Ruma Das

Nitrogen (N) fertilization is playing a vital role in increasing crop production and ensuring food security. The global population which is growing exponentially has reached nearly 7.5 billion in 2015 (from 1.65 billion in 1900).The sole reason behind this is synthetic nitrogen fertilizer, it alone supported 3.5 billion people otherwise it would be somewhere around 3.5-4 billion. Imbalanced use of N fertilizer leads to N deficient condition which affects plants growth and development also in N surplus condition it has a huge negative impact on environment and human welfare. It includes negative effects on biodiversity, eutrophication, nitrate accumulation in waters, acidification of soil and water bodies, nitrous oxide emissions and risks to human health due to exposure to ozone and particulate matter. In agricultural systems, when fertilizer is applied to crop is mainly prone to losses through ammonia (NH3) volatilisation, nitrate (NO3-) leaching and denitrification. Loss of N in the form of NH3 and NO3- mainly depends on various factors like temperature, soil pH, soil moisture, soil properties, plant characteristics, seasonal fluctuations. An integrated approach is must to minimize N losses and increase crop yield. In broader sense, options to minimize NH3 volatilization and NO3 leaching are fertilizer, soil and irrigation based management strategies. Fertilizer management options like 4R nutrient stewardship concept applying the Right Source of nutrients, at the Right Rate, at the Right Time and in the Right Place. Managing soil by practicing conservational tillage with crop based scheduled irrigation. This small change in nutrient, soil and irrigation management find way to make improvements in the nutrient use efficiency, profitability in farming, environmental safety and sustainable ecosystem with fertilizers in the developing world.

Irrespective of treatments, available K decreased in limed over that of un-limed soil. In general, available K progressively increased in both un-limed and half limed soils up to 60 day period of incubation but thereafter showed a decreasing trend on 90th day of the experiment. However, full limed soil showed a different trend of results. Available K increased up to 30th day, thereafter decreased on 60th day then again increased on 90th day of the experiment. The results thus revealed that available K is not retained in the soil for longer period rather it is converted to other forms at the later stage of the experiment.