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Irrigation of Forages with Rendering Plant Wastewater: Forage Yield and Nitrogen Dynamics
Author(s) -
Bole J. B.,
Gould W. D.
Publication year - 1985
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1985.00472425001400010025x
Subject(s) - phalaris arundinacea , wastewater , agronomy , irrigation , nutrient , environmental science , fertilizer , medicago sativa , forage , biology , environmental engineering , wetland , ecology
Wastewater from an animal by‐product rendering plant containing N, P, and biochemical oxygen demand (BOD) at greater than 500, 60, and 500 mg L −1 , respectively, was applied to irrigated forages to study the suitability of forage species and the fate of applied nutrients. Applications of 10 and 20 cm yr −1 supplied the nutrients at rates in excess of crop requirements. The treatments were compared with irrigation water and with water supplemented with either fertilizer N and P or C as sugar at rates similar to those in the wastewater. Reed canarygrass ( Phalaris arundinacea L.) yields were doubled by the application of 10 cm yr −1 of wastewater as compared with irrigation water treatments, but alfalfa ( Medicago sativa L.) yields were not significantly affected. Doubling the wastewater application rate or adding comparable rates of N and P fertilizer did not further increase yields. The wastewater‐irrigated alfalfa contained NO 3 − ‐N levels of 1500 to 1600 mg kg −1 plant material, while reed canarygrass contained about 3000 to 3400. Both these levels would be considered potentially unsafe for livestock feed. There was an accumulation of soil NO 3 − ‐N levels of up to 30 to 40 mg kg −1 soil throughout the surface 120 cm of soil after 5 yr of irrigation with 10 cm yr −1 of wastewater and two to three times this level with 20 cm yr −1 of wastewater. Higher levels of NO 3 − ‐N were observed in the soil when N was applied as fertilizer. Soil NH 4 + ‐N levels were not greatly affected. A nitrogen balance over 6 yr at the high application rate suggested plant uptake, soil NO 3 − ‐N, and losses accounted for 30, 25, and 45% of wastewater N and 29, 39, and 32% of fertilizer N. A 1‐yr 15 N balance after 3 yr of irrigation indicated uptake, soil NO 3 − ‐N, and unaccounted‐for N was about 10, 19, and 71% for wastewater and 15, 33, and 52% for fertilizer N. The greater losses of wastewater N compared with fertilizer N were attributed to enhanced denitrification due to oxidizable C in the wastewater. Attempts to simulate this effect with C as sugar were not effective.