PHYSICAL COMPATIBILITY OF AGROCHEMICAL TANK MIXTURES COMMONLYUSED IN PIGEONPEA (Cajanus cajan (L.) Millsp.)

Abstract

Tank mixing of insecticides, fungicides and fertilizers is a common practice in pigeonpea cultivation to reduce labour, time and
application costs. However, information on the compatibility of commonly used agrochemicals is limited. The present study was
conducted during 2011–12 at the Regional Agricultural Research Station (RARS), Warangal, India to evaluate the physical compatibility
of 25 agrochemicals comprising 20 insecticides (including botanical insecticides), two fungicides and urea, commonly used in pigeonpea
crop. The compatibility of the combinations was tested without adding adjuvants. A total of 300 possible combinations were tested
under laboratory conditions using the jar test method at their respective recommended doses. Compatibility was assessed based on
the occurrence of precipitation, flocculation, layer separation, gelatinization, viscosity changes and exothermic reactions. Among the
300 combinations evaluated, only three combinations viz., NSKE + thiodicarb, NSKE + mancozeb and NSKE + copper oxychloride
showed clear evidence of incompatibility due to persistent precipitate formation. Several other combinations exhibited temporary
precipitate or supernatant formation, which disappeared or dissolved upon agitation, indicating the need for continuous stirring during
field application. Exothermic reactions were not observed in any treatment. The study demonstrated that the majority of commonly
used agrochemical combinations are physically compatible for tank mixing. However, further studies on phytotoxicity, biological
efficacy and field performance in pigeonpea are required before recommending these mixtures for large-scale use.