WATER MANAGEMENT GOALS : salinity and sodicity aspects Profitable crop yields

1. WATER MANAGEMENT GOALS: • salinity and sodicity aspects • Profitablecropyields • ECiwand ECe • Maintain or improvesoil physical properties. • EC/SAR • Consider environmentalimpacts (N, P, TDS, pesticides)– subsurface flows to aquifers and surface return flows to streams

2. Fertilizer management:take into account the N and S content in the irrigation water. • 5 ppm N in irrigation water times 2.7 equals 13 lbs of N per acre-foot of water. • 5.3 ppm SO4 equals 4.7 lbs of S per acre foot. See the footnotes for how this was calculated.

3. Liming potential: The waters of SE Mo have a ‘hardness’ (Ca and Mg carbonates) that range from 50 to about 400 mg/L. • 200 mg/L of ‘hardness’ has a calcium carbonate equivalent to about 500 lbs per acre foot of water. • Impacts of liming potential on zinc nutrition.

4. Ion Toxicity concerns: Na, Cl, B • Operation concerns:prevent clogging(Fe problem)

5. Electrical conductivity, EC A quick method to measure the salinity of water. EC is approximately one-tenth of the total dissolved cation, or anion concentration. EC units for salt tolerance: dS/m or mmho/cm not micromho/cm (μmho/cm) 5 mmho/cm = 5 dS/m = 5000 μmho/cm

6. Sodium Adsorption Ratio, SAR • Based on the sodium, calcium and magnesium concentration in solution • SAR = Na/{sqrt(Ca + Mg)/2} • A rapid method to estimate the exchangeable sodium percentage. • ESP  SAR

7. Remember water quality indices • EC (electrical conductivity) is the salinity index. ECiw for irrigation water and ECe for water extracted from a saturated soil paste. • SAR (sodium adsorption index) is the sodicity index. SAR is about equal to the exchangeable sodium percentage.

8. Excess salinity  drought Upon sudden exposure to salinity 1. Plants wilt but in a few hours 2. Plants recover

10. Excess salinity increases the energy plants must expend to grow: when levels are excessive, plant growth rates and yields are reduced. The salinity of the soil water reduces crop growth if the average rootzone salinity, (ECe), exceeds the threshold level for the crop.

11. Saturation extract electrical conductivity, ECe Soil Surface ECiw Average Rootzone Salinity, ECe Bottom of the rootzone

12. YIELD RESPONSE TO SALINITY Average Rootzone Salinity, ECe 100 % Threshold salinity Crop Yield Slope 0 %

13. Crop salt tolerance

17. Chloride and sodium -- can damage some plants, but this depends on the irrigation method • Surface or drip irrigation: potential problem for trees and shrubs, usually not for grass, grain, fiber, and forage crops. • Sprinkler irrigation:which wets the leaves intermittently during the day can damage leaves for many plants, ifthe sodium or chloride concentration in the irrigation water is greater than 5 meq/l.

18. Na/Cl foliar damage from sprinkler irrigation, concentrations in meq/L.

19. Growth stage effects: exceptions to the time-depth average assumption. • Germination: Salt stress delays germination. • Emergence: Plants are sensitive during emergence and early seedling development. • Reproductive stages: Salinity stress during spike differentiation reduces yield.

20. Climate • “Climate probably influences the response of plants to salinity as much as, if not more than, any other factor. Most crops can tolerate greater salt stress if the weather is cool and humid than when it is hot and dry.” Maas, 1990. • These effects have been observed on alfalfa, strawberry clover, and salt grass.

21. Fertility-salinity interactions • Grattan, S.R., and C.M. Grieve. 1999. Salinity-mineral nutrient relations in horticultural crops. Scientia Horticulturae 78:127-157. • Shalhevet, Y. 1994. Using water of marginal quality for crop production: major issues. Agr. Water Management 25:233-269.

22. Nitrogen • Nitrogen applied above levels considered optimum under non-saline conditions will not increase plant growth in saline soils. • Saline conditions reduce plant growth, thereby reducing nitrogen needed by the crop.

23. Effects of salinity and sodicity on water infiltration into soils.

24. Water in an unsaturated coarse-textured soil.

25. Possible arrangements of quartz particles, clay domains, and organic matter in a soil aggregate.

26. Dr. J. P. (Jim) QuirkDept. Soil Science and Plant Nutrition, Un. of W. Australia, Nedlands, WA

27. At A, the permeability was reduced 15 %: Quirks choice -- first observable impaired soil structure (TEC). At B, drainage water was turbid -- dispersed clay (TUC) Relative Hydraulic Conductivity 1.2 0.3 Salinity, dS/m

28. Mechanisms Swelling - blocking conducting pores Aggregate failure -- unequal swelling throughout the soil Deflocculation -- clay particles separated to distance where repulsive forces dominate -clays disperse and move

29. McNeal and Coleman, 1966California Soils The data obtained by McNeal is in reasonable agreement with the TEC function of Quirk and Schofield

30. From hydraulic conductivity to infiltration -- from within the soil to the soil surface. Impact of water drops, rapid soil wetting, overland water flow cause physical disintegration of soil aggregates, clay dispersion and compaction at the soil surface.

31. Infiltration rates are particularly sensitive to salinity and SAR At the soil surface both are closely linked to the SAR and salinity of the irrigation water. At the soil surface, the EC and SAR of the soil quickly approaches that of the irrigation water.

32. RNa is the same as SAR.

34. Photo taken through a microscope (60x) showing three clay layers.

36. TEC TUC

39. Rainfall -- major hazard • Rainfall coupled with irrigation with low sodicity waters (5 < SAR < 10) may cause enhance runoff and erosion. • Fresh organic matter content and crop/stubble cover can be expected to compensate (somewhat) the effect of rainfall on soils irrigated with low sodicity waters. • Available data indicate these effects can not be predicted – be a good observer/manager.

40. Iron problem • Most of the groundwaters in SE Missouri have moderate clogging potentials due to their iron contents. • The red numbers in the following table are the percentages of the groundwaters that have iron concentrations in the range shown by the white numbers.

41. Iron clogging potential Ferrous iron is much more soluble than ferric iron. Oxidation of ferrous iron to ferric iron, by bacteria or by air, results in a formation of ochre and/or bacterial slimes. These can clug intake screens of wells, and the filters, laterals and emitters of a drip irrigation system

42. Iron – ochre, red oxide films, and bacterial slimes • Exposure of well waters to air will cause iron to be oxidized: red oxide films on exposed surfaces is one result, another is large deposits of iron oxide in pipes known as ochre, • In anaerobic well waters, bacteria grow just below the static level of a well where pumping agitates and aerates the water. Iron bacteria obtain their energy from oxidizing iron. Once started iron bacteria develop slimes throughout the interior of the well casing, mainlines, and laterals.

43. Iron removal • Aeration • Clorination (also kills bacteria) • Settling basins • Filtration

44. Well treatment for iron clogging • Chlorination • Acid treatment • Brushing More details are given by Juhdorff – see footnote for citation.

45. Iron and manganese • Manganese is usually also present in waters that contain iron.

46. Water quality criteria for drip irrigation The clogging potential due to oxidation of manganese ranges from moderate to high for most of the groundwaters. Manganese chemistry is similar to iron chemistry.

47. Water quality criteria for drip irrigation Acidification of water to a pH of about 6.5 will reduce clogging due to precipitation of Calcium as calcium carbonate, also referred to as soil lime.

48. Know the chemical composition of the water. • Consultants and Specialist are available who can help interpret the chemical composition.

49. Thanks for the opportunity. J. D. (Jim) Oster Emeritus Specialist University of Ca. Oster@mail.ucr.edu