Comparison of Surface Water or Treated Municipal Wastewater Irrigation on Alfalfa Establishment, Soil Fertility, and Soil Microbial Conditions

Water scarcity for agricultural irrigation is increasing globally while generation of treated municipal wastewater (TWW) is increasing due to urban expansion. Municipalities seek uses for their TWW, which is safe to apply to forage crops. Alfalfa (Medicago sativa) is the most important forage crop worldwide being adapted to a wide range of environmental factors, including irrigation with low quality water. A strip plot study with four replications at New Mexico State University’s Rex E. Kirksey Agricultural Science Center at Tucumcari, NM USA, compared the effects of surface water (SW) and TWW on alfalfa establishment and soil fertility and microbial growth. Alfalfa established equally well when irrigated with equal amounts of TWW or SW. After one year, the application of TWW increased soil P and plant N and P more so than SW. Most microbial soil health indicators were positively increased by alfalfa establishment in virgin soil; however, the effect was greater with TWW compared with SW (1147, 1184, 1961, and 4991 nmol g−1 for total microbial biomass of soil irrigated with SW and TWW at seeding and after one year, respectively, LSD0.05 = 710). Thus, TWW irrigation could reduce applied fertilizer P to meet alfalfa’s requirement and increase soil health compared with SW