To find out the response of castor (GCH 10) to spacing and nitrogen under irrigated condition, a field experiment was conducted at three agricultural research stations of Anand Agricultural University, Viz., Derol, Sansoli and Khandha for consecutive two years during late kharif season of 2020-21 and 2021-22. The experiment was laid out in factorial randomized block design with four replications. The results indicated that spacing treatment S1: 120 x 60 cm recorded significantly the highest plant population, plant height, length of raceme, number of capsule/plant, number of raceme/plant, seed yield and NPK uptake over treatment S2: 150 x 75 cm in overall pooled results. Nitrogen levels treatment N3: 150 kg N/ha + 1 litre Azotobacter/ha produced significantly the highest length of raceme, number of capsule/plant and number of raceme/plant and seed yield which was statistically at par with treatment N1: 120 kg N/ha + 1 litre Azotobacter/ha and treatment N4: 180 kg N/ha in overall pooled results. Treatments receiving inoculation of Azotobacter showed higher soil Azotobacter and total microbial population as compared to their corresponding chemical fertilizer treatments. Moreover, spacing didn't affected soil microbial population. As there is an increase in fertilizer dose, soil microbial population showed decreasing trend at all the three locations.
