Irrigation of Corn with Simulated Municipal Sewage Effluent

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Abstract
A field study was conducted to evaluate the effects of applying 25, 50, 100, and 200 cm of simulated municipal sewage effluent to corn (Zea mays L.) grown on a tile‐drained loam soil. A soil water balance was determined by measuring rainfall, irrigation, evapotranspiration, and tile flow. Deep percolation losses were estimated by difference. The effects of these annual loading rates were determined by measuring corn silage and grain yields. Silage yields were maximized at the 50‐cm loading rate, however, the grain yields were maximized at the 200‐ and 100‐cm rates in 1973 and 1974, respectively. The fate of applied nutrients was determined by measuring losses through drainage water, uptake by the corn, and changes within the soil profile. Nitrogen losses in the drainage water ranged from 0.1 to 18 kg ha−1 year−1 with maximum weekly losses of 3 kg/ha at the 100‐ and 200‐cm loading rates. The P concentration in drainage water was higher than expected due to an apparent short circuiting of the effluent through sand smears; however, the maximum loss was only 0.6 kg ha−1 year−1. Potassium losses ranged from 0.2 to 8.5 kg ha−1 year−1. Nitrogen recovery through plant uptake at the 25‐, 50‐, and 100‐cm loading rates exceeded 40% of the N applied through effluent and starter fertilizer when the corn was harvested as silage. Nitrogen uptake in the grain at these loading rates exceeded 50% in 1973, but was much lower in 1974. When the entire plant was harvested, P uptake at the 25‐ and 50‐cm loading rates exceeded the P applied; however, at the 100‐ and 200‐cm rates or when only the grain was harvested, P uptake was less indicating a gradual buildup in the soil. The K uptake exceeded 90% when the corn was harvested as silage, but was < 40% if only the grain was removed. The distribution of NO3 and Cl and the Cl/NO3 ratios suggested that much of the unrecovered N was denitrified. Measurements of exchangeable K and Na indicated that if effluents which are low in K and high in Na are to be renovated through land disposal supplemental K must be applied.

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