The results of laboratory experiments to determine the effort of pulling sunflower seeds from the head receptacles of some hybrids

The practicability of conducting laboratory experiments to determine the effort of pulling oilseeds from the sunflower head with the integration of the results obtained in the form of empirical quantities or converted coefficients into mechanical and mathematical expressions is substantiated. The reasons for harvesting sunflower seeds at the latest date with a moisture content of oilseeds of 5.5–7.0 % are given. A description of the design and the principle of use of the laboratory installation is presented. A methodology for conducting experiments on four hybrids Gorfield, Immi, Status and Cherry at a moisture content of oilseeds of 5.5–6.0 % is compiled, characteristics of anthodia and oilseeds are given. Based on the data obtained, experimental dependences were constructed showing a change in the pulling force Fpull depending on the location of the oilseeds. Thus, in the Gorfield, Cherry and Status hybrids, the maximum pulling force was set in the central zone of the head and amounted to 3.285, 2.511 and 1.303 N subsequently. The minimum pulling forces of the Gorfield and Status varieties were set in the middle and pericentral zones and amounted to 1.124 and 0.578 N, respectively. In the peripheral zone, these values increase slightly to 1.247 and 0.985 N, respectively. In the Cherry hybrid, the F value in the middle (0.919 N) and peripheral (0.916 N) zones was almost equal. In the Immi hybrid, the highest value was observed in the peripheral zone (0.920 N), the minimum in the central zone (0.213 N). Quadratic polynomial equations describing the dependences and confidence coefficients of the approximation are obtained. The pulling force of hollow-grain achenes and oilseeds located near empty nests of bracts is determined.