A GENERAL-APPROACH TO DETERMINE THE EFFECT OF ACCURACY OF SOWING TECHNIQUE ON YIELD PER AREA

Caused by nonperfect seed placement accuracy of sowing machines as wel l as by many other abiotic and biotic factors the resulting plant stan ds exhibit nonregular plant distributions. Based on several simplifyin g assumptions a stochastic approach provides a quantitative determinat ion of the effects of accuracy of sowing technique on yield per area. In this approach, two random variables are assigned to each individual plant: single plant yield E and single plant area A, which is calcula ted in this paper by the construction and quadrature of the so-called Thiessen-polygons. The yield per area F is calculated as the expectati on of the ratio E/A. By assuming a deterministic mathematical relation ship between E and A, the calculation of F reduces to the calculation of the expectation of a function of only one random variable A. A simp le approximation with sufficient accuracy for many applications only d epends on the mean and on the variance of the areas of the individual plants. For demonstration purposes, the theoretical approaches and res ults have been finally applied to three data sets for drilled seeds of winter oilseed rape (plant density: 60 plants/m(2) and distance betwe en rows: 10 cm). These data sets exhibit different accuracies of the l ongitudinal distributions within rows which have been quantitatively m easured by the coefficient of variation for the distances between plan ts within rows: Yield depression increases with an increasing variabil ity of plant distances within rows.