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A field experiment was conducted during rabi 2009 -10 on sandy loam soil at Student’s Farm, College of Agriculture, Rajendranagar, Acharya N.G Ranga Agricultural University, Hyderabad, A.P, India to study the effect of organic manures in combination with inorganic nitrogen fertilizer on soil available nutrients status, nutrient uptake and enzymes ( urease and dehydrogenase) activity of soil after harvest of safflower (Carthamus tinctorius L.) The highest available nitrogen (212.19. a kg ha-1), P2O5 (33.89 kg ha-1), K2O (433.07 kg ha-1), urease activity (6.97 μg of NH4 + released g-1soil h-1) and dehydrogenase activity (12.29 mg of TPF produced g-1soil d-1) were recorded in the treatment receiving 50 % N through inorganic fertilizer + 50 % N through vermicompost. The highest N, P and K uptake was observed in the same treatment.
safflower, Urease activity and Dehydrogenase activity
Safflower (Carthamus tinctorius L) is an ancient crop of india, cultivated during the winter season. It is grown for orange-red dye (carthamin) extracted from its brilliantly coloured florets and for much valued oil. Oil being rich in polyunsaturated fatty acid (linoleic 78%), plays an important role in reducing the blood cholesterol level. Crop cultivation under nutrient stress environment besides, poor crop managements are the major reasons for low productivity (623 kg ha-1) of the crop. India occupies the second place in safflower production in the world. Currently, it grows in an area of 2.29 lakh. ha. with a production of 1.42 lakh tonnes (2010-11). The general per hectare yields of safflower in india (642 kg ha-1) is low when compared to other leading counties and world average (890 kg ha-1) (1). Significant efforts have been made to economise the use of fertilizers in field crops through application of biofertilizers and organic matter. Longterm fertilizer experiments shows that applications of fertilizers alone has a deleterious effect on soil health and crop productivity (2). Integration of various sources of organic and inorganic fertilizers is more suitable because this reduces the application of chemical fertilizers and cost of cultivation, besides being an environmental friendly approach (3). Combined use of organic and inorganic sources of fertilizers increases the production and profitability of field crops and helps in maintaining the fertility status of soil.
From the above results, it can be inferred that integrated use of inorganic and organic sources of N will significantly increased available P and K status of the soil when compared with the application of N solely through chemical fertilizer. This can be ascribed to slow decomposition of organic manures which in turn increase the nutrient availability through enhanced microbial activities and release of nutrient from exchange sites. Among the treatments, the treatment received 50 % N through inorganic fertilizer + 50 % N through vermicompost recorded the highest seed yield, Drymatter , avalable nutrient (N, P2O5 and K2O), urease and dehydrogenase activity at harvest stage of crop growth compared to the corresponding combinations.
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