Nitrogen release, sediment outflow and water quality parameters with uncoated and neem coated urea application from selected land slopes under simulated rainfall conditions
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Date
2020-09
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
The nutrients loss from fertilized agricultural lands not only results in the reduction of fertility of soil but also the accumulation of these chemicals in various water bodies produce harmful toxic effects rendering it unfit for human as well as for animal consumption. Urea fertilizer is highly soluble in water and volatile in nature and constitutes about 82% of the nitrogenous fertilizer used in India. The various pathways of nitrogen loss are volatilization, leaching, de-nitrification and through runoff. To minimize the
nitrogen losses and environmental hazards, it becomes imperative to improve the efficiency of nitrogen use by controlling nitrogen release rate of urea as per the plants’ need. To accomplish this task, slowrelease fertilizers (SRF) are produced by coating urea with neem and other biodegradable materials. This neem coated urea helps in retaining nutrients for a longer time and ensures nitrogen availability to plants for significantly longer periods than an uncoated urea fertilizer. In this study extensive experimentation
was done in the open field on experimental plots using uncoated and neem coated urea to study their nitrogen release pattern and its effects on sediment outflow and water quality parameters under varying rainfall intensity and different land slope conditions. To create controlled conditions of rainfall, artificial rainfall was generated by developing a portable rainfall simulation system which was capable of producing rainfall almost similar to natural rainfall with complete manual control. As per mandate of this study, apart from control (No crop i.e., bare soil), the nitrogen release rate, sediment outflow and water quality parameters were observed from (i) maize crop land and (ii) marigold crop land. Soil samples and runoff samples were collected and analysed to determine the status of nitrogen content in the soil and runoff water quality parameters such as TDS, pH and electrical conductivity on 2nd day, 6th day, 10th day and 14th after coated and uncoated urea applications. It was observed that developed portable rainfall simulator generated rainfall very similar to natural rainfall. The soil nitrogen content both in case of ordinary urea as well as neem coated urea applications was high in the beginning and decreased with time till 14th day. In case of ordinary urea, the rate of decrease in soil nitrogen content was very fast in the beginning (during 2nd day to 6th day) while in case of neem coated urea, the nitrogen release rate was slow and steady throughout the period. It thus implied that in case of neem coated urea application, the nitrogen becomes available to soil at a uniform rate for longer duration in bare land as well in crop land conditions. The percent nitrogen release up to 14th day after application of uncoated and neem coated urea with maize crop conditions was recorded to be 32.06% and 24.20% at 0% land slope, 33.11% and 25.23% at 2% land slope, 34.22% and 27.43% at 4% land slope, 37.68% and 30.60% at 8% land slope and 39.54% and 31.16% at 12% land slope, respectively under similar conditions. Similarly, sediment out flow and
runoff water quality parameters were observed and analysed to see the effect of coated and uncoated urea applications under various combinations of input variables. To quantify the effect of involved variables on nitrogen release and water quality parameters, mathematical relationships were also developed for various combinations of the input variables.