Development of a windrower for dual-purpose hemp (cannabis sativa)

Hemp (cannabis sativa) is a dual-purpose crop; the seed and the fibre have to be harvested separately. A hemp windrower was developed to create two separate windrows, one for seed-heads and one for fibre-stalks. The hemp windrower was a modified version of a commercial self-propelled windrower. The original header-lifting mechanism was modified, which increased the maximum header lifting height from 1.08 to 1.58 m for cutting seed-heads. To deliver the seed-head windrow from the cutting height to the ground, a foldable sliding conveying system was designed and attached to the windrower header. When conveying seed-heads, the slide should be inclined at an angle which is greater than the sliding-friction angle of the hemp (25° in the studied case). The hemp windrower was tested in the field and results showed that it fulfilled the design objectives. Specific research was conducted to investigate the mechanical impact on the seed-head during windrow delivery processes. A lower draper speed resulted in a reduced mechanical impact on the seed-head, which may reduce the potential seed loss associated with shattering. The relationship between seed-head length and the plant height was established for selecting the cutting height for seed-head windrowing. From the relationship, the cutting heights for the hemp fields having an average total height of 1.71 and 1.56 m were estimated as 1.40 and 1.29 m, respectively. These cutting heights minimised the percentage of seed in the fibre-stalk windrow and the presence of fibre-stalk in the seed-head windrow.