In a paper by the Huazhong Agricultural University, the factors that influence the fiber yield of hemp plants are explored.
The abstract reads: "Hemp is one of the most important green (i.e., environmentally sustainable) fibers. Planting density, nitrogen (N), phosphorus (P) and potassium (K) significantly affect the yield of hemp fiber. By optimizing the above main four cultivation factors is an important way to achieve sustainable development of high-fiber yield hemp crops. In this study, the effects of individual factors and factor × factor interactions on the yield of hemp fiber over two trial years were investigated by the central composite design with four factors, namely planting density, nitrogen application, phosphorus application, and potassium application rate. The influences of these four test factors on the yield of hemp fibers were in the order nitrogen fertilizer (X2) > planting density (X1) > potassium fertilizer (X4) > phosphate fertilizer (X3). To obtain yields of hemp with high-quality fiber greater than 2200 kg ha−1, the optimal range of cultivation conditions were planting density 329,950–371,500 plants/ha, nitrogen application rate 251–273 kg ha−1, phosphorus application rate 85–95 kg ha−1, and potassium application rate 212–238 kg ha−1. This study can provide important technical and theoretical support for the high-yield cultivation of hemp fiber into the future."