INTEGRATION OF LIQUID MANURE INTO CONSERVATION TILLAGE CORN SYSTEMS
Intensive cultivation and chemical fertilizer application resulting from traditional management practices in 
southwestern Ontario, Canada, require high energy input and cause soil loss. Four field experiments were conducted over 
three years in four mixed farms under no–tillage and minimum tillage corn (Zea mays L.) systems. The effects of fertilizer 
source and manure application timing, rate, and method on soil nutrient concentrations, corn grain yields, and groundwater 
nitrate concentrations were investigated. Three experiments included three basic treatments of fertilizer source: inorganic 
(chemical) fertilizer, liquid manure, and a combination of inorganic fertilizer and liquid manure. The other experiment 
included five treatments: pre–plant manure with and without incorporation by an aeration implement, side–dress manure with 
and without incorporation by a disc implement, and side–dress inorganic fertilizer. 
Soil samples (0–300 or 0–600 mm depth) for analysis of soil nitrate–nitrogen (NO3–N), phosphorus (P), and potassium 
(K) concentrations were taken periodically each year, including soil residual NO3–N concentrations measured in the fall after 
harvest. Weed biomass and corn grain yields were also measured. In general, higher NO3–N concentrations were observed 
in those plots where nitrogen sources had been applied shortly before soil sampling. Trends of residual NO3–N concentrations 
varied among experiments, and results were inconclusive. Two–fold higher P concentrations were observed in the manured 
plots than in the inorganically fertilized plots as a result of higher P2O5 inputs from swine manure. Farmers who apply liquid 
manure to their no–tillage cornfields should be prepared for the possibility of additional weed pressure, especially using 
pre–plant manure application or side–dressing manure without a starter fertilizer. A 6% increased or comparative corn grain 
yield was achieved using liquid manure as a fertilizer source when weeds were not a problem. Considering the reduced risk 
of P runoff and the increased yield potential, the combined treatments, including pre–plant manure with side–dress inorganic 
fertilizer and starter fertilizer with side–dress manure, are recommended.