14 before planting and 16.93 after planting in one cube compared to adding (Compost + ChM) having value of 14.14 before planting and after planting 13.31, it may be due to volatilization of N under alkaline condition. After adding crops by-products to compost, it was noticed that increase is clear after adding the cotton and wheat residues to the compost. Soil reaction (pH) Adding (ChM) and agricultural byproducts to the compost increased the pH values for compost to become 5.92 before planting and 5.85 after planting. Electric conductivity (EC). In general, using compost plus plant residues without animal wastes gave the highest values of EC, while these values were decreased with adding both ChM and FYM but this decrease was less with FYM than ChM before and after planting. Nitrogen, phosphorus and potassium (%). The highest N,P and K content after applying the fertilizer resulting from adding the ChM and the agricultural by products to the compost. 2. Spinach Growth characteristics and Nutrients Status. Growth characteristics. The highest fresh and dry weights of spinach was obtained by applying ChM with compost compared to the control (C0), and applying compost with (FYM) produced fresh weight less than ChM and in the same time more than compost alone. In succession, the weights was close or equal when adding fertilizer to agricultural (vegetable) by-products. Chemical content. The content of chlorophyll (a & b), N, P, K, Fe and Zn were increased with applying (ChM) with compost compared to the treatment applying (FYM) and the lowest values were obtained applying compost without any addition. Applying agricultural by-products revealed a difference in the chemical traits among the studied treatments. The highest values were obtained with applying the agricultural by-products of the bean plant to the compost at both studied periods, while the lowest content values resulted from treating with compost plus wheat straw at 21 days and 45 days from planting. NO3 content. A decrease in the concentration of NO3 was observed when agricultural by-products and organic additives were applied to spinach. The lowest concentration with applying (ChM) to the compost followed by (FYM)and the lowest values were obtained applying compost without any addition. All applications of vegetable agricultural byproducts had an effect on the content of (NO3) with different degree where its value differed from one treatment to another. After applying two types of animal and plant additives to the compost, the results differed where NO3 concentration significantly decreased compared to other treatments without additives to plant agricultural by-products mixed with compost. Addition of (ChM) to the compost gave the best results after its evaluation. where (ChM) treatment caused an accumulation of NO3 in spinach with less level than others. Vitamin C The concentration of vitamin C was increased with applying (ChM) with compost compared to the treatment applying (FYM) and the lowest values were obtained applying compost without any addition. Applying agricultural by-products revealed a difference in the value of vitamin C among the studied treatments. The highest values were obtained with applying the agricultural by-products of the bean plant to the compost at both studied periods, while the lowest content values resulted from treating with compost plus wheat straw at 21 days and 45 days from planting. CONCLUSION :- According to the obtained results in this investigation, the soil addition of agricultural organic fertilizers [mixing and compressing organic manures (FYM and ChM) with agricultural by-products as cubic blocks] is an important practice to enhance plant growth and increase crop yields as well as preserve soil fertility and productivity.