Middle East Journal of Agriculture Research ISSN 2077-4605 Volume : 04 | Issue : 04 | Oct.-Dec. | 2015 Pages: 735-744 Corresponding Author: Soha S. M. Mostafa, Soils, Water and Environment Research Institute, Agricultural Research Center (ARC), Egypt. E-mail: sohaaasayed@yahoo.com 735 Comparative Evaluation of Biological Treatments and Mineral NPK on Rice Productivity in Alkaline-Saline Soil Yahia I. Mahmoud, Soha S.M. Mostafa and Faten M. Mohamed Soils, Water and Environment Research Institute (SWERI), Agricultural Research Center (ARC), Egypt ABSTRACT A field experiment was conducted at Sahl El-Hussinia Station, El-Sharkia Governorate, Egypt, during the summer seasons of 2012 to study the individual and combined effecs of N2-fixing bacteria (Azotobacter chroococcum, Klebsiella pneumonia and Colstridium pastereurianm) and cyanobacteria (Nostoc muscorum, Nostoc humifusum, Anabaena oryzae, Wollea sp, Phormedium sp and Spirulina platensis) compared to Cyanobacterin (commercial bio-product for rice) on growth, yield and yield components of rice (cv-Giza 178). Inoculation with biological treatments positively affected the soil biofertility through enhancing soil biological activity in terms of dehydrogenase and nitrogenase activities which in turn supported the growth of rice plant. The treatment of 75% NPK + N2-fixing bacteria + cyanobacteria recorded the highest plant height, number of panicles/plant, weight of 1000-grain and plant biomass (rice straw and grain yields) compared to the other tested treatments. Also, this treatment increased significantly the total contents of N, P and K in plants. Inoculation with N2-fixing bacteria + cyanobacteria together with 50% mineral NPK level supported rice growth under saline conditions. While, significant enhance of nitrogen fixing potential was recorded by the biological treatments involving the combination of bacteria-cyanobacteria strains. The treatment of 75% NPK + N2-fixing bacteria + cyanobacteria in increasing the growth and grain yield of rice and improving soil health, besides mineral NPK saved 25 to 50%. The study authenticated the positive effects of co-inoculation with bacterial and cyanobacterial strains on rice crop production. Key words: PGPR, bacteria, cyanobacteria, Cyanobacterin, rice, saline soil Introduction In Egypt, climate change is manifested in drought and salinization of its soils and water bodies. Total cropped (cultivated) area has increased from 4.7 million ha in 1982 to 6.5 million ha in 2003. Of these, one million ha of irrigated area suffers from problems of salinization (FAO, 2005). The main problem at Sahl El- Hossynia soil is related to high salinity conditions. Soil degradation caused by salinization and sodication is a universal concern. Saline (EC > 4 dSm-1), or salt affected soil is a major environmental issue, as it limits plant growth and development, causing productivity losses (Qadir et al., 2008). Improving the fertility of the saline soil is an utmost necessary from the agriculture point of view. Rice (Oryza sativa L.) is one of the most prominent food crops globally, and represents the staple diet for almost half of the human population of the world, which accounts for 23% of the world’s calorie intake (Bernier et al. 2008). It is estimated that there will be about 8 million people by the year 2020, requiring 760 million tons of rice. This means that the production of rice needs to be increased by 2% per year to meet future demands. This will require double the amount of currently applied synthetic fertilizers, which is neither economically feasible nor environmentally desirable. In order to make rice cultivation sustainable and less dependent on chemical fertilizers, it is important to know how to use the plant growth promoting rhizobacteria (PGPR) that can biologically fix nitrogen, solubilize phosphorus and induce some substances like indole acetic acid (IAA) that can contribute to the improvement of rice growth (Keyeo et al. 2011). Aerobic free living N2-fixing microbes include Azotobacter, Beijerinckia, Azonomas etc., facultative anerobes include Klebsiella, anaerobic bacteria like Clostridium acetobutylicum, C. pasteurianum, photosynthetic bacteria like Chlorobium, Rhodospirillium etc. (Schlegel, 1991). Plant growth promoting activity has been reported in bacterial isolates belonging to several genera such as Burkholderia, Bacillus, Pseudomonas, Azotobacter, Azospirillum and Acetobacter (Khalid et al. 2004; Herman et al. 2008). It has been established that among cyanobacteria, both heterocystous and non heterocystous forms, Anabaena, Nostoc, Trichodesmium, Lyngbya, Plectonema etc. fix nitrogen (Rao and Burns, 1990; Schlegel, 1991). In cyanobacteria, a light and thick walled cell structure called heterocyst is the point where nitrogen fixation takes place. However, in members like Lyngbya and Plectonema where heterocyst is absent, nitrogen fixation occurs in internally organized cells (Schlegel, 1991). There are reports that some cyanobacteria can grow successfully on saline soil