Impact of Reverse Osmosis Waste Water On Soil Quality in a Semi-Arid Soil.

Soil quality indicators (SQI) were assessed in two 0.2 ha fields in northern New Mexico. Forty geo-referenced soil samples were collected, each from a field that had been cleared of native vegetation, tilled, and sowed with a dry pasture mix (Hycrest Crested Wheatgrass, Intermediate Wheatgrass, Lincoln Smooth Brome Grass, Russian Wild Rye, Dryland Alfalfa, and Pauite Orchard Grass) treated with RO reject waste water (electrical conductivity 2.73 dS/m) through 15.2 cm gated irrigation pipe for two consecutive years (WW) and an adjacent field of native vegetation that received  only rainfall (CO). SQI included mean weight diameter of the dry aggregates (MWD), dry aggregates > 2 mm (D > 2 mm), dry aggregates < 0.25 mm (D < 0.25 mm), wet aggregate stability, permanganate oxidizable carbon (POXC), soil organic carbon (SOC), EC, pH, sand, silt and clay contents, and chemical parameters (NO₃-N, P, Ca, Mg, Na, Zn, Fe, Mn and Cu). The WW field had significantly higher EC, ranging from 0.37 – 6.56 dS/m, while the EC of the CO field ranged from 0.04 – 2.65 dS/m. Apart from salinity problem, WW field generally had more favorable SQI than the CO field. SQI that proved more favorable in the WW field included MWD, D>2 mm, D<0.25 mm, POXC, K, Ca, Mg and Zn perhaps due to the pasture mix and irrigation. Measurements were slightly less variable in the WW compared to the CO field. However, the SQI influenced the variability more than the treatment effect. The most variable measurements were EC, D > 2 mm, NO₃-N, P and Na, while the least variable measurements were pH, POXC and sand content. Although the WW field had more favorable SQI than the CO field, the increased EC will be a major constraint to crop production unless a good salinity management plan is put in place.