EVALUATION OF DIFFERENT TECHNIQUES FOR LIQUID MANURE APPLICATION ON GRASSLAND

Four different techniques for applying liquid manure on grassland were evaluated in two grass fields to examine the impact of each technique on the environment and agronomic response. The techniques studied were injection (IJ), sub–canopy banding using a sleighfoot (SF), incorporation using an aerator (AR), and surface banding using a dribble bar (DB). The environmental impact of each technique on the odor concentration and ammonia volatilization was assessed, and agronomic responses were measured by grass damage and grass yield. Among the four techniques, the IJ resulted in lower ammonia and odor concentrations on the land surface immediately after manure application. However, its odor concentration was significantly higher than the background value because of the manure pooling on the soil surface. The injector had the potential to cause grass damage associated with its soil cutting action. However, an over 100% increase in grass yield was achieved when the injection was used, in comparison to the control plot. This increase in yield can be attributed to the efficiency of the injection in placing the manure in the soil where the nutrients present in the manure can be made readily available. The availability of nutrients compensated the loss of yield associated with the cutting action of the injector. The yield response for the SF, AR, and DB was comparable to that of the IJ, except for the SF in one field having a lower yield owing to the grass damage caused by raking during the operation. The AR technique was the only one, which showed yield response at the earlier harvest. The DB and AR techniques resulted in the highest and second highest level, respectively, of ammonia concentration from the soil surface.