Importance of micronutrients in crop nutrition

Transcription

1 Importance of micronutrients in crop nutrition R.W. Bell, B. Dell, and L. Huang We thank Prof. B. Rerkasem, R. Brennan, ACIAR, ARC Outline Essential elements Classical approach for assessing micronutrient limitations Residual value of micronutrient fertilizers New evidence of micronutrient disorders Recalcitrant micronutrient problems Mapping location of micronutrient deficiencies Correcting market failure in the adoption of micronutrient fertilizers Conclusions 1

2 Importance Impact per unit area Yield Crop quality Seed vigour N fixation Human/ animal nutrition Inefficient use of inputs X Area affected Topsoil Subsoil Residual value Genotypes Essential elements No new essential micronutrients discovered since Ni (1987) Continuing work on Si New understanding of behaviour of B in plants new evidence of B requirements in animal and human nutrition New emphasis on impacts for human health Photos: B Wood, USDA 2

3 Classical approach for assessing micronutrient limitations Soil analysis surveys Field trials Critical levels Fertiliser rates and types Crop species requirements Mapping location of micronutrient deficiencies Based on location of responsive sites Based on soil types 3

4 Residual value of micronutrient fertilizers Identification of deficiency Rates, forms for correction Residual effectiveness Soils Yield Element No. year production supported by.75 kg Zn /ha applied once Yield (t/ha) Zn removed (g/ha) Zn added (g/ha) Zn balance (g/ha) Wool Wheat Lupin Canola No. years 18 Brennan, unpublished 24 4

5 Estimating residual Zn 8 Zinc (g/ha) Grain yield (t/ha) No Zn +Zn enriched Zn supply Avail Zn sand Avail Zn clay Based on Brennan 24 Boron residual value B movement in soils B reactions in soils B toxicity risk from B fertiliser B inputs and outputs in rice-based cropping systems 5

6 Soil properties Alluvial Jiangshan Udi- Red Jiangshan Hapl- Bluepurple Jiashan Aquent Taxonomfluvenudult ph (KCl) OM g/kg Clay g/kg ECEC cmolc/kg B mg/kg B application rates (kg B/ha) Borax Yr 1 Yr 2 Yr 3 Treatments / /3.3 6

7 B distribution (mg CaCl 2 extr B/kg) by depth in Blue-purple soil * * * Borax rates (kg/ha) * -1 cm 1-2 cm 2-4 cm 4-6 cm B distribution (mg CaCl 2 extr B/kg) by depth in Alluvial soil Borax rates (kg/ha) * * * * * * * -1 cm 1-2 cm 2-4 cm 4-6 cm 6-8 cm 7

8 Effect of repeated B application on oilseed rape yield 1.2 Seed yield (t/ha) or Soil B (mg/kg) 1.8 * *.6.4 * F-F Fertiliser Borax rates (kg/ha) Seed yield Red Seed yield Alluvial Soil B Red Soil B Alluvial B removal in grain and straw B removed in grain each year (g B/ha) B removed in straw each year (g B/ha) % of B in 15 kg borax removed after 3 years in straw and grain

9 Conclusions borax at 3-8 x recommended rates has low risk of inducing B toxicity low risk of B toxicity consistent with low extractable B levels in fertilised soils leaching loss of B is minimal B removal in harvested crop products is significant in triple cropping system single application of 1.65 kg B/ha effective on all soils for 3 years New evidence of micronutrient disorders Changing lowland farming systems Intensification Direct seedling declining sub-soil levels Upland farming systems Legumes, oilseeds Plantation forestry Hostile sub-soils 9

10 Change in incidence of micronutrient deficiencies- Punjab 6 % of samples Zn Cu Fe Mn Nayyar et al. (1999) Sub-soil Hostile sub-soils Acidity Alkalinity Salinity Physical constraints Low micronutrients in sub-soils Zn, Mn, Cu, B 1

11 Low micronutrients in subsoil Rape Seed yield (g/plant) Zn effic. (%) +Zn 2 cm ZY821 -Zn 9 +Zn ± Zn XZ Naren cm CSIRO Grewal et al Wheat sterility Gaping glumes Low grain set Low yield South Asia, Southeast Asia China Brazil 11

12 Effect of low B (3 days) on pollen viability in wheat Treatment stage FCR test at anthesis (% +B) -B (pre-meiosis to meiosis) 61 -B (meiosis to late tetrad) 8 -B (young microspore to mit-i) 56 -B (mit-i to mit-ii) 42 Huang et al. 2 Pollen viability (%) by FCR test Short term B deficiency - pollen quality B + B SW 41 Fang 6 NaChiangmai et al

13 Ear boron on D5 B (µm) B concentration (mg/kg) B distribution (%) Fang 6 SW 41 Fang 6 SW NaChiangmai et al. 24 New approaches weight of evidence modeling B risk map Wong and Bell, unpublished 13

14 8 7 B risk factor soil ph 1 ph (CaCl2) Ho t CaCl 2 -extr B (mg/kg) B risk factor 2- Clay in topsoil Clay (%) 14

15 B risk factor 3- Geology Improved mapping Soil attribute or soil maps Fertilizer suppliers Geology Location and properties of responsive soils Risk maps Research Sponsors Crop tolerance Planners 15

16 Partnership- Correcting market failure in the adoption of micronutrient fertilizers C FF S P G Conclusions Assess extent and severity of sub-soil limitations Spatial technologies to define affected areas Quantify residual value Efficient cultivars Partnerships 16