Dr. Calvin Trostle, Professor & Extension Agronomist, Lubbock, (806) 723-8432, email@example.com
In a previous Row Crops Newsletter in 2016 I wrote on this topic. In dry years I receive a few more inquiries about salinity across the western part of the state. This is due to potential salt accumulation from irrigation waters without flushing rainfall.
Several recent questions are addressed here in terms of salt issues affecting potential cover crops, salt removal from soils, and winter small grains suitability.
Previously I noted the primary resource Texas A&M AgriLife uses, “Irrigation Water Quality Standards and Salinity Management Strategies,”
http://soiltesting.tamu.edu/publications/B-1667.pdf, compiled by Dr. Guy Fipps, Texas A&M AgriLife Extension biological and agricultural engineering, firstname.lastname@example.org An additional irrigation and salinity resource faculty in the Texas A&M agriculture program is Dr. Dana Porter, Extension irrigation engineer, Lubbock, email@example.com
The Texas A&M AgriLife Extension soil test lab offers salinity testing for irrigation waters and soils, see http://soiltesting.tamu.edu/webpages/forms.html Two forms are of interest. This includes the water submittal form and also the soil submittal form (Option #4 is the analysis to require for a detailed soil salinity test).
Here is a brief answer to the above three issues that have been raised since the November 2016 newsletter.
• Cover crops and salinity tolerance. The document above does not give salt tolerances for most species found in a cover crop mix. For winter cover crops, you typically need at least one component species that produces significant biomass. That choice would be barley. Other cover crop species that are minor components of the mix may not contribute that much. I am not sure of salt tolerances of popular winter cover crop legumes like hairy vetch or Austrian winter pea. I don’t expect them to be any better than average. Ask your seed supplier about salt tolerances if you are planting a cover crop mix where salinity may be an issue.
• Removal of salts from a field. It is a popular thought—planting a crop species that has high salt tolerance and salt uptake (accumulation) then harvest and remove from the field. This concept in theory is sound but the reality is that you don’t remove enough salts relative to the total amount of salts in the field to make much difference. Flushing with irrigation if available may be a better strategy. If you have a field that soil tests 2,000 ppm Total Dissolved Soils, that is 4,000 lbs. of salt in the top 6”. There is likely a lot more deeper in the soil. If you harvest 5 tons of dry matter from a crop that is 3% salt constituents, you have removed just 300 lbs. That is likely an optimistic scenario. Information on what species are salt accumulators for this purpose is scarce. Also, is the biomass removed useful for any other purpose, like forage? If not, then this may further not be a feasible strategy.
• Salinity and small grains. Barley is the standard for cool-season plants that have salt tolerance. According to the above guide, the salt tolerance is significantly higher than wheat, barley, rye or oats. Common grain or forage barleys like TAMbar 500 & 501 are salt tolerant. The Arizona Crop Improvement Association, https://www.arizonacrop.org/, markets ‘Solar’ barley, which is a spring type that grows OK in fall plantings in the Texas High Plains south of Amarillo and in far west Texas toward El Paso. AgriLife testing a precursor called ‘Solum’ which at our Pecos field station grew in the saltiest field conditions when even TAMbar lines would not. Solar has even higher salt tolerance. No Texas seed dealer carries Solar, but seed is available in Arizona. Contact ACIA for referral to suppliers for Solar seed. If you are struggling with high salt issues, I recommend you consider trying a small amount of Solar to see how it performs.