Performance of thresher using two types of knives in compost production for forest nurseries

Plant residue of forest nurseries is among the best available raw materials for producing compost to amend and strengthen forest nurseries soil. The size of raw materials has a major effect on shortening the time of composting as well as on increasing its quality. The mechanism, availability and working convenience with the threshers in different site conditions to convert plant residue into small pieces that are suitable for composting shows the suitability of threshers for such tasks. In this research, two kinds of knives with flat and sharp edges applicable to threshers were designed and applied to study the crushing quality of common plant residues. Treatments included pine cones, branches of deciduous, pine branches, coarse plants, herbs and pine needles. The performance of both flat and sharp edge knives were evaluated in a design with three repetitions. For most samples, the results showed that performance of the sharp knife exceeded that of flat knife. The crushing quality of different materials in different dimensions were significantly different at the α = 0.01 level. The time performance of sharp knife with an average mean 0.069290 kg per second was far better than flat knife with an average mean of 0.035661 kg per second. Sharp knife performed best for grinding pine cones with an average 0.01321 kg per second. Generally, more uniform and brittle plant residue can be crushed in a shorter time. Finally, the efficiency of threshers system with the designed knife is acceptable and suitable for the crushing of plant residue.