It is possible only by useing slow release coated material and the depth of plecement.

Even foliar application interminantaly

The soil nitrogen is used more efficiently that soluble fertilizer nitrogen.

The increase of soil organic matter will be accompanied by greater total soil nitrogen.

The use of nitrogen fixing legume cropping can increase both the soil organic matter and the nitrogen level this nitrogen is used more effectively as it available based on the increased soil biological activity with mirrors the plant needs.

An excellent discussion point because N is complex macro nutrient to deal with. One simple way to achieve higher U use efficiency is break the total requirements into two to four applications to reduce losses in the form of soil solution and in gaseous form. But this also depends on soil-water status and other factors. Grateful for initiating this discussion point. Best regards.

Thank you @Vaibhav, Paul Reed, and Yadunath for your valuable inputs and initiation of discussion.

Application of top dressing by split application approach in situations where there is too much rain to prevent erosion of the N fertilizer could also suffice

Nitrogen losses can be caused by volatilization of ammoniac in case of application of urea or ammonium. Nitrogen can also be lossed as nitrate by leaching.

In the US farmers use thiosulfate (S2O3) to slow down the transformation from urea into ammonium which gives a significant reduction of losses caused by volatilization. Additional the thiosulfate reduces the transformation into nitrate so that leaching is reduced as well.

Of course split application of nitrogen and implication directly into the soil will give a reduction of losses as well.

Thank you for initiating a discussion on timely needed topic. I agree with Dr. Yugunath. For upland crops adding Nitrogen fertilizers with organic matter at suitable ratios will give better results. Another thing is, farmers applied more nitrogen than plant can absorb at different age of those plants. Specially, for field crops, excess amount of Nitrogen is applied as the basal dressing. Therefore , soil analysis before starting the season is very much important.

1. Soil test based N application

2. Leaf color chart or sensor based application

3. Foliar application at critical stages along with reduced soil N application rates

I am thankful to Dr.Subba Rao, the former Director of Indian Institute of Soil Science, Bhopal for initiating eye opening for discussion and which may further helpful in future research planning on this topic. I salute you Sir.

Nitrogen being the most important highly soluble and volatilizable essential macronutrient, the use efficiency of nitrogen can be enhanced by understanding the mechanism of dissolution and loss of nitrogen from the applied fertilizer. Dr.Buta Singh Dhillon has enlighten the technology such as soil test or soil test crop response based N application, Use of sensor such as chlorophyll/ SPAD meter or Leaf Colour Chart Split application of nitrogenous fertilizer (as suggested by Kafula Chisanga and Yadunath Bajgai) and foliar application which aims to reduce the nitrogen application rate. Besides, the modified or coated fertilizer may reduce the dissolution of the applied nitrogenous fertilizer so as to enhance the availability of release nitrogen for crop uptake which improve the nitrogenous fertilizer.

An another approach to improve N use efficiency is the identifying crop varieties with higher N use efficiency may also be more helpful not only interms of more grain yield per kg of applied nitrogen but also reduce nitrate pollution in the ground water. The nitrogen use efficiency are calculated based on the relationship between the crop response and the quantity of nitrogen applied or uptake by crop. The terms such as partial factor productivity, agronomic efficiency, physiological efficiency and recovery efficiency.

I have classified the rice varieties grown all over Tamil Nadu into 4 classes such as Efficient and responsive varieties, Efficient and non responsive varieties, non-efficient and responsive varieties and Non-efficient and non-responsive varieties based on the agronomic and physiological N use efficiencies under project sponsored by Department of Science and Technology, Govt. of India. The attached articles may give details on this. Further, this identification and selection of varieties with highly efficient and non-responsive may be highly useful in Organic agriculture.

I am very grateful to Annangi Subba Rao for initiating discussion on the much researchable area.

I am thankful to Buta Singh Dhillon Kafula Chisanga Yadunath Bajgai for active participation and expressing their views.

Avoiding indiscriminate use of nitrogenous fertilizers is one of the most important aspects of achieving higher degree of efficiencies.. application should be based on soil type, like sandy soils need more split application due to more leaching losses of nitrogen applied as basal application..use of ammonical and nitrate fertilizers based in soil pH may also influence efficiency as NH4+ creates acidity while NO3- results in increasing soil pH, so to have neutral pH for optimum Nutrient balance, these fertilizers must be applied accordingly..proper time of application is one of the most important principles so as to satisfy time of demand with application time..amount of application must be based on soil test values, STCR or DRIS..however slow release nitrogen fertilizer also enhance application efficiency without losses..proper application of nitrogen in soil where organic matter has to be added also ensure fast decomposition thereby release of nitrogen slowly and will be taken up by crop efficiently...avoiding use of nitrate fertilizers in waterlogged soil may enhance use efficiencies... Inclusion of legume in cropping system also add nitrogen whereby leeser application is required from outer source hence more efficiency..

https://www.researchgate.net/profile/Jothimani-Subbiah/post/Practical_ways_to_increase_the_nitrogen_use_efficiency_in_crops_and_cropping_systems/attachment/6156a115b3729f0f61892008/AS%3A1073976189140992%401633067285094/download/published+II.pdf

Increased nitrogen efficiency can be shown in traditional mixed farming. The Hawaiian system of growing padi poi was combined with the dual use of padi for fish production. The fish would generate manure for the taro poi production the hraves of the fish will circulate the nitrogen out of the water and give it a human population which outwise would suffer from protein deficiency.

Other systems would be padi rice azoola fish system. These systems when optimally run will provide optimization of the nitrogen without massive fertilizer requirement and their design requires the elimination of toxic agrichemical inputs with their issues.

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Controlled-Release N Fertilizers can be used . Slow-release N fertilizers used to control proportion of fertilizers available at one time also efficient nitrogen use means a kind of cost saving. Can use Urea-Formaldehydes so we must supply in varying rates . Thereby the varying rate of urea & formaldehyde will give Greater urea also more available N

A simple practical method to increase N use efficiency is to break the calculated dose into several applications. Avoiding applications before rain or flood irrigation could reduce the losses through run off and seepage. Thank you for very pertinent question.

I find interesting replies by learned colleagues on the important topic raised for discussion .The foremost measure or practice to efficiently use applied N is to use efficient cultivar or variety.As the N from soil organic matter or applied manure is slowly mineralized and available to plant, it is efficiently utilized.Designed manure/ organic source combinations may release N coinciding with N demand at different growth stages.Among the sources for efficient N use, the neem coated urea, a nitrification inhibitor became popular in India.The GOI, fertilizer industry and farmers deserve appreciation for this success.Though good amount of research work is available on slow and controlled release N fertilizers, the cost of those fertilizers is high and farmers may not be able afford to use them. How to reduce the cost of production is a question ? The split application of urea coinciding with important growth stages of crop and also irrigation schedules also became popular among farmers.Placement of urea super granules or briquettes has also been advocated in lowland rice but this technology needs an applicator to place the supergranules deep in soil. It is claimed that this technology has been a success in Bangladesh with the efforts of IFDC.Use of leaf colour chart or chlorophyll meter is also advocated for application of N at certain critical growth stages in crops like rice and wheat with varying success and popularity as they need special aids .

The following points can be kept in mind when one desires to efficiently manage the N in crops or cropping systems.1. One should not apply more nitrogen than required at a particular growth stage of crop.2.Before application of fertilizer N, it is desired to measure the residual N in soil.3 When working out the N requirement of crops, the linear plateau models should be used to avoid unnecessary application of higher rate of N application.4.When practicing split application of N, the basal dose can be reduced as the plant N requirement at that stage may not be high.5.When applying the fertilizer, N placement may be preferred over broadcast application.6.When applying N in splits, the dose can be adjusted by observing the crop or using some sensing device like chlorophyll meter or leaf colour chart etc 7.Rainfall , irrigation or moisture regimes in soil should be kept in view before application of N fertilizer.8. As weeds compete with crops for moisture and nutrients, appropriate weed control at an early stage of crop is a must.9.N fertilizer requirement can be reduced by appropriately including legumes in cropping system.10.Any available source of organics may invariably be used along with fertilizer N.

Can we plan to reduce the use of at least 25 percent of the N fertilizer currently being used in cereal based cropping systems by using organic manures or legumes in rotations in different areas? Can we practically work out the recommendations in different universities and provide practical recommendations to farmers through extenson agencies in the university jurisdiction areas ?

Organic manure can be considered as controlled-release fertilizers but the problem in organic manure is low Nutrient concentration.its readily depend on decomposition rates , by any chance it can carry Weed seed, diseases, soluble salts sometimes . Standard N fertilizer crop use rates are usually 40-70%. the rest is is leached, denitrified. i hope its possible with crop rotation of legumes in different areas because crop rotation with legumes will probably improve the soil structure and fertility as well. and also reduce soil erosion and supply the nitrogen which is removed by corn-like grain crops. here we can carry out soil samples and soil tests to identify the nitrogen content in soil Annangi Subba Rao @

Sachini Thisara Jayamali As you have stated, the major opportunities for supplying N to cropping systems are fertilizers, manures and introduction of legumes in the system. If one follows conservation agriculture, in situ residue recycling is possible. Otherwise, the residues are returned to soil through livestock as manure or compost.There are technologies available for preparing and efficiently applying manures which needs to be popularized among farmers.The nitrogen use efficiency may be still lower than what you stated, may be in the range of 30 (especially in rice) to 50 % or slightly more in crops like wheat and maize. Even soil test methods are not so efficient( even difficult) in assessing N requirement of crops. Actually it is yield level or yield goal of farmers which decides N application rate. At least 50% of the N uptake equivalent has to be supplied through fertilizers and rest through soil organic matter, manure and legumes etc.

Totally agreed though standard typical fertilizer efficiencies are 30-50%for N. it can be lesser than that

• Fertilizer is one management option used almost universally .Must replace soil nutrients lost by harvest. Chemical fertilize should be supplied to recover the nutrient loss by harvest . yes Soil nutrients typically present in finite amounts, do not replenish themselves alone. Thereby in scales of land management and soil fertility management must be carried effectively with chemical fertilizer too . but in that case must be careful else .Farmers may be the primary cause of non-point-source pollution if the fertilizer application rates exceed the correct supplying rate Annangi Subba Rao

You can apply slow releasing N fertilizer in split doses. In addition to that as soil amendment, suitable percentage of organic manure such as compost, green leaves, animal manure (i.e cow dung , poultry manure etc.), vermicomposting could be done to increase the efficiency of absorbing Nitrogen. In addition to this rotation with legumes in the previous season could also be done. What many research showed is the application of nitrogen fertilizer in basal is too much.

During the cropping season, increased synchronization between crop demand and supply from all sources, including fertilizer, is the optimal strategy to maximize fertilizer N application to field crops. This strategy is based on providing optimum amounts of fertilizer N to optimally meet crop N requirement at appropriate crop growth stages. One of the ways increasingly being utilized to identify the proper quantity of fertilizer N to be given in-season is to employ canopy reflectance sensors, chlorophyll meters, or even leaf color charts.

I agree with most of the points raised by different colleagues and by Dr. Subba Rao himself. Based on some of my experience with fertilizer N, practical ways to increase fertilizer N use efficiency will always revolve around the 4Rs - right amount, right time of application, right source and right placement or application method. These are well known but most of the time not followed very well. Of these, generally, farmers give the most emphasis on the amount of N and time of application, possible because of a direct link with economics. But the fact remains that all the 4Rs are important. And if one is changed all others are also get changed. I believe, amount of fertilizer N should be the starting point. We can definitely improve fertilizer N use efficiency by applying fertilizer N as per the need of the crop in a given field. Then we need to split the total amount of fertilizer N in smaller doses (say 2 or 3) but the split doses must be applied as per N supplying capacity of the soil. The time of application of split doses of N needs to be defined by crop N need at different growth stages as well as how much N is going to be made available from the soil. Fertilizer N should preferably be incorporated into the soil, particularly if the source of N is fertilizer like urea. In case we can afford to apply controlled-release N fertilizers, placement will be different. Thus practical ways to increase N use efficiency cannot be very straightforward. One needs to go in a very systematic way. I attach some of my publications which should be useful.

El mejor metodo para medir la eficiencia de uso del fertilizante nitrogenado es el marcado con N-15. DE ensayos realizados en el mundo, la mejor forma de aumentar la eficiencia de uso del nitrogeno es aplicando en forma fraccionada de acuerdo a la demanda del cultivo y enterrarlo por los menos 5 cm. Si se aplica en la superficie se pierde por lo menos un 50%. Si se aplica toda la dosis de una sola vez se pierde por lixiviacion por lo menos el 40%. Por eso es que en ferirrigacion donde el fertilizante nitrogenado se incorpora con cada riego se logran eficiencias del 80%.

Nitrogen fertilizer is a critical input in agriculture for increasing and sustaining crop production .But its use efficiency in crops is low (30-50 per cent). During the cropping season, increased synchronization between crop demand and supply from all sources, including fertilizer, is the optimal strategy to maximize fertilizer N application to field crops. This strategy is based on providing optimum amounts of fertilizer N to optimally meet crop N requirement at appropriate crop growth stages. Avoiding use of nitrate fertilizers in waterlogged soil may enhance use efficiencies. Inclusion of legume in cropping system also add nitrogen whereby lesser application is required from outer source hence more efficiency. Increased nitrogen efficiency can be shown in traditional mixed farming. These are need for discussion and documentation of best methods or techniques of N application and management of N fertilizers under field conditions and documenting the same for the benefit of farmers.

An another approach to improve N use efficiency is the identifying crop varieties with higher N use efficiency may also be more helpful not only interims of more grain yield per kg of applied nitrogen but also reduce nitrate pollution in the ground water. The nitrogen use efficiency is calculated based on the relationship between the crop response and the quantity of nitrogen applied or uptake by crop. The terms such as partial factor productivity, agronomic efficiency, physiological efficiency and recovery efficiency.

When soil and environmental conditions are favorable for nitrate losses, treatment with a stabilizer will often increase fertilizer N efficiency. Controlled-release fertilizers can be grouped into compounds of low solubility and coated water- soluble fertilizers and or highly erodible soils, conservation tillage can help to improve soil structure and reduce N loss through runoff. Planting a winter cover crop can help reduce leaching. Cover crops that build soil organic matter may also help to slow the release of N and provide continuous N nutrition to crops. Avoiding use of nitrate fertilizers in waterlogged soil may enhance use efficiencies. Inclusion of legume in cropping system also add nitrogen whereby lesser application is required from outer source hence more efficiency. Increased nitrogen efficiency can be shown in traditional mixed farming. Moreover, Increasing organic matter levels not only improves the nutrient holding capacity (fertility) but also the soil structure as it binds soils, increasing the water holding capacity and aeration. Crops with a large root mass and prolific architecture will have a better ability to scavenge for soil nutrients.

Dear Dr Annangi Subba Rao . See the following useful RG link: Article Diverse concepts of breeding for nitrogen use efficiency. A review

Kindly see also the following useful RG link: Article Biochemical and Genetic Approaches Improving Nitrogen Use Ef...

Also check please the following useful RG link: Article Review: Strategies to increase nitrogen use efficiency of sp...

Aref Wazwaz Rk Naresh Agree , both improved agronomic practices and breeding for efficient genotypes of crops may help to increase the N use efficiency.

I support this idea. More researches need to be carried out on Agronomic practices.