FIELD DRAINAGE

Sun (Auckland), Volume IV, Issue 1022, 12 July 1930, Page 27

FIELD DRAINAGE

FIGURES FROM U.S.A. An attempt to assist the farmer to carry out field drainage more economically received recognition at the British Koyal Agricultural Society’s Show at Newport by the award of a silver medal to a simple form of excavator. This implement is cabledrawn and works to a depth of about 22iu. in two cuts, effecting a great saving iu the cost of trench-digging. An exhaustive study of the cost of tile drainage has been made over some 14 years in Minnesota. Though the actual costs incurred duriug a period (1908-21), marked by widely varying economic conditions, cannot be taken as a definite basis for final conclusions, they are useful for making comparisons and working out percentages. The percentages of costs are as follow: —Engineering ahd supervision, 5.3; tiles (including freight, and haulage), 46.2; trenching and laying and refilling trenches, 43.6: miscellaneous, 1.9. These figures though applicable to American conditions, are enough to show what a large proportion of the total cost centres round the tiles, it is calculated that with a small horse-drawn excavator one machine-hour is equal to 4.4 man-hours, while one machinehour of a motor-driven excavator is equivalent, to 5.4 mau-hours. Useful tables and graphs are given, showing the hours required to dig trenches of various depths for varying diameters of tile under varying conditions of soil. Thus, to dig a trench 3ft deep for a tile 4.Sin in diameter, will take per 100 ft in easy ground 6.27 hours; in average ground, 7.32 hours, and in hard ground, 10.21 hours. Rainwater, it is stated, penetrates the.soil mainly when the soil is cultivated and the differences in temperature between the soil and the air are of the greatest importance in soilmoisture movement. Vertical movements occur only to the depths to which daily variations of temperature take effect. This depth, under the condition of the test, was found to be about 3ft.