Assessment of suitability of different extractants for estimation of available boron status in Soils ARITRA SAHA, PABITRA KUMAR MANI & GORACHAND HAZRA Department of Agricultural Chemistry and Soil Science Bidhan Chandra Krishi Viswavidyalaya Mohanpur - 741252, Nadia, West Bengal Email ID: aritra205@gmail.com Fig 1: Effect of different levels of B application to wheat on Dry matter yield (g pot-1) at different growth stages. INTRODUCTION Boron Extractant Soil: extractant Procedure 0.02 M hot CaCl2 (HCC) 1:2 Reflux 10 Min 0.5 M Potassium dihydrogen phosphate (PDP) Shake 1 hr 0.01 M Tartaric acid (TA) Shake 1hr 0.01 M CaCl2+ 0.05M Mannitol (pH 8.5) (MCC) Boron deficiency affects crop growth in light textured acidic Inceptisols and Entisols which receives a larger amount of annual precipitation causing leaching loss. Initial available B status should be estimated with utmost care because excess B application above optimum dose poses toxicity problems in plant. Several extractants have been reported by many researchers which differ in their mechanisms to extract B from soil exchange phase. Therefore, no single extractant could be used for predicting B status of all soils or all crops. The present investigation aims to screen out few extractants for predicting the available B status of soil. Fig 2: Effect of different levels of B application on B uptake (µg pot -1) of wheat plant at different growth stages. RESULTS & DISCUSSION Table 1: Some important physico-chemical properties of the Experimental soils. Districts (Coochbehar, Jalpaiguri, Dinajpur (N), Nadia, Hooghly, Burdwan, Bankura) pH Org. C (g kg-1) Clay content ( g kg-1) Range 4.9-7.8 5.7-11.7 130-460 Mean 5.86 8.4 261 OBJECTIVES To assess the relative suitability of four extractants for assessment of available B status in the experimental soils of West Bengal. Table 4: Pearson correlation coefficients(r) between BPY and uptake of B by Wheat and extractable B content of the experimental soils. MATERIALS AND METHODS Table 2: Extractable B contents (mg kg-1) of the Experimental soils. 21 Bulk soil samples from seven districts of West Bengal has been collected and used for pot culture experiment at Central Research Farm, BCKV, WB. Extractant Growth Stages BPY B uptake HCC PI 0.681** 0.906** S 0.553** 0.914** G 0.763** 0.918** PDP 0.597** 0.727** 0.516** 0.711* 0.606** 0.717** TA 0.552* 0.686** 0.514* 0.674** 0.518* 0.669** MCC 0.136 0.386 0.022 0.397 0.172 0.348 Avail. B (HCC)* Avail. B (PDP)* (TA)* (MCC)* Range 0.351-1.108 0.310-0.730 0.228-0.530 0.065-0.428 Mean 0.660 0.487 0.391 0.211 POT CULTURE EXPERIMENT: Treatments (4) 0, 0.25, 0.5, 1.0 mg kg-1 B No. of Replication 4 N:P:K 150:60:40 Experimental Design CRD Crop Wheat ( CV K-1006) Sampling Stages Panicle Initiation & Maturity Parameters Recorded Dry Matter Yield, B Concn. of Shoot & Grain Table 3. Pearson correlation coefficients (r) between extractable B content and soil properties: Extractant pH Org. Carbon Clay content HCC 0.442* 0.554** 0.737** PDP 0.459* 0.421 0.701** TA 0.428 0.587** 0.571** MCC 0.210 0.334 0.304 SOIL ANALYSIS : ( ** and * correlation is significant at 0.01 and 0.05 probability levels respectively.) Oxidizable Organic Carbon Wet digestion Method (Walkley and Black, 1934) pH Soil: water 1::2.5 (Jackson, 1973) Mechanical analysis Boyoucous hydrometer method (Gee and Bouder, 1986) ) Available B Azomethine-H method (Wolf, 1971) [BPY = Bray’s percent yield. PI, S, G = Plants at panicle initiation, straw at harvesting and grains of wheat respectively.] CONCLUSION Hot Calcium chloride has been found to have highest correlation among all the extractants with almost all plant parameters. Order of the Efficiency of the extractants : HCC > PDP > TA > MCC Available B (HCC extractable) was found to be correlated with organic carbon and clay content. This suggests that Organic carbon and clay content have major influence in determining the availability of B.