Ladha Seminar 24 Nov 2005

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The Continuing Nitrogen Enigma J.K. Ladha INTERNATIONAL RICE RESEARCH INSTITUTE NEW DELHI, INDIA J.K.Ladha@CGIAR.ORG “If the DNA is the thread of life then the nitrogen is the bread of life”

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Is it going to be a surprise? Motivation? Discussion – interactive and share diverse views Recent in-house discussion, Recent review in Ad. in Agronomy on Efficiency of Fertilizer Nitrogen in Cereal Production: Retrospects and Prospects by Ladha, Pathak, Krupnik, Six, Van Kessel, and No one else was speaking today (thanksgiving day). “The Continuing Nitrogen Enigma” J.K. Ladha, IRRI

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Outline Nitrogen: Some facts. Global trends of food production and N use. Declining N use efficiency. Increasing trends of N use: Challenges. Improving N use efficiency and minimizing N leakage: Opportunities. Conclusion: N Sustainability Framework.

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After water, nitrogen is the most important input required for crop production. Soil (Organic/BNF) Fertilizer (Inorganic/ Mineral)

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Reducing hunger Improving nutrition Sparing natural ecosystem from conversion to agriculture

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Global Fertilizer Nitrogen Consumption Year N consumption (Million t) Ave. yearly increase rate: 5.4% Increased by 6.4 times in 39 years Source: (FAO, 2002)

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2050 Global population 50% > Global grain demand 100% > Global fertilizer demand 50-70% >

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Nitrogen Use Efficiency Terms AEN = Biomass/N supply REN = Plant N/N supply PEN = Biomass/N uptake

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Nitrogen-use Efficiency Terms and their Calculationa Agronomic efficiency (AE) Recovery efficiency (RE) Physiological efficiency (PE) Efficiency ratio Total N supply (TN) or plant N uptake Grain yield (YT) or grain N (GT) Grain yield (Y0) or grain N (G0) Grain yield (YF) or grain N (GF) Aboveground biomass (MT) or aboveground N uptake (UT) Aboveground biomass (M0) or aboveground N uptake (U0) Aboveground biomass (MF) or aboveground N uptake (UF) Soil N supply (SN) or plant N uptake in a plot that received no fertilizer N (U0) Fertilizer N supply (FN) or difference in N uptake with different levels of fertilizer N (UF) (1) YT/TN (7) GT/TN (13) YT/UT (8) UT/TN (9) G0/SN (10) U0/SN (11) GF/FN (12) UF/FN (2) MT/TN (3) Y0/SN (4) M0/SN (5) YF/FN (6) MF/FN (15) Y0/U0 (16) M0/U0 (17) YF/UF (18) MF/UF (14) MT/UT aYT , Y0 , YF , grain yield in treatments with total N (TN, soil + fertilizer), soil N (SN), and fertilizer N (FN) supply MT , M0 , MF , aboveground plant biomass in treatments with total N (TN, soil + fertilizer), soil N (SN), and fertilizer N (FN) supply GT , G0 , GF , N uptake in grain in treatments with total N (TN, soil + fertilizer), soil N (SN), and fertilizer N (FN) supply UT , U0 , UF , N uptake in total aboveground plant biomass in treatments with total N (TN, soil + fertilizer), soil N (SN), and fertilizer N (FN) supply

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Region/ RENTa RENT15Nb Crop Mean Mean Africa Australia Europe America Asia Average/total Maize Rice Wheat Average/total 0.37 0.41 0.61 0.36 0.44 0.44 0.40 0.44 0.45 0.44 aRENT=recovery efficiency of fertilizer N based on total plant N (kg N taken kg-1 N applied) bRENT15 N=recovery of 15N-labeled fertilizer N based on total plant N (kg N taken kg-1 N applied) Statistics of various N-use efficiency terms for cereals in various regions 0.54 0.43 0.69 0.44 0.47 0.51 0.63 0.44 0.54 0.51 Descriptive statistics of N recovery efficiency for cereals in various regions

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44 – 51% REN in first crop 5.7 – 7.1% REN in five succeeding crops Summary 20 – 30% REN in Rainfeds 30 – 40% REN in Irrigated 200 studies (with 500 – 800 data points) conducted across the globe in a wide diversity of ecologies

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* Annual global cereal production divided by annual global application of N fertilizer. Global Trend of Fertilizer N Use Efficiency of Cereal Production* Source: (FAO, 2001)

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Reasons of Declining N Use Efficiency Year of Rice-Wheat Cultivation Soil Total N (g kg-1) T5: y = -0.03*x + 0.99 R2 = 0.94* Soil N reserve declining Source: Bhandari, Ladha, Pathak, Padre, Dawe, and Gupta (2002), SSSAJ 60:162. Ludhiana, India

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2. Soil N supply pattern changing Source: Ladha, Dawe, Ventura, Singh, and Watanabe (2000), SSSAJ 64:1993. Reasons of Declining N Use Efficiency

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3. Misuse (or excess) of N Rice-Vegetable (Philippines): 500 kg N ha-1 (Tripathi and Ladha, 2000, SSSAJ) Rice-Rice (China): 450 kg N ha-1 (Peng et al., 2004) Rice-Wheat (India): 350 kg N ha-1 (Ladha et al., 2003) Reasons of Declining N Use Efficiency

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Increasing Trends of N Use: Challenges Political Economical Environmental

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World Middle East Oil Reserves (Billion Barrels) Reserve Remaining at 1989 Production Rates (Number of Years) 1,011 660 44 110 Source: State of the World (1991) World Fossil Oil Reserve Political Challenge…

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Fertilizer N Costing Agriculture More Than US$ 45 Billion per Year Economical Challenge…

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N2 Unreactive Pool 4 x 109 Tg Biotic 90-130 Biotic 90-130 Preindustrial Industrial Reactive Pool of N (N2 Fixation Tg/year) Environmental Challenge… (1 Tg = 10 12 g)

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Potential Adverse Impacts of Excessive Use of Reactive N on Ecosystem Functioning Global warming because of increased emission of nitrous oxide, a potent greenhouse gas. Depletion of stratospheric ozone by nitrous oxide. Air pollution produced by nitrogen gases (nitric oxide and nitrogen dioxide). Acid deposition by nitrogen oxide. Eutrophication because of high nitrate in aquatic ecosystems. Loss of biological diversity, especially losses of plants adapted to efficient use of N. Loss of soil nutrients such as calcium and potassium. Methemoglobinemia in infants because of increased nitrate ions in water and food.

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27 Feb 30 Apr 15 May 30 May 15 Jun 15 Jul 2 Aug 18 Aug 31 Aug 15 Sep 30 Sep 15 Oct 30 Oct 15 Nov 30 Nov 15 Dec 30 Dec 20 15 10 5 0 Lower elevation Middle elevation Higher elevation Source: Shrestha and Ladha, 1998. Temporal and Spatial Variation in NO3- – N in Groundwater of Tube Wells in Rice-Sweetpepper System, Ilocos Norte, Philippines, 1995. NO3–N (mg L-1) WHO reccomendation for maximum contaminant level for drinking water of 10 mg L-1

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Nitrate Hot Spots

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What are the Factors Influence N Use Efficiency?

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Soil C/N Fertilizer N Soil inorganic N Mineralization Fertilizer delivery Demand Irradiance, temperature, water, pests/diseases, available non-N nutri-ents and crop cultivars Uptake Crop N Fertilizer-N efficiency Atmosphere Groundwater Atmosphere Surface water Denitrification Leaching/runoff Volatilization Erosion Water/soil Water pH Water Supply Factors controlling fertilizer-N efficiency Losses Water and temperature

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Ludhiana y = 10.8x 0 20 40 60 80 100 120 140 160 180 200 NPK Cumulative Rice-Wheat System Yield (Mg ha-1) 0.45 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 Initial Soil C (%) Year Pantnagar Cumulative Rice-Wheat System Yield (Mg ha-1) y = 8.6x Year 0 20 40 60 80 100 120 140 160 180 200 NPK 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 Initial Soil C (%) 1.42

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Climatic Potential Yields of RW Systems at Ludhiana and Pantnagar Year Yield (Mg ha-1 yr-1) Time Trend of Potential System Yield

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How to Improve N Use Efficiency and Minimize Leakage of N into Environment?

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Soil N Supply Plant N Demand Synchronize Mineral fertilizer Organics Residue GM How to Improve N Use Efficiency and Minimize Leakage of N into Environment?

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Strategies to Improve NUE Resource Management Fertilizer N Plant-need based application Slow release formulations Organic N Manipulation of residue L/N Genetic Manipulation Genotype Improvement Acquisition Usage pattern N2 fix-symbiosis

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N Loss – N Synchrony Relationship N Synchrony Loss of N Fertilizer N management Organic N management NUE efficient genotype N2 fixing (legume like)

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Fertilizer N Management tools / tactics – a comparison

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Real-Time N Management Also called crop need-based N management. Developed based on leaf photosynthesis, tillering, and leaf area growth. Aim to achieve optimum leaf N status throughout growing season. Leaf N content is a sensitive indicator of dynamic changes in crop N demand. The key is to establish the method for rapid diagnosis of leaf N status.

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SPAD Meter Leaf Color Chart

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Relationship Between Leaf N Content and SPAD Values Source: Peng et al, 1995; Com. Soil. Sci. Plant Anal. 26:927 Na (g m-2)

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PI PI + 9d FL Pool LCC Score Relationship Between Leaf Color Chart Scores and SPAD Values IRRI, Philippines ZAU, China UCD, USA R2 = 0.81 R2 = 0.69 R2 = 0.72 R2 = 0.90 PI PI + 9d FL Pool R2 = 0.77 R2 = 0.70 R2 = 0.75 R2 = 0.87 PI PI + 9d FL Pool R2 = 0.66 R2 = 0.81 R2 = 0.62 R2 = 0.85 SPAD Value LCC (IRRI) = -1.61 + 0.138 SPAD LCC (ZAU) = -0.95 + 0.164 SPAD LCC (UCD) = -1.53 + 0.191 SPAD If SPAD = 35 LCC (IRRI) = 3.2 LCC (ZAU) = 4.8 LCC (UCD) = 5.2 Source: Yang et al., 2003 Agron J.

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Real-Time N Management with SPAD or LCC SPAD = 35, LCC = 3 15 DAT Flowering Days after transplanting (DAT) Leaf N status Na = 1.4 g m-2 A single SPAD or LCC value could be used as a threshold for timing N topdressing for a given cultivar.

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N Saved and Grain Yield Increase with the Use of LCC Over the Farmers’ Practice, 1998-2000 Country Year No. of farms N saved kg h-1 Grain yield Increase (%) Philippines 1998-2000 74 7.8 3.70 Vietnam 1998-2000 96 19.8 3.40 Indonesia 1998-1999 120 19.5 1.80 India 1999 228 21.8 7.96 Source: Balasubramanian et al., 2000.

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LCC, a Thermometer Can I have similar ‘thermometer’ for other crops like wheat, and for K and P? LCC is a N thermometer which tells me when plant is hungry It is simple and has increased my knowledge about N This allows me to control excess or misuse of N

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Placing Fertilizer with Sowing and with Residue Mulch

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Chlorophyll Meter Readings in Wheat Meerut, India, 2001–2002 CT ZT BPW BPW 38.1 38.1 42.6 45.0 42.2 43.9 44.8 47.6 43.6 43.7 45.1 48.3 39.9 41.2 43.9 45.9 38.6 39.5 41.5 45.7 39.3 38.1 38.8 42.6 43.0 41.5 45.8 43.1 43.3 43.0 45.4 42.8 41.6 41.6 44.3 42.1 40.0 41.2 42.4 42.3 SPAD 5/1 9/1 17/1 23/1 30/1 6/2 13/2 20/2 27/2 6/3 Treat- ments NB * N applied basally in all pots; 50% N in CT, ZT, and BPW, and 100% N in BPWNB. ** Split N applied to CT and ZT on Jan. 5 and 30, 2002; to BPW on Feb. 7, 2002.

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N Loss – N Synchrony Relationship N Synchrony Loss of N Fertilizer N management Organic N management NUE efficient genotype N2 fixing (legume like)

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N use efficiency GY/N or HI/%N NCE – biomass Photosynthesis Flag leaf N import/export Tiller growth dynamic NCE – grain Sink formation Sink filling Panicle topomorphology Root characteristics affecting N uptake Root length density Root senescence O2 and C supply Rhizospheric acidification N uptake from plow Soil and sub soil N acquisition Plant N/Available N Rhizospheric BNF

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Hypothetical Response Curves of Three Cultivars Differing in Agronomic Fitness and N-use Efficiency Grain Yield Available N Superior Efficient Inefficient Inferior Superior- Inferior = HI Efficient- Inefficient = %N HI %N

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Grain Yield Response of Selected Medium and late Duration Rice Lines as Affected by Different N Levels Late Late Medium Medium

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Frontier Project: Assessing Opportunities for Nitrogen Fixation in Rice, A Global Collaborative Initiative Biological nitrogen fixation

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Minimize soil disturbance. Avoid cycles of soil flooding/drying. Avoid dry fallow. Practice crop diversity. Use quality residue. Replenish soil nutrients. Apply plant need-based N. Deep place fertilizer N into soil. Total pool  Available pool A B * Nutrient Ymax Nutrient NUE max Maintaining soil N base Achieving optimum economic returns Maintaining quality of air and water N Sustainability Framework System monitoring

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The Continuing Nitrogen Enigma The origins of the enigma are associated with 3 difficulties in measuring The changes in total soil N content The input of BNF The losses of N from soil-plant system Dennis Greenland and Iwao Watanabe, 1982

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Nitrogen balances established. BNF and N losses quantified Soil N replenishing mechanisms of BNF established Smart N timing/rate established, and globally adopted Great N Achievements

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Is Nitrogen Still an Enigma?

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Thank you for coming and Thank you for your attention.