Prefabricated Ditch Linings by raz34238

VIEWS: 55 PAGES: 3

									Prefabricated Ditch Linings
          effectiveness of various types of liners in small irrigation
          ditches under study for control of seepage and vegetation
                                                                                                                       Verne H. Scott

Certain prefabricated materials                ond, 8’ widths are a minimum if the            have been made during the past three
used as linings in small irrigation ditches    lining is to run lengthwise down a ditch       years. Films 1?&8 thousandths of an
to control seepage and vegetation have         and longitudinal joints or seams are to        inch-mils-have     been used. In general,
shown considerable promise. Neverthe-          be avoided. Widths of 10’-16’ are quite        proper formulation of plastic film is im-
less, their use is limited-to some extent      often required. However, the smooth sur-       portant in providing characteristics
-by     relatively high initial cost and       faces of these linings-combined with the       needed to withstand exposure to sunlight
questionable longevity under the variety       elimination of weeds and grasses-re-           and wetting and drying. Black poly-
of field conditions which exist on irri-       sult in greater water carrying capacity.       ethylene film has exhibited longer Lasting
gated farms. However, increased produc-        Lined ditches can carry the same rate of       characteristics than the same thickness
tion and availability of some of the new       flow with a smaller ditch cross section        of vinyl film. Both have considerable ex-
materials-such as plastics-are lower-          than unlined weed infested ditches.            tensibility and pliability necessary in
ing costs to a point where replacement             Some linings are available only in 3’      conforming to irregularities in the ditch
may be economical on a 1-3 year basis.         widths and thereby require transverse          bank. In most cases some trimming of
   Several different types of materials-       joints. These increase installation time,      the banks and bottom of the ditch is
asphalt, asbestos, woodfiber, plastic          and the potential of leakage through           necessary prior to installation of these
coated kraft papers, and vinyl and poly-       poor joints is greater.                        materials so that sharp projections-
ethylene films-have been evaluated in              Thickness is an important character-       such as dead stalks of weeds and large
the field and laboratory during the past       istic of linings. In general, greater thick-   irregular clods of soil-are removed.
three years.                                   ness means longer life through more               Some difficulty has been encountered
   The width, length, and thickness of         resistance to sunlight and water, and          during installation of these lightweight
the available materials vary and proper        less chance of damage by hoofs of ani-         films when the wind velocity exceeds
width and length are important in mini-        mals or gnawing by rodents. On the other       8-10 miles per hour. This applies par-
mizing the number of joints and installa-      hand, greater thickness usually results        ticularly to the plastic coated papers
tion labor. For most farm lateral ditches      in more cost for transportation and in-        which are relatively brittle and tear
carrying a flow of 1 4 cubic feet per sec-     stallation labor, and less pliability and      easily when subjected to excessive stress.
                                               extensibility to fit irregularities of the
     Use of slphons In ditch with vegetation   ditch banks and bottom. Some types of          Comparlson of llned and unlined rwtlons on
              controlled by lining.            linings must be buried or covered by a                      vegetotlve control.
                                               layer of soil-a minimum of 6”-as          in
                                               the cases of asphalt and asbestos linings
                                                ‘/1fif’-1h’’in thickness.
                                                   Field experience with buried linings
                                               has not been satisfactory. Labor, equip-
                                               ment and time required to overexcavate
                                               and backfill for a buried lining are not
                                               practical nor economical for the small
                                                farm laterals.
                                                   Satisfactory service has been obtained
                                               with asphalt mats %“-?/z”       in thickness
                                               which do not require a protective earth
                                               cover. After three years in the field
                                               linings of this type have deteriorated
                                                only slightly, properly cemented asphalt
                                               joints are tight, and no vegetation has
                                               penetrated the lining. Results thus far
                                                indicate this lining should provide good
                                               control of seepage and vegetation for 10
                                                years or more under ordinary field con-
                                                ditions. At least ?/Z” thick material is
                                                needed to give some protection from
                                                penetration by animal hoofs.
                                                   If a ditch is badly infested with vege-
                                                tative growth prior to the installation of
                                                lining material, a soil sterilant should be
                                                applied to ensure protection from weeds
                                                working their way through joints.
                                                   Several experimental field installations
                                                of vinyl and polyethylene plastic film

28                                                                        C A L I F O R N I A AGRICULTURE, APRIL, 1957
   Experimental sections installed dur-         Siphons were used on one farm to con-                       PENETRATION
ing 1956 included: three 8 mil poly-         vey the water from the lined sections into                    Continued from page 23
ethylene, two 4 mil polyethylene, and        furrows for irrigating corn. To prime
one section each of a 50 pound and a         these siphons some pumping action is                unless they are very sandy, water pene-
90 pound water resistant antifungicidal      required, which oftentimes resulted in              tration is exceedingly slow. Apparently
treated kraft paper coated with 1 mil        the inlet end of the siphon jabbing the             the basic cause is the failure of the clay
black polyethylene. These installations      lining. None of the linings on this farm            fraction to cement coarser particles to-
were made on three farms in Yuba             were damaged by this action.                        gether.
County. In each case the soil was very          In a ponding test-to      evaluate the              The worst of these soils have certain
sandy and high seepage losses were sus-      amount of water lost by seepage-the                 characteristics by which they may be
pected, vegetative growth was a prob-        loss through the unlined section was                recognized. The first time a loose seedbed
lem, and considerable time was required      over seven times that of the lined section          is flooded the soil slakes down until
for the water to reach the fields to be      or approximately 7.7 cubic feet per                 there is no trace of clods remaining. The
irrigated.                                   square foot per 24 hours. Undoubtedly               surface is smooth and becomes hard on
   The linings were installed in all sec-    this rate would not be maintained during            drying. Few cracks appear, and these are
tions after the ditches had been formed      each irrigation throughout the season.              fine hairline cracks. It is difficult to dig,
with conventional ditching equipment.        However-assuming       the average s e e p          and yet the soil crumbles readily when
A minimum of hand labor was necessary        age loss for the entire season was only             a dry clod is crushed in the hand, with
to prepare the ditch sides and bottom for    half of the measured amount-the cost                formation of an excessive amount of fine
lining. A shallow trench--4”-6”-was          of the lining and installation could be             dust. Roadways become covered with a
dug just over the top of the ditch bank.     recovered in one average season, based              thick layer of powdery dust. There is
The edges of the lining were laid into       on a total cost of the water alone of ap-           almost no lateral movement of water
this trench and backfilled by hand.          proximately $5 per acre foot. Savings in            from furrows even when the bottom and
   At the end of the season the sections     irrigation labor costs also could be                sides of furrows have not been compacted
were carefully inspected. All were in        realized.                                           by tillage or traffic. These characteristics
good condition. There was little differ-        One farmer in Yuba County had to                 may also be determined by laboratory
ence between the 4 mil and the 8 mil         double the number of siphons he had                 tests, and better tests may be available
linings, although some damage was ob-        been using because of the amount of                 soon which will aid in the diagnosis of
served in the 4 mil due to either pecking    water saved by a plastic lining.                    less serious problems.
of birds or clawing or gnawing of ro-           Mechanical methods of laying light-                 More and more problems are being in-
dents or small animals. This damage was      weight films-to eliminate some of the in-           vestigated which are caused by this con-
all above the water line and therefore       stallation labor-are being studied. Also            dition. It is especially serious because
did not reduce the linings’ effectiveness    rolling the lining up at the end of a sea-          the difficulty lies in an inherent charac-
for seepage control.                         son and storing it for use the next year            teristic of the soil which cannot be
   No difference was detected between        is being investigated.                              changed by any economical means
the two weights of poly coated papers.                                                           known at present.
Some deterioration of both resulted near       Verne H . Scott is Associate Professor of Irri-      Diagnosing the cause or causes of
the edges where a wicking action of          gation, University of California, Davis.            slow water penetration into soil is im-
water occurred.                                Donald Fox, Farm Advisor, Yuba County,            portant because there is no other way to
   All linings were very effective in con-   Jack A . Corry, Senior Engineering Aid, Uni-
                                             versity of California, Davis, and William Wu,       determine whether or not a proposed
trolling vegetative growth beneath the       formerly Senior Engineering Aid, assisted in        treatment will be effective. Some soil con-
lining.                                      the studies reported here.                          ditions respond to proper treatment, and
                                                                                                 a marked-if only partial-improvement
             Making measurements during a hepage ponding test.
                                                                                                 results. Others have not yielded to any
                                                                                                 treatment yet developed. Research is in
                                                                                                 progress on the basic behavior of soils
                                                                                                 which will point the way in minimizing
                                                                                                 the problem, and these studies may sug-
                                                                                                 gest new, effective, treatments.
                                                                                                    In the meantime, careful soil manage-
                                                                                                 ment is essential to keep conditions as
                                                                                                 favorable as possible. In cases where
                                                                                                 water penetration rates are not too slow,
                                                                                                 crop growth can be improved and yields
                                                                                                 increased by better management of irri-
                                                                                                 gation water. A practice which is effec-
                                                                                                 tive for deep rooted crops on deep soils
                                                                                                 is prolonged preirrigation for annuals
                                                                                                 or winter irrigation of perennials. If the
                                                                                                 poor physical condition of the soil does
                                                                                                 not seriously limit root development, a
                                                                                                 maximum amount of reserve moisture is
                                                                                                 stored in the subsoil. During the summer
                                                                                                 months when it is difficult or impossible
                                                                                                 to replenish the water in the soil as
                                                                                                 rapidly as it is used by the crop, the re-
                                                                                                 serve subsoil moisture may determine
                                                                                                 whether or not there is an adequate sup-
                                                                                                  ply of water.
                                                                                                             Concluded on page 37

CALIFORNIA AGRICULTURE, APRIL, 1957                                                                                                        29
             MOVEMENT                             Studies of moisture movement in soils             irrigated crops, water temperature may
                                               in the liquid phase are made under con-              become a factor of considerable impor-
          Continued from page 24
                                               stant temperature conditions. Thermal                tance in the selection of crops and their
phere suction value-about 75% of the           gradients within the soil column, which              management for maximum yield and
available water has been removed from          result in water vapor diffusion, can cause           minimum unit cost.
the Fallbrook soil and approximately           significant disturbances to the measured                Franklin C . Raney is Principal Laboratory
60% from the Holtville soil.                   liquid flow.                                         Technician in Irrigation, University of Cali-
   Further studies of moisture extraction                                                           fornia, Davis.
                                                 S. 1. Richards is Associate Irrigation Engi-
from soils are being made under con-           neer, University of California, Riverside.             Robert M . Hagan is Associate Professor of
trolled conditions without using plants.         L. V . Weeks is Senior Laboratory Technician,      Irrigation, University o f California, Davis.
Soil columns are positioned horizontally       University of California, Riverside.                   Dwight C. Finfrock is Associate Specialist in
and brought to equilibrium with water at                                                            Agronomy and Superintendent of the Biggs
                                                 The above progress report is based on Re-          Rice Experiment Station, University of Cali-
approximately 30 millibars. This is often      search Project N o . 1546                            fornia, Davis.
a value read on tensiometers following an                                                              Bruce Wylie, Glenn County rice grower; the
irrigation in the field. A constant suction                                                         Glenn-Colusa Irrigation District, and Milton D.
is then applied at one end of a soil col-                   PENETRATION                             Miller, Extension Agronomist, University of
umn, by applying a controlled vacuum to                    Continued from page 29                   California, Davis, participated in the studies re-
                                                                                                    ported in the above article.
one side of a porous ceramic disc the
other side of which is in direct contact          In most cases not enough water can
with the soil. The lower left graph on         be stored in the soil to last throughout
page 24 shows the accumulated water ex-        the season. Where water penetration is                           MEASUREMENT
tracted from soil columns when the suc-        slow, more water can be applied by irri-                         Continued from page 22
tion of 900 millibars was maintained           gating more frequently or by increasing
                                               the time the water is on the land surface            grove was on a two week irrigation
constant. The extracted water was meas-                                                             schedule. The irrigation water applied
ured in surface inches in relation to the      at each irrigation. Both approaches have
                                               advantages and limitations. More fre-                July 19 and August 3 reached the 12”
area of the soil column.                                                                            soil depth but did not wet the soil at the
   In the same length of time, 80% more        quent irrigation may be accomplished
                                               without any other change in the system               18” depth to field capacity.
water was extracted from a column of soil                                                              The time and place to use either tensi-
14” long compared with the same column         or in practice, but has the disadvantage
                                               of higher labor costs. It may be an in-              ometers or blocks depends to a large ex-
when it was cut down to 7“ in length.                                                               tent on climatic conditions and soil types
This would indicate that, for this Fall-       adequate measure for the more difficult
                                               problems. Prolonged irrigation may re-               and to a lesser extent on the nature of
brook sandy loam, root-free portions of                                                             the crop. In inland areas of southern
the soil 7” away from roots can make           quire substantial changes such as con-
                                               verting from furrows to basins in which              California where high water losses may
substantial contributions to water ex-                                                              cause stress conditions in plants, timing
tracted by roots.                              water can be ponded for long periods or
                                               using small furrows to insure better cov-            of irrigations becomes very important.
   Soils vary greatly in their ability to                                                           Tensiometers have proved to be valuable
conduct water. A comparison of three           erage of border strips with small streams.
                                               Irrigation of crops susceptible to injury            tools for timing irrigations in citrus and
soil types shows that under the same con-                                                           avocado groves. However, in the more
trolled laboratory conditions the water        or disease under prolonged irrigation
                                               can not be managed in this way, and the              humid areas where irrigations are inter-
extracted from a Ramona sandy loam soil                                                             mittent, along with rainfall, resistance
was approximately twice as much as             practice may encourage growth of water-
                                               loving weeds. However, such methods                  blocks are used with satisfactory results.
from a Fallbrook sandy loam and three-                                                              Resistance blocks made of gypsum rather
fold that from a Yolo loam. The curves         may be the only means of increasing the
                                               productivity of soils with very slow water           than fiberglass or nylon are generally
comparing various soils were all ob-                                                                preferred in agricultural soils.
tained using 14” soil columns.                 penetration even though changes in c r o p
                                               ping pattern or farming operations are                  The neutron method is still a research
   For these studies of soil moisture                                                               tool although it might be valuable on
movement, fragmented soil samples              required.
                                                                                                    large agricultural acreages.
were screened and compacted in the col-           D. W . Henderson is Assistant Professor of Ir-    --
umns. Further studies will be made on          rigation, University of California,Davis.              L. H. Stolzy is Assistant Irrigation Engineer,
                                                  J . A . Vonioril is Assistant Professor of Soil   University of California, Riverside.
undisturbed cores.
   If only moisture flow rates are meas-       Physics, University of California,Davis.               G. A. Cahoon is Assistant Horticulturist, Uni-
                                                                                                    versity of California, Riverside.
ured-to compare the ability of various                                                                T . E. Szuszkiewirz is Senior Laboratory Tech-
soils to conduct water-the        size and                  TEMPERATURE                             nician, University of Californin, Riverside.
shape of the soil sample and suction                                                                  The above progress report is based on Re-
                                                           Continued from page 20
equipment would need to be standard-                                                                search Project N o . 1612.
ized. However, when continuous records         ing facility must provide for maximum
of the moisture suction values are ob-         energy capture, discharge water at a tem-
tained at various locations along the soil     perature giving maximum rice yields, oc-                              QUALITY
column, as well as moisture extraction         cupy a minimum land area, with reason-
rates, computations can be made express-                                                                        Continued from page 31
                                               able installation and maintenance costs.
ing the conductivity values of a soil as a        From experience in rice irrigation,               in the Imperial Valley. Here Colorado
function of the moisture suction. These        water temperature may be expected to                 River water is used for irrigation and
values are characteristic of the soil and      influence the growth of other crops. How-            contains large quantities of sulfate,
independent of the methods of measure-         ever, it is difficult to predict the influence       which produces this toxic symptom.
ment. They can be used to characterize         of water temperature on yields because
different soils or study the effects of soil                                                          L. D. Doneen is Professor of Irrigation, lini-
                                               of its numerous direct and indirect ef-              versity of California,Davis.
management practices on the same soil.         fects on the plant. In addition to the cold            D. W . Henderson is Assistant Professor of
Also, when suction values in the field are     water damage reported here, crop injury              Irrigation, University of California,Davis.
measured by tensiometers, flow rates can       is sometimes associated with warm water.                The above progress report is based on Re-
be estimated.                                     As more is learned about its effects on           search Project No. 1529.

CALIFORNIA AGRICULTURE, APRIL, 1957                                                                                                                37

								
To top