Intercropping System with Combined Application of Azospirillum and Pseudomonas fluorescens Reduces Root Rot Incidence Caused by Rhizoctonia bataticola and Increases Seed Cotton Yield

Root rot caused by Rhizoctonia bataticola is a serious threat in cotton. Field experiments were conducted to study the influences of intercropping system in cotton with inorganic fertilizer and two bioinoculants (Azospirillum and Pseudomonas) on root rot incidence and yield of cotton. The results revealed that among the intercropping systems, cotton intercropping with Sesbania aculeata (1:1 ratio) recorded the highest rhizosphere colonization of Pseudomonas fluorescens in the year 2007 and 2008 and the lowest root rot incidence of 1.40, 2.49 and 3.90; 1.02, 2.22 and 5.98% at the vegetative, flowering and maturity stages in the year 2007 and 2008, respectively. From nutrient management practices, integration of Azospirillum and Pseudomonas with 50% recommended dose of NPK recorded the highest rhizosphere colonization of P.fluorescens in both years and the lowest root rot incidence of 1.40, 2.32 and 3.36; 1.07, 2.01 and 5.25% at vegetative, flowering and maturity stages in 2007 and 2008, respectively. Cotton+S.aculeata recorded the maximum number of sympodial branches (23.5 and 20.62/plant in 2007 and 2008, respectively) and the highest seed cotton yield of 2010 and 1894kg/ha. The highest cotton equivalent yield (CEY) of 2052 and 1895kg/ha was recorded in cotton+onion system, which was closely followed by cotton+S.aculeata system that had the CEY of 2010 and 1894kg/ha in 2007 and 2008, respectively. The increased CEY is due to increased cost of onion compared with S.aculeata. Combined application of 100% recommended dose of NPK and bioinoculants recorded the seed cotton yield of 2227 and 1983kg/ha and CEY of 2460 and 2190kg/ha in 2007 and 2008, respectively. The lowest root rot incidence and increased yield in cotton+S.aculeata combined with 50% NPK and bioinoculants could be due to synergistic effect among the bioinoculants and S.aculeata.