Effects of Treated Municipal Waste Water on Growth, Fiber, Protein, and Amino Acid Content of Sorghum Grain

Experiments were conducted at Tucson, Arizona, to study effects of treated municipal waste water on growth, fiber, protein, and amino acid content of grain from sorghum (Sorghum bicolor (L.) Moench.). Sorghum grain was grown in two soil types: (i) Comoro sandy loam, and (ii) Grade silt loam. Three irrigation and fertilizer treatments were used: (i) well water plus suggested amounts of nitrogen (N), phosphorus (P), and potassium (K) (112, 35, and 1 kg/ha of N, P, and K, respectively); (ii) well water plus N, P, and K from commercial sources in amounts equal to those found in waste water (224, 73, and 140 kg/ha of N, P, and K, respectively); and (iii) waste water from an activated sludge sewage plant (224, 73, and 140 kg/ha of N, P, and K, respectively). When sorghum was grown for grain in Comoro sandy loam, average number of days from planting to maturity, leaf length, and grain yield were higher in plots that received waste water than in plots that received well water and suggested amounts of N, P, and K. Sorghum grown with waste water produced higher grain yields than when grown with synthetic waste water. The plant growth response of sorghum to waste water, when grown in Grabe silt loam, was similar to that observed when the crop was produced in Comoro sandy loam. Sorghum grain grown with all irrigation and fertilizer treatments contained similar amounts of total protein. In sandy loam soil, grain from sorghum grown with simulated waste water and waste water alone contained less cystine, glycine, and histidine than did grain produced with suggested culture. Grain grown with all treatments, in both soil types, contained similar amounts of leucine, methionine, threonine, and tyrosine. Municipal waste water may be an effective source of irrigation water and plant nutrients in the production of high yields of high quality sorghum grain for livestock feed in the irrigated areas of the southwestern U. S.