CATION-EXCHANGE CAPACITY OF ROOTS IN RELATION TO RESPONSE OF FERTILIZER NUTRIENTS IN SALT-AFFECTED SOIL

An experiment was conducted during 1988 at Varanasi to study the catio n-exchange capacity of roots as affected by N,P,K,Fe,Mn,Zn and farmyar d manure + N in gypsum-amended, salt-affected soil (Typic Natraqualf) and its relationship with dry-matter accumulation and nutrients uptake at different physiological stages of rice (Oryza sativa L.) and wheat (Triticum aestivum L. emend. Fiori & Paol.). The application of N and Zn significantly increased the cation-exchange capacity of roots at f lowering stage of rice respectively from 6.21 to 9.62 meq/100 g and 9. 90 to 12.20 meq/100 g and of wheat from 5.80 to 9.81 meq/100 g and 8.9 6 to 13.82 meq/100 g. The magnitude of response with combined applicat ion of farmyard manure and N was much higher, ie 9.62-13.80 meq/100 g and 9.81-13.82 meq/100 g at flowering stage of rice and wheat respecti vely. The nutrient uptake also followed a similar trend of nutrient re sponse, indicating no necessity of Zn application where farmyard manur e is adequately used.