FIELD DRAINAGE.

Putaruru Press, Volume VIII, Issue 349, 31 July 1930, Page 6

FIELD DRAINAGE.

A NEW EXCAVATOR. An attempt to assist the farmer to earry out field drainage more economically received recognition at the British Royal Agricultural Society’s Show at Newport by the award of a silver medal to a simple form of excavator. This implement is cable-drawn and works to a depth of about 22in. in two cuts, effecting a great saving in 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 during 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 follows:—Engineering and supervision, 8.3: tiles (including freight and haulage) 40.2; 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 manhours, while rine machine-hour of a motordriven'excavator is equivalent to 8.4 man-hours. Useful tables and graphs are diven, 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 4-6 in. 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 soil-moisture movement. Vortical movement occurs only to the depths to which daily variations of temperature take effect. This depth, under the conditions of the test, was found to be about 3ft.