Pocket Injection of Liquid Manure in Forage Fields.

Injection of liquid manure has been recognized as an effective practice to minimise adverse environmental impacts, such as odour emission, nutrient volatilization and runoff. However, injection in forage fields using tillage tools, such as sweeps, discs, and chisels may cause severe damage to the crops due to the high soil disturbance of these tillage tools. In this study, a low soil disturbance injection method, named pocket injection, was proposed and then a pocket manure injector was developed for forage or no-till fields. The two major components of a pocket manure injector are an aerator and a pulsing meter. The working principle is that the rolling tines of the aerator create pockets (voids) in the soil, and the pulsing meter delivers pulses of liquid manure with each pulse being placed into a pocket. Three prototypes of the pulsing meter were designed, fabricated, and tested in laboratory conditions. The final prototype of the pulsing meter was adapted onto the existing AerWay aerator to form a field pocket manure injector. The pocket injector was tested in two forage fields (clay loam and sandy soil). Measurements were performed on pocket characteristics and manure distribution in the soil around a pocket. Results showed that on average, the rolling tines of the AerWay created 146,199 pockets/ha in the clay loam and 125,313 pockets/ha in the sandy soil, under a common lateral tine spacing of 0.19 m. The mean pocket volumes varied between 69 and 303 ml in the clay loam soil and between 88 and 197 ml in the sandy soil, depending on the injection depth and the tine shaft angle. The information on the number of the pocket per hectare and the pocket volume can be used to determine the potential application rate of a pocket injector. Overall, greater depth and larger shaft angle resulted in larger pocket volume, and therefore, higher manure application rates. The field tests also showed that the pulsing meter had the desired function of providing a pulsing flow of liquid. Following the pocket injection, the vertical manure distribution around a pocket in the clay loam (wet) was found to be limited within the injection depth, and the lateral distribution varied from 55 to 100 mm. The vertical manure distribution in the sandy soil was 30% greater than the injection depth and the lateral distribution varied from 90 to 150 mm.