Intercropping System with Combined Application of A zospirillum and P seudomonas fluorescens Reduces Root Rot Incidence Caused by R hizoctonia bataticola and Increases Seed Cotton Yield

Root rot caused by R hizoctonia 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 ( A zospirillum and P seudomonas) on root rot incidence and yield of cotton. The results revealed that among the intercropping systems, cotton intercropping with S esbania aculeata (1 : 1 ratio) recorded the highest rhizosphere colonization of P seudomonas 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 A zospirillum and P seudomonas 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 1894 kg/ha. The highest cotton equivalent yield ( CEY ) of 2052 and 1895 kg/ha was recorded in cotton + onion system, which was closely followed by cotton +  S . aculeata system that had the CEY of 2010 and 1894 kg/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 1983 kg/ha and CEY of 2460 and 2190 kg/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 .