NITROGEN, PHOSPHORUS AND POTASSIUM REQUIREMENTS OF RABI ONION BASED ON TARGETTED YIELD CONCEPT
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Date
27-01-99
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MAHATMA PHULE KRISHI VIDYAPEETH RAHURI - 413722, DIST. AHMEDNAGAR MAHARASHTRA STATE, INDIA
Abstract
Field experiments were conducted on the research farm of the Soil Test Crop Response Correlation Project, M. P. K. V.Rahuri for evaluation of scientific basis for calculating the nurient requriement of rabi onion. The experiments were conducted on Otur series (Typic Chromustert) during the 1996-97 and 1997-98. Based on the fertility gradient approach ( Ramamoorthy et al,1967) 1967 ) four fertility gradients were prepared by applying graded levels of NPK fertilizers and an exhaust crop of maize for fodder was sown to stabilize soil available N, P and K. There were 21 selected treatment combinations of N (0,50,100,150 and 200 kg ha"1), P2Os (0,50,100 and 150 kg ha1) and Kp ( 0, 50 and 100 kg ha "') with 6 control superimposed in each fertility gradient strip and onion was grown as a test crop on these plots. Initial soil samples were collected and analysed for available N,P and K and after harvest, onion bulb and top samples were analysed for their NPK content. At harvest yields were recorded and using the concentration of nutrients, the uptake of NPK by plants calculated. The data on initial soil test values for available NPK .yield of onion, uptake of NPK by onion crop and fertilizer NPK applied were used to calculate the basic parameters viz., nutrient requirement, per cent contribution from soil and fertilizer nutrients. From these basic parameters, fertilizer prescription equations for onion ( rabi ) were mathematically computed. The nutrient requirement for production of one tonne of onion were 1.134 kg N, 1.172 kg P205 and 2.04 kg K,0. The per cent contribution from soil nutrients was 11.25 N , 55.35 P2Os and 7.37 K,0 and per cent contribution from fertilizer for nitrogen was 21.01, P2Os 29.35 and 66.18 for K p .Making the use of basic data the fertilizer prescription equations for onion were worked out. FN = 5.40T - 0.54 SN FP205 = 4.00 T - 4.32 SP FK.0 = 3.10 T - 0.13 SK Where FN, FP20 5 and F K,0 are fertilizer nutrients in kg ha ', T is yield target in t ha"1 and SN ,SP and SK are soil available N P K in kg ha'. Using these equations, ready reckoners for fertilizer dose for onion for different yield targets at different soil test values were calculated. The validity of these equations were tested by conducting two follow - up trials at two different locations on different soil types during the rabi 1998. The results showed that yield targets of 30, 40 and 50 t ha 1 were acheived within + 6 - 8 per cent variation. Application of fertilizer for yield targets of 30, 40 and 50 t ha ' resulted in higher yields and higher returns per rupee spent on fertilizer than that of the general reccommended dose and as per soil test treatments and was found to be beneficial and economical. The studies also suggest the possibility of making fertilizer recommendation to the farmers considering their financial condition.