Personally, I would prefer the EC, for simple monitoring as it is much easier to measure it in the field than the more tedious laboratory based TDS method, which can give varying results for even the same sample based on variation of the sample holding time. Also it is quite easy to develop empirical relationships between the two, the TDS often being of the order of 6 times greater than the EC when EC is measured in mS/meter and TDS in mg/l. 

Hi Jenkins Macedo; It is one and only important parameter is Electrical conductivity my dear. Thanks

Wow. Sounds like one method is much easier, but what about accuracy? 

My dear James R Knaub; it is most simple and accurate method for measuring total salt concentration in irrigation waters. Thanks.

Fully agree with Sarwan! In fact in many systems it can even be upgraded to direct online monitoring with remote transmission of results.

My Dear Jenkins Macedo; SAR is not an indicator of salinity. It represent alkalinity/sodicity. Hence it is no way concern with salinity experiments. Yes here with this water you will not find any ill effect on spinach crop as you yourself is mentioning that it is salt tolerant yes it is. Go ahead if going to take spinach crop for commercial production. Yes soil type should not be clayey. Thanks

Dr. Dubey, thanks for pointing that out. Yes, SAR measures the sodicity and salinity is measured by EC.

The salt balance depends on the water balance. Irrigation can cause waterlogging, and through evaporation, the water evaporates and the salt stays and becomes more concentrated, waterlogging causes salinity. Salt is left behind on the surface after evaporation because plants do not take op the salts, this leads to an accumulation of salts over the years. In areas with shallow water tables, saline water also comes to the surface by capillary rise. To prevent salanization, extra water is put on the land to

flush the salts away. 

http://www.bebuffered.com/downloads/conjunctivewatermanagement_usingthefullpotential_vandenborn.pdf

Dear Prof. Krishnan Umachnadran ji; Yes you are right at most of the time main culprit for salinity is excess presence of water in soil column. Hence good water management practices always keep salinity problems away. But once it arises it is much more difficult to reclaim in comparison of alkali/sodic soil. Thanks

@ Sarwan, rightly said , Water management is one of the key factor in Agriculture.

Economic efficiency is achieved when the marginal benefit of water application (including groundwater replenishment) equals its cost (including environmental impacts), and when values are equated across uses of water (factoring in the cost of transporting water from one setting to another). Efficiency of agricultural water use is achieved by various means, including the adoption of irrigation technology, fallowing land and crop shifting.

Hey Guys,

Thanks for the energetic exchanges. It is well established that in order to maintain a healthy soil for crop water use efficiency; that is, one that is not salinized or sodic, a steady-state condition has to be present. The amount of salt or total dissolved salts inflow through the system has to be equaled to outflow; that is, what is going out of the system. Soil salinization can be influenced by the evapoconcentration process (Hanson et al. 2006).

For the efficiency aspect factored in by Dr. K. Umachandran, we employed several monitoring measures to determine the acceptable moisture content of the soil before each irrigation event. We monitored daily precipitation, installed an evaporation pan ( E pan) to monitor daily evaporation rate and use that to calculate evapotranspiration factoring in the reference crop coefficient (K Pan) (water spinach, so we used that the  K pan for spinach) using equation 1:

• ETo = K pan x E pan     Equation [1]

where ETo is evapotranspiration, K pan is the reference crop coefficient and E pan is the daily evaporation rate (determined from the evaporation pan).

In the event of precipitation, we estimated recharge by calculating the water balance at the reference field by measuring precipitation installed at the weather station with a rain gauge and used the following equation to estimate recharge from precipitation to determine if irrigation should or should not be carried out:

• CR = P - ETo                  Equation [2]

Where CR is the computed recharge, P is the measured precipitation (mm) and ETo is the  daily evapotranspiration calculated from equation 1.

Further more, we measured soil moisture on a daily basis to determine the % of available soil moisture content prior to scheduling irrigation. The weather station also measure temperature (air and soil) RH and dew point.

All these measures were put in place to make sure that irrigation water use was effective and to limit over or under irrigating the experimental unit with the crop water requirement.

For the preference between EC and TDS, il is clear that EC is a faster measurement which would provide the condutivity of the soil for a daily check up.  However, TDS would quatify the disolved solid content of the soil. Both analysis would give en indication of how much salt may be present, but they are not specific in terms of the composition of the different type of salts that can be found in the soil.  if the idea is to have a quick information about the salt condition of the soil, then EC is the fast way to go, but I would from time to time do a TDS analysis as a complement of information.  Now, an information that would provide a basis for remediation (if there is a need) would require a composition analysis that would offer the quantity of each salt that may be present.

I hope this can help.  Thank you.

Sure. It helped. We did measure both EC and TDS at the field from irrigation water use (ECiw) and also at the potential root depth of the experimental crop (0-30cm) to determined the concentrated salt at the root zone (ECe). A detailed chemical analysis of the irrigated water also points to further understand the chemical composition. Nevertheless, the content of the dissolved salts and or EC changed over time and space across the experimental units, but significantly below levels that would trigger salinity (EC & TDS) or sodicity (SAR), etc. But, you are right. Thanks.

Macedo:

This debate is very interesting.

Thank you!

Thanks Andrea, not really a debate. Just interesting exchange relevant to the field. Best

My Dear I like your interest in the field of salinity. Keep it up. I also spent about 34 years in this field. Love it. Regards

Hi Ashwani,

The chemical analysis of water sample collected looked into some of the parameters you listed. Thanks

I would say nitrate and phosphate are two big problems for groundwater contamination from the agricultural areas.

Hello Yue, thanks for the input. Very well said that the overall groundwater quality is essential and the concentration of nitrate and phosphate are key elements to explored. However, we are more interested in groundwater quality suitable for agriculture.

Investigation of Groundwater Quality and Its Suitability to Irrigated  Agriculture in Coimbatore District,Tamil Nadu, India

SAR= Na/ (Ca+Mg)/2 (where, all ionic concentrations are expressed in milli equivalents per litre.) There were no much variations in SAR concentration between 2005 and 2008. In 2005,in pre­ monsoon period SAR values are >26 in north eastern portion and the lowest ratio locations of

Hi Krishan,

I did download the paper posted. Thanks.

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http://indiatoday.intoday.in/story/india-today-best-city-awards-2014-venkaiah-naidu-aroon-purie-shekhar-gupta-chennai/1/403196.html

Dear All,

Dear Macedo,

Many thanks for valuable information exchange on the issue; I could use these information even for my lecturers. This question is also very interesting for our arid country. We use mostly EC as it is much easier to measure it using conductometer and water hardness (WH). WH is very important parameter because it is frequently leads to plugging and blocking of sprinkler.

With best wishes

Bakhtiyor

Well taken Bakhtiyor Karimov .

Bakhtiyor Karimov @@@@@@@@@@