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Little or no seepage will result when a concrete pipe is used through these soils. |
Four factors influencing an irrigation system are independent of soil type. |
These are costs, contour of the land, weed contamination and the effect on cultivation practice. |
The cost of outlets such as ditch structures and pipe line valves is extra over and above the cost of the ditches and pipe lines themselves. |
It is difficult to compare them since they serve a specialized type of conduit. |
Some of the effects resulting from soil type-such as washing-come after delivery of the water by these outlets. |
Basins, checks, and borders are basically alike, being for the most part flat areas surrounded by earthen levees which hold the water flooded over them until it infiltrates the soil. |
Basins are generally smaller, such as the square-leveed areas about individual trees. |
Borders or checks are usually long and narrow with the slope down the length in the direction of irrigation. |
There are several methods for applying water to the soil-basins, furrows, checks, borders and sprinklers. |
The cross slope-the narrow way of borders and checks-is restricted to twotenths of one foot or less between the borders. |
Sometimes the cross slope, and at other times the available water supply control the spacing of the levees. |
Other irrigation devices may be used to advantage under certain conditions. |
One such device is the syphon which conducts the water over the ditch bank to the field, eliminating the cutting of ditchbanks and effecting a saving in irrigation labor. |
Continued on page 10 |
COMPARISON OF DITCH AND PIPE LINE IRRIGATION IN RELATION TO VARIOUS FACTORS |
Factor Soil Type Ditch Pipe Line |
Sand High-wasteful Slight to none |
Seepage Loam Moderate-occasionally wasteful Slight to none |
Clay Low-negligible waste Slight to none |
Sand Washing a problem Less washing than ditch |
Operation Loam Some washing-may be high Limited washing to none |
simplicity Clay Little or no washing None |
Sand Difficult to keep in shape |
Maintenance Loam More stable than sand None |
Clay Relatively stable-keeps shape |
Sand Often not suitable for burrowing |
Rodent None |
destruction Loam Burrowed readily and frequently |
Clay Burrowed readily and frequently |
Must be remade frequently to plug ro- Long-15 to 20 years or |
Life All types dent holes and control weed growth more |
for all soil types |
Higher-from 55c for 8 |
First cost All types Low-few cents per ft. |
to $1.50 for 18" (ap- |
prox. |
price laid in field) |
Weed con- All types Always a hazard, sometimes serious None |
Interference Below ground-little or |
with cultiva- All types Often definite obstruction to cultivation no interference |
Can disregard grade of |
Contour of land if all points are |
the land All types Must have fall toward point of delivery below elevation of |
supply, which may be |
Black-end of Pear problem is subject of extensive field and laboratory studies |
Intensive investigations have been conducted in the field and in the laboratory since about 1930 regarding blackend or hard-end condition of pears and the relation of the rootstock to the incidence of the disease. |
Investigations were extended to include many thousands of trees whose rootstocks were known. |
The greatest incidence of the disorder occurred on the Japanese stock-P. |
pyrifolia-although black-end was found on pear trees propagated on P. |
ussuriensis, P. |
betulafolia and Kieffer seedling roots. |
Although the trouble has been found on trees that were said to be propagated on P. |
calleryana stock, it always has been small in amount. |
There have been a few cases where black-end has occurred on what has seemed to be French-P. |
communis-rootstock. |
The occurrence on |
French root however, has been so rare that the question might well be raised whether these particular trees might not be propagated on hybrid stock. |
Records have been kept of the performance of individual trees over a period of years. |
The trouble does not spread throughout the orchard. |
All degrees of severity have been found; trees tend to hold their relative positions from year to year with respect to the amount of black-end produced. |
The curve of incidence of the disease has been obtained by counting the number of black-end fruits on selected trees at weekly intervals. |
A number of materials have been applied to the soil and injected into black- |
Continued from page 6 |
The spud ditch finds favor in peat areas where the water table is already reasonably high. |
It simply saturates the surrounding peat mass with water by rapid percolation through the porous peat. |
Cost of irrigation naturally varies with |
end trees. |
Among those applied to the soil have been: A complete fertilizer, beet lime, sulfur, iron sulfate, a combination of manure and lime. |
Oxalic acid, tartaric acid, citric acid, iron sulfate, copper sulfate, boric acid, and a mixture of 12 different salts containing copper, boron, manganese, molybdenum, zinc, thorium, barium, strontium, tungsten, chromium, cadmium, and cobalt have been injected into the trees. |
None of the soil applications or tree injections has changed the black-end condition of the trees. |
Reciprocal and intermediate grafts have been made in an effort to transmit the disease. |
In the intermediate grafts root pieces were used as the intermediates, some having soil filled boxes built around them. |
None of the grafting experiments has been successful in transmitting the disease. |
Several thousand inarched trees have been observed. |
None of them has cured the disorder except when the original stock has been separated and the top caused to stand upon the inarches. |
Young trees have been produced by propagating Bartlett on piece roots obtained from trees that produced black-end Continued on page 15 |
If this total lift is in a well and a sprinkler system is operating requiring a pipe line pressure of about 40 pounds per square inch at the pump discharge, the pumping cost is increased by approximately $3 per acre-foot. |
the type of system used. |
It costs about $3 to pump one acre-foot of water where the total lift is 100 feet. |
In contrast, some supplies for gravity systems cost as little as 50 cents or less per acre-foot. |
The cost of gravity or ditch water depends upon the gross cost of the project and how rapidly it is being amortized. |
N. |
Johnston is Associate Professor of Irrigation, and Associate Irrigation Engineer in the Experiment Station, Davis. |
Rate of Water Supply and Length of Run for Various Types of Irrigation and Slopes of Land |
Slope of Coarse sandy soils Medium silt loam Very heavy clay soils |
Type of irrigation land |
in ft./100' Supply needed Length of run Supply needed Length of run Supply needed Length of run |
02' 20 cubic feet per second/acre 5 cfs 2 cfs |
Basin 25' 20 cfs/acre 5 cfs 2 cfs |
58' 20 cfs/acre 5 cfs 2 cfs |
8-12 20 cfs/acre 5 cfs 2 cfs |
0-2' 1.5 cfs/10' 220' .5 cfs/10' 550-880' .3 cfs/10' to 1,000 |
Border or Check 25' width 220' width 550-880' width to 1,000 |
58' 220' 550-880 to 1,000 |
8-12' 220' 550-880' to 1,000 |
0-2' .02 cfs each 220' .01 cfs ea. |
440-660' .005 cfs ea. |
880' |
Furrow 25' .02 cfs each contour .005 cfs ea. |