Magazine: (Part.4) Managing Turfgrass Using Poor Quality Water
By Jerry Spencer in Consultancy on 9th Dec 2007 8:00
For the start of this article click below
Part 1
Part 2
Part 3
PART 4
DEALING WITH THE PROBLEM
Soil amendments
Gypsum
Gypsum
Gypsum, calcium sulphate, can improve soil structure and water penetration. On heavy soils gypsum improves soil aeration, facilitating root growth. Gypsum can alleviate sodic soils, that is, soils significantly downgraded by the presence of sodium salts, but only where high water tables and poor irrigation management are not the cause.
Before applying gypsum it is advisable to check that low organic matter level is not the primary cause of the soil problems being experienced. Even when tests indicate gypsum application is needed, increasing organic matter levels will enhance the benefit obtained from gypsum application.
Gypsum works in two ways:
1. Electrolyte effect - is short term (1-12 months) ceasing when all the gypsum has dissolved. Each irrigation dissolves some of the gypsum raising the electrolyte concentration of the soil water which decreases soil dispersion (a cause of soil crusting). This is the predominant process occurring when gypsum is applied to sandy loams and loams.
2. Exchange effect - is longer term (12-24 months). The addition of high concentrations of calcium to the soil displaces sodium salts attached to clay particles. Sodium salts then enter the soil solution and are leached below the rootzone by irrigation. Displacement of the sodium salts helps to prevent surface crusting and clay dispersion in the rootzone. This is the predominant process occurring when gypsum is applied to clay soils.
Types and quality
Gypsum is available in two forms. "Flour" gypsum looks like coarse flour and varies in colour from white to pink. "Seed" gypsum consists of crystals usually a few millimetres in size. "Flour" gypsum is faster acting and is used when a quick response is needed whereas "seed" gypsum is used if a long term response is desired.
Different sources of gypsum contain differing amounts of impurities. Impurities such as sand have no detrimental effect except increasing the freight cost per tonne of actual gypsum. Knowing the percentage of actual gypsum is also important for determining the application rate per hectare. The proportion of actual gypsum should preferably be above 80 %
Many gypsum deposits contain sodium chloride. Gypsum used for agricultural purposes should not contain more than 2 % sodium chloride and this should be confirmed by a recent analytical report from the supplier.
In relation to using liquid gypsum, lime etc these tend to give a rapid but short term result at the appropriate rate but are significantly more expensive.
In terms of economy you are looking at (lowest cost at top)
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Product
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Cost
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Longevity
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Gypsum
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Cheap
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Long
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Gypsum prill
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Medium
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Long
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Gypsum Liquid
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Expensive
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Short
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Linear Polyacrilamides
Consider this
· As irrigation levels are decreased and water restrictions introduced, salt accumulation will become an increasingly important and troublesome problem.
· It will be necessary in the future to use more and more recycled water for irrigation of turf areas.
Bearing this in mind the use of polymers such as these is worth considering. They are able to:
- Increase water use efficiency
- Enhance soil permeability and infiltration rates
- Reduce irrigation frequency
- Reducing compaction
- Stop erosion and water run-off
- Increase turf performance (especially in structureless soils in areas subject to drought).
Turf Managers may well be familiar with one group of polymers already and these are the water holding crystals. However, there are in fact two distinct types of polymers that have been studied and recent trials on turf are showing considerable promise in relation to their use. These polymers can be either soluble or insoluble in water.The two different types of polymers used in landscaping and horticulture may cause confusion. Water absorbing, gel forming polymers, are an aid for increasing water holding capacity of sandy soils or of well drained synthetic potting media which do not have the ability to hold as much moisture as loam or clay soils. The advantages of the gel polymers are that they reduce the frequency of irrigation and the soil moisture becomes more constant. These gels store water in soil and, in contrast, the other polymers bind soil particles for structural soil enhancement. For gels, the polymers are bridged between adjacent molecules and are thus cross-linked to make them insoluble so that they act like sponges.
Water-soluble linear anionic polymers are a single chain of an enormous number with repeating units. These polymers are designed to bind together thousands of soil particles and form a latticework in and around soil crumbs. In time this polymer also becomes water-insoluble in the soil.
Water-soluble Polymers
They were the first ones to be developed, primarily to aggregate and stabilise soils, combat erosion and improve percolation. Paton Fertilizers recently carried out phytotoxicity trials on turf using both a liquid and coated fertilizer formulations with interesting results. Linear water-soluble polymers have structures along the following lines:
Benefits of water-soluble polymeric soil conditioners
Prior to commencing these trials, considerable work has been carried out overseas in both Europe and Asia and
the success of PAM in modifying calcareous nonfertile land near Dijon in France is a well-known example of its application. A common trait of tropical soils in intense high rainfall regions, is that they suffer from a decrease in aggregate stability and a increase in bulk density. PAM has proved to be effective against soil erosion and work in Indonesia with PAM has made it possible to reduce soil losses under rainfall from 17 000 to 4000 kg ha-1. The permeable layer of soil produced by the conditioner stabilises the soil, thus preventing runoff with a further benefit being that the penetrability of water in a PAM treated soil increases by a factor of 2.5 while its mean diffusivity increases four fold.
The effect of polymeric soil conditioners on plant growth and crop yield has also been extensively studied. The rates of germination and emergence of a number of plants such as tomato, lettuce or maize increased markedly in the presence of the conditioner (Wallace and Wallace 1986a). Other studies (Batyuk et al. 1973) have shown that the yield of (sugar beets) is increased while the requirements for irrigation decreased by the use of conditioners such as this.
Wallace and Wallace (1986b) showed that very low concentrations of a mixture of PAM and a polysaccharide (below 0.001% or 22 kg ha-1) have a favourable effect on the physical properties of soils, particularly regarding percolation and infiltration rates as well as the size of soil particles. These very low rates of soil conditioners now make their use economically feasible.
Where salts and sodium are soil problems, treatment and leaching are more easily accomplished with less irrigation water when soils are prepared with water-soluble PAM.
Use of water-soluble PAM makes it possible to more easily use recycled water for irrigation without causing compaction of the soil.
The water-soluble PAM also makes it possible to more efficiently use any low-quality water for irrigation.
Over the last few years we have been carrying out a lot of work in relation to dealing with high sodium soils. The end result has been the introduction of Pedocare® Ultimer.
I hope the above helps clarify the issues that you face and also shows you how you can overcome the problems associated with using effluent water.
Thanks To Jerry Spencer from ETP for the great Article.
Click Logo for more on ETP
References for the 4 part article are as follows.
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BATYUK VP, MALAKHOVA Zh V and FENENKO LM. 1973. Use of polymers to maintain soil fertility I, p. 75 - 84. In : OROSHAEMYKH P, EGOROV V and KRUSKII NK.. eds. Probl. Genezisa Melior. Moscow : Pochv. Inst.
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Butler JD and L.Wu.1992.Salinity and turfgrass culture. In D.V.Waddington,R.N.Carrow,and R.C.Shearman (eds.) Turfgrass,pp.207–229.Series No.32.Madison:American Society of Agronomy
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Harivandi MA Interpreting Irrigation water test results University of Calfifornia Division of Agriculture and Natural Resources
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Irrigation with Reclaimed Municipal Wastewater – A guidance manual. Report No. 841-1wr. California State Water
Resources Control Board, Sacramento, CA; and from D. S. Farnham et al. 1985. Water Quality: Its Effects on Ornamental
Plants. University of California Division of Agriculture and Natural Resources Publication 2995.
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Lentz, R.D., and R.E. Sojka. 1996. Five-year research summary using PAM in furrow irrigation. p.20-27. In R.E. Sojka and R.D. Lentz (ed.) Managing Irrigation-Induced Erosion and Infiltration with Polyacrylamide. Proc., College of Southern Idaho, Twin Falls, ID, 6-8 May, 1996. Univ. of Idaho Misc. Publ. 101-96.
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Malik, M, C. Amrhein, and J. Letey. 1991a. Polyacrylamide to improve water flow and salt removal in a high shrink-swell soil. Soil Sci. Soc. Am. J. 55:1664-1667
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Orts, W.J., R.E. Sojka, G.M. Glenn, and R.A. Gross. 2001. Biopolymer additives for the reduction of soil erosion losses during irrigation. Pages 102-116. In: R.A. Gross and Carmen Scholz (eds.) Biopolymers from Polysaccharides and Agroproteins. ACS Series 786. Am. Chem. Soc., Washington, DC.
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WALLACE A and WALLACE GA. 1986a. Effects of soil conditioners on emergence and growth of tomato, cotton and lettuce seedlings. Soil Science 141 (5) : 313 - 316.
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WALLACE A and WALLACE GA. 1986b. Effects of very low rates of synthetic soil conditioners on soils. Soil Science 141 (5) : 324 - 327.
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Wallace, A., and G.A. Wallace. 1996. Need for solution or exchangeable calcium and/or critical EC level for flocculation of clay by polyacrylamides. p. 59-63. IN: R.E. Sojka and R.D. Lentz (eds.) Managing Irrigation-Induced Erosion and Infiltration with Polyacrylamide. Proc., College of Southern Idaho, Twin Falls, ID 6-8 May, 1996. Univ. of Idaho Misc. Publ. No. 101-96.
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Westcot DW and R. S. Ayers. 1984. Irrigation water quality criteria. In G. S. Pettygrove and T. Asano (eds.)
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the success of PAM in modifying calcareous nonfertile land near Dijon in France is a well-known example of its application. A common trait of tropical soils in intense high rainfall regions, is that they suffer from a decrease in aggregate stability and a increase in bulk density. PAM has proved to be effective against soil erosion and work in Indonesia with PAM has made it possible to reduce soil losses under rainfall from 17 000 to 4000 kg ha-1. The permeable layer of soil produced by the conditioner stabilises the soil, thus preventing runoff with a further benefit being that the penetrability of water in a PAM treated soil increases by a factor of 2.5 while its mean diffusivity increases four fold.
