Effect of Straw on Yield Components of Rice (Oryza sativa L.) Under Rice-Rice Cropping System

Field experiments were conducted at the Directorate of Rice Research experimental farm, ICRISAT campus, Patancheru, Hyderabad, during 1998–2000 for five consecutive seasons (three wet and two dry seasons) with five treatments T1 – 100 % straw incorporation; T2 – 50 % straw incorporation; T3 – 100 % straw + green manure (GM) incorporation; T4 – 100 % straw burning and T5 – 100 % straw removal (control)] along with the recommended dose of fertilizers to evaluate the effect of different crop residue management (CRM) practices on yield components and yield of rice in rice–rice cropping sequence. The ammonium N measured at active tillering was higher in 100 % straw‐added plots over 50 % straw addition and straw removal with maximum values in the straw + GM‐incorporated plots. Among the yield components, tillers, panicles and spikelets were influenced from the second season of residue incorporation with significant increase in 100 % straw‐added treatments. The increase in tiller and panicle number could be attributed to the increased NH₄‐N in these treatments, which is evident from the significant correlation between tiller number and NH₄‐N (r = 0.82**) and panicle number and NH₄‐N (r = 0.87**). The influence of residue treatments on rice grain yield was observed from the third season onwards where incorporation of straw alone or in combination with GM and burning of straw significantly increased grain and straw yields. Grain yield showed significant positive correlation with the number of tillers (r = 0.74*–0.81**) and panicles (r = 0.74*–0.84**) in three treatments (T1, T3 andT4) where grain yields were significantly higher. The regression analysis showed that 57–66 % and 64–75 % of the variation in yield could be explained by tillers and panicles together in these three treatments during wet and dry seasons respectively. Thus, CRM practices such as addition of 100 % straw either alone or with GM and straw burning influenced the yield components (tillers, panicles and spikelets) positively and thereby increased rice grain yields.