Nitrogen can only be fixed and made available to plants through biological and chemical nitrogen fixation such as from nitrogen fertilizers and also through atmospheric nitrogen addition. Nitrogen comes in different forms, Ammonium, Nitrate and Urea Nitrogen with nitrate nitrogen being the most abundant with easy uptake and favors soil retention, unlike ammonium nitrogen which requires more oxygen to be metabolized in the roots of plants where it reacts with sugars. Urea nitrogen, on the other hand, is a waste form of nitrogen.

Until and unless we have soils rich in organic carbon, it is very difficult.

OC levels in north India hover around 0.2-0.3% (general) which indicates that soil may not be able to sustain without chemical fertilizer.

Unlike virgin soils having OC>4-5%, where one can think of some thing like that.

Split N applications at best growth stages having ample soil moisture , band placement and applying close to root zone and incorporation there off in soil will have wonderful effect on increasing NUE for any field crop.

Thank you sir, the information provided is really informative.

Neem coated Urea may be better option for maximum utilization of fertilizer.

We can make available maximum nitrogen for plant by many ways like:

1 -Nitrogen fertilizer timing:Ity was advisable to apply Nitrogen fertilizers as close as possible to the period of rapid crop uptake .

2 - Timing and risk of N loss : The period with the greatest risk of N loss is spring, when soils tend to be wet and before rapid crop growth begins to pump water out of the soil.

3 - Applying N close to the period of maximum crop growthز

4 - Fertilizer application rate : Nitrogen fertilizer rate is one of the most important N management variables, both economically and environmentally. The amount of N fertilizer needed to optimize crop yield often differs significantly from one field to another, and from one part of a field to another part .

6 - Nitrogen fertilizer sources : Ammonium nitrate, anhydrous ammonia, urea and urea-ammonium nitrate (UAN) solution are the four main N fertilizer sources .

7 - Application methods and placement. Nitrogen fertilizer materials lend themselves to a range of application methods, including broadcast application, surface banding, knife or coulter injection and application with the planter. Choice of method and placement is related to the source of N .

8 -Additives to reduce losses : There are two main additives available that help to reduce losses from N fertilizer, Agrotain and N-Serve. Both are effective at reducing the risk of N loss in certain N management systems. N-Serve is a nitrification inhibitor that is used mainly with anhydrous ammonia. Although it can be used with other N sources, its benefits are most proven with ammonia.

In addition to all the recommendations given, you can also promote the conditions to increase the populations and activity of nitrogen-fixing micro-organisms, both symbiotic (Rhodobium legumes) and associative and even endophytic.

Dear Ranveer, your question is very important. I appreciate the answers and comments given by other researchers. As you know N is the most important yield limiting factor after water. Because of the vaery mobile nature of the nutrient, the global N-use efficiency is very low, i.e. about 33%, the rest is unaccounted for and lost through leaching, denitrification and volatalization to the atmosphere. This is really very immense when it is translated in terms of money and environmental pollution. The following are some of the mechanisms which can be considered in optimizing the availability of N to plants.

1. Improving the soil organic mater content of the soil: an approach into the building up of organic matter in the soil may improve the overall soil biophysical and chemical properties, there by improving the nutrient retention and water content of the soil.

2. Integrated application of organic fertilizer and mineral N fertilizer: This is another approach to improve the availability of N to plants and sustainability of soil health and fertility.

3. Time and method of application: Application of N in split and at proper time is very crucial in terms of optimizing N availability and productivity of crops, and also quality of crop products.

4. sources of N fertilizers: When mineral N fertilizers are selected, soil types and properties need to be given special consideration. Because some N fertilizer sources have acidifying effects on soils, specially soils which are prone to soil acidification.

5. Amout or rate of N fertilizer should also be carefully calculated based on the soil fertility status and requirement of a particular crop and crop variety.

It is very hard to replace the inorganic nitrogen with organic sources. It is also very wrong notion that we cannot increase the efficiency of applied inorganic nitrogen while comparing the organic sources of nitrogen. Fertigation has been the defining success in this regard with huge range of annual as well as perennial crops.

How we can make available maximum Nitrogen (N) to plants ?

1. Apply correct application method

2. Apply night time

3. Insure field moisture maintenance, some soils rapidly dry up

4. Apply when seedlings achieved the stage of more and strong roots

5. Leaf applied nitrogen can not fully uptake, so avoid it.

Please, Read this famous article in this regards,

Article Role of Nitrogen for Plant Growth and Development: A review

Best regards, SJ

While we are always talking about nitrogen applied to the soil through fertilizers, manures and biological nitrogen fixation, we often do not give any weightage to nitrogen already present in the soil. This nitrogen is present in organic combinations in the soil and in much large amount than what we are applying through fertilizers or manures. In fact, this soil nitrogen determines, in a way, the health of the soil as well. How this nitrogen slowly becomes available for plant uptake during the crop growth season determines the fertilizer use efficiency. Thus, to understand the complete picture of nitrogen availability, both soil nitrogen and fertilizer nitrogen will have to be considered. It may be interesting to note that even when large amount of fertilizer N is applied to a crop, more nitrogen is taken up by the crop from soil rather than from the fertilizer.

we can apply slow release fertilizer; inclusion of different types of coatings; modifying biochar with urea fertilizers etc. These approaches can be better solutions.