Abstract:
One of the major constraints associated with onion (Allium cepa L.) cultivation is
improper nutrient management. This necessitates to ascertain an efficient and
economical integrated approach with renewable source such as organic manure and
biofertilizers. In this context a field experiment was carried out at Acharya
N.G.Ranga Agricultural university, Hyderabad, India to study the productivity and
soil fertility status as influenced by integrated nutrient management in onion using cv.
N-53. The twelve treatments arranged in randomized complete block design which
consisted of two kinds of organic manure i.e. farmyard manure (FYM) and
vermicompost (VC) alone and in combination with two kinds of bio fertilizers
(Azotobacter chroococum and Azospirillum brasilianse ) and chemical fertilizers
which were tested in comparison with recommended dose of fertilizers (RDF) as
control. The amount of FYM and vermicompost applied was calculated on the basis of
their results of chemical analysis for NPK. Roots were dipped into the slurry of
biofertilizer (1 kg in 10 liters) for 20 minutes before planting and thirty days after
transplanting the soil between the seedling rows was also treated with biofertilizers at
the rate of 2 kg per ha. Productivity indicated by yield and harvest index and soil
fertility indicated by available NPK in soil after harvest were significantly increased
with the application of biofertilizer in combination with 50% N through organic
manure (FYM or VC) and rest of 50% N and 100% PK through chemical fertilizer.
Those were significantly superior to the application of 50% recommended N through
organic manure with 50% N and 100% PK through chemical fertilizer, application of
chemical fertilizer (control) alone and application of organic manure alone,
respectively. Judicious application of bio fertilizers, organic manure and chemical
fertilizer increased 22% more yield over control (RDF) and economic analysis
revealed that highest net return and benefit cost ratio obtained when FYM used as an
organic source which replaced the 50% of recommended dose of inorganic nitrogen.
Bacterial population of Azotobacter and Azospirillum in soil after harvest was
markedly increased with integrated use of bio fertilizer, organic manure and chemical
fertilizer system and was reduced with the exclusive application of chemical
fertilizers. The results indicated that integrated nutrient management with
biofertilizer (Azotobacter and Azospirillum) in combination with 50% inorganic N
through organic manure (VC or FYM) and rest of the N and PK through chemical
fertilizer is considered most useful for obtaining maximum yield with higher fertility
status in soil for onion cultivation.
