International Journal of Environmental & Agriculture Research (IJOEAR) ISSN:[2454-1850] [Vol-2, Issue-12, December- 2016] Page | 89 Impact of organic and conventional practices on, soil health and crop yield under tropical and subtropical environment of Bangladesh M. Nazim Uddin 1 , M Alamgir Siddiqy 2 , Mahamud Hossain Al-Mamun 3 , F Islam 4 , GMA Halim 5 , Md. Latiful Bari 6 1,2,3,4,5 Horticulture Research Center, Bangladesh Agricultural Research Institute (BARI), Gazipur, Bangladesh 6 Center for Advanced Research in Sciences, University of Dhaka Dhaka-1000, Bangladesh Abstract— This study was carried out to evaluate the improvement of soil fertility and crop yield using formulated organic fertilizers in a Randomized Complete Block Design (RCBD) from October 2008 to April 2015 and the test crop was tomato, eggplant, cabbage and cauliflower. The physicochemical properties, behavior and persistence of plant beneficial microorganisms including nitrogen fixing bacteria, (e.g. Rhizobium sp., Azotobacter sp.), phosphate solubilizing bacteria e.g. (Bacillus sp. Pseudomonas sp., Phosphobacteria), Aspergillus sp. and Trichoderma sp., in the amended/ non-amended block were evaluated each year. The soil beneficial microbial populations and health properties including pH, nitrogen content, organic matter, phosphorus, K, Ca, and S, increased significantly in the compost-amended soils compared to the conventional practices. The total nitrogen (N) content and the organic matter of compost amended soil were 215% and 200% higher respectively than that of conventional practices (CP). Furthermore, significant increase of available organic matter, N, P, & K was observed in the compost-amended soils compared to conventional and control block. Furthermore, microbial population showed significant linear correlations with the organic matter contents of the soils and yearly vegetables yield increased gradually and was reached to almost identical to conventional field within 5 years, implying that the soil amended with BIOFER compost increased the soil fertility, and vegetables yields. Thus, application of BAOFER compost at the rate of 15 t/ha/year was found adequate in improving the vegetable yields and soil health in open field cultivation under subtropical climatic conditions. Keywords— Organic; conventional; production practices; soil microorganisms; soil health; crop yield and tropical environment. I. INTRODUCTION In the last four decades Organic Farming (OF) has increased substantially around the world including small holding countries of Asia and Africa (Willer and Lernoud 2015.). The aim of of is to produce safe food in sufficient quantity while being environmental friendly and attain sustainability. Being a tropical and subtropical country like Bangladesh, the major challenges for OF are yield of crops, optimization of the nutrients cycling of the agro-ecosystem and development of more suitable alternative soil fertility strategies. Soil organic matter (SOM) is a key indicator of fertility; affects crop growth and yield, either directly by supplying nutrients or indirectly by modifying the soil physical properties, thereby improving the root environment and, thus, stimulating plant growth(Chang, et al 2007). Pimental, et al. 2005 indicated that the highest total aerial dry matter and grain yields were associated with the highest organic matter contents of the soils. In addition, crop production based on the use of organic manures rather than chemical fertilizers is assumed to be a more sustainable type of agriculture. In recent years, the application of organic fertilizer has received great attention from environmentalists, agriculturists and consumers alike (Chang, et al., 2007). Gabriel et al., 2010 found that depending on crops, soil and weather conditions, organically managed crops yields on a per ha basis was equal to those from conventional agriculture. Organic farming has become very popular and is steadily increasing the area of production around the globe and possesses the highest in Asia. For growing vegetable crops organically, it is required an adequate and continuous supply of essential nutrients for proper growth and maximal high quality yields. But, low yields associate to starvation of plants from slow releasing organic fertlizers, difficulties in weed control, and cumbersome pest management methods are the main concern against organic agriculture. Ponisio et al 2014 to their meta analysis showed that organic yields are only 19.2% (+3.7%) lower than conventional yields, a smaller yield gap than previous estimates and effects of crop types and management practices on the yield gap, two agricultural diversification practices, multi-cropping and crop rotations, substantially reduce the yield gap (to 9+4% and 8+5%, respectively) when the methods were applied in only organic systems. The nutrients released after the biological breakdown of the soil organic matters supply the nutrients essential for plant growth in organic farming. However,