Basu Dev Regmi School of Earth and Environment

Transcription

1 Basu Dev Regmi School of Earth and Environment Basu was born and raised in the rural mountains of Nepal. He did undergraduate (B Sc. Ag) degree from Tribhuvan University, and M. Sc. (Agri. Systems) at Asian Institute of Technology, Bangkok, Thailand. Basu worked with agricultural research and development in Thailand and Nepal. He worked with the bilateral project funded by Swiss government and implemented by the Nepalese government for 5 and half years as theme leader of soil fertility and plant nutrition discipline before joining UWA. Having motivated to work in rural communities, he has seen and experienced the different dimensions of problems in these communities. His PhD research aims at investigating the dynamics of zinc (Zn) in biological and conventional farming systems, in WA. How best we can load the Zn into edible parts of the crops is the main interest of work.

2 Dynamics of zinc accumulation in wheat grains grown in the soils of conventional and biological farming systems Basu Dev Regmi School of Earth and Environment Soil Science and Plant Nutrition Supervisors: W/Prof Zed Rengel and Dr Hossein Khabaz-Saberi

3 Content 1. Background Role of Zn in plant Zinc in soil and its trend Global scenario of Zn (impact on human..) and role of Australia Zinc with respect to farming practice 2. Method and Materials 3. Results 4. Conclusion

4 Role of Zn in plant Stimulate germination in low Zn soils Involves many cellular process (enzyme activation...) production of auxin, an essential growth hormone regulates starch formation and proper root development biosynthesis of chlorophyll and carbohydrates enable plants to withstand lower air temperatures helps in the biosynthesis of cytochrome; a pigment, and maintains plasma membrane integrity, and synthesis of leaf cuticle... Cont Background

5 Effects of zinc deficiency on metabolic processes associated with growth Source: Mac Donald, Cont Background

6 Zn in soils Among micronutrients in soil, low Zn availability is most widespread Cereals growing areas are particularly affected by low Zn (Cakmak et al, 1998, Singh et al 2005) Among cereals, wheat is the most sensitive to Zn deficiency (Cakmak et al, 1998, Kabata-Pendias, 2001, Alvarez and Gonzalez, 2006) Post green revolution: increased crop production with increased use of mineral fertilizers Increased use of mineral fertilizers led to higher production hence depleted d inherent soil fertility (nutrient t mining) i Mostly macro-elements are taken into consideration (N P K) Imbalance among plant nutrients.. Cont Background

7 5 th out of 10 Risk Factors in Developing eloping Countries to Cause of Disease Burden (WHO, 2002) About 3 billion people e are affected by low Zn (Stein et al 2007) Over 1 million child death due to Zn with Vitamin A (The Lancet Maternal and Child Undernutrition Series January 2008) Zinc affects a range of functions: Immunity Growth Brain development Reproduction Sexual Formation

8 Current concentration of Zn in cereal grains mg/kg Phytate Phenolic compounds.. Required concentration of Zn in cereal grains mg/kg for human consumption Increasing micronutrient density in edible parts of plant highly desirable Zn ++ Cont Background

9 Zn Deficiency: Global Nutritional Problem in Soils Widespread Zn Deficiency Medium Zn Deficiency Alloway, IZA Publications, Brussels Cont Background

10 Countries at Risk of Zinc Deficiency in Children Black et al The Lancet Maternal and Child Undernutrition Series

11 Market destination of Australian bulk wheat exports (- 13 million t) Cont Background

12 Increasing on the awareness on soil health, environment,.. Organic farming and product are preferred Biological farming systems are not organic farming systems Biological farming systems (BF) is combination of orgainc and conventional, which aims to achieve optimum yield by balanced use of organic and mineral fertilizers. Conventional farming system (CF) aims to achieve highest possible yield through the use of mineral fertilizers and other external inputs. How farming practices impact the nutritional quality of grains, in particular grain Zn density? Cont Background

13 Aims Characterize the distribution of fzn fractions of soils (two farming systems) Characterize the concentration and content of Zn in shoot and seed of wheat grown in two soils

14 2. Method and Materials Identification of appropriate sites: - with history of conventional or biological farming - the same soil type, adjacent paddocks We identified Dalwallinu as an appropriate site for soil collection : Biological paddock: " S, " E Conventional paddock: " S, " E

15 History of biologically and conventionally managed soils in Dalwallinu Farming Crop rotation systems Biological Clover Brown Whe Wheat Green Wheat Wheat Green wheat Manure at Manure Manure Conventional Wheat Wheat Whe Wheat Wheat Wheat Oats Wheat Wheat at Source: Rob Harris, farmer, Dalwallinu Cont Method and Materials

16 Cont Method and Materials Soil Properties ph H 2 O (CaCl 2 ) 4.9 (5.7) Site OM (%) 0.9 NO 3 N (mg/kg) 9.5 NH 4 -N (mg/kg) 2 Phosphorous (mg/g) (5.9) (5.44) Soil Properties 2008 ph H 2 O (CaCl 2 ) 5.1 (5.4) OM (%) Dalwallinu (Lat ' 166 " S and Long ' 377 " E) Potassium (mg/g) 42 DTPA Zn (mg/kg) 0.36 Total Zn (mg/kg) 10 NO 3 N (mg/kg) 13 NH 4 -N (mg/kg) 2 Phosphorous (mg/g) 22 Potassium (mg/g) 60 DTPA Zn (mg/kg) 0.62 Total Zn (mg/kg) 12.5 Merredin (Lat ' 530 " S and Long ' 879 " E), Biological paddock

17 1. Characterization of soil Zn: Sequential fractionation as outlined by Iwasaki and Yoshikawa (1990, 1993). Total Zinc by aqua-regia DTPA - extractable Zn Cont Method and Materials

18 Sequential fractionations methods Fraction Chemicals/methods 1 Water soluble (WS) 2 Exchangeable (EX) Specifically adsorbed (SA) 1.5gm soils in 25mL MQ water shaken for 16 hours Wash with 10mL of MQ water and 25 ml of 0.5 M Calcium Nitrate Ca(NO 3 ) 2. 4H 2 O for 16 hours Wash with 10mL of MQ water and 25 ml of 0.05M Lead Nitrate Pb(NO 3 ) M Ammonium Acetate (CH 3 COONH 4 ) for 2 hours Wash with 10mL of MQ water and Acidsoluble (AS) 25 ml of 25mL Acetic Acid CH 3 COOH/LMQ water for 2 Manganese (Mn)-oxide-occluded (Mn-OX) 6 Organic matter occluded (OM) 7 amorphous iron (Fe)-oxide-bound (AFe-OX) crystalline Fe-oxide-bound (CFe-OX) hours Wash with 10mL of MQ water and 50 ml of 0.1 M Hydroxylamine Hydrochloride NH 2 OH.HCl for 30 min Wash with 10mL of MQ water and 50 ml of 0.1 M Potassium pyrophosphate K 4 P 2 O 7 for 2 hours Wash with 10mL of MQ water and 50 ml of 0.1M Oxalic acid (COOH) 2. 2H 2 O and 0.157M Ammonium Oxalate (NH 4 ) 2 C 2 O 4 for 4 hours Wash with 10mL of MQ water and 50 ml of ( 0.1 M Oxalic acid (COOH) 2. 2H 2 O, 0.175M 8 Ammonium Oxalate (NH 4 ) 2 C 2 O 4 01M 0.1 Ascorbic acid C 6 H 8 O 6 for 30 min boiling bath 9 Residual (RES) 10 Total (TZn) Total Zinc Sum of all fractions (as Alvaraz, et.al.,2006) Aqua-regia

19 2. Glasshouse experiment on Zn loading into wheat grains: Soils : Biological and Conventional Farming Systems Genotypes: Excalibur (Zn-efficient), and Kukri (Zn-inefficient) Zn fertilisation: 0, 0.1, and 1.0 mg/kg Zn source: ZnEDTA and ZnSO 4 Cont Method and Materials

20 Results Zinc in soils Fertilizers, OM decay... Total Residual Different fractions

21 Distribution ib ti of different fractions of Zn in soils Important to understand the Zn fractionation in soil for resources application (fertilizers) Previous studies: soil properties influence the transport of trace metals the soil-crop continuum. I looked at the fractions as influenced by farming practices

22 0.6 Distribution of differenct Zn fractions in soils of two farming systems, Dalwallinu CF BF 0.5 mg/kg g Zinc in WS EX SA AS Mn-OX OM AFe-OX CFe-OX Different Zn Fractions

23 Residual and total Zn in mg/kg Zinc Res -Zn Total - Zn

24 Distribution of zinc fractions (%) in soils from the two different farming systems, Dalwallinu ---- Dalwallinu 100 Zinc fractions Conventional Biological i l Farming 90 CF BF Farming systems systems 80 cent Per WS EX SA AS Mn OX OM AFe OX CFe OX RES Total sum of total fraction Residual 100 Total 100

25 Correlation coefficient among different Zn fractions in soils WS Ex SA AS MnOx OM O AmFeOx Cr FeOx Res TZn WS Ex SA AS MnOx OM O AMFe ox CrFeO x Res TZn numbers with red marks are significant 0.05 probability levels

26 Zinc in vegetative tissues and grains

27 There is difference in growth No visible Zn deficiency symptoms appeared (4 th week) 0 mg/kg g.1 mg/kg 1 mg/kg ph 4.9 DTPA Zn 0.36 mg/kg Wheat (Kukri) grown in conventional soils, Dalwallinu

28 Zn concentration in wheat shoot grown in different soils for 7 weeks Zn concentr ration (mg/kg) 80 Zn 0 mg/kg soil Zn 0.1 mg/kg soil Zn 1mg/kg soil a 70 Zn 0 mg/kg soil Zn 0.1 mg/kg soil Zn 1mg/kg soil a b 40 bc b bc a a b b d d Zn SO4 ZnEDTA ZnSO4 ZnEDTA Zn concentr ration (mg/kg) 60 a 50 a a 40 b b 30 c c c 20 d d d d 10 0 Zn SO4 ZnEDTA ZnSO4 ZnEDTA Excalibur Kukri Excalibur Kukri Biological Farming Systems (Dalwillinu) Conventional Farming Systems (Dalwallinu ) Mean values with the same letters are not significantly different by Tukey s HSDα α = 0.05 Soils : Significant (Tukey s HSD α = 0.01 ) Zn level : Significant (Tukey s HSD α = 0.01 ) Zn Source : Significant (Tukey s HSD α = 0.05 ) Genotypes : Non-Significant

29 Concentration (mg/kg DW) of seed Zn Farming Wheat ZnSO 4 4( (mg/kg g soil) ZnEDTA(mg/kg g soil) Systems Genotypes Biological Excalibur 26c 26c 36a 26c 29b 36a Kukri 22cd 23d 32b 22cd 26c 31b Conventional Excalibur 21d 23cd 25c 22cd 26c 42a Kukri 21d 18d 20d 21cd 22cd 27b Mean values with the same letter are not significantly different by Tukey s HSD α = 0.05 Soils : Significant (Tukey s HSD α = 0.05 ) Zn level : Significant (Tukey s HSD α = 0.01 ) Zn Source : Significant (Tukey s HSD α = 0.05 ) Genotypes : Significant (Tukey s HSDα α = 0.05 )

30 Seed Zn content ent (µg/seed) Zn Conte Density of Zn is higher: Zn fertilizer level and sources (ZnEDTA doing better) Excalibur (Zn efficient genotypes) Biologically managed soils

31 Internal mobilization/translocation is better in Zn efficient Genotypes?? mg/kg mg/kg Excalibur (Zn-efficient) Kukri (Zn-inefficient) Critical Zn concentration in youngest leaf <15 mg/kg

32 Zinc fractions and their relative availability to plant SN Fractions Availabilit Sources ph, Clay content OM content Soil types.. h ( ) d b d ( ) Capacity of plant to solubalize inactive forms of Zn 1 Water soluble (WS) 5: Readily Davis and Leckie 2 Exchangeable (EX) 5: Readily 3 Specifically adsorbed (SA) 3: Available 4 Acid soluble (AS) 3: Available 5 Manganese (Mn)-oxide-occluded (Mn-OX) 2:Limited 6 organic matter occluded (OM) 3: Available 7 amorphous iron (Fe)-oxide-bound (AFe-OX) 0-2 limited 8 crystalline Fe-oxide-bound (CFe-OX) 0-2 limited 9 Residual (RES) 0-1 limited 10 Total 1 0 as least to 5 as very high y Nalovic 1978, Lindsay 1979 Liang et al 1990, Sharad et al 2001, Alvaraz, et.al.,2006 Adhikari et al 2007, Rico, et al 2008

33 Correlation coefficient among shoot and seed Zn concentration, and different Zn fractions in soils SN Fractions Shoot Zn Seed Zn 1 Water soluble (WS) 0.66* 0.71* 2 Exchangeable (EX) 0.55* 0.88** 3 Specifically adsorbed (SA) Acid soluble (AS) * 5 Manganese (Mn)-oxide-occluded (Mn-OX) * 6 organic matter occluded (OM) 0.75** 0.54* 7 amorphous iron (Fe)-oxide-bound (AFe OX) 8 crystalline Fe-oxide-bound (CFe-OX) Residual (RES) Total (TZn) 0.84** 0.37 * and ** are significant at 0.05 and 0.01 probability levels, respectively Harmsen 1977, Sharad et al 2001, Adhikari et al, 2007

34 Conclusions: Biologically managed soil has higher proportion of available and total Zn content than conventionally managed soils More inactive forms in conventional than biological soil (residual pool=85% vs 80%) Important fractions for crop nutrition i.e. water soluble, exchangeable, acid soluble and organically-occluded fractions are higher in biological than conventional soil Excalibur (Zn-efficient genotype) loaded significantly more Zn (31-85 mg/kg DW) into grains than Zn-inefficient Kukri (21-65 mg/kg DW) (translocation of shoot Zn into seed ) -- breeding ZnEDTA fertiliser was more effective than ZnSO 4, but relatively high cost limits the practical use of ZnEDTA Growing/promoting grain legumes or crops that can solubalize the inactive forms of Zn to plant (Biological farming approach to be promoted)

35 Acknowledgements UWA/IPRS scholarships ARC linkage project (with DAFWA and ERA sustainable) W/Prof. Z Rengel Hossein Saberi Paul Damon, Mike Smirk.. This is the way to my home

36 Conclusions: Biologically managed soil has higher proportion of available and total Zn content than conventionally managed soils More inactive forms in conventional than biological soil (residual pool=85% vs 80%) Important fractions for crop nutrition i.e. water soluble, exchangeable, acid soluble and organically-occluded fractions are higher in biological than conventional soil Excalibur (Zn-efficient genotype) loaded significantly more Zn (31-85 mg/kg DW) into grains than Zn-inefficient Kukri (21-65 mg/kg DW) (translocation of shoot Zn into seed ) -- breeding ZnEDTA fertiliser was more effective than ZnSO 4, but relatively high cost limits the practical use of ZnEDTA Growing/promoting grain legumes or crops that can solubalize the inactive forms of Zn to plant (Biological farming approach to be promoted)