INTEGRATION OF LIQUID MANURE INTO CONSERVATION TILLAGE CORN SYSTEMS

Abstract

Intensive cultivation and chemical fertilizer application resulting from traditional management practices insouthwestern Ontario, Canada, require high energy input and cause soil loss. Four field experiments were conducted overthree years in four mixed farms under notillage and minimum tillage corn (Zea mays L.) systems. The effects of fertilizersource and manure application timing, rate, and method on soil nutrient concentrations, corn grain yields, and groundwaternitrate 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 experimentincluded five treatments: preplant manure with and without incorporation by an aeration implement, sidedress manure withand without incorporation by a disc implement, and sidedress inorganic fertilizer.<br><br>Soil samples (0300 or 0600 mm depth) for analysis of soil nitratenitrogen (NO3N), phosphorus (P), and potassium(K) concentrations were taken periodically each year, including soil residual NO3N concentrations measured in the fall afterharvest. Weed biomass and corn grain yields were also measured. In general, higher NO3N concentrations were observedin those plots where nitrogen sources had been applied shortly before soil sampling. Trends of residual NO3N concentrationsvaried among experiments, and results were inconclusive. Twofold higher P concentrations were observed in the manuredplots than in the inorganically fertilized plots as a result of higher P2O5 inputs from swine manure. Farmers who apply liquidmanure to their notillage cornfields should be prepared for the possibility of additional weed pressure, especially usingpreplant manure application or sidedressing manure without a starter fertilizer. A 6% increased or comparative corn grainyield was achieved using liquid manure as a fertilizer source when weeds were not a problem. Considering the reduced riskof P runoff and the increased yield potential, the combined treatments, including preplant manure with sidedress inorganicfertilizer and starter fertilizer with sidedress manure, are recommended.