Abstract

Bt transgenic hybrid cotton productivity and profitability could not be sustained after 2007 in India which necessitated to investigate into the nutrient needs of transgenic Bt hybrid cotton and their intercropping systems. Seven Bt transgenic hybrid cotton intercropping systems with four fertilizer management practices and two plant spacings were evaluated in split plot design during 2010-12 in Vertisols at Central institute for Cotton Research, Nagpur, India. Present recommendation of Pigeon pea refugea as stripcropping (2:8) with transgenic Bt hybrid cotton reduced seed cotton yield by 69%, therefore, not accepted by 82% farmers. Tagetus sp. or Dolichus lab lab were advocated as better refugea with economic advantage of US $ 600 ha-1 with C: B ratio of 1:2.8. However, a net a profitability of US $768 and 662 ha-1 with a C:B ratio of 1:3.7 and 1:3 were achieved in intercropping with roselle or soybean compared to US $ 348 C:B ratio of 1:2.5 only with transgenic Bt hybrid cotton alone. This study also breaks the myth of 30% extra fertilizer dose for transgenic Bt hybrid cotton, which requires 90:20:37 N:P:K kgha-1 only and soybean intercropping requires additional 14:13:0 N:P:K kg ha-1. Any deficiencies arising can be economically corrected with two prophylactic foliar sprays of NMgB after square initiation. NPK uptake, nutrient and fertilizer use efficiencies were significantly improved in transgenic Bt hybrid cotton and intercropping with soybean and roselle (except PUE). Hand weeding cost was minimum in soybean and maximum in roselle with Pendimethalin PPI rotated with Pyrithiobac Na EPE.

Key words: Transgenic Bt hybrid cotton, fertilizer use efficiency, intercropping, small farms, soybean.