Abstract
Ahmed, M. 2005. Screening of boron efficient wheat genotypes and assessing boron requirement for wheat-Fallow-T. Aman Rice cropping pattern. Ph.D. Dissertation. Dept. of Soil Science, Bangladesh Agricultural University, Mymensingh.
A study was undertaken to determine the critical limit of boron for wheat, screen out the boron efficient wheat genotypes and find out the suitable dose of boron for Wheat - Fallow - T. Aman rice cropping pattern. The amount of extractable boron varied markedly depending on the sampling locations and extractants used. The efficiency of different boron extractants followed the order: Mannitol > HCI > Hot water-charcoal > Hot water-CaCl2. Although the ability of boron extraction was different for these four extractants, their trends of boron displacement from soil into solution were similar as indicated by the positive relationships amongst them. The critical level of extractable boron for wheat was found to be 0.14, 0.30, 0.34 and 0.31 mg kg for hot water-CaCl2, hot water-charcoal, HCl and mannitol extractions, respectively. Several experiments (sand culture and field) were carried out to evaluate 37 wheat genotypes (varieties and lines) for boron efficiency (tolerance to boron deficiency). Two Thai wheat varieties such as SW 41 (boron inefficient) and Fang 60 (boron efficient) were used as the checks. Performances of varieties were compared with respect to pollen viability, grain set index, tissue boron concentration and grain yield. Wheat genotypes responded differently to boron deficiency. Pollen viability was found to be 67% in Kanchan, 35% in Gourab, 80% in Sourav, 90% in Fang 60 and 25% in SW 41 where B was not added. Pollen viability of all varieties crossed 90% when boron was applied. Based on grain set index, Sourav was found as the moderately boron efficient variety. The experiments of assessing boron requirement for the Wheat - Fallow - T. Aman rice cropping pattern were conducted at Bangladesh Agricultural University (BAU) farm, Mymensingh and at Regional Agricultural Research Station (RARS) farm, Jamalpur during 2001-02 and 2002-03 rabi seasons. Results on the yield & yield components, nutrients concentrations (N, P, K, S, Zn & B) and soil properties (pH, organic carbon, total N and available P, K, S, Zn & B contents) due to boron treatments have been evaluated. Both crops responded to boron application significantly, whereas wheat crop was more responsive. The grain yield was strongly correlated with grain set and boron uptake. Application of boron at 1 kg ha1 for wheat can be sufficient to overcome boron deficiency and ensure satisfactory yields of the cropping pattern studied.