Harper, Jayson K.

Peralta, Richard C.

Shulstad, Robert N.

English

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Economic feasibility of on-farm reserVOIrs for irrigation water C. 2·I.~u for soybeans, the value of foregone pro-duction is less than the difference between the present values of well and reservoir costs. Thus, at current commodity prices. a new reservoir is a cheaper source of water than a new irrigation well. Since investment costs per acre foot of storage decline with Robert N. Shulstad, Jayson K. Harper and Richard C, Peralta D ECLINING groundwater levels and institutional and economic bar-riers to the use of surface water supplies threaten the continuation of irrigated crop production in many parts of the Grand Prai-rie region of Arkansas. A study was con-ducted to evaluate the economic feasibility of constructing more on-farm reservoirs for irrigation use rather than drilling new irri-gation wells. Reservoir costs include construction, em-bankment stabilization and treatment, pumping plant costs, seasonal operating costs and the value of foregone production. The cost savings derived from constructing and operating a reservoir compared to a well system must exceed the net value of the crop production foregone at the reservoir site in order for construction to be economically desirable. Present value of foregone production was estimated on the basis of economic returns as reported in the 1983 Arkansas Rice and Soybean budgets and assuming prices of $4.90lbushel for rice and $6.00lbushel for soybeans, with a rotation of two years in soybeans and one year in rice (S-S-R) over 50 years discounted at 75h%. The results show values ranging from $298 per acre for soils yielding 20 bul A of soybeans and I 00 bul A of rice to $1,207 per acre for soils yielding 30 bul A beans and 120 bul A rice. Table 1 shows the amount of seepage in acre feet per year, the acres of watershed required to fill the reservoir assuming a 50% delivery ratio, the present value of costs of a well system equivalent to the reservoir. the present value of the costs of the reservoir system, and the difference between the pres-ent value of the costs of the well and res-ervoir systems for selected hydrologic soil groups of Arkansas County. The difference reported in the far right column is considered the maximum value of foregone production allowable to make the reservoir alternative more attractive than the groundwater alter-native. Table 2 shows the value of foregone pro-duction from 30 acres of land in a 5-5-R rotation discounted at 1'%% under a range of rice and soybean prices and a yield of 25 bulA soybeans and IlObulArice. The solid line marks the economic feasibility boundary for reservoir construction for a reservoir four feet deep. Reservoir construc-tion is economically feasible at any combi-ARKANSAS FARM RESEARCH, JULy-AUGUST 1985 nation of prices to the left of the feasibility boundary. At these prices the savings from reservoir use are more than the value of foregone production. Thus, as long as soy-bean prices are $7.25/bu or less, rice prices can be as high as $4. 90/bu and maintain a profitable situation for the use of land to construct a reservoir instead of investing in a new well. The starred line in Table 2 represents the feasibility boundary for reservoirs five feet deep and the dotted line is for a depth of six feet. Given the 5-S-R rotation, the economic feasibility of reservoir construction is much more sensitive to changes in soybean prices than it is to changes in rice prices. At prices of $4.90lbu of rice and $6.001 increasing reservoir capacity. the larger res-ervoirs would be economical over a larger range of prices and yields than the smaller reservoirs. In all likelihood, the real cost of energy for irrigation pumping will rise faster than real commodity prices. This assump-tion and the decreasing water table would cause the present cost of the well alternative to rise more than the reservoir alternative and make the construction of reservoirs more desirable. Or. Shulstad is a professor and head and Mr. Harper is a former graduate assistant in the Department of Agricultural Economics and Rural Sociology. Dr. Per-alta is an assistant professor in the Department of Agricultural Engineering. Table 1. Characteristics and economic considerations for constructing a 3D-acre reservoir. 5 feet deep with 123 acre feet capacity in Arkansas County in 1983. Hydrologic Seepage Acres of Present Value of Costs Soil Soil Group ac ft/yr Watershed Well Reservoir Diff. ....................... $ ....................... Acadia 0 24.5 154.9 86,079 53,664 32,415 Amagon H-S 0 8.0 135.4 86,079 53,151 32,938 Calhoun 0 15.2 143.9 86,079 53,375 32,704 Crowley 0 16.0 144.8 B6,079 53,400 32,679 Falaya C 73.7 299.0 86,079 55,196 30,883 Grenada C 12.3 197.1 86,079 53,285 32,794 Herbert C 167.6 454.9 86,079 58,118 27,961 Loring C 46.0 253.1 86,079 54,334 31,745 Sharkey 0 1.6 127.8 86,079 52,952 33,127 Norwood SL B 73.7 446.3 86,079 55,196 30,B83 Table 2, Net present value of foregone production' for a two-year soybean, one-year rice rotation: 30-acre reservoir, moderate productivity soil (Yield Per Acre: Soybeans-25 bu., Rice-ll0 bU.) Soybean Price 4.60 4.90 Rice Price (dollars per bushel) 5.20 5.50 5.BO $!bu. 5.50 ....................... c ................................ $ ....................................................... . 15,227 19,622 24,016 28,411 i ...... ~~:~?~ 5.75 6.00 16.709 18,191 19,673 21,155 21,104 25,498 22,586 26,980 24,068 28,462 25,549 29,944 : l 31,374 ! 29,893 r ... ~~.~~~~:~~~.~~~~~.·· : 34.338 : 6.25 6.50 6.75 7.00 7.25 7.50 7.75 8.00 22,637 27,031 : ........ ~~ .. ~~~ ...... j 35,820 24,119 28,513 : 32,908 37,302 : ................. . 29,995 : 34,390 .----3-1.-47-7-': 35,871 ....................... : 25,601 27.083 38,784 40,266 28,564 : 32,959 37,353 41,748 l : 30,046 34,441 38,835 43,230 aDlscounted at 7 %% for fifty years. 34,287 35,769 37,251 38,733 40,215 41,696 43,178 44,660 46,142 47,624 Values left of lines represent prices at which a reseNoir is more economical than a well at reservoir depths of 4 feet ,5feet···**and6feet ...... . 7 Composition of basal diet Ingredients Yellow corn Soybean meal Dehydrated alfalfa meal Wheat shorts Dicalcium phosphate Ground limestone Salt Vitamin premix2 Trace mineral premixJ Iinternational Feed Number. A PPROXIMA TEL Y two-thirds of the phosphorus in feed ingredi-ents derived from seeds and grains are pres-ent as phytate, the salts of myo-inositol hexaphosphate. Phytate complexes with cations, primarily calcium, in the digestive tract of animal!. Calcium phytate is one of the most insoluble salts of phytate. Once this complex has been formed, the phos-phorus cannot be utilized by animals unless the phosphoric ester is hydrolyzed, a process which requires phytase. The phosphorus in phytate is unavailable to monogastric ani-mals, but phytate can be hydrolyzed by ruminants because of microbial phytase in the rumen. An experiment was conducted to determine if phytate is hydrolyzed in the digestive tract of rabbits, which are pseudo-ruminants. New Zealand White-Californian crossed rabbits were raised at the Univer-sity of Arkansas Experiment Station until they were weaned at five weeks of age. At weaning, the rabbits were housed in gal-vanized metal metabolism cages measuring 45 X 42.5 X 32,5 cm. The cages had wire mesh floors to allow free passage of urine and feces into collection pans. Two rabbits of the same sex and similar size were placed in each cage. One cage constituted a replicate, and there were eight replicates per diet. There were equal numbers of male and female rabbits on each diet. The ex-periment was conducted in a temperature-controlled room with a range of 20 to 22.2 C, and the room was illuminated 24 hours per day. The compositon of the basal diet is shown in the table. The dietary treatments were the basal diet or blends comprised of 60% basal diet plus 40% of corn or wheat shorts or 75% of the basal diet plus 25% of soy-bean meal or wheat bran. The feed was pelleted in a small laboratory pellet machine (California Pellet Mill Co.). The pellets were 4 mm in diameter and about 5 to 8 mm long. Approximately 10% water was used as a pellet binder. IFN' % 4-02-935 46.60 5-04-604 9.50 1-00-023 30.00 4-05-201 11.80 6-01-080 .75 6-02-632 .25 .50 .50 .10 2Furnished the following per pound of diet: vitamin A, 3,000JU; vitamin OJ, 100OlCU; vitamin E, 3JU; menadione sodium bisulfite complex, 2mg; riboflavin, 3mg; niacin, 30 mg; d-calcium pantothenate, 5mg; choline chloride, 225mg; thiamin, .5mg; pyridoxine, 5mg; vitamin 8 12, 5ug; d-biotin, 24ug, folacin, .3mg; ethoxyquin, 57mg; and selenium, 45ug. 3Furnished the following per pound of diet (mg/lb): Mn, 45; Fe, 45: Zn, 45; Cu, 5; I, .45; Co, .5. 8 The rabbit pairs were randomly assigned to an experimental diet. They wer~ fed the experimental diets free choice for a one-week adaptation period followed by a five-day collection period. Fresh water was pro-vided at all times in individual stainless steel watering cans attached to each cage. During the collection period, fresh feed was weighed daily and uneaten feed was re-weighed and discarded. Feed intake was recorded daily for each pen of rabbits during the collection period. The cages were equipped with stainless steel pans for collection of feces and urine. Feces were collected from each cage at the same time daily and dried overnight in tared aluminum pans at 55 C in a forced draft oven. After drying, the fecal samples were allowed to attain equilibrium with the air moisture for approximately one hour. They were then weighed and frozen in air-tight plastic bags. At the end of the collection period, the daily fecal samples were thawed and pooled by replicate. Each pooled replicate of feces was cleaned to remove hair and ground through a I mm screen in an intermediate model Wiley Mill. A subsample was taken from each ground composite and stored in air-tight containers until analyzed. Each diet was sampled at the beginning and again at the end of the collection period. The two samples from each diet were composited, ground, and stored similar to the fecal sam-ples. Triplicate samples of feed and feces were used for analyses of phytate phospho-rus. Corn, SBM, wheat shorts and wheat bran all contain phytate and are ingredients commonly used in animal feeds. Phytate phosphorus in the diets (mg/g of diet) were: basal, 2.11; basal + soybean meal, 2.51; basal + wheat bran, 4. 19; basal + wheat shorts, 3.85; and basal + corn, 1.77. No phytate was found in the feces of rabbits fed any of the diets. which indicates that all of the phytate phosphorus was hydrolyzed from the diets. Neither the source of the ingredients fed, nor their phytate content, influenced the amount· of phytate hydro-lyzed. The ability of rabbits to hydrolyze the phytate phosphorus in diets adequate in cal-cium suggests enzymatic hydrolysis. possibly by bacterial phytase in the cecum. Most rations formulated for monogastric animals are based on "available" rather than total phosphorus. These data suggest that rabbit rations can be based on total phosphorus. Drs. Nelson and Daniels are professors in the De· partment of Animal Sciences; Mr. Shriver and Ms. Kirby are graduate assistant and research assistant, respectively. ARKANSAS FARM RESEARCH, JULy·AuGUST 1985 

Economic feasibility of on‑farm reservoirs for irrigation water

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Economic feasibility of on‑farm reservoirs for irrigation water

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