Modeling the response of onion crop to deficit irrigation

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1 Journal of Agrcultural Technology 01 Vol. 8(1): Avalable onlne Journal of Agrcultural Technology 01, Vol. 8(1): ISSN Modelng the response of onon crop to defct rrgaton Muhammad Nazeer 1* and Hussan Al 1 Department of Water Management, Khyber Pakhtunkhwa Agrcultural Unversty, Peshawar 5500, Pakstan Agrculture Research Insttute (Tarnab) Peshawar, KPK, 5500, Pakstan Muhammad Nazeer and Hussan Al (01) Modelng the response of onon crop to defct rrgaton. Journal of Agrcultural Technology 8(1): Proper rrgaton plannng s not only essental for water savng, but also for yeld enhancement and t s only possble when an accurate and relable decson makng tool (DMT) has been adopted. A best agrculture model s that whch has dynamc clmatc, sol and crop components. AquaCrop s one of the models extensvely used for rrgaton plannng purposes. To evaluate t performance an expermental feld was lad down n Agrcultural Research Insttute (ARI) Tarnab, Peshawar, Pakstan, durng 011, usng onon as a test crop. Four dfferent rrgaton treatments of 100, 80, 60 and 40% of crop water requrements (CWR) were appled on each growth stage. Two statstcal parameters ncludng root mean square error (RME) and Nash Coeffcent of effcency (NCE) were used as performance ndctors. Results ndcated that the bomass and yeld estmated through model showed overestmaton for all rrgaton treatments; smlarly underestmaton was observed for water productvty wthout any dscrmnaton among full and sever water stress condtons. The performance of model to estmate bomass, yeld and water productvty was not satsfactory, confrmed by performance ndctors. The unrelablty and dfferences n results may be due to other factors ncludng crop structure and phenology, rather than clmatc, sol and water supply parameters. For better performance of water productvty model adopted for global agrculture estmaton, focus should also be gven to undergrounds stems and bulb lke crop along wth cereals and cash crops to obtan more realstc results. Key words: AquaCrop, Water stress, Bomass, yeld and Btter gourd Introducton Proper water management practces are the need of the day. Water one of the most mportant natural recourse has drect nfluence on our socal lfe. To ensure food securty t s must to use the water wsely n order to enhance food producton whle save water as much possble or n other words to ncrease water use effcency of feld crops. World populaton s ncreasng day by day whch pose a serous threat on future agrculture producton especally n areas * Correspondng author: Muhammad Nazeer; e-mal: nazeer_aup@yahoo.com 393

2 where water s the most lmtng factor for agrculture producton. Besdes the ncreasng demand of water for other purposes (ndustry and domestc use), degradaton of water qualty wll also lmt the water avalablty for agrculture sector n the comng future (FAO, 56). So the only tool to overcome ths phenomenon s the enhancng of water use effcency, t s also called water productvty. The largest sector of water consumpton s agrculture, so ncreasng water use effcency wll not only ncrease agrculture producton but wll also save the water for other purposes. Vegetable producton n Pakstan s very low despte havng surplus labour and fertle land sutable for growng a varety of vegetables n the country. Vegetable producton n the country could be enhanced n three possble ways such as by allocatng more area, by developng and adoptng new technologes and by utlzng the avalable resources more effcently (Bakhsh et al., 007). Onon s one of the mportant vegetable crops, and t yeld and grade are very responsve to careful rrgaton schedulng and mantenance of optmum sol mosture (Shock et al., 1998). Bekele et al. (007) concluded that water defct at frst and fourth growth stages, gave non-sgnfcantly dfferent yeld from the optmum rrgaton applcaton. However t s reported that when water stress was mposed 30 days after transplantng for a perod of 15 days, leaf area and bulb growth were consderably decreased wth a reducton of 17 6% n onon yeld (Bhatt et al., 006). Sol water stress caused by wthholdng rrgaton at both the thrd-leaf and seven-leaf stages reduced onon yeld by 6% (Pelter et al., 004). Advancement n technology has brought myrad changes n every feld of lfe. Lke other scence dscplnes, model smulaton has taken prestgous poston n agrculture water management (Nazeer, 009). Models are manly used as predcton tools to make the rght decson for future scenaro. As water s the man drven factor for all crop process and has drect effect on plant survval, so man focus was gven on water models n last few decades. AQUACROP s one of the models extensvely used n the feld of water management throughout the world n order to estmate bomass (B), harvest ndex (HI) and fnally yeld (Y) under dfferent clmatc and water applcaton condtons. Many researchers (Hsao et al., 009, Heng et al., 009, Raes et al., 009, Steven et al., 009, Greets et al., 009, Araya et al., 010) conducted studes on dfferent crops (manly cereals) usng AquaCrop model and results they obtaned were satsfactory n full rrgaton whle severed water stress msestmated bomass and yeld. However lttle wok has been done takng vegetables n to account, n ths study we used btter gourd as a test crop to evaluate the performance evaluaton of the AquaCrop model. 394

3 Journal of Agrcultural Technology 01, Vol. 8(1): Materals and methods Clmatc data Clmatc data requred for model as nput nclude maxmum and mnmum temperature ( C), evapotarnsparton (mm/day) and ranfall (mm). However for determnaton of evapotranspraton the humdty (%), wnd speed (km/day) and sunshne (hours) data s requred. All the requred clmatc data was collected on daly base (converted to monthly) from weather staton nstalled nsde the feld. Crop data Crop data was obtaned from an expermental feld. The experment was lad n Randomzed Complete Block Desgn (RCBD) wth splt plot arrangement. The row to row and plant to plant dstance was kept m and respectvely. The crop component dvded to 4 sub-components ncludng ntal canopy, canopy development, flowerng and yeld formaton and rootng depth. The later two were observed vsually whle the canopy was measured n feld at regular ntervals. Sol data The model requred full dataset of a gven sol texture ncludng wltng pont, feld capacty, bulk densty, hydraulc conductvty, saturaton, totally avalable water (TAW) and t nutrents (fertlty) status.. All these parameters were determned through dfferent technques, as shown n Table.1. The sol of the expermental feld was found sandy clay loam and the fertlty was mproved trough fertlzer applcaton at regular nterval before each rrgaton event. Table 1. Sol propertes of the research ste Propertes Sol texture Wltng pont Feld capacty Bulk densty Saturaton Avalable water Hydraulc connectvty Nutrents status Value Sandy clay loam 18.% by volume 8.1% by volume 1.51g/cm 3 43% 0.10cm/cm 7.86mm/hr poor 395

4 Irrgaton Applcaton Sxteen subplots were prepared accordng to four dfferent water applcaton treatments. One cultvar (Swat-I), same sowng date (03 feb011), same fertlzer doses were used n order to remove the ambgutes. 40, 60, 80 and 100% rrgaton were appled accordng to crop water requrements on growth stage base. The crop water requrements were determned through CROPWAT programme Water use effcency Water use effcency or water productvty was determned accordng usng followng equatons Y WUE (1) ET Where Y s the yeld n kg / m 3 and ET s Evapotarnspraton n mm (converted to m 3 ) whle the water productvty for bomass was determned through followng equaton; B BWUE () ET Where B s fnal aboveground bomass n kg /m 3. Model Descrpton AquaCrop s FAO s crop water productvty smulaton model resultng from the revson of the FAO Irrgaton and Dranage Paper No. 33 Yeld Response to Water. Smlarly to many other crop-growth models, AquaCrop further develops a structure (sub-model components) that ncludes: the sol, wth ts water balance; the crop, wth ts development, growth and yeld; the atmosphere, wth ts thermal regme, ranfall, evaporatve demand and carbon doxde concentraton (CO ); and the management, wth ts major agronomc practce such as rrgaton and fertlzaton. Smulaton runs of AquaCrop are executed wth daly tme steps, usng ether calendar days or growng degree days. Several features dstngush AquaCrop from other crop-growth models achevng a new level of smplcty, robustness and accuracy. 396

5 Journal of Agrcultural Technology 01, Vol. 8(1): Model data engne AquaCrop has four man components the clmate, crop, sol and management. Each component has sub-components as shown n Fgure-1. Data was collected accordngly. Model smulaton Fg.1. Model data engne The model was run for four dfferent rrgaton treatments, keepng n mnd the varaton of the nput data of the crop affected by dfferent rrgaton depths. However the sol and clmate data were keep the same for all cases. Performance Evaluaton Indcators (statstcal parameters) The followng ndctors were used for the performance of the model usng a spread sheet. 397

6 Root Mean Square Error (RMSE) Ths ndcator wll show the overall devaton between observed and smulated values. N O S 1 RMSE (3) N Where S s smulated value, O s observed value (actually measured), and N s number of observatons. For better model performance the value of RMSE should be near to zero. Nash Coeffcent of Effcency (NCE) Nash and Sutclffe ( 1970) derved an equaton n order to fnd out how much the overall devaton between observed and smulated values departs from the overall devaton between observed values ( O ) and ther mean value ( O ). NCE has the ablty to fnd out how the model workng durng the smulaton process. Furthermore the RMSE s unable to detect large devaton between observed and smulated values, whle the NCE accounts for the dfferent devatons, as they depart from mean value so the smaller the departure from mean value the hgher the performng effcency of the model. NCE value rangng from to +1, wth better model smulaton effcency when values are closer to +1. N 0 O o S E 1 N (4) O O Results and dscusson The smulated and observed bomass and yeld of onon crop affected by dfferent rrgaton depths are shown n Fgures. and 3 respectvely. The Shapro-Wlk (1965) normalty test (ft curve) was appled on smulated and observed data and t was found sgnfcant havng 0.56 and 0.6 values of standard devaton for bomass and yeld respectvely. The model overestmated the bomass and yeld for optmum wth out dscrmnaton among full and defct water supply. The unrelable results obtaned here may be due to crop phenology. Much work has been done on cereal and other vegetable crops whle no one have taken bulbs nto account, so there s no proper lterature to confrm these results wth ther fndngs. Results obtaned n ths study are n 398

7 Journal of Agrcultural Technology 01, Vol. 8(1): contrast wth that of Steduto et al. (007) and Hsao et al. (009), who reported that the model s unable to predct severe water defct condtons due to dfferent growth stages and sol mosture characterstcs. Many scentsts (Heng et al., 009; Raes et al., 009; Steven et al., 009; Greets et al., 009 and Araya et al., 010) also reported that the maxmum yeld smulated by AquaCrop was underestmated whereas mnmum yeld was slghtly overestmated. 10 Measured Smulated 8 Bomass(ton/ha) CWR 80CWR 60CWR 40CWR Fg.. Comparson between observed and smulated values of bomass for dfferent rrgaton treatments 5 4 Measured Smulated Yeld (ton/ha) CWR 80CWR 60CWR 40CWR X Data Fg. 3. Comparson between observed and smulated values of yeld for dfferent rrgaton treatments The model performance was evaluated through statstcal parameters shown n Tables. 1. The performance ndcators show varous results for observed and smulated values of bomass and yeld. The RMSE was 399

8 unsatsfactory for bomass estmaton whle NCE was n poor agreement between observed data and model smulated data for bomass. Smlarly results were obtaned for the yeld wth lower value of RMSE (0.6) and NCE (0.4). The water productvty of dfferent rrgaton depths for bomass and yeld of onon crop are shown n Fgure. 4 and 5. Recprocal results were obtaned as n case of bomass and yeld. The water productvty for bomass and yeld were underestmated by the model n all case of water applcaton gnorng the fact of severe water stress condton. The normalty curve was passed between smulated and observed values and sgnfcant varaton was found whch s confrmed by 0.69 and 1.06 standard devaton for bomass and yeld water productvty respectvely. 5 Bomass water productvty (kg/m3) Measured Smulated 0 100CWR 80CWR 60CWR 40CWR Fg. 4. Comparson between observed and smulated values of bomass water productvty for dfferent rrgaton treatments 3.0 Yeld water poductvty (kg/m3) Measured Smulated CWR 80CWR 60CWR 40CWR Fg. 5. Comparson between observed and smulated values of yeld water productvty for dfferent rrgaton treatments 400

9 Journal of Agrcultural Technology 01, Vol. 8(1): The model performance evaluaton for water productvty of bomass and yeld are shown n Table 1. RMSE and NCE were n poor agreement for bomass n all case of the water productvty estmated by the model. Smlarly trend was observed for yeld water productvty. No clear-cut dfferences were observed for dfferent treatments. Although the model ndcated over and under estmaton for dfferent crop parameters ncludng bomass, yeld and water productvty. In the lght of the results the model s not sutable or less satsfactory for underground stems or bulbs smulaton. Concluson The model overestmated bomass and yeld as well as underestmated water productvty for all rrgaton treatments wthout any dscrmnaton of full and defct water supply condtons. Model evaluaton usng RMSE and NCE showed that model performed unsatsfactory for bomass, yeld and water productvty. The comparson between observed and smulated results for four dfferent rrgaton treatments showed unrelable results. Ths s not the drawback of the model but the type of crop phenology. To mprove the relablty of ths model and ts usage n water management focus should be gven on onon lke crops Acknowledgements Thanks are extended to Food and Agrculture Organzaton (Italy), UN Water Decade Programme (Germany) and Mnstry of Water and Energy (Iran) for provdng fnancal assstance to attend AquaCrop nternatonal workshop. References Araya, A., Keesstra, S.D. and Stroosnjder, L. (010). Smulatng yeld response to water of Teff (Eragroststef) wth FAO s AquaCrop model. Feld.Crop Res.116: Bakhsh, K., Ahmad, B., Hassan, S. and Gll, Z. A. (007). An analyss of techncal effcency of growng btter gourd n pakstan Punjab. Pak. J. of Agr. Sc. 44: Bekele, S. and Tlahun, K. (007). Regulated defct rrgaton schedulng of onon n a semard regon of Ethopa. Agrc. Wat. Manag. 89: Bhatt, R.M., Rao, N.K., Srnvasa, G. and Veere, R. (006). Response of bulb onon (Allum cepa L.) to water stress: photosynthess, stomatal conductance and osmotc adjustment. Indan J. Hort. 63:0-5. Geerts, S., Raes, D., Garca, M., Mranda, R., Cuscanqu, J.A., Taboada, C., Mendoza, J. and Steduto, P. (009). Smulatng Yeld Response of Qunoa to Water Avalablty wth AquaCrop, Agron J, 101: Heng, L.K., Hsao, T.C., Evett, S., Howell, T. and Steduto, P. (009). Valdatng the FAO AquaCrop Model for Irrgated and Water Defcent Feld Maze. Agron J, 101:

10 Hsao, T.C., Heng, L.K., Steduto, P., Lara, R., Raes, D., and Fereres, E. (009). AquaCrop- The FAO Crop Model to Smulate Yeld Response to Water: III. Parameterzaton and Testng for Maze. Agron J, 101: Nash, J.E. and Sutclff, J.V. (1970). Rver flow forecastng through conceptual models. I. A dscusson of prncples. J. Hydrol. 10:8 90. Nazeer, M. (009). Smulaton of maze crop under rrgated and ranfed condtons wth CropWat model. J. of Agr. and Bo. Sc.4: Pelter, G.Q., Mttelstad, R. and Redulla, C.A. (004). Effects of water stress at specfc growth stages on onon bulb yeld and qualty. Agrc. Wat. Manag. 68: Raes, D., Steduto, P., Hsao, T.C. and Fereres, E. (009). AquaCrop-The FAO Crop Model to Smulate Yeld Response to Water: II. Man Algorthms and Software Descrpton Agron J, 101: Shapro, S.S. and Wlk, M.B. (1965). An analyss of varance test for normalty (complete samples), Bometrka, 5: Shock, C.C., Febert, E.B.G. and Saunders, L.D. (1998). Onon yeld and qualty affected by sol water potental as rrgaton threshold. Hort. Scence 33: Steduto, P., Hsao, T.C. and Fereres, E. (007). On the conservatve behavour of bomass water productvty. Irrg. Sc., 5: Steven, R.E. and Tolk, J.A. (009). Introducton: Can Water Use Effcency Be Modeled Well Enough to Impact Crop Management. Agronomy J. 101: (Publshed n January 01) 40