IPADS Soil Fertility Management 4 NITROGEN

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Loraine Mills
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1 International Program in Agricultural Development Studies (IPADS) 20 January 2016 IPADS Soil Fertility Management 4 NITROGEN Department of Global Agricultural Sciences IPADS Kensuke OKADA (akokada@mail.ecc.u tokyo.ac.jp) ipads.jp/soil 1 (Llanos Orientales in Colombia, photo by KO)

2 IMPORTANCE OF N IN PLANTS

3 N of primary importance as plant nutrient (Havlin et al. 2005) 17 essential elements 9 elements 8 elements Sodium (Na), Cobalt (Co), Vanadium (Va) and Silicon (Si)

4 Importance of N in plant (1) Protein Ribulose bisphosphate carboxylase Accounts for 50% of soluble leaf protein in C 3 plants (20 30% of total leaf nitrogen) and 30% of soluble leaf protein in C 4 plants (5 9% of total leaf nitrogen). (Wikipedia)

5 Importance of N in plant (2) Nucleic acids

6 Importance of N in plant (3) Chlorophyll N deficiency Yellow and necrotic leaves From lower leaves

7 N FROM FERTILIZERS

8 N fertilizers (Havlin et al. 2005) niter 硝石 nitratine チリ硝石

9 Chilean nitrates

10 Haber Bosch process 1909 experimental scale 1931 industrial scale N 2 (g) + 3H 2 (g) 2NH 3 (g)

12 Urea to ammonium Urea hydrolysis : rapid in warm, moist soils (several days) Depending on the ph, NH 3+ volatized Urease is abudant in the soils, especially with high OM It is sometimes slow in cold seasons (p.152)

13 Slow release nitrogen fertilizers (Havlin et al. 2005)

14 N CONVERSION IN SOILS

15 N cycle (Havlin et al. 2005)

16 N input and loss (Havlin et al. 2005)

17 Mineralization 1 : Aminization Mineralization : Conversion of organic N to NH 4 + by bacteria (neutral to alkaline soils) by fungi (acidic soils)

18 Mineralization 2 : Ammonification

19 C:N ratio effects on mineralization and immobilization (Havlin et al. 2005)

20 C:N ratio effects on mineralization and immobilization (Havlin et al. 2005)

21 Nitrification

22 Factors affecting nitrification Soil ph : (optimum 8.5) inhibited in acid soils Temperature : Slow in low temperature Soil aeration : accumulation of NH 4+ in paddy field

23 PLANTS ABSORPTION, TRANSLOCATION AND UTILIZATION OF N

24 Ion transport pathway in roots

26 Nitrate Ammonia (Nitrate reduction) NO 3 ー 1 NO 2-2 NH 4 OH(hydroxylamine) NH 3 (1 Nitrate reductase in cytoplasm) (2Nitrite reductase in chloroplast) Irreversible processes take place in roots/leaves depending on the plant species Energy requiring process

27 Ammonia to Amino acids 1. Glutamine synthetase Glutamate + ATP + NH 3 Glutamine + ADP + phosphate

28 OTHER N DYNAMICS IN THE SOILS AND THE LOSS

29 Changes and flow of N from soil to plant (Havlin et al. 2005)

30 Denitrification Under anaerobic conditions Factors affecting denitrification 1. Decomposable OM 2. Soil water content 3. Aeration 4. Soil ph <5.0 no denitrification <6.0, 6.5 N 2 O is dominant > N 2 5. Temperature

31 Volatilization of Ammonium

32 Nitrate leaching

33 NITROGEN FIXATION IN LEGUMES

34 N 2 fixation by grain legumes in Africa (Giller et al. 1997)

35 N 2 fixation by shrubs and trees in the tropics (Giller et al. 1997)

36 Factors affecting N2 fixation 1. Soil ph 2. Aeration 3. Mineral nutrient status 4. Phytosynthesis and climate

37 Water logging problem of pigeonpea during rainy season in the semi arid tropics, at a Vertisol field at ICRISAT (K Okada )

38 Waterlogging of pigeonpea in an Vertisol field (K Okada)

39 Measuring gas permeability in an Alfisol field (Okada et al. 1991)

40 Sampling soil air for the measurement of oxygen concentration (Okada et al. 1991) (K. Okada)

41 (Okada et al. 1991)

42 Flat bed Ridge and furrow (K Okada)

43 Distribution of oxygen concentration in the soil air under flatbed configuration vs. ridge furrow configuration (Okada et al. 1991)

44 Effect of reduced oxygen concentration in soil on the respiration of roots and nodules (Okada et al. 1991) N 2 fixation Respiration Effect on root respiration Effect on nodule respiration Pigeonpea Soybean

45 ISSUES IN NITROGEN MANAGEMENT

46 Issues in nitrogen management Alkaline soils Ammonium volatilization Flooding/Poor aeration Denitrification, low N 2 fixation Low temperature Slow mineralization Sandy soils / nitrate accumulation / high rainfall Leaching Residue application Immobilization Excess or deficient N application Need for the decision support system Split plot application

Plants, soil, and nutrients. Created in partnership with Alex Lindsey, Ph.D., The Ohio State University

Plants, soil, and nutrients. Created in partnership with Alex Lindsey, Ph.D., The Ohio State University Plants, soil, and nutrients Created in partnership with Alex Lindsey, Ph.D., The Ohio State University Where do plants get their nutrients? Atmospheric deposition (N, S) Irrigation water Shallow groundwater