DISTRIBUTION OF PLANT AVAILABLE BORON IN MAJOR SOIL TYPES AND THEIR CORRELATION WITH OTHER PROPERTIES OF THE SOILM.S. Anitha, K.S. Anil Kumar and G.M. Prashantha
An investigation was undertaken to study the plant available boron content in major soil types and cropping systems of Southern Karnataka. For assessing available boron status, Samples were drawn from the dominant soils and cropping systems: Northern dry zone, Central dry zone, Eastern dry zone, Southern dry zone, Southern transitional zone, Northern transitional zone, Hilly zone and Coastal zone representing the map units of 1:250,000 scale. Available boron was estimated with Azomethine-H solution with absorbance of spectrophotometer at a wavelength of 420 nm. The results revealed that hot water soluble boron of soils ranged from 0.01 to 1.55 mg kg-1. The data obtained was super imposed to prepare maps of available boron status of soils with the help of satellite imaginary interpretation. The data showed that boron deficient soils were more frequently encountered in Udupi (Coastal zone), Chikmagalore (Hilly zone), Kodagu (Hilly zone), Shimoga (Southern Transitional zone), Hassan (Southern Transitional zone), Chamarajnagar (southern dry zone), some parts of Uttar kannada (Coastal zone), Belgaum (Northern Transitional zone) and Tumkur (Eastern dry zone) and 40 soil samples (48 %) were sufficient in available boron. Northern dry zone recorded higher soil available boron (1.55 mg kg-1soil) and Coastal zone least (0.01 mg kg-1soil) and for others boron content ranged from 0.11 mg kg-1 soil to 1.09 mg kg-1soil. Deficiency of available boron was noticed in rice based cropping systems of coastal and Hill zone experiencing of high rainfall. Climatic analysis can tell about the chances of boron deficiency, as deficiency of boron in soil is always associated with heavy rainfall due to leaching of highly soluble boron by rain water and that the acid conditions may delay the weathering of boron-bearing minerals like tourmaline. The methodology should be useful in determining the effects of soil management practices on soil boron status and in monitoring changes in boron distribution with time due to the various soil practices.
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