Land Application: Agricultural Crop Responses

The value of sewage sludge and biosolids has been recognized for decades. With the advent of sewage treatment in the 1880s, some limited land application occurred. When the activated sludge process was initiated, the use of sludge as organic fertilizer material became of interest. Although for centuries human waste has been applied to soils as a fertilizer for crops, very little has been documented about the benefit of biosolids in agriculture. Bartow and Hatfield reported that when 1 ton per acre of activated sludge was used, the yield of lettuce increased by 50% and radishes by 300%, compared to check plots. Yields were statistically significantly higher than the control in 1970 and 1973, even with lower rates of application. In other years, although there were differences because of the variation in the data, the results were not statistically significant. Considerable research has been carried out on the application of biosolids to forestland.