G. Hristova*, P. Veleva
Department of Agricultural Engineering, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria
(Manuscript received 30 August 2021; accepted for publication 4 March 2022)
Abstract. The present research was conducted to investigate the influence of annual precipitation on the depth of soil tillage with a disc harrow and to monitor their effect on the productivity of wheat grown by conventional technology. The study is based on a perennial field experiment on chernozem soils in the land of the Chirpan region located in central Bulgaria. Annual precipitation data were taken from the local GeoScan Meteo station. Data on the depth of disking, applied twice or three times during the monitored years according to climatic conditions, were measured with a linear meter. A moderate correlation (r = 0.568; 0.356; 0.383) between the annual precipitation and the depth of disking during the three agricultural years was found. Four regression models (Linear, Inverse, Quadratic, and Compound) describing the relation between them have been developed. From the obtained models’ coefficients of determination (R2) for the three examined years the Quadratic model best expresses the relation between the investigated parameters (R2 = 0.172; 0.216 и 0.186). Statistically significant differences between the average wheat yield in the first and third agricultural year, as well as between the second and third agricultural year were obtained. It was found (R2 = 0.362) that the depth of disking affects the productivity of wheat grown by conventional technology about 36.2%.