Identification and Management of New Mexico's Saline and Sodium Affected Soils

Eleven Master Gardener presentations were made regarding soil salinity for Chaves, Colfax, Dona Ana, Eddy, Lea, Los Alamos, Otero, Sandoval, Santa Fe, Socorro, and Valencia counties. Additional lectures were given in El Paso (Pecan growers) and Albuquerque (Compost Operators) regarding soil salinity and sodium affected soils. Pre- and post-tests of 10 questions were given to most of the counties. Test scores increased from an average pretest score of 72% right to 88% after the lecture. The best improvement in test scores came from correctly describing salinity and plant response. Phone conversations with clients that had saline or sodic soils were a testament to the value of adding a calcium source (gypsum) and excess water. Twelve phone-in clients were advised to test their irrigation water if they were on wells or avoid using softened water if using municipal water.

Reclaiming sodic soils with gypsum was a difficult process for many clients submitting samples from the Rio Grande Basin. Some value-marts carried gypsum but not all these types of stores carried this source of calcium. Fertilizer dealers in agricultural areas carried limited supplies. Other areas that needed gypsum were too far from a dealer or other source to effectively address sodic soil concerns. One client stated that he would consider the cost of bringing gypsum in from a southwest Texas mine if more than one client or a fertilizer company would be interested in sharing the cost. Based on phone conversations, approximately 25% of the clientele tried to find a source of gypsum to address sodic soils. In light of the lack of gypsum, clientele were advised to substitute 1 pound of elemental sulfur for every 5 pounds of recommended gypsum if their soil contained free lime. Clients stated that elemental sulfur was easier to find than gypsum. However, not all clientele had sufficient soil lime to accomplish the substitution.

Before and after test questions regarding salinity indicated a 75% improvement in understanding why soil testing is important for identifying saline and sodic soils. Eighty percent of those workshop attendees who had never submitted soil samples indicated they would have their soil tested for salinity.

The NM Vine and Wine Society Conference budgeted an hour of time to review soil testing and water analysis. Several vineyard owners submitted samples over the next few months and called with questions. Two alfalfa growers were contacted after their soils were found to be saline. One was in the zone where a non-dormant, salt tolerant variety of alfalfa could be grown. Client stated that the crop is doing better than before the new variety.

Salinity and its management was also incorporated into the Master Gardener program. Previous experience shows that it may take two years for clients to begin adapting salinity control practices.

Only one client re-submitted a soil sample to determine if amending and leaching did the job to lower the sodium and total salt content of the soil. This person had a small parcel of land where the soil could be made into basins and filled with water from a hose and allowed to percolate. Most clients where that recommendation was put into practice have not resubmitted a sample.

The Compost Operator Certification Course is another workshop where salinity and sodium concerns are shared with those responsible for making compost in their community (mostly municipal solid waste facilities but also private and county composters). Problematic composts are usually diluted with low salt content compost and additives are kept out of the pile to maintain low salt content compost. Eighty percent of the compost operators are able to keep their compost to less than 10 mmhos/cm.

Eighteen percent of the 826 in-state soil samples submitted to NMSU SWAT lab for salinity analysis were considered sodium affected and twenty percent were saline. The highest percentage of samples that were sodic came from Dona Ana County (37%) and Socorro County (36%), followed by San Juan (33%, Union (29%), Luna (26%), Valencia (24%), McKinley (21%), Bernalillo (20%), Eddy (20%), Hidalgo (19%), Sandoval (17%). Grant, Otero, Quay, Rio Arriba, Santa Fe, and Sierra counties had 10% or less sodic soils reported. For those clients contacted, gypsum was not readily available for large scale application. However, home and garden centers did carry the small containers for small plots. Pecan growers are using gypsum on land that has been identified as sodic.

The majority of saline soils were also sodic but not all. Leaching is the best management practice for those with good drainage. One Valencia County client with a high water table reported that increasing the soil depth with extra soil and establishing a gravel drain with perforated pipe allowed him to have a better garden. Eddy County reported the highest percentage of saline soils with 47% followed by Curry County (41%), Otero (43%), San Juan 33%), Socorro (32%), Bernalillo (28%), Taos (27%), Valencia (24%), Chaves (23%), Colfax (22%), Dona Ana and McKinley (21%), Luna (16%), Santa Fe (15%), Union (14%), and the rest with less than 10%.

Most clients reported using heavy applications of manure or compost, often times over several years. Some of the field soils had been receiving green water from dairy farms and had elevated salinity. Clients were instructed to base applications on nutrient and salt content after having the material tested. Those that did were still able to apply organic amendments but at a reduced rate to strike a balance with nutrition and salinity.