Regression Equations for Predicting the Effect of Tine Width on Draught and Soil

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Abstract: Experiments were conducted in an indoor soil bin filled with sandy clay loam soil. Tests were carried out with tillage tines to study the effect tool width on soil disturbance and draught. Depth of operation was held constant at 35 mm and then at 70 mm while speed was varied at three levels of 1.0, 3.6 and 9.0 km/h. The widths of the tines tested were 10, 20, 31, 40, 51, 88, 126, 163 and 200 mm. The cone penetration resistance of the soil varied from 400 to 600 kPa. Draught was measured with a load cell while soil disturbance was measured with a profile meter and meter rule. Draught increased at a decreasing rate with tine width. Quadratic models best fitted the data points with high R2 values. The increase in draught was affected by the forward speed since higher draught values were obtained at higher speed. Results show that the parameters of soil disturbance increased with increase in tine width, except height of ridge (hr), which did not show any specific trend. The specific draught was highest (10.63 N/cm) with tine T20 while Tine T1 had the least specific draught of 5.2 N/cm.

Key words: Soil bin, tillage tines, draught, soil disturbance parameters, rake angle, forward speed, regression analysis.

1. Introduction

Draught is an important parameter for measuring and evaluating implement performance for energy requirements. Many researchers investigated draught of tillage tools [1-6]. Soil moisture content is an important factor in regard to both draught and quality of work. A dry soil requires an excessive power and also accelerates wear of the cutting edges. In USDA soil bin tests, an increase of moisture content from 9.1 to 11.7% (db) reduced the specific draught in a fine sandy loam by 15 to 35% [7]. Other pertinent factors include the degree of soil compaction, the previous tillage treatments and the type, presence or absence of cover crop

Soil profile or soil redistribution after tillage operation is important in several aspects such as incorporating manure and crop residues and protecting soil from wind and water erosion [8]. They also reported that the study of soil profile and soil redistribution by tillage has progressed slowly due to complexity, which involves many factors such as soil types and properties, types of tillage tools and their operational parameters. It was reported [9] in a study with sweeps that the ridge height and the lateral distance, increased with increasing travel speed. It also reported [10] that higher speed and larger rate angle of sweep resulted in more soil movement creating higher ridges. Also, Sharifat et al. [11] studied soil lateral movement under different soil conditions with a sweep and a furrow opener at speeds of 5 to 8 km/h and they concluded that different tools created different geometries of soil profiles; the parameters of soil profile were also affected by tillage

both increased for all the tines as the moisture content increased in the range. However, the maximum width of cut increased for narrow tines (T1, T5) but decreased for wide tine (T20) in the moisture content range.

3.3 Regression Analysis of Soil Disturbance Parameters

Statistical analysis was carried out using Excel 2007 software package to regress the maximum width of soil throw (TDW) as dependent variable on the other soil disturbance parameters (as independent variables) including Wfs and SDR for the three selected tines (T1, T5, T20).

The multiple regression equation obtained is presented in Eq. (1) using the regression data described in sections 3.2. 12.

RRD

31.

sandy loam soil, Canadian Biosystem Engineering 46(2004) 21-25.

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