Effect of biofertilizers on the growth, yield and nitrogen economy of sesame grown in summer rice fallows

Abstract

A field experiment was conducted in the rice fallows of Agricultural Research Station, Mannuthy, during the summer season (January – April) of 1995, to find out the effectiveness of biofertilizers on the growth, yield and N economy of sesame. The experiment was laid out in randomised block design with 1.4 treatments replicated thrice. The treatments included were, the recommended dose of inorganic N,@30 kg/ha alone, inoculation of Azospirillum or Azotobacter along with 50 percent, 25 percent or no inorganic N, either with or without lime and an absolute control. Most of the growth characters, yield attributes and yield were highest in the plots applied with the recommended dose of 30 kg inorganic N/ha alone. The crop nutrient uptake and available soil nutrients were also higher in the above treatment. The better initial physical, chemical and biological conditions of the soil, along with the added inorganic N fertilizer @30 kg/ha might have contributed to a better nutrient supply from the initial growth period itself. Though, both the microbes, Azospirillum and Azotobacter showed almost similar performances regarding various parameters, a slightly better response was shown by Azospirillum in most cases. This might be due to the fact that Azospirillum is a better root colonizer than the freeliving Azotobacter, which led to better nutrient uptake and ultimately yield of the crop, compared to Azotobacter inoculated treatments. Lime application, along with the inoculation of acid tolerant strains of the microbes, had no profound influence on the parameters studied. Thus, the study revealed the necessity of the application of recommended dose of inorganic N fertilizer @30 kg/ha for sesame grown in summer rice fallows. It also showed the lesser possibility of inorganic N substitution with Azospirillum or Azotobacter inoculation in such a situation. Moreover, liming could not bring about any significant influence on the activity of acid tolerant strains of either Azospirillum on Azotobacter.