Comparison of Soil Tests for Predicting Boron Deficiency and Response of Pea to Boron Application on Acid Alfisols

The available B in 20 acid Alfisols of East Khasi Hills. Meghalaya was determined using six extractants. Of these only four. viz. mannitol-CaCl₂, hot water (reflux method), hot water (boiling) and DTPA-NH₄HCO₃ were found promising and the critical limits of available B were 1.0, 0.7, 0.7 and 0.6 ppm, respectively. Soils containing available B below the critical limit responded appreciably to B fertilization. The amount of B extracted by these extractants was positively and significantly correlated with Bray's per cent dry matter yield. B concentration and B uptake in shoots and negatively correlated with Ca/B ratio in shoots and exchangeable soil Ca content. The mannitol-CaCl₂ was adjudged as the most efficient extractant. B concentration and Ca/B ratio in 55-day-old pea shoots proved dependable tissue tests for predicting B deficiency in pea; the critical limits being 23.8 mg kg⁻¹ and 233, respectively.