EFFECT OF BIOFERTILIZERS ON NITROGEN AND PHOSPHORUS ECONOMY IN SUGARCANE CROP

摘要

A field experiment was conducted for three crop seasons (2003-06) in silty loam soil at the Sugarcane Breeding Institute, Regional Centre, Karnal (Haryana) to evaluate the efficacy of biofertilizers on plant and ratoon crops of sugarcane. Treatments comprised three combinations of bioagents I.e.Azotobacter chroococcum + phosphate solubilizing bacteria (PSB - Bacillus megaterium), Azospirillum brazilense + PSB and Acetobacter diazotrophicus alone each tested at 75 and 50 per cent N and P doses in comparison to recommended doses (150 kg N and 50 Kg P_2O_5 ha~(-1)). A high sugar early maturing variety Co 89003 was tried. Biofertilizer cultures were mixed with compost manure and applied @ 10 kg ha~(-1) each in two equal splits in vicinity of root zone at 30 and 60 days after planting followed by immediate hoeing. Amongst the biofertilizers, Azospirillum + PSB was found the best in both the plant and ratoon crops. Its application along with 75% recommended doses of N and P (112.5 kg N and 37.5 kg P_2O_5 ha~(-1)) along with biofertilizer recorded as much cane yield as with 150 kg N and 50 kg P_2O_5 ha~(-1) alone. However, reducing doses to 50 % (75 kg N and 25 kg P_2O_5 ha~(-1)) along with biofertilizers reduced the cane and sugar yields of plant and ratoon crops significantly. Juice quality was not altered by fertility treatments in plant as well as in ratoon crops. In ratoon crop Azospirillum + PSB and Acetobacter were found equally effective and when applied with 75% N and P gave significantly higher cane yield than 75 % N and P applied without biofertilizers. CCS t ha~(-1) followed similar trends to cane yields ha~(-1) in both the crops. Response of biofertilizers decreases with increasing fertility levels. Thus, 25% of inorganic N and P could be saved by the use of these biofertilizers.