Dear Anoop,

The quality of water used for irrigation is a critical parameter for the crop yield, maintaining soil productivity and environmental protection. Thus, the physical and chemical soil properties, such as its structure (stability of aggregates) and permeability, are very sensitive to the type of potentially exchangeable ions present in irrigation waters.

The quality of the irrigation water can be best determined by chemical analysis in the laboratory. The most important factors in determining the required water quality in agriculture are:

pH, Risk of Salinity, Sodium Hazard (Sodium Adsorption Degree), Carbonate and bicarbonates in relation to the contents of Ca and Mg, Other trace elements, Toxic anions,  Free chlorine.

There are quality standards for irrigation water such as those proposed by United States Department of Agriculture (USDA).

With my best regards

Prof. Bachir ACHOUR

I strongly feel  the quality of irrigation water contributes to crop yield and quality both. The cationic composition of water also lessens the nutrient requirement of any crop.

Thats a very intersting point Bachir , you added quality of irrigation water is related to soil quality , and hence afffects both crop yield and quality. 

Dr Srivastava, I appreciate your set of questions , so practical in nature. there are very limited efforts undertaken in this direction to quantify the contribution of quality of irrigation water to crop yield and quality. Nutrient like potassium has been attempted for its contribution , and how the k-requirement could be reduced , is an interesting addition . But it remains to be seen , how quality is affected . We all know the contribution of quality of irrigation water through a number of nutrients being added . Surely total dissolved solids , which take into account the different cations like K, Ca, Mg , Fe , etc they all go into the soil environment.

Let me start the whole discussion with thanks to my learned colleagues who responded so vividly . I was trying to see whether we have a comprehensive criteria for classifying the quality of irrigation water for irrigation to soils of different texture and crops as well . This is the part , I still remember my learned colleagues Dr Nazir and Dr Qadir , sometime back , we just touched upon these issues. Anyway , I am trying to give further supplements. There is no universal criteria for classifying the quality of irrigation water . On this score , I think ,Bachir will agree with me . Infact  this prompted me to post this very sub-question . The most striking part of best criteria is the limit to which crop yield is affected . For example , with reference to barley crop , irrigation water having salinity of 5.3 ds/m , there is no likelihood of adverse effect on yield , but 10%, 25% and %0% yield reductions have been noticed  at water EC level of 6.7, 8.7 and 12.0 dS/m , respectively .  However , such information does not reveal  about such effects on what kind of soil texture ?.This is the most missing part. While evaluating irrigation water , boron sensitivity is also one such additional criterion ( Crops like alfalfa, sugar beet , tomato can tolerate boron concentration upto 6mg/L) .

An excellnt work of Ayers and Westcot (1985) further provided a better version  of water quality criteria by incorporating the soil texture . For example , a soil having clay content of less than 10% like typical sandy loam , loam soils , water Ec level upto 8.0 could be afforded , while those soils with caly content of more than 30% , even water EC of 1.5 dS/m could be hazardous .  Such information could be more effective with the information on crops to complete the whole story in one time.

I am enclosing two excellent PDFs for your reference please and carry the discussion forward .

We all often debate about the success of some crop in specific region for soil and water quality but hardly take precisely the merits of irrigation water to success of crops in both yield and quality. Probably nutrients supplied through irrigation water would be more assimilable by crops than through fertilizers.

Dear Annop,

Let me add a few words to my first comment.

To determine the degree of suitability of water for irrigation, it is necessary to consider the problems related to its content of salts, for its action on the soil permeability, the presence of toxic ions for growth plant and side effects on the appearance of the plant. A California university consultant committee has developed guidance for interpreting the quality of irrigation water according to the consequences listed above. These recommendations have some flexibility and try to assess the long-term risk on agricultural production. They should be adjusted based on experience gained on soil, crops and irrigation methods. Usage limits must be considered within the range 10% to 20% given the many variables that are involved in plant production. It is assumed that the water used in average conditions of soil texture, drainage, climate, amount applied and tolerance of crop in salts. The proposed classification into "without problem", "growing problem", "serious problems" is more or less arbitrary but based on a large number of observations, field studies, pilot stations, conducted over 40 years.

"Without problems" means that for water with has a content less than that indicated, the irrigator should not have difficulty for both soil and crops. In contrast, "serious problem" implies for the irrigator a pejoration of soil and plants at more or less long term. Between the two classes ("growing problems"), the user should gradually follow the evolution of the problems. Accompanying actions should be recommended to compensate for any degradation due to water quality in the way of irrigating in particular. The recommendations concern the types of irrigation (flooding, spraying, ...). The new relationship concepts between soil, plant and water have been taken into account.

With my best regards

Prof. Bachir ACHOUR

Dr. Anoop, thank you for the very pertinent question and your consistent contribution in areas of soil, water and plant interactions. I found the comment by Prof. Bachir very relevant to the discussion.

It is obvious that quality of irrigation water may have a profound effect on crop growth and productivity, and soil properties after irrigation. Texture of irrigated soil is important in addition to salinity and sodium adsorption ratio of irrigation water when considering the suitability of irrigation water. Appropriate information is required in relation to the contribution of soil texture on the accumulation of salts, development of soil sodicity and the crop growth condition under different soil environments. Excessive salt can limit crop yield or may even prohibit crop growth. On the other hand, the presence of salt in too little amount may reduce water infiltration, which may have impact on crop growth and yield. So an understanding of the quality of water used for irrigation and its potential negative effects on crop growth is essential to avoid drawbacks and optimize yield. Dissolved salts, irrigation water salinity, soil salinity and leaching may be considered beneficial among the parameters in characterizing irrigation water quality and estimating yield potential. The reference below may give additional information.

Stephen R. Grattan. 2002. Irrigation water salinity and crop production. University of California, Davis.

Thanks friends for responding so nicely and so effectively starting from Prof Bachir , Dr Singh , Dr Deka , Ms Reyhaneh , Dr Getachew for making this discussion interesting , since the discussion needs still many  more responses before some concrete information could be drawn from this post .  The most important aspect this post was , how to quantify the amounts of nutrients credited to  a crop total nutrient requirement . This is only possible , unless , we know the nutrient composition of the irrigation water being used . I was vehemently trying to get some information on these aspects , unfortunately , very little , I could gather . So , whatever , I got , I am trying to share with you all my friends.  However , how much of the nutrients ,( especially nitrogen )  in irrigation water should be credited as fertilizer value to a crop is a  debatable issue, since it is still not clear if crops can make use of nitrate in irrigation water when concentration is less than 20 ppm nitrate . According to studies by Cahn and Smith ,  irrigation contains on an average , 0.20-2.0 mg/L phosphate  , 0.60-3.30 mg/L nitrate-N , 1.3-3.7 mg/l potassium ,0.50-4.50 mg/L iron , 0.40-0.80 mg/l manganese , with EC of 0.20-0.50 dS/m . This was the basis of computing the   nitrogen ( For example ) accredited to lettuce crop grown on soil of coarse texture having clay content of 10-15%  and WHC of 20-25%.

The soil nitrogen level that optimizes lettuce growth ( For example ) is considered to be in the range of 15-25 ppm nitrate -n. But this concentration is expressed in terms of weight of N per weight of soil  ( mg N/kg soil ) .Considering the soil moisture by 20-25% by weight , the nitrate concentration in soil  would range between 60-120 ppm nitrate -N.

An excellent account of micronutrients accredited through irrigation water has been worked out by Hundal et al for alluvial plains of northwest India. According to their study , as much as 64-360 g/ha Zn , 13-62 g/ha Cu , 141-644 g/ha Fe  and 044-3.15 kg/ha B was added through irrigation water  in wheat crop   . While there were three times more amount of micronutrients were deposited in subsequent paddy crop ( Enclose PDF for reference )  . Such studies provide ample proofs , how irrigation water quality adds to both yield and quality .

Dr Srivastava, this is a good piece of information something we hardly care and something which can surely cut down the nutrient requirement of crop substantially. Friends can you share your experiences on other crops.

Anoop Sir,

Water quality parameters are well known : pH, EC, SAR, RSC, B, No3, F, Cl, Sediments, Colour, Smell, etc.,

Mostly few laboratories test these parameters. Only pH and EC are the two parameters tested often.  If these show some  inferior quality then other parameters like SAR and RSC are also tested. If nitrates are ,more in irrigation water that may add to ground water. If chlorides are more that water is not used for quality crops like potato.

Boron though essential for plants, its requirement is so narrow, if it exceeds 2 ppm in soil may become toxic.

Florine if present in irrigation water, lead to growth of microbes and leads to bad smell. The fodder if irrigated with such waters lead to some disease in animals those feed on the same.  Sediments, colour and smell should not be there for clear and clean water.

If pH is more (>7.75) it indicates the presence of carbonates or sodium. The effect can be reduced by inclusion of Ca in irrigation waters.  If is  EC is more (>2.0 dS/m) the salts should be removed before irrigating to any crop.

Soil testing facility is not easily available to all the farmers! Unless there is serious problem in irrigation water, farmer will not think of testing it.  The test procedure are only in books. They seldom reach farmers!

There should be a support process to farmers in getting good price for their farm produce if they follow all the scientific recommendations!

Govt should evolve such steps

regards

raj

Dr Bashir , why most of the consequences of irrigation water is addressed with respect to potential salinity buildup in terms of changes in soil physical properties , interaction with nutrient availability . with exception of boron , nitrate and potassium to some extent , there is hardly any classification of irrigation water quality for specific crop or specific soil ?.

Ms Reyhaneh , we don't see much work on classification of irrigation water quality fro non-agricultural purpose , exept the criteria used for classification of water fro different heavy metals as pollutants or fro contaminated waters . But , we need a different classification fro use of decontaminated water for irrigation , if I am not wrong.

Friends , let me add further , from where I left yesterday about the quantity of micronutrients added through irrigation water under wheat-paddy crop sequence on alluvial plains of northwest  India. The amount  of nutrients added through the irrigation water and their crop responses ,  is further conditioned by the landform/physiography of a field coupled with other conventionally used soil physico-chemical and biological properties.

That's a good point Dr Singh , you have raised , let other colleagues interact on this issue.

Ms Reyhaneh and Dr Singh , the criteria for appraisal of irrigation water suitable for non-agricultural purpose are not so precisely defined . but criteria for defining the quality of irrigation water for contamination or pollutants are very well streamlined. These contaminants are classed as water pollutants, bacterial water contaminants, sulphate water contaminants, well water contaminants, mineral water impurities, water turbidity , waste water contaminants, non-biodegradable water contaminants and , water impurity of colloidal property. These contaminants can be further shortlisted as : nutrients , bulk organic hydrocarbons , halogenated hydrocarbons ( For example DDT, PCBs) , polycyclic hydrocarbons ( For example petroleum products)  and metals and metalloids . Often , the se contaminants are also classified on the basis of source of origin , like point source ( Definite site of origin )  and non-point source ( Undefined site of origin ) . Some literature classify water pollutants as organic , inorganic ,  radioactive  and acid/base.Hope , these will further help in onward discussion on the subject .

You may refer to various publications under the aegis of ICAR's Coordinated Research Project since 1972 i.e. AICRP- Management of Salt-affected Soils and Use of Saline Waters in Agriculture" on the subject and  also go through their  "Water qulity guidelines"

Thanks Dr Minas for nice update . We need some information on the subject where non-saline normal water ( Canal or well water ) is used for irrigation to  different crops , annual or perennial . To what an extent ,  nutrients are  added through irrigation water to any crop , which goes unaccounted , not considered into the nutrient budget of the crops grown under  any condition .    Looking forward to your responses . 

Nice information , you attached Dr Srivastava about the amount of micronutrients added to wheat-rice cropping system on alluvial plains . Don't you think , this amount of nutrients will vary according to crop water requirement or number irrigations given in crop annual cycle . Off course , perennial crops will be much benefitted with such attempt compared annual crops .

Friends while talking about the water quality vis-a-vis crop quality , an excellent review wa spublished way back in 1994 by Dr Shalhevet ( DOI: 10.1016/0378-3774(94) 90063) on the subject covering use of marginal quality irrigation water for crop production highlighted various aspects of irrigation water quality in relation to quality of different crops. However , coming back to use of saline water for irrigation , adjusting the TDS with EC on different textured soils is much bigger and complex exercise( Some PDFs enclosed for reference please) .Stine et al 2006 ( J.Food Prot.69: 2029-35) proposed the water quality on microbial load basis . later Allende and Monaghan ( 2015, Int.J.Environ. Res. Public. Health 12: 7457-7477)) advocated microbial water quality requirement for different leafy vegetables  .

Friends the composition of irrigation water which is mostly ground water is heavily dependent on the nutrients trapped inside different strata of soil and their texture and aggregate formation to filter the rain water through whole soil matrix. In that case don't you feel quality of irrigation water is as important as the quality of soil, both collectively deciding  the crop response.

Friends how many of you think crop quality and irrigation water quality are interrelated and why so?

Dr Deka , I fully endorse your comments  about water quality , how the ionic composition of the water available  for irrigation  is developed.  Dr Singh , I find strong correlation between quality of the irrigation water and quality of various crops . The basic reasons , though , still not so candid , in terms of types of crops grown to cationic or anionic composition of irrigation water , since I see very limited literature published and available in  public domain.  

To all the scientist forum,

It is evident that the quality of water affects crop yield level. The literature on quality of irrigation water and its effects on crop yield is available with CSSRI, Karnal. India

Plenty of work is carried out at sub centers also :

1. ARS, Gangavathi, Karnataka : under AICRP on saline water

2.....

..

Thanks

Dr Rajakumar , I agree with your comments .  We are not talking about the saline irrigation . Quality of saline water is different than the  normal water. how the quality of irrigation water( Preferably ground water ) across acid soil zone to basalt zone to alluvial soil zone , are different to each other , and how do they inflict the crop quality plus yield off course.

I feel quality of irrigation water from underground source is strongly dependent on nature of soil. In acid soil zone water iron toxicity and aluminium as well while in salt affected areas water is saline. In acid soil zone such acidic water is a boon to some crops like Khasi mandarin, pineapple, tea etc...large number of crops including quality. 

Anoop Sir,

As you said, the topic of discussion is not on saline water,  the intention of the question posed here is on behavior of quality of irrigation water  across acid soil and zone to basalt zone.  Is that right?

Ans,:

Normal water tries to pull the pH to neutral from either side.

EC will come to normal, if water is used at optimum.

Dissolved salts are normal, hence no deleterious can be expected.

If it only contains more than critical levels of all those parameters I said earlier, will have negative effect on soil. and crop.  I have given some examples above.

This work has been done at the centers said above in previous answer

Coming to the 'Ground waters for irrigation' 

In acid soil zones, the pH of ground water will be below 6.5, hence there will not be much change in the said parameter.

In basalt zone where Ca, Mg, Na and K cations and CO3, HCO3, Cl anions are more in ground waters, will add to soil on irrigation. Hence buildup of these may be seen if they are not leached down .

If irrigation water contains more nitrogen then Nitrogen oversupply leads to

 •Lodging with wind or heavy precipitation due to excessive growth

 •Delayed maturity    •Susceptibility to fungal diseases

 •Reduced flower production    •Poor fruit flavour

 •Low vitamin and sugar content of fruits and vegetables

It leads to blue baby disease in human. and etc.,

Other parameters will also have influencing nature on quality of crops.

Thanks

Dr Rajakumar please throw some light on the contribution of nutrients like P,K,Fe, Mn, Zn which we should take into account while nutrient budgeting of crop so that judicious use of both soil and water could be made.

Yes Dr Rajakumar , we have chosen to concentrate on quality of non-saline/sodic irrigation water,  how its composition affects the checks and balances  of different nutrient across different crops , the least debated issue. I am enclosing one PDF dedicating the evaluation of irrigation water quality for citrus. Dr Deka , I agree with you quality of irrigation water comensurates with  the quality of soil , unless otherwise. I think , Dr Rajakumar made a significant comment in this regard.

Can any one of you throw some light, why irrigation water is acidic in nature  in acid soil areas and saline in nature in salt affected soil areas. While it is just neutral in normal soil areas.

I endorse Dr. Anoop Kumar's view point that our classification criteria are not so much detailed in which soil texture and drainage are addressed. We still need so much detail now.

Just in response to Sikha Deka query, I will add that pH of water depends upon on the type and quantity of dissolved salts. A water having very less salts (a few ppm) is always very close to natural water which is neutral. Water from acidic soils have Al and Fe salts while from alkaline soils it has Na, Ca and Mg that make the water acidic or alkaline respectively. 

I agree with the view of Nazir.

Nice information , you attached Dr Srivastava about the amount of micronutrients added to wheat-rice cropping system on alluvial plains . Don't you think , this amount of nutrients will vary according to crop water requirement or number irrigations given in crop annual cycle . Off course , perennial crops will be much benefitted with such attempt compared annual crops .

Friends how many of you think crop quality and irrigation water quality are interrelated and why so.

Dr. Singh, If the water is categorized as normal having EC, SAR and RSC within limits, with no heavy metal and pathogen infestation, then it will not affect crop quality if nutrition is not a problem in the soil. If, soil is deficient in any nutrient and water contains that nutrient it will improve crop quality. However, if the water is saline, sodic or saline sodic or contain contaminants, it will definitely affect crop quality negatively. Hence, all the factors are relative and are to be seen as packages of conditions.

 Dr Srivastava,

Good reading in the attached pdf's...thank you.

I have seen some previous references to Calcium and it's importance in leaching Sodium from soils, particularly in irrigated arid and semi arid lands.

The below article authored by Robert Norton, Grain Research and Development Corporation, Australia warrants a read.

For water and soil we should be focussing a little more on available Calcium.

http://www.grdc.com.au/Research-and-Development/GRDC-Update-Papers/2013/02/Focus-on-calcium-Its-role-in-crop-production

Thanks to share of an important question, that the effect of water quality have to do with texture of soil in which the plant grows where consists of the soil solution which benefits the plant thus production may increase if you use good soil with low-quality water, and here I do not mean salt water because quickly affect plant even in good soils.

Apart from its composition, determination of suitability of specific water requires that specifications of conditions of its use (soil, climate, crops, etc.), irriga- tion, and other management practices be followed. Because of inherent problems in integrating the effects of the above factors, it is difficult to develop rigid standards for universal use. Therefore, broad guidelines for assessing suitability of irrigation waters have been suggested from time to time for average use conditions (USSL 1954; Ayers and Westcot 1985). However, it is widely acknowledged that the earlier guidelines were very conservative since these were based mainly on the response of soils rather than the crop responses under diverse field conditions. Based upon the field experiences and the results of long-term experimentation, guidelines were recommended (Table 11.12) for their wider applicability in different agro-ecological zones of India (Minhas and Gupta 1992c). Though developed for the monsoonal climate, these can also be applied to areas with seasonal rainfall. For meeting site-specific water quality objectives, factors like water quality parameters, soil texture, crop tolerances, and rainfall have been given due consideration. Some of the addendums added to these guidelines include use of gypsum for saline water having SAR > 20 and/or Mg/Ca > 3 and rich in silica; fallowing during rainy season when SAR > 20 and higher salinity waters are used in low rainfall areas; additional phosphorous application, especially when Cl/SO4 > 2.0, using canal water preferably at early growth stages, including presowing irrigation for conjunctive use with saline waters; putting 20% extra seed rate and a quick postsowing irrigation (within 2–3 days) to help bet- ter germination when ECw < ECe (0–45 cm soil at harvest of rabi crops); saline water irrigation just before the onset of monsoons to lower soil salinity and raise the antecedent soil moisture for greater salt removal by rains; use of organic materials in saline environment to improve crop yields (for soils having (i) shallow water table (within 1.5 m in kharif ), and (ii) hard subsoil layers, the next lower ECiw/alternate modes of irrigation (canal/saline) is applicable). Similarly, the guidelines for alkali waters were based upon RSC/SAR and texture of soils for varying cropping intensity and amend- ments. These were later modified by Minhas and Sharma (2006), who proposed permissible limits in terms of adj.RNa for the sustainable use of alkali waters for different rainfall regions and the cropping sequences (Table 11.13). As expected, waters with a relatively high adj.RNa could be utilized for sustained irrigation in fallow/cotton–wheat followed by millet–wheat rotations, whereas paddy– wheat seems to be the most unsustainable system, since the permissible values of adj.RNa  were just about half of the former. Similarly, the role of rainfall in enhancing the use of alkali water is also evi- dent; that is, on average, it should be possible to use water with 1.8 *adj.RNa under conditions where the annual rainfall is >600 mm compared to drier regions (550 mm, upper limit of RSC range is safe

3.  For double cropping, RSC neutralization with gypsum is essential based on the quantity of water used during rabi season; grow less-water-requiring crops during

kharif; avoid growing rice

Source:  Minhas, P.S. and Gupta, R.K., Quality of Irrigation Water—Assessment and Management, p. 123, ICAR, New Delhi, 1992c.

Note:   Textural criteria should be applicable for all soil layers down to at least 1.5 m depth.

In areas where groundwater table reaches within 1.5 m at any time of the year or a hard subsoil layer is present in the root zone, the limits of the next finer textural class should be used.

Fluorine is at times a problem and limits should be worked out.

TABLE 11.13

Permissible Limits of adj.RNa in Irrigation Water for Sustaining Yields under Different Cropping Sequences

Permissible adj.RNa for Sustainable Yields for Rainfall Zone (cm)

Cropping Sequence

60

Fallow–wheat

16

21

27

Maize/millet–wheat

14

17

23

Paddy–wheat

6

9

14

Cotton–wheat

14

20

26

Source:   Minhas, P.S. and Sharma, D.R., J. Indian Soc. Soil Sci., 54,

331–338, 2006.

.

Very useful data have been uploaded by Minhas.