Effect of chemical composition of crop residues on nitrogen mineralization

Slides prepared for MSc seminar

1. WELCOME 1

2. Effect of Chemical Composition of Crop-residues on Nitrogen Mineralization Harsha, M. PALB7338 1 st seminar On 2

3. Flow of Seminar Introduction Types of crop residues Composition of plant materials Factors affecting crop residue decomposition Decomposition rates of crop residues Nitrogen Nitrogen mineralization Research papers Conclusion 3

4. Introduction Crop residues are the parts of the plant left in the field after crops have been harvested and thrashed or left after pastures are grazed. These materials have at times been regarded as waste materials that require disposal but it has become increasingly realized that they are important natural resources and not wastes Ex: Stalks, stems, leaves, roots, and weeds . 4

5. Types of crop residues Crop residues After harvest residues Field residues Materials left in an agricultural field after the crop has been harvested. Ex: stalks, stubble (stems), leaves, and seed pods Good management – Increase efficiency of irrigation  control of erosion Materials left after the crop is processed into a usable resource Ex:  husks, seeds, bagasse, molasses and roots Used as animal fodder, soil amendment, fertilizers. 5

6. Types of Agricultural residues Crop residues: Agro-industrial residues: Agricultural residues Materials could be of different sizes, shapes, forms and densities like straw, stalks, sticks, leaves, haulms, fibrous materials, roots, branches and twigs . Are the by-product of the post harvest processes of crops such as cleaning, threshing, linting, sieving and crushing. These could be in the form of husk, dust, baggase, straws, shells and coir pith etc.

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8. Composition of plant materials 8

9. Factors affecting crop residue decomposition Soil Temperature : Max @ 31 to 33 C Decomposition proceeds slowly at soil temperatures below 14 C and above 35 C. Soil Moisture : Max @ 60% water holding capacity Soil Nutrient Content : high residual inorganic nitrogen Decomposition is greater Tillage, Soil Management Crop Residue Composition 9

10. Crop Residue Composition : Physical : relative particle size of a crop residue Chemical : Hemicellulose, cellulose, lignin fractions, C:N, initial residue N content, polyphenols, soluble C, (lignin + polyphenol): N, lignin: N 10

11. Quality of Residues N content or C:N ratio, lignin and polyphenol High N content in the material favours net mineralization High concentrations of lignin , polyphenol - little mineralization Residues with high concentration of N and low concentrations of lignin and polyphenol - high quality residues Low N concentration and high lignin and polyphenol -low quality residues 11

12. C:N C:N ratio is important because due to the fact that it has a direct impact on residue decomposition. Optimum C:N ratio is 24:1 for desired decomposition of our crop residue. Higher the ratio, the longer it takes for the material to decompose. Likewise, if the ratio is smaller, the plant material will decompose rapidly. 12

13. C:N Ratio of Different Sources 13

14. Lignin and Polyphenols The threshold value for lignin is 15%, 3– 4% for polyphenol and 10 for the ratio L+PP: N. The formation of stable polymers between polyphenolics and amino groups and/or binding of lignin to cellulose affect decomposition rate 14

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16. Decomposition Rates of Crop residues Rapid Very slow Sugars and Starches Proteins Hemicellulose Cellulose Fats, Waxes and Oils Lignin Cellulose Lignin 16

17. Nitrogen Nitrogen is the most abundant element (78%) in atmosphere N content in soil : 0.02 to 0.44% Average N% in plant tissue 1.5% Bulk total N in organic form & only 2% in inorganic form 17

18. An essential constituent of proteins and is present in many compounds of great physiological importance in plant metabolism Is an integral part of chlorophyll Imparts vigorous vegetative growth and dark green colour to plants Governs utilization of potassium, phosphorus and other elements Role of Nitrogen 18

19. Soil Nitrogen Organic Inorganic Hydrolysable-N Non-hydrolysable-N NH 4 -N NO 3 -N NO 2 -N Hydrolysable-N Amino sugar Amino Acid Acid soluble humin Fixed NH 4 + Insoluble humin Different forms of soil-Nitrogen 19 Forms of nitrogen

20. Sources of N in soil Fertilizers 1. chemical fertilizers Ex: 2. Bio fertilizers Ex: Green manures Organic wastes Rain water (18kg N/ha/year) Biological nitrogen fixation Crop residues (5 to 20 kg N/ha) 20

21. Nitrogen transformation in soil Major processes of N transformation: Microbial transformation Mineralization Denitrification Immobilization Biological N fixation 2. Chemical transformation Non BNF Hydrolysis Volatilization 3. Physical transformation Leaching Runoff 21

22. Mineralization Organic N R-NH 2 (Amine) NH 4 + (Ammonium) NO 2 - (Nitrite) NO 3 - (Nitrate) 22 Process of breaking of organic nitrogen compound by microorganisms into inorganic nitrogen forms 3 steps Aminization Ammonification Nitrification 1 & 2 are by heterotrophic micro organisms 3 by autotrophic soil bacteria

23. Aminization Process of enzymatic digestion by non specific heterotrophic microbes by which protein and protienacious compounds are decomposed into aminoacids , amides and amines Proteins R-NH 2 + CO 2 + Energy + Other products (Amines) Heterotrophic Micro-organisms Also known as proteolysis Aminization occurs both in aerobic and anaerobic condition Under aerobic condition Under anaerobic condition End products CO 2 , (NH 4 ) 2 SO 4 and H 2 O NH 3 , NH 2 , CO 2 , organic acids, H 2 S etc 23

24. Ammonification Process of reduction of amines to ammonium by heterotrophic microorganisms R-NH 2 + H 2 O NH 3 + R-OH + energy NH 3 + H 2 O NH 4 + + OH - 2NH 3 + H 2 CO 3 (NH 4 ) 2 CO 3 2NH 4 + + CO 3 2- Effectively carried out in aerobic soils with basic cations p H altered in flooded soils due to production of OH - & carbonates Enzymatic Hydrolysis 24

25. Nitrification Process of enzymatic oxidation of ammonia to nitrate by microbial action 2 steps involved 2 organisms involved are nitrosomanas & nitrobacter NH 4 + NO 2 - NO 3 - 2NH 4 + + 3O 2 2 NO 2 - + 2H 2 O + 4H + 2 NO 2 - + O 2 NO 3 - + 2H + Nitrosomanas Nitrobacter 25

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27. Factors affecting N mineralization Nature of organic materials Soil moisture Soil temperature Alternative wetting and drying Amount and sources of applied nitrogen Soil reaction Chemical inhibitors Aeration Soil plant interaction

28. RESEARCH PAPERS 28

29. Effect of Chemical Composition of Plant Residues on Nitrogen Mineralization Srinivas et al., 2006 Objectives : To determine the chemical composition of several commonly available plant residues To examine the effect of residue quality on N mineralization. Paper 1 29

30. Plant residues (20) 7 crop and 13 tree Dried 60˚C and ground Carbon Wet oxidation Nitrogen (Kjeldahl) Lignin: Acid Detergent Fiber (ADF) Total soluble polyphenol Folin -Denis method Material and methods Acacia nilotica , Albizia lebbeck , Annona squamosa Azadirachta indica Cajanus cajan Calliandra calothyrsus Cassia siamea Dalbergia sissoo, Gliricidia sepium Hardwickia binata Leucaena leucocephala Prosopis juliflora Tamarindus indica Castor (Ricinus communis ) Horse gram ( Dolichos biflorus ) Paddy (Oryza sativa) Pearl millet ( Pennisetum glaucum ) Sorghum (Sorghum bicolor ) Sugarcane (Saccharum officinarum ) Sunflower (Helianthus annuus ) 30

31. PROPERTIES VALUES Texture Sandy loam sand 76.4 % Silt 5.00 % Clay 18.6 % BD 1.62 Mg/m 3 Moisture retention 109.5 g/kg at 0.03 Mpa pH 6.68 EC 0.86 dS /m CEC 11.64 cmol (P + )/kg OC 4.05 g/kg Available N 62.8 mg/kg Available P 10.4 mg/kg Available K 79.4 mg/kg Table 1: Properties of the soil Soil is preincubated 31

32. Laboratory Incubation Studies : Preincubated soil 1 L jars With 3 replication 1kg 9Mg/ha dry wt 7 Crop residues & 13 tree prunnings Incubated in BOD incubator @ 25±°C For 100days Control Soil samples drawn @ 3, 7, 12, 20 & 100 days interval incubated 21 treatment 3 replication 32

33. Cumulative net N mineralized from plant residues in each time period Total mineral N in treated soil Total mineral N in control soil - Initial residue-N added to each treatment = Mineral N(NH 4 +NO 2 +NO 3 ) by steam distillation in presence of MgO and finely ground Devarda’s alloy. 33

34. Results and Discussion 34

35. Plants residues mean N(0.8%) L(6.47%),pp(0.75%)< tree residues mean N(2.55%), L(8.36%),pp (3.85%) Table 2: chemical composition of the residues 35

36. Fig. 1: Per cent N mineralized from plant residues at different intervals during incubation paddy s.c. Percent N mineralized from residues after 100 days is from 20.67% in sugarcane trash to 81.89% in G. sepium . Over 70% of the N from residues was released from high quality residues ( G. sepium 81.89 %, A. lebbeck 73.94%, L. leucocephala 70.87%). 36

37. Residue quality – N mineralization relationships Fig 2: Relationships between residue quality parameters and N mineralization for All residues 37

38. Relationships between residue quality parameters and N mineralization for tree residues 38

39. Relationships between residue quality parameters and N mineralization for crop residues 39

40. Conclusion High quality residues (L. leucocephala and G.sepium ) with high N and low lignin and polyphenol concentrations, released N rapidly. Low quality residues (sugar cane trash and paddy straw) immobilized N for long periods. Residues of intermediate quality (C. siamea and C. cajan ) immobilized N for some time and released it later. The per cent N mineralized from residues was strongly correlated with N concentration and other quality parameters involving N concentration (C:N ratio Polyphenol to N ratio, lignin + Polyphenol to N ratio) N concentration and C/N ratio are sound criteria for predicting N release and no need to determine lignin and polyphenol concentrations. If N concentration is lower 40

41. Nitrogen Mineralization from Soil Amended with Gliricidia and Sorghum Residues Sridevi et al ., 2006 Paper 2 Objective: To study the mineralization of N from sorghum straw and gliricidia prunings - two residues of contrasting quality, and their insoluble or fibre fractions. 41

42. Material and methods PROPERTIES VALUES Texture Sandy loam sand 80.5 % Silt 3.65 % Clay 15.85 % BD 1.64 Mg /m 3 Moisture retention 103.4 g /kg at 0.03 Mpa pH 5.53 EC 0.51 dS /m CEC 10.52 cmol (P + ) OC 5.39 g /kg Total N 560 mg /kg Table 1: Important properties of the soil preincubated 42

43. Incubation : Pre incubated soil 150ml beakers 50g Sorghum straw Gliricidia prunings Sorghum straw NDF Gliricidia prunings NDF Equivalent to 60 kg N/ha Bring the soil moisture to 75% of field capacity 1L jars With 10ml water Control 3 replications 5 treatments Incubated @ 25±1 C Sampling 5, 10, 15, 30, 45, 60, 75 and 90 days Mineral-N (NH 4 + N0 2 + N0 3 ) NDF: neutral detergent fiber 43 Residue fractionation

44. Results and Discussion 44

45. Table 1: R esidue Fractionation of Crop Residues Residue Soluble fractions (% ) Fiber (%) N g kg -1 C/N Sorghum straw 21.4 78.6 5.32 77.3 Straw NDF (neutral detergent fiber) 2.63 160.8 Glyricidia prunings 53.3 46.7 28.60 13.4 Pruning NDF 15.36 26.6 45

46. Table 2: Effect of amendments on cumulative N mineralized (mg/kg soil) at different incubation periods ̵ ̵ 46

47. Fig. 1: Rates of N mineralization from soil amended with residues and residue fractions 47

48. Conclusions Residues with large fiber fractions of extremely low N concentration cause considerable immobilization of N Residues with smaller fiber fractions of relatively higher N concentration release N fairly rapidly. The composition of residues in terms of soluble and fibre fractions determines whether, and to what extent, N is immobilized or mineralized. 48

49. Decomposition and Nitrogen mineralization of Individual and Mixed Maize and Soybean Residue Gezahegn et al ., 2016 Objective: To determine decomposition rate and N mineralization of individual and mixed maize and soybean residue under laboratory conditions. Paper 3 49

50. MATERIAL AND METHODS The soil sample (0-30 cm) was collected from each plot of maize and soybean field after harvest. Dried, ground, sieved (< 2 mm), and all the visible organic residues were removed by hand after sieving, and stored @ 5 ° C. Table 1: Initial chemical properties of the soil used in the experiment (n=3) Soil Properties Value ±SD pH 6.18± 0.19 Total N (%) 0.15 ±0.01 Available P (mg/kg) 20.0 ±1.95 Exchangable K ( cmolc /kg) 0.33 ± 0.12 CEC ( cmolc /kg) 18.5 ± 0.37 OM (%) 2.55 ± 0.32 Texture Sandy loam 50

51. Collection of plant residues The stover of soybean and maize were collected from 10 random plants from each plot in each replicate and combined. The residues were dried for 72 h at 65°C, ground to < 2 mm. Maize and soybean residues were ground separately to avoid contamination. For maize + soybean residue treatment, the residue was mixed after grinding. Chemical Characteristics of Plant Residues like Total N and C, Hemicellulose, Lignin, Cellulose are analysed. 51

52. 250g pre incubated moist soil Mixed with Residues @ 0.35g/100g soil & control (Maize, soybean, M+SB, without residue) weighed Incubated in dark 25 ˚ C with 60% FC for 90days Soil mineral N(NH 4 + + NO 3 - ) 15 30 45 60 75 90 10g sampling Net N mineralization (Treatments- contro l) ( T1 Maize T2 Soybean T3 Maize +soybean control) CRD with 3 replications SOIL INCUBATION 52

53. Results and discussion 53

54. Table 2: Initial Chemical properties of crop residues: 54

55. Fig 1 : Patterns of N released from maize, soybean and maize + soybean residue during 90 day incubation period Order of N released: Soybean residue (98. 4 mg/kg soil) > Mixture of maize and Soybean residue (67.9 mg/kg soil) > Maize residue (44.3mg/kg soil) > Control (29.2 mg/kg soil) 55

56. Fig 2: Net N mineralization of crop residue decomposition during 90 days decomposition Soybean: 18.6 to 207.4mg/kg Maize(15-60): -10.75 to -3.69 mg/kg Maize+SB:10.8 to 115.8mg/kg Maize(after 60) : 6.23 to 15.05 mg/kg 56

57. Relationship between Cumulative N Mineralization and Residue-Quality Characteristics 57

58. CONCLUSIONS The rate of decomposition of crop residue was highly influenced by the C:N ratio, N content and the composition of the cell wall particularly the lignin content. Residues containing soybean had a faster rate of decomposition and release a significant amount of N compared to maize residues. Incorporation of soybean residue will have a positive influence on subsequent crops from the rapid release of nutrients present in it and it can be a potential source of mineral N in the low input agriculture. Combination of high and low-quality organic materials resulted in better N use through slowing the fast release of nutrients of high quality residue and reducing immobilization of N from the lower quality 58

59. Impact of the addition of different plant residues on nitrogen mineralization–immobilization turnover and carbon content of a soil incubated under laboratory conditions Kaleeem Abbasi et al., 2015 Objectives: ( i ) To examine the initial biochemical composition and quality characteristics of on-farm available plant residues (ii) To quantify the N-release potential (mineralization) of the residues added to a soil incubated under controlled laboratory conditions (25°C) 59 Paper 4

60. Material and methods Soil samples Soil samples were collected from a depth of 0–15cm. The soil samples from all the selected plots were thoroughly mixed to get a composite sample. The field-fresh soil was passed through a 4mm sieve to eliminate coarse rock and plant material, thoroughly mixed and stored at 4 ◦ C before use. A subsample of about 0.5kg was taken, air dried, passed through a 2mm sieve and used for the determination of physical and chemical characteristics Plant residues Plant residues were washed with running tap water, rinsed three times with distilled water, dried at 65 ◦ C for 48h, milled and passed through a 1mm sieve. Analyzed for their C, N, lignin and polyphenol concentrations. 60

61. Table 1. Selected physicochemical properties of the soil used in the study. Soil properties Values Bulk density 1.2 Mg/m 3 Particle density 2.48 Mg/m 3 Porosity 48.3 % Texture class clay loam pH 7.2 CEC 7.3 cmol / kg Organic matter 10.4 g/kg Organic C 6.03 cmol /kg Total N 0.58 g/kg C :N ratio 10:1 Total mineral N 8.7 mg/kg Total organic N 591.0 mg/kg P 3.4 mg/kg K 88.0 61

62. Laboratory Incubation Study T1: Glycine max shoot T2: Glycine max root T3: Trifolium repens shoot T4: Trifolium repens root T5: Zea mays shoot T6: Zea mays root T7: Populus euramericana leaves T8: Robinia pseudoacacia leaves T9: Elaeagnus umbellata 100g of soil @ rate equivalent to 200mg/kg control RCBD 10 treatments 3 replications Incubated @ 25°C Sampling @ 0, 7, 14, 21, 28, 42, 60, 80, 100, 120 days Analyzed for Total mineral nitrogen (TMN) Net cumulative N mineralized (NCNM) 62

63. Results And Discussion 63

64. Table 2. Mean biochemical composition of the plant residues used in the experiment (n=3). Total N contents of the legume residues were higher compared to the non-legumes. The roots were characterized by high C, Lignin and Polyphenol contents and lower N concentration. Leaves rich in Polyphenol and total N. 64

65. Table 3. Mean changes in the concentration of total mineral N of a soil amended with different plant residues and incubated at 25°C under controlled laboratory conditions during a 120-day period (n=3). G max shoot G max root Z mays shoot Z mays root T repens shoot T repens root P. euramericana R. pseudoacacia E. umbellata The mean values show that legumes collectively release 85 mg N/kg compared to 20 mg N/kg by maize and 58 mg N/kg by leaves of the non-legumes trees. 65

66. Figure 1. Net cumulative N mineralized from the added plant residues at different incubation periods. Legend: T1: Glycine max shoot T2: Glycine max root 16% T3: Zea mays shoot T4: Zea mays root T5 : Trifolium repens shoot T6 : Trifolium repens root T7 : Populus euramericana leaves 8% T8 : Robinia pseudoacacia leaves 21% T9 : Elaeagnus umbellata leaves . 21% 54% 21% 66

67. Table 4: Pearson linear correlation coefficients between initial quality characteristics of the plant residues and net N mineralization and correlation within plant-quality characteristics 67

68. Conclusions Residue N concentration and C:N ratio, lignin contents of plant residues also appeared to be an important factor in predicting the net N mineralization of plant residues Shoots of Glycine max and Trifolium repens and leaves of Robinia pseudoacacia and Elaeagnus umbellate exhibited a substantial mineralization potential, shows can produce high-quality residues Plant residues showing rapid mineralization can be used for early N demands of a crop Residues with high C:N and LG contents immobilize N and thus can help to counter the N loss. 68

69. SUMMARY Addition of plant residues to the soil is an effective method for sustaining soil organic matter concentration, improving biological activities, physical properties and nutrient availabilities. The N content, C:N ratio, lignin content and polyphenol content are the major determinants of residue quality in turn N mineralization Soluble and fibre fractions of crop residues also determines N mineralization If one residue shows faster mineralization & other show slower, then their mixture decompose and release N faster Controlled conditions with ground residues provides some understanding about the potentials of residues of different plant species to mineralize N 69

70. Thanking You 70