Nitrogen use efficiency

Nitrogen use efficiency and techniques to improve nitrogen use efficiency

1. NITROGEN USE EFFICIENCY & TECHNIQUES TO IMPROVE NUE BY: Harini.P 2018019036

2. Introduction Nitrogen is yield limiting nutrient in crop production Plant utilize nitrogen in the form of nitrate - NO 3 - (aerobic condition) and ammoniacal form – NH 4 + (anaerobic condition) ( oldroyd & Dixon,2014) Nitrogen fertilization is indispensable for crop production, but the availability in soil is insufficient & external application is essential, results in demand for N fertilizer Nitrogen is the integral part of nucleic acid, protein, enzymes and have a positive association with the grain yield (Fageria & Baligar, 2005 ) According to Hierel et al., only 30-40% of applied nitrogen is taken up of crops, remaining is lost to the environment 

3. Nitrogen losses Leaching(20%) : nitrate form of N is mobile & not strongly absorbed- sandy soil + sufficient water move N away from soil profile Denitrification(19%) : microbial mediated reduction of nitrate form of N to various forms of gases under anaerobic condition - heavy texture soil with poor drainage susceptible to this loss (Mosier et al., 2001) Volatilization(21%) : nitrogen is lost in the form of ammonia gas   occurs where organic manure and broadcasting of chemical fertilizer (Bolan & Hedley,2003) Erosion and runoff : Loss through water (humid and sub-humid areas) & wind erosion (arid and semi-arid areas). At heavy rain nitrate nitrogen will be lost through run of (Fageria., 2002)

4. Nitrogen use efficiency NUE is defined as the ratio of grain yield per unit available nitrogen in soil including the present residual soil & fertilizer nitrogen The efficiency of nitrogen is about 30-50% NUE is a complex trait - Used as a metric to relate N uptake with the quantity of N applied Leguminous crops have high NUE than cereals                   NUE =  Yield / N available

5. NUE ( Good et al., 2004) DEFINITION FORMULA Nitrogen use efficiency(NUE) Total biomass/ N supply Uptake efficiency(UpE) Plant N content / N supply Utilization efficiency(UtE) Grain mass / plant N content

6. Parameters of NUE Apparent recovery - quantity absorbed per unit of nitrogen applied Agronomic efficiency of N – economic production obtained per unit of nitrogen applied Production efficiency of N - biological production obtained per unit of nitrogen applied

7. Sources of variation of NUE Species and cultivar - are expected to play a primary role: the genotype affects both the N uptake and the use of absorbed N because every genotype has its own morphological and functional characteristics for roots, leaves, etc. (Schenk, 2006 ) Environmental factors - N availability through effects of mineralisation and leaching (Agostini et al., 2010) Crop management - crop density( plant population), spatial arrangement, N fertilization rate, application methods and water management Abiotic and biotic stress ( Yong- Zhan et al., 1996)

8. Consequences due to low NUE Groundwater pollution : N lost beyond root zone in nitrate form cause ground water pollution Eutrophication : process of enrichment of water bodies with chemicals especially N,P that can cause excess algal growth – cause shortage of oxygen and toxic to aquatic communities (Baligar et al.,) Nitrogen deposition : ammonia emitted to atmosphere through volatilization return to earth surface as co-deposition with sulphur dioxide gas ( Buresh et al., 2004) Green house effect : nitrous oxide formed through Denitrification is important greenhouse gas responsible for 5% global climatic change (Shoji et al., 2001)

9. Techniques to improve NUE Management practices : 4R concept ( Alva et al., 2011)

10. Improved practices Site specific nitrogen management – field specific nitrogen management strategies that include quantitative knowledge of field specific variability in crop N requirement & expected soil N supplying power Real time N management - N is applied only when the leaf N content is below a critical level. The improvement in the synchrony between crop N demand and the N supply from soil or the applied N fertilizer Fixed time N management - In this approach the timing and number of N applications are fixed while the rate of each N applications varies across season and location .

11. Tools of SSNM Chlorophyll meter - relative measures of leaf chlorophyll content that is directly proportional to leaf N content Leaf colour chart – economical and easy diagnostic tool which help farmer in making decisions regarding N application in standing crop. It uses relative greenness of leaves as a indicator of the N content Crop canopy reflectance sensors - variations in reflectance( lighter in colour, smaller in size)

12. Nutrient expert based N management – emerging diagnostic tool input variables such as fertilizer are applied in 4R concept as per demand of crop plants (Pampolino et al., 2012) Variable rate N application – the other method of measuring nitrogen is assess canopy of growing crop using optical sensors and create variable rate N application maps which is used for the optimisation of nitrogen rates based on the information.

13. Enhanced use efficiency fertilizer Slow release fertilizer : nitrate containing fertilizer are susceptible to leaching whereas ammonium and amide fertilizer are prone to volatilization. These compounds can reduce N losses due to their potential to delayed N release pattern which may improve synchronization.

14. a) Organic N low solubility compounds - urea formaldehyde(biological decomposing), IBDU(chemically decomposing) b) Fertilizers N with physical barriers that coat fertilizers – contains organic polymer, resins & inorganic material such as sulphur e.g. Neem coated urea, sulphur coated urea c) Inorganic low solubility compounds – metal ammonium phosphates

15. Nitrification inhibitors : these check bacterial oxidation of ammonium-N into nitrate-N and ensure high concentration of ammoniacal form of nitrogen in soil ex: dicyandiamide, nitrapyrin Urease inhibitor : inhibition of urea hydrolysis occurs by prevent or suppress over a certain period of time the transformation of amide-N in urea to ammonium hydroxide and ammonium through the hydrolytic action of the enzyme urease. e.g. thiosulphate, NBPT Integrated nitrogen management : optimum use of indigenous N compounds(crop residue, organic manure, BNF) as well as chemical N fertilizer & their complementary interactions increase NUE

16. Nitrogen bacteria teach us that Nature, with her sophisticated forms of the chemistry of living matter, still understands and utilizes methods, which we do not as yet know how to imitate - Fritz Haber