A Study related to the influence of the speed of a Machine-tractor aggregate and soil moisture on plowing depth

The influence of soil moisture and operational speed of a machine-tractor aggregate on plowing depth were investigated. The study is based on a one-year field try on the territory of Chirpan Region, in the central part of Bulgaria (42°09'07"N25°20'54E). Experiments were conducted on two parcels with sizes – 1000 m length and 45 m width. The technological operation Plowing was carried out with a five-corpus turning plow, aggregated to a tractor with 200 hp at two speeds – 4.5 km/h and 6 km/h. The momentous soil moisture was measured with a soil moist meter AM-128 SOIL in different points of the experimental field before conducting the technological operation. The actual working depth received after the operation with the machine-tractor aggregate was measured using a linear meter. Based on the applied ANOVA it was established that the average values of the parameter Plowing Depth at both aggregate working speeds were statistically significant at a level p < 0.05. The correlation analysis registered strong positive relation between the Aggregate Speed and Plowing Depth (r = 0.923), as well as a strong negative correlation between the Soil Moisture and Aggregate Speed (r = -0.943), and between Soil Moisture and Plowing Depth (r = -0.860). A multivariate regression analysis was applied related to the influence of aggregate s working speed and soil moisture to keep the assigned plowing depth. Two regression models were compared (Linear and Non-linear). According to the received coefficients of determination, the Linear model (R2 = 0.968) described well the relations between the examined parameters, but the Non-linear model was more appropriate (R2 = 0.977). Taking into account the graphics describing the Non-linear regression model it was established that the assigned working depth of the machine-tractor aggregate could be kept at the moisture of 70-80% and aggregate speed of 4.5-5 km/h.