This article throws light upon the top two ways to increase nitrogen use efficiency. The ways are: 1. Minimizing Nitrogen Loss with Proper Management of Nitrogen 2. Minimizing Nitrogen Loss with Proper Water Management.
Way # 1. Minimizing Nitrogen Loss with Proper Management of Nitrogen:
(a) Deep placement of N fertilizers in a field before transplanting/sowing increases the nitrogen use efficiency. The loss would be minimum.
(b) Ammonia volatilization losses in flooded soils range from negligible to almost 60% of applied nitrogen. In recent studies NH3 loss from Ammonium sulphate (NH4)2 SO4 was 0.2-6.8 per cent and that from urea 1-20 per cent. Through incorporation of ammonium fertilizers like Ammonium sulphate into the soil minimizes NH3 volatilization loss.
(c) The loss of NH3 varies from 27 to 47% when urea is applied on surface as top dressing at 14 or 27 days after transplanting of rice crop. Rates of NH3 loss were limited to 10-15% when urea was applied at the pancile initiation stage.
(d) Nitrogenous fertilizers should be applied in split dose (or instalment) to minimize the losses.
(e) Use of slow and controlled-release fertilizers. Fertilizers that releaseâ€”their plant nutrients slowly throughout the growing season (or for longer period), have a number of potential advantages. Slow release volatilisation loss and sustain the crop with adequate N nutrition throughout the growing season.
(f) Use of nitrification inhibitors increase the controlled availability of plant nutrients. The inhibitor is block the conversion of ammonium to nitrate-nitrogen by inhibiting Nitrosomonas (bacteria) growth or activity. The inhibitors are dicyandiamide (DCD), acetone extract of neem etc.
A group of organic compounds in neem seed known as meliacins are responsible for inhibiting nitrification. Urea treated with neem cake inhibited nitrification by 40 and 74 per cent at the end of 1 and 2 weeks of incubation, respectively. The coating technique used coal tar solution in kerosene oil (1 kg/2 litres, enough for 100 kg urea) as sticker to hold the finely produced neem cake.
One quintal urea is transferred to a seed treatment drum and coal tax-kerosene solution is added in parts while rotating the drum. Neem cake (15-20 kg) is then added and the content of the drum is rotated and thus the neem cake is ready for use. The technique is simple and being used only on individual farmer’s level. This technique could not go to the industrial level.
A new technique involving neem oil micro-emulsion has been developed at IARI, New Delhi for coating urea. Urea coated with micro-emulsion has shown definite advantage in nitrogen use efficiency. The technology has two major advantages (i) only 0.5 kg neem oil is needed, per tonne of urea and (ii) the product is also eco-friendly.
(g) Application of fertilizers at proper time.
(h) Use of soil amendments as corrective methods.
(i) Volatilisation losses from nitrogenous fertilizer may be minimized by mixing the urea and. soil in 1 : 5 ratio. The mixture should be used after drying in under shade. Likewise, nitrogenous fertilizer may be mixed with oilseed or neem cake before broadcasting.
Way # 2. Minimizing Nitrogen Loss with Proper Water Management:
(a) For minimizing the denitirification loss in the field arrangement for proper drainage should be done. Proper aeration would decrease the de-nitrification loss.
(b) Optimum use of irrigation water would reduce the leaching loss.
(c) Applying the first dose of nitrogen to a puddled field without any standing water and then introducing water at 4 days transplanting.
(3) Weed Control. Loss of N can be minimized by removal of weeds from the field.
(4) Varietal Differences in Nitrogen-use Efficiency. Rice variety IR 42 uses N more efficiently than IR 36 and IR 8. Variety like IR 42 should be used for increasing N- efficiency.