Nitrogen (N) is an essential plant nutrient, therefore, N-deficient soils affect plant growth and development. The excessive and unwise application of N fertilizers result in nutrient losses and lower nutrient use efficiency that leads to the low crop productivity. Ammonia volatilization causes a major loss after N fertilization that causes environmental pollution. This experiment was conducted to evaluate the effectiveness of coating and uncoating N fertilizer in enhancing yield and nutrient-use efficiency with reduced ammonia emissions. The recommended rate of nitrogen and phosphorus, urea and di-ammonium phosphate (DAP) fertilizers were coated manually with 1% polymer solution. DAP (coated/uncoated) and potassium were applied at the time of sowing as subsurface application. While urea (coated/uncoated) was applied as surface and subsurface application. Results showed that nutrient use efficiencies of wheat were found to be maximum with the subsurface application of coated N fertilizer which increased nutrient-use efficiency by 44.57 (N), 44.56 (P) and 44.53% (K) higher than the surface application of uncoated N fertilizer. Ammonia emissions were found the lowest with subsurface-applied coated N fertilizer. Thus, coated fertilizer applied via subsurface was found the best technique to overcome the ammonia volatilization with an improvement in the yield and nutrient-use efficiency of wheat.

Plant nutrition is an essential element for crop production and enormous amounts of fertilizers are used in agricultural systems. However, these sources emit toxic gasses and compounds in the environment that not only deteriorate soil quality but also cause a reduction in the use efficiency of applied nutrients. Therefore, the value addition of these fertilizer sources by coating micronutrients, microbes, polymers or other organic and inorganic compounds have been advocated recently. The present study aimed to evaluate the effectiveness of value-added fertilizer sources for growth and yield improvement of Zea mays (Pioneer-30T60) and Oryza sativa (Super Basmati-515) with a reduction in ammonia volatilization and an improvement in nutrient recovery by crop grains. Different phosphorus (P), potassium (K) and nitrogen (N) fertilizer sources (Di-ammonium phosphate (DAP), polymer coated DAP, zarkhez plus NPK, urea, polymer-coated urea and zabardast urea) were used in different combinations keeping one control for N. The results revealed that maximum growth, yield and nutrient recovery was shown by polymer-coated urea and DAP followed by zarkhez plus NPK and zabardast urea. Moreover, a minimum ammonia emission was recorded by polymer-coated fertilizers, but other value-added fertilizers were found inefficient in reducing ammonia emission, though these sources improved all growth and yield attributes. Nutrient recovery efficiency was patterned as; polymer coated fertilizers > zarkhez plus NPK + zabardast urea > zarkhez plus NPK + urea > DAP + zabardast urea > DAP + urea > DAP. Thus, the use of polymer-coated fertilizers was beneficial for both the reduction in ammonia volatilization and for improving nutrient use efficiency with maximum crop benefits.

Coating materials generally a provide physical barrier to control instant dissolution of the urea fertilizer thereby delaying its consequent reactions in soil. The use of zinc salt as coating material causes slow dissolution of urea due to physical impact and hence minimizes immediate urea hydrolysis, ammonia (NH3) volatilization and enhances N utilization in crop production. The current investigation studied the impact of Bioactive Zincated urea on NH3 losses, yield parameters and quality traits of maize and rice crops grown under field conditions. Treatments included Bioactive zincated urea (ZU) was applied at 100%, 90% and 80% of recommended N rates (RNR) (125 and 160 kg N ha-1 for rice and maize, respectively) having a control (zero N application), conventional urea at RNR (CU100) without Zn and along with Zn (CU+Zn) treatments. The NH3 losses were recorded at 2, 4, 7 and 14 days after application of each split application of N treatments. The results indicated 117 and 6% increase in maize grain and 167 and 2.7% in total paddy yield as compared to control (no Zn) and CU+Zn, respectively while the corresponding increase in grain Zn concentration was 37 and 15% in maize and 25 and 14% in rice, respectively. Similarly, the corresponding grain N increases were 16 and 22%. Furthermore, ZU100 application markedly decreased NH3 volatilization (5 to 14% in maize and 2 to 24% in rice field) as compared to CU100. The studies clearly elucidates the effectiveness of Bioactive zincated urea in increasing yield and quality of crops (rice and maize); the lower N application (up to 80% of RNR) is possible without imminent impact on crop yield as well as on environment owing to lower N losses.

The major cause of reduced Zn availability to plants in Pakistan is unfavorable soil factors (alkaline pH and calcareousness). Different strategies can be adopted, to enhance the Zn bioavailability in the rhizosphere and cereals. Among all strategies, a novel technique is the coating of Zn on macronutrient fertilizers like urea. By adopting this technique, dual benefits can be achieved for example Zn and N become available to plants and on the other hand, the loss of urea can be minimized. Firstly, Engro Zabardast Urea was taken from Engro Fertilizers Pvt. Ltd and evaluated for coating effect on urease activity and Zinc release pattern with time (up to 70 days). Then 100%, 90%, 85%, and 80% recommended EZU (Engro Zabardast Urea) were tested to find out the increase in urea efficiency by coating. From the results of the release experiment, it was concluded that EZU @ 90% of the recommended dose showed maximum results of Zn release respective to time and vice versa for urease activity. Secondly, a pot experiment was conducted to evaluate the above-mentioned prepared products on agronomic parameters and Zn and nitrogen concentration in 45 days of maize seedlings. Zn concentration in maize seedlings increased with the application of 90 and 85% of the recommended EZU, respectively. Similar results were found under field conditions with the application of 90% of recommended EZU growth, physiological parameters, and grains and stover yield were improved and Zn contents in grains were enhanced. From the results of all experiments, it can be concluded that EZU is a fantastic product not only to increase Zn bioavailability/fortification but also to reduce nitrogen losses. This product has the potential to reduce the use of plain urea by up to 10%. This ecofriendly approach cannot only reduce extra labor costs but also the ignorance of Zn application by the farming community can also be addressed.