Modeling crop cultivation pattern based on virtual water trade: evidence from Marvdasht in southern Iran

Transcription

1 Iran Agrcultural Research (2015) 34(2) Shraz Unversty Modelng crop cultvaton pattern based on vrtual water trade: evdence from Marvdasht n southern Iran M. Bakhshoodeh, H. Dehghanpur * Department of Agrcultural Economc, College of Agrculture, Shraz Unversty, Shraz, I. R. Iran * Correspondng Author: hdehghanpur@gmal.com ARTICLE INFO Artcle hstory: Receved 24 December 2011 Accepted 3 May 2014 Avalable onlne 16 December 2015 ABSTRACT- Ths study ams to model optmal cultvaton pattern based on the maxmzaton of mportng vrtual water and socal net ncome of major crops n Marvdasht, Iran. For ths purpose, a lnear programmng model was developed consderng constrants of vrtual water and land lmtatons followed by other models to nclude employment restrctons. Based on the fndngs, wheat and tomato were recognzed as optmal products for the regon. Regardng the vrtual water mports, wheat has an advantage over tomato whle the producton of tomato needs a relatvely consderable number of workers whch leads to the mprovement of employment n the studed areas. Keywords: Vrtual water Cultvaton pattern Employment Marvdasht INTRODUCTION Vrtual water, defned as water used for producng one unt of agrcultural product, s a crteron and fundamental tool for the real consumpton of water n a country for agrcultural products (Allan, 1997). The volume of vrtual water for destned countres may be equally measured as the amount of water needed to domestcally produce mported agrcultural products. Snce transferrng a huge amount of food s easer than transferrng a huge volume of water, the global exchange of fundamental commodtes s a way to balance water resources n countres facng water shortage. Vrtual water along wth local or ndgenous water secures water requrements on natonal level (Allen, 1997). The exchange of vrtual water nsde and/or among the countres, and even among the contnents, can be consdered as a tool for ncreasng the effcency of water consumpton on the global level, achevng water securty n regons wth water shortage and removng envronmental lmtaton by determnng sutable places for producton (Turton, 2000). Ths s a way to acheve food securty by purchasng a part of the requred food rather than usng the lmted resources of water for producng all knds of food nternally (Wchelns, 2001). Consderng the volume of vrtual water recorded n food mportaton of countres wth water shortage, a closer relaton s observed between water retanng and dependency on food mportaton (Ok et al., 2001). Vrtual water puts agrcultural and economcal concepts together wth focus on water as a key agent n producton (Wchlenz, 2001). Therefore, a regon, a provnce, or a country that specally has ntense fluctuaton n ranng and atmospherc change can remarkably reduce ts water consumpton by mportng a part of food rather than producng all requred food nternally. Ths fact forms the man nfrastructure of vrtual water approach that encourages food exchangng as a way to promote effcency of water consumpton and to balance water resources n low water regons and countres for savng water n natonal and nternatonal levels. Accordng to the fact that food producton needs much more water than drnkng and hygenc servces (Zehnder and Rehler, 2002), exchangng agrcultural products s consdered as a useful mechansm to redstrbute hgh volume of water and save t n mportng countres (Delgado et al., 2003). Consderng vrtual water as a vtal crteron for the optmal use of water resources and decreasng ts waste and losses manly n ard and sem-ard countres such as Iran where effcency of water consumpton s typcally very low and farmng depends manly on rrgaton and to prevent over pressure on water resources n such countres, products wth lower water requrements are much more effcent than usng the rare water resources to produce products that need a hgh volume of ths resource. To determne an optmal cultvaton pattern, many studes have focused on low water consumpton n farms, rsk-takng nfluence on producton, prcng effect, water qualfcaton effect, proportonal advantage and seasonal plantng as the objectves of ther models (Howary and Azaz, 2001; Benly and Kedul, 2003).

2 Bakhshoodeh and Dehghanpur / Iran Agrcultural Research (2015) 34(2)29-34 Although such studes offer those products wth hgh proftablty and lower water consumpton, selectng optmal plantng model based on the crteron of vrtual water seems to be essental n water demand management. Ths not only mproves regon-plantng patterns but also enhances agrcultural products trade. Although the subject of vrtual water s manly a concern on the country level, because of the exstence of expanded watershed basns n the country, ths study focuses on examnng the cultvaton pattern n Marvdasht basn n Fars provnce, Iran, whch s wellknown enough for ts share n total agrcultural producton n the country. In ths research, frst, the volume of vrtual water s calculated for selected agrcultural man products of the selected regon ncludng wheat, barley, rce, potato and so on. Then, an optmal pattern of cultvaton s determned by applyng lner programmng models that are based on the volume of vrtual water of the products as well as on the employment restrctons. MATERIALS AND METHODS In order to calculate the volume of vrtual water for studed agrcultural products, the amount of consumed water of ndvdual products (CWU) s calculated at the frst stage through Eq. 1 and then the rato of water consumed by ts correspondng yeld (Eq. 2) s used for the determnaton of the amount of vrtual water consumpton (VWC) of that product. CWU jt =ET ajt /Effcency (1) CWU jt VWC jt = (2) Yeld jt where VWC jt s the amount of vrtual water of crop n area j at year t measured n m 3 /kg and ET ajt s water requrement of crop n area j at year t n m 3 /ha. Water requrement s the amount of water needed by the plant n an agrcultural perod (Farsh et al., 1997). Yeld jt s the yeld of crop n area j n year t measured n kg/ha and * CWU s the amount of crop consumpton water n area j at year t n m 3 /ha obtaned from Eq. 1. Effcency stands for the effcency of rrgaton that vares based on varous rrgaton methods. On average, the effcency of dfferent knds of rrgaton method consdered n ths study was 36% (The Iranan Agrculture Mnstry, 2003). The requred water of a crop vares each year due to dfferent weather condtons; however, because of the lack of needed data, t was assumed to reman unchanged over the studed years. The objectve functon n ths model has two parts. (Eq. 3). Whle the frst part exhbts maxmzaton of socal benefts, the second part s desgned to show maxmum ncome resultng from net mports of * Crop Water Use mentoned products nto the basn. Thus, the structure of the model n ths study s: Max: Y [( SP SC ) VWC Pw ] X + P NM (3) Y s the yeld of product, C s nternal consumpton of product, SP s socal value or shadow prce of product n the regon that s calculated by adjustng global prce of the products n local currency (Ral), SC stands for socal costs of unt producton of product n the regon excludng water costs, X s the total area under cultvaton of product, NM s net mports of product, VWC s the amount of vrtual water, whch equals that for one klogram of ganed product (based on cubc meter/ kg) and W s the total amount of water avalable n the regon. P w exhbts socal cost per cubc meter of water. The model has three constrants for land, water and trade balance. Snce the lands under cultvaton are equal to a certan amount as X, so the land constrant appears as (Eq. 4). n X X = 1 (4) The volume of water used n the regon s gven at W and ncludes underground, canal and rver waters. The amount of water used n each hectare s obtaned from the amount of vrtual water multpled by product yeld. The total amount of water used wthn the regon s also obtaned by summng water consumpton of all products. The water constrant s therefore expressed as (Eq. 5). n ( Y VWC X ) W (5) = 1 Fnally, we defne the followng constrant (Eq. 6). for trade balance. Clearly, t states that the excess consumpton of agrcultural products s exported from the regon and any shortage n nternal use s provded through mports. X Y NM C (6) Data on mports and exports, total producton, land under cultvaton and yelds of products were obtaned from the yearbooks of the Iranan Agrcultural Mnstry branch n Fars provnce. Other data ncludng world prces of products and cost ndces were taken from the World Bank publcatons. Furthermore, the domestc and relatve prces of products and wages were obtaned from publcatons of the Statstcs Centre of Iran. RESULTS AND DISCUSSION The calculated amounts of vrtual water are represented n Table 1. As shown, wheat and barley need less water as compared to other products, and tomato and sugar beet use less vrtual water due to ther hgh yelds. The hghest amount of vrtual water s attrbuted to rce. Consderng the volume of vrtual water used by these products, mportng one klogram of wheat, barley, rce, corn, tomato and sugar beet mples mportng vrtually 1.7, 2.9, 7.2, 3.7, 0.6 and 0.8 m 3 water, respectvely. 30

3 Bakhshoodeh and Dehghanpur / Iran Agrcultural Research (2015) 34(2)29-34 Comparng vrtual water of the crops per kg sounds unfar due to dsparty of ther yelds and values per hectare and so we calculated the vrtual water per 1000 Rals values of the products. As shown n the fourth column of Table 1, the correspondng ratos vary between 0.2 and 2.8. Whlst the lowest amount of vrtual water was attrbuted to tomato based on ts yeld, barley s recognzed so through adjustng vrtual water by total value products. The results of the products' socal benefts have been shown n the last row of Table 1. Table 1. Water used, vrtual water, yeld, vrtual water to value of total product (VTP) and socal profts of products n Marvdasht wheat barley rce corn tomato sugar beet Used water per hectare (m 3 /ha) Yeld ( kg/ha) Vrtual water (M 3 /kg) Vrtual water to VTP (m 3 per 1000 Rals) Net socal proft per ha (mllon Rals) Based on the last row of the Table 1, only wheat has comparatve advantage n producton as shown by ts net socal proft of 10.3 mllon Rals per ha. The fgures for other products are negatve mplyng that they have socal loss, the largest of whch s related to tomatoes. The optmal croppng pattern n the regon can be recognzed by a model that maxmzes smultaneously both the socal beneft and vrtual water mport. Model results are shown n Table 2. As can be seen, wheat and maze wth land areas of almost 120 and 38 thousands ha, respectvely, are the two products wthn the optmal cultvaton model. The optmum land areas under cultvaton of wheat and maze rse respectvely by 90 and 230 percent, compared to the exstng land areas and other products that are excluded from the croppng pattern. Moreover, socal net proft per hectare s expected to sharply ncrease at the optmum cultvaton pattern. The model also confrms the comparatve advantage of wheat n the regon. Table 2. Results of dfferent cultvaton patterns n Marvdasht area (2007) Patterns A bearable exstng pattern (thousand ha) Maxmum socal beneft wthout adjustment factors (thousand ha) Provdng land to mantan current levels of employment (thousand ha) Notwthstandng the ncrease of employment land (thousand ha) Land restrcted fertlzers (thousand ha) land bound to mantan the current employment, fertlzer and the current water restrctons (thousand ha) Source: research fndngs Product Wheat barley rce corn tomato sugar beet net socal proft 10 6 Rals net vrtual water mport 10 6 M 3 In addton to optmal croppng pattern, net mports of the products are shown n Table 2. Accordngly, the optmzaton of land results n ncreasng the mports of net vrtual water by 50%. In other words, rearrangng agrcultural exports from the regon would prevent sendng out 963 mllon cubc meters of water by utlzng the optmal land allocaton. As was dscussed earler, wheat and maze have fewer values n terms of vrtual water n cubc meters per kg and also n cubc meters per 1000 Rals than other products. In general, replacng products that requre low water wth those whch need hgh water requrements s one of the optons for mprovng the agrcultural products. In other words, products wth hgh water productvty should be replaced wth low water productvty products to ncrease the water use effcency and thus to obtan hgh economc value per unt of water and to save water for other essental domestc uses. The results show that shadow prce per one cubc meter of water s 828 Rals and water usng between and cubc meters does not change the objectve functon. Despte the fact that the reducton of water through mports n low water crcumstances s sgnfcantly reasonable by tself, t s coupled wth some adverse effects such as reducton n employment. The employment rates, measured by workng persons per day (PPD), decreases nearly persons 31

4 Bakhshoodeh and Dehghanpur / Iran Agrcultural Research (2015) 34(2)29-34 daly n current stuaton to almost workng persons per day (PPD), applyng the optmum cultvaton pattern. Ths reveals that producng hgh water requrng products also requre more labor and swtchng to low water requrng products causes employment to be reduced as well. Therefore, determnng land cultvaton pattern based on vrtual water should be accompaned wth possble changes n employment n the regon. Snce the government polcy s to keep the employment rates stable n the country as well as n the regon, a cultvaton pattern cannot be consdered optmum f t causes some farmers to lose ther jobs. Thus, the model s rerun n such a way that the current level of employment s kept unchanged. Moreover, the optmum pattern results n a 40 percent ncrease n the consumpton of fertlzers n the regon creatng envronmental polluton and worsenng the qualty of groundwater. Thus, lessenng water consumpton may rase varous sde effects and therefore t needs to be clearly justfed such that the optmum pattern contans lower levels of water consumpton whle t keeps employment and prevents further consumpton of fertlzer. The ssue of mantanng employment level s consdered below together wth some further constrants n order to acheve a real optmal pattern for the regon (Table 2). Employment mantanng croppng pattern The optmal croppng pattern that maxmzes proft and socal mport of vrtual water wth lmted employment n the regonal level, shown n Table 2, ncludes only two crops,.e. wheat and tomato wth land under cultvaton of 98 and 32 thousand hectares, respectvely. Ths exhbts an ncrease n the lands of the two products by 55% and 580%, respectvely. The reason behnd the rapd ncluson of tomato n ths pattern s due to labor ntensve feature of ths product. Although the pattern stll shows net socal loss, the correspondng fgure decreases to bllon Rals that s sgnfcantly less than that of croppng pattern wthout lmtaton on employment. Moreover, the net vrtual water mport of products specfed n watershed area s shown n Table 2. Accordng to the optmal croppng pattern, the net mport of water ncreases to 1705 mllon cubc meters and 192 mllon cubc meters of water s expected to be added to regonal water resources ndcatng a decrease of 742 mllon cubc meters compared to croppng pattern wthout employment restrctons. Croppng pattern wth employment ncreasng n the regon The results of the model wth lmted employment showed that employment between and workng persons per day (PPD) wll not change the objectve functon. Therefore, employment can be rsen up by 117% from 1,821,437 to 3,959,050 persons,.e further jobs per day, wthout any change n the value of objectve functon of the orgnal optmum pattern. The respected fndngs of such ncrease n employment level are shown n Table 2. Implementng ths plan causes the cultvated area of wheat and tomato to ncrease to 114 and 28 thousand hectares, respectvely, ndcatng 81% and 496% growths compared to the exstng lands of these two products. Agan, cultvated lands of barley, rce, maze and sugar beet are zero. Socal net proft per hectare of land s Rals at the optmum level. Accordng to the optmum croppng model, net mport of water wll rse to mllon cubc meters ( mcm) and 181 mllon cubc meters of water may beaded to regonal water resources. Ths s equvalent to 9% of water used n the regon. Thus, for moderatng the negatve consequences of unemployment n the optmal croppng pattern based on vrtual water, t s preferred to mantan the relatve level of employment consderaton along wth the goal of maxmzng vrtual water mport. Lmtng chemcal fertlzer croppng pattern The regonal optmal croppng pattern that maxmzes proft and socal mport of vrtual water and constrans the chemcal fertlzer use s shown n Table 3. Under ths model, the pattern ncludes wheat and maze wth land areas of and 38 thousand hectares, respectvely, mplyng 90% ncrease of the former product and 84% decrease of the latter when compared wth exstng land areas of these two products. The socal net proft per hectare of land reaches to bllon Rals ndcatng bllon Rals ncrease from that n the current pattern. Net vrtual water mport of mllon cubc meters n the exstng pattern reaches mllon cubc meters and water exports from the regon decreases by 966 mllon cubc meters. The consumed nputs through the exstng pattern, optmal croppng pattern and cultvaton model wth the lmt of chemcal fertlzer reducton are shown n Table 4. As was dscussed above, by takng nto account one sngle objectve,.e. maxmzng mported vrtual water, would result n a pattern that can only satsfy the consdered objectve, whle t s necessary to suggest a pattern that ncludes all the goals at the same tme. In other words, the advantage of maxmzng hgh vrtual water mports should not lead to gnorng ts correspondng costs. In ths context, a pattern that takes all the goals nto account s ntroduced n the next secton. By keepng the exstent levels of employment, consumpton of avalable fertlzers and water results n an optmal croppng pattern s shown n Table 4. At the optmal level, wheat, rce and tomato ncluded n the model accounted for 76.6, 29.4 and 10.5 thousand hectares of avalable lands respectvely revealng 22% and 123% ncrease of wheat and tomato cultvaton areas and 10% decrease n land under cultvaton of rce whlst the other products are excluded from the model. The correspondng net vrtual water mport reaches -791 mcm that s 1105 mcm hgher than that of the orgnal optmal croppng pattern. Because the other products have less water use effcency and socal welfare. 32

5 Bakhshoodeh and Dehghanpur / Iran Agrcultural Research (2015) 34(2)29-34 As shown n Table 3, consumptons of nputs except labor and herbcdes ncrease through ths pattern. Table 3. Total amount of nputs used n the exstng cultvaton model and the model maxmzng socal beneft Descrpton The total consumpton of nputs Manufacturer maxmum socal beneft changes Rato changes to exstng model(%) Anmal manure tons Herbcdes tons Insectcde tons Fungcde tons Phosphate fertlzer tons Urea fertlzer tons Potassum fertlzer tons Labor (person days) Water consumpton Mllon cubc meter Source: research fndngs Table 4. Total amount of nputs used n the exstng cultvaton model and the model maxmzng socal beneft and model wth the constrants of fertlzers ttle Total amount of nputs used n the exstng cultvaton model Total used nputs n maxmzng socal beneft and model wth the constrants of fertlzers Rato changes to exstng model (%) Anmal manure tons Herbcdes tons Insectcde tons Fungcde tons Phosphate fertlzer tons Urea fertlzer tons Potassum fertlzer tons Labor (person days) Water consumpton Mllon cubc meter Source: research fndngs CONCLUSIONS Based on the fndngs of ths study, t can be concluded that focusng on maxmzaton of mportng vrtual water wthout regardng other vtal ssues ncludng employment and avalable nputs forced us to cultvate a few crops such as wheat and corn that need less water. In order to create or to keep job opportuntes, however, the cultvaton patterns n a regon should be determned such that maxmzng mports of vrtual water and socal benefts s accompaned wth ntroducng extra polces to guarantee that the current level of employment can be kept n the regon. Based on the results, we recommend ncludng wheat, rce and tomato at the cultvaton pattern of the studed regon as a pattern by whch matter of vrtual water s consdered together wth employment and optmum use of nputs at the same tme. REFERENCES Allan, J.A. (1997). Vrtual water : a long-term soluton for water short Mddle Eastern economes. Paper presented at the 1997 Brtsh Assocaton Festval of Scence, Unversty of Leeds, UK. Benl, B., & Kodal, S. (2003). A nonlnear model for farm optmzaton wth adequate and lmted water supples: Applcaton to the South- east Anatola project (GAP) regon. Agrculture and Water Management. 62: Delgado, C., Mark, R., Hennng, S., Smeon, E., & Claude, C. (2003). Lvestock to 2020: the next food revoluton, Food, Agrculture and Envronment Dscusson Paper 28. Internatonal Food Polcy Research Insttute. Iranan Mnstry of Agrculture, (2003). Comparatve advantage of selected agrcultural products. Plannng and Economc Dep. Research Insttute of Plannng and Agrcultural Economcs. Turton, A.R. (2000). Precptaton, people, ppelnes and power: Towards vrtual water based poltcal ecology dscourse. MEWREW Occasonal paper, water ssues study group, School of Orental and Afrcan Studes (SOAS) Unversty of London. Wchelns, D. (2001). The role of vrtual water n efforts to acheve food securty and other natonal goals, wth an example from Egypt. Agrcultural Water Management, 49: Zehnder, A.J.B., & Reller, A. (2002). Water ssues. Edtoral pdf. 33

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