Perfor. of Summer forage legumes in Pothowar Boron (B) deficiencies occur over a wider range of soils and crops in the world. Different sources of fertilizers are used to supply sufficient amounts of B for healthier plant growth. The effectiveness of crushed ore colemanite as B source for rice crop under flooded calcareous soil was evaluated in a glass house study. We studied the effects of powder colemanite (PC) and granular colemanite (GC) at the rates of 0, 1, 2, and 3 kg B ha -1 on growth and yield parameters of rice crop. Powder colemanite application at 2 and 3 kg B ha -1 significantly increased plant height, number of tillers and panicles plant -1 , number of grains panicle -1 , weight of 1000 grains and B concentration in grain compared to those observed due to application of 0 and 1 kg B ha -1 . Rice crop applied B at 3 kg ha -1 in the form of PC produced significantly (18% increase over control) higher grain yield than 0 kg B ha -1 treatment. The effectiveness of PC was higher in terms of yield and yield parameters of rice than the GC, The B source of PC was very effective in supplying B to rice crop, however GC applied pots produced significantly lower yields because of its larger particle size which was the controlling factor in B release from the fertilizer. Key words: Boron, rice, colemanite, calcareous soil, rice grain INTRODUCTION Rice is a vital food crop and occupies a position of over whelming importance in the global food system. It belongs to the Gramineae family and the half world population eats it as a main part of their daily diets (Benton, 2003). Irrigated and lowland rainfed rice systems account for about 80% of the worldwide harvested rice area and 92% of the total production (Dobermann 2000). To keep pace with population growth, rice yields in both the irrigated and rainfed lowland environments must increase by 25% over the next 20 years (IRRI, 2008). Fertilizer use in rice predominantly pertains to only macro nutrients thus one major cause of low rice productivity is imbalanced nutrient management (Rashid, 2002). Micronutrient deficiency is one of the major causes of the declining productivity trends in rice growing countries (Mohanty, 1999). Boron deficiencies occur over a much wider range of soils and crops in comparison to deficiencies of any other micronutrient elements (Yan, 2006). Boron is essential for plant physiological functions such as nucleic acid metabolism, carbohydrate and protein metabolism, indole acetic acid metabolism, cell wall synthesis, cell wall structure, membrane integrity and function, sugar translocation and phenol metabolism (Goldbach, 2001). Boron seed coating has also been tested in rice (Rehman et al., 2012). There are two types of B fertilizer sources, the refined completely soluble materials which can be conveniently applied either in solution or as solids, and the crushed ores which have variable chemical and physical properties (Bell, 2008). The refined products are Sodium tetra borate, (Na 2 B 4 O 7 ·5H 2 O) borax (Na 2 B 4 O 7 ·10H 2 O), sodium penta-borate (Na 2 B 10 O 16 ·10H 2 O), solubor (Na 2 B 8 O 13 ·4H 2 O) and boric acid (H 3 BO 3 ). The crushed ores are colemanite (Ca 2 B 6 O 11 . 5H 2 O), ulexite (Na 2 O.2CaO. 5B 2 O 3 .16H 2 O), datolite (2CaO.B 2 O 3 .2SiO 2 .H 2 O), hydroboracite (CaO.MgO.3B 2 O 3 .6H 2 O) and ascharite (2MgO.B 2 O 3 .H 2 O). Sodium pentaborates and boric acid are easily dissolved in soils and are quickly available for plant uptake, but at the same time B can be leached from the soil root zone. Only two crushed ores ulexite and colemanite are used for soil application (Bell, 2008). These two crushed ores can be satisfactorily applied to the soil to provide season long B supply for a crop. Crushed ore colemanite is a cheap and slow release source of B in comparison to refined products but this B source is not widely used as fertilizer. Byers et al., (2001) conducted a grlass house experiment on alfalfa to evaluate the effectiveness of four B fertilizers; Granubor, Hydroboracite, Ulexite and Colemanite. He found that in the first cutting of the crop there was difference in B sources, however by the third and fourth cuttings, there was no significant difference among the four fertilizer sources. Very few studies on crushed ores as B fertilizers for crops had been reported. Most studies on ores have been carried out in pots with toxicity and leaching in mind rather than crop response (Shorrocks, 1997). The objective of this study was to evaluate the efficacy of crushed borate ore colemanite as B source for rice under flooded calcareous soil condition. Pak. J. Agri. Sci., Vol. 50(1), 37-42; 2013 ISSN (Print) 0552-9034, ISSN (Online) 2076-0906 http://www.pakjas.com.pk EFFICACY OF CRUSHED ORE COLEMANITE AS BORON FERTILIZER FOR RICE GROWN UNDER CALCAREOUS SOIL CONDITIONS M. Saleem 1,* , Y.M. Khanif 2 , C.I. Fauziah 2 , A.W. Samsuri 2 and B. Hafeez 1 1 Agriculture Research Institute, Tando Jam, Pakistan 2 Dept. of Land Management, Faculty of Agriculture, University Putra Malaysia, Selangor Dar ul Ehsan, Malaysia Corresponding author’s e-mail: sarkisaleem@yahoo.com