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Subject: Agronomy × Author: Basavanneppa M.A. × Start date: 2010 × Thesis Type: Ph.D ×
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    ThesisItemOpen Access
    Endotoxin Expression as Influenced by Nutrient Levels and Nitrogen Split Application and Refuge Crop Management in Bt Cotton Under Irrigation
    (UAS Dharwad, 2012) Basavanneppa M.A.; V.V. Angadi
    Among two field experiments conducted at Agricultural Research Station, Siruguppa during 2007-08 and 2008-09, the experiment entitled “d-endotoxin expression as influenced by nutrient levels and N split application on Bt cotton (Gossypium hirsutum L.) genotypes under irrigation” was laid out in split-split plot design with V1: MECH-162 Bt, V2: RCH-2 Bt, V3: JK-Durga Bt (BG-I) and V4: MRC-7201 (BG-II) genotypes as main plots, nutrient levels F1: 120:60:60 (Recommended), F2:160:80:80 and F3: 200:100:100 (Farmers’ practice) N:P2O5:K2O kg ha-1 as sub plots and nitrogen split application A: 50% N as basal + 50% N in three equal splits at 50, 80 and 110 DAS + foliar spray of urea @ 2% at 80 and 100 DAS and B: 12.5% N as basal and at 30, 90 and 120 DAS and 50% N at 60 DAS with foliar spray of urea @ 2% at 105 and 135 DAS as sub-sub plots. Second experiment on “Standardization of refuge crops/cropping systems in Bt cotton under irrigation” was laid out in RCBD with T1: 100 % Bt cotton , T2: Bt cotton (80%) + Non Bt cotton (20% as border crop), T3: Bt cotton + Non Bt cotton (8:2 row proportion), T4: Bt cotton + okra-chickpea (8:2 row proportion), T5: Bt cotton + pigeonpea (8:2 row proportion), T6: Bt cotton + maize (One week advance sowing) – chickpea (8:2 row proportion) and T7: Bt cotton + maize – chickpea (8:2 row proportion). Significantly higher seed cotton yield was recorded with MECH-162 Bt (2537 kg ha- 1) followed by RCH-2Bt. Application of 200:100:100 N:P2O5:K2O kg ha-1 recorded higher seed cotton yield (2515 kg ha-1) compared to other nutrient levels. Split application of 12.5% N as basal and at 30, 90 and 120 DAS and 50% N at 60 DAS with foliar spray of urea @ 2% at 105 and 135 DAS produced significantly higher seed cotton yield (2397 kg ha-1). V1F3B recorded significantly higher yield (2736 kg ha-1), gross return (Rs. 76600 ha-1), net return (Rs. 52690 ha-1) and B: C ratio (3.21). Higher d-endotoxin concentration (2.67 μg g-1) was observed with V3F3B at 45 DAS. Seeding with 100% Bt cotton (T1) recorded significantly superior seed cotton yield (1942 kg ha-1) compared to other treatments. Whereas, Bt cotton + okra-chickpea (8:2 row proportion) recorded highest Bt cotton equivalent yield (2446 kg ha-1), gross return (Rs 68481 ha-1), net return (46585 ha-1) and B: C ratio (3.13), which were on par with those of 100% Bt cotton.