Boron status of soils as affected by different soil characteristics - pH, CaCO3, organic matter and clay contents

In Pakistan, the soils are mostly developed from calcareous, alluvial and loessial deposits of late Pleistocene age located partially on old river terrace and relatively on the channel-levee-remnants, therefore micronutrient instigate from weathering of rock parent materials and their deficiencies are wide spread because of intensive cultivation and more nutrient uptake than application. This study was started to determine the authentic information about boron status of calcareous soils having alkaline pH and low organic matter (OM) contents under canal and tube well irrigated areas of Punjab. Soil samples were collected from eighty-one sites of five district of Punjab. Soil samples were analyzed for pHs, texture, ECe, total N, Extractable K, Olsen P, CaCO3, OM and 0.05 M HCI extractable B. The textural analysis exhibited that 28% area had more clay contents and was classified as heavy textured, 42% had loamy texture while 30% had sandy or light textured. The results revealed that more B was observed in clay textured soils. In case of pH, 83% area (68 sites) had pH greater than or equal to 8.00 while 13 sites had pH ranged from 7.50 to 8.00 and only one site has pH less than 7.50. Incredibly low OM was observed in surveyed area and it was less than 1% in all the 81 samples (100% area was low in OM). Similarly CaCO3 contents were in the rang of 2.14 to 9.72% and about 92% area surveyed had CaCO3 contents in the range of 3-10%. The data regarding B concentration in soil reflected an atrocious depiction of B deficiency in the surveyed soils and exhibited that out of 81 samples, 66 sites (82%) had B concentration in the range of 0.10 to 0.45 mug g-1 and were fall in the deficient range (i.e. less than 0.50 the critical level) while 12 sites (15%) having B concentration in the range of 0.46 to 0.55 mug g-1 and only 3 samples had B range 0.56-0.91 mug g-1. Correlation analysis exhibited that soil B is positively correlated with OM and clay content of soil while it had strong negative correlation with CaCO3 content and pH.