Saving Water in Chufa Cultivation by Using Flat RaisedBeds and Drip Irrigation

N. Pascual-Seva1; A. San Bautista2; S. López-Galarza3; J. V. Maroto4; and B. Pascual5

Abstract: Chufa, also known as tigernut, is a typical crop in Valencia, Spain, where it is cultivated in ridges with furrow irrigation. This paperexamines the effects of the planting strategy (PS) and irrigation system (IS) on yield and irrigation water use efficiency (IWUE) on the basis ofthe results from a two-year study. The authors analyzed three PS, ridges with a plant row (R) and flat raised beds containing two (B2) or three(B3) plant rows and compared two IS, furrow (FI) and drip irrigation (DI). Irrigation was based on the volumetric soil water content (VSWC),continuously monitored with capacitance sensors. Each irrigation event started when the VSWC in R dropped to 60 or 80% of the fieldcapacity in FI or DI, respectively. Beds and ridges were irrigated simultaneously and for the same duration. There were differences among ISand PS, with DI and B2 obtaining the highest yield. On average, DI produced higher IWUE values than FI; the highest IWUE was obtained inR for DI, and the lowest IWUE was obtained in R for FI. Thus, modifications to the PS and the IS in chufa cultivation will increase IWUE andlead to major water savings. DOI: 10.1061/(ASCE)IR.1943-4774.0000659. © 2013 American Society of Civil Engineers.

Author keywords: Irrigation practices; Furrow irrigation; Trickle irrigation; Yield; Field tests; Water use efficiency.

Introduction

Chufa, also known as tigernut, is the botanical variety sativus ofCyperus esculentus L. Currently, it is an important vegetable cropin the Huerta Norte area in Valencia, Spain. Approximately 500 haare dedicated to the chufa crop with 6.5 × 106 t grown annually ata value of 4 million euros. Chufa tubers are used to produce a bev-erage called horchata, which is a popular, refreshing, and whole-some drink in Spain. Spain produces approximately 46 × 106 L ofhorchata annually, representing a retail market value of 32 millioneuros (Instituto Nacional de Estadística 2012). Horchata hasrecently become popular in other countries, such as France, U.K.,the United States, and Argentina. Fresh chufa tubers can alsobe consumed on their own after soaking. In Spain, because ofincreasing interest in this crop, the Regional Administration ofthe Valencian Community has developed specific legislation re-garding chufa quality parameters (Conselleria de Agricultura,Pesca y Alimentación 2010). Increasing interest in chufa cultiva-tion, mostly for food technology and biodiesel production, hasalso been reported in Brazil, Cameroon, China, Egypt, Hungary,the Republic of Korea, Poland, Turkey, and the US (Pascual-Sevaet al. 2009).

Chufa is usually cultivated in rotation with other crops such aspotato, onion, lettuce, escarole, and red cabbage. It has traditionallybeen cultivated in ridges, with a plant row and furrow irrigation.The chufa is planted in April, the specific date depending onthe previous crop and spring rainfall. Seedbed preparation entailstwo crossed passes with a rotary tiller. Tubers are planted at a den-sity of 120 kg ha−1 on parabolic shaped ridges, which are normally0.20 m high; the spacing between ridge top centers is 0.60 m; andthe base width is 0.12 m, with approximately 10 cm betweentubers. The aboveground biomass is burned around the beginningof November, after it has dried, and the chufa tubers are thenmechanically harvested when the soil water content is suitable.

Currently, there is a debate (Pascual-Seva et al. 2012) as towhether conventional plant spacing leads to the maximum yieldin chufa and other crops, especially root and tuber crops, includingpotato, carrot, and onion. These crops have traditionally beencultivated in a ridged system (single row planting system), but ithas been reported that other, higher-density planting systems, suchas double row planting systems and flat raised beds, can increasethe yield without negatively affecting product quality (Mundy et al.1999; Essah and Honeycutt 2004).

Locally made field equipment is used for chufa cultivation,especially mechanical planters and harvesters, with harvestersspecifically adapted to the ridge spacing and designed to covertwo ridges per harvester pass. This is most likely the reasonwhy other planting systems have rarely been evaluated in the past.However, slight changes in locally made machinery can allow forthe cultivation of chufa in flat raised beds.

Chufa cultivation uses large amounts of water in the order of10,000 m3 ha−1 year−1 (Pascual-Seva et al. 2010). As reportedby Stegman et al. (1980), water management objectives typicallyinvolve some form of timing criteria for water application. In ad-dition, in the study region, growers consider other factors such asplant and soil appearance, but they do not consider factors such assoil matric potential or root zone water content. Growers use theirown experience to decide the duration of irrigation. They usuallyblock the furrows at the downstream ends to eliminate surface run-off. Currently, the quality of the water used is acceptable, there areno limitations on supply, and water is not expensive. Most of the

1Postdoctoral Associate, Dept. Producción Vegetal, Univ. Politècnica deValència, Camino de Vera s/n, 46022 Valencia, Spain. E-mail: nupasse@prv.upv.es

2Assistant Professor, Dept. Producción Vegetal, Univ. Politècnica deValència, Camino de Vera s/n, 46022 Valencia, Spain. E-mail: asanbau@prv.upv.es

3Professor, Dept. Producción Vegetal, Univ. Politècnica de València,Camino de Vera s/n, 46022 Valencia, Spain. E-mail: slopez@prv.upv.es

4Professor, Dept. Producción Vegetal, Univ. Politècnica de València,Camino de Vera s/n, 46022 Valencia, Spain. E-mail: jmaroto@prv.upv.es

5Professor, Dept. Producción Vegetal, Univ. Politècnica de València,Camino de Vera s/n, 46022 Valencia, Spain (corresponding author). E-mail:bpascual@prv.upv.es

Note. This manuscript was submitted on February 28, 2013; approvedon August 12, 2013; published online on August 14, 2013. Discussion per-iod open until March 31, 2014; separate discussions must be submitted forindividual papers. This paper is part of the Journal of Irrigation and Drai-nage Engineering, © ASCE, ISSN 0733-9437/04013008(7)/$25.00.

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crops in the area have shallow root systems; in the case of chufa, theroot depth does not exceed 20 cm. These properties, in addition tothe lack of parameters such as soil matric potential or root zonewater content, make it difficult to obtain good application efficien-cies (AE), especially in sandy soils. The European Water Frame-work Directive 2000/60 (The European Parliament and the Councilof the European Union 2000) is based on a precautionary principle,meaning that actions need to be taken as a preventive measure and,thus, water use for chufa cultivation is a practice for improvement.Moreover, drought periods are longer and more frequent, whilewater is being diverted for other uses.

Irrigation water use efficiency (IWUE) is defined as the increasein yield under irrigated production compared with that under dry-land production (Bos 1980). This term has also been used to relateyield to the volume of irrigation water applied (IWA) (Tolk andHowell 2003). An increase in IWUE can be achieved by both anincrease in crop yield and a reduction of gross water use throughimprovements in irrigation efficiency (Playán and Mateos 2006).

The authors of this paper analyzed how two cultivation factors[planting strategy (PS) and irrigation system (IS)] affected yieldand IWUE. They analyzed three PS, ridges (with a plant row,R) and flat raised beds with two (B2) or three (B3) plant rowsand compared two IS: furrow irrigation (FI) and drip irrigation(DI). They also considered the effect of the plant row position(PRP) within the raised beds for differences between plants grownin the north (N), central (C), and south (S) rows. To reduce waterconsumption, they based the irrigation strategy on the volumetricsoil water content (VSWC). They performed this work to comple-ment two other studies. The first of these studies compared theproductive response of the chufa crop with three DI strategies(Pascual-Seva et al. 2010), considering as refill points (RP), orVSWC before each irrigation event, three different percentages(70, 80, and 90%) of field capacity (FC). The second study com-pared the chufa crop performance under ridge and bed cultivationwith FI (Pascual-Seva et al. 2012).

Materials and Methods

The authors conducted experiments over two consecutive growingseasons (GS) in 2007 and 2008 in two adjacent commercial plotsnext to the campus of the Univ. Politècnica de València (UPV),Spain (39°38′N, 0°22′W), within the main chufa production area.These plots were representative of the fields in the region. To avoidsoil nutrient exhaustion problems resulting from serial chufa crops,the authors used two different plots in the two years of this study.Both plots were situated next to the UPV farm to facilitate the useof an installed DI system, an irrigation setup that is not common inthe area. Different farmers owned the two plots; therefore, the plotshad different backgrounds. According to Papadakis’s agro-climaticclassification (Ministerio de Obras Públicas y Transportes 1992),the climate was subtropical Mediterranean (Su, Me) with hot,dry summers and an average annual rainfall of approximately450 mm that was irregularly distributed throughout the year, withapproximately 40% falling in autumn.

The soils at the site were deep with a coarse texture (sand inthe 2007 plot and loamy sand in the 2008 plot) and classifiedas anthropic torrifluvents according to USDA Soil Taxonomy(Soil Survey Staff 2010). Analyses indicated that the soils had aslightly or moderately alkaline pH and were highly fertile with highorganic matter content and high available phosphorous and potas-sium concentrations (Table 1).

Water for DI was pumped from a well (EC ¼ 1.6 dSm−1;Sodium adsorption ratioðadjustedÞ ¼ 2.9; pH = 7.4). Water for FI

came from the Mestalla canal, which flows from the Turia river(EC ¼ 1.4 dSm−1; SARðadjustedÞ ¼ 2.7; pH ¼ 7.2). Both irrigationwaters showed no restrictions in terms of salinity for nonsensitivecrops, such as chufa, or permeability (Ayers and Westcot 1994).However, there were certain restrictions in the water deliverythrough FI, because growers could only irrigate for three straightdays, followed by three days with no water available for irrigation.The authors measured and recorded the water flow and the irriga-tion water applied (IWA) in FI with an area velocity flow module(ISCO 2150, Teledyne ISCO, Lincoln, NE).

The authors followed standard cultivation practices during thecrop period, as described by Pascual et al. (1997). The followingdates corresponded to planting, straw burning, and tuber harvesting:• April 23, 2007; November 20, 2007; and January 17, 2008 in

the first GS, and• April 24, 2008; November 7, 2008; and January 27, 2009 in the

second GS.The authors furrowed the plots at the time of planting with a

precision mechanical planter for ridges and with a precisionmechanical planter hitched to the three-point hitch of a horticulturaltractor for the flat raised beds. They planted tubers at a depth of10 cm and spaced 10 cm apart within rows, which were spaced30 cm apart in beds. They made the ridges and beds by using adisk plough and a plough, respectively, coupled to the planters.They adapted the bed width in B3 to the existing harvesters; theflat, raised part of bed B3 was 90 cm wide (the distance fromthe bed center-to-center was 120 cm). The distance from the bedcenter-to-center in B2 was 80 cm, and the ridges were spaced 60 cmapart. The corresponding planting densities were 180 kg ha−1 (B2and B3) and 120 kg ha−1 (R). The beds and ridges were orientedlengthwise from west to east. The furrow length was 80 m in bothyears. The average furrow slope was approximately 0.1% in allcases. In FI, the authors blocked the furrows at the downstreamends to eliminate surface runoff. The irrigators chose the applica-tion time on the basis of their own experience, which, in turn,reflected regional practices.

Nutrient management was in accordance with local practices.Basal dressing, which was applied on the day before planting,consisted of 2 kgm−2 of sheep manure [57.2% dry weight(DW); 60.9% organic matter DW] and 90 gm−2 of 15∶15∶15(N∶P2O5∶K2O). In FI, top dressing consisted of 3.12 gm−2 of Nas KNO3 applied through the irrigation system in two applicationseach year (July 12, 2007 and July, 26, 2007; July 3, 2008 andJuly 30, 2008). The top dressing in DI was based on Hoagland’sNo. 2 nutrient solution (Maynard and Hochmuth 1997) [EC ¼2.31 dSm−1; pH adjusted to 6.1; macronutrient concentrations

Table 1. Granulometric and Chemical Characteristics of Soils Used inEach Growing Season

Characteristics of soils 2007 2008

Granulometric characteristics — —Sand (%) 87.3 85.3Silt (%) 10.0 10.0Clay (%) 2.7 4.7Texture Sand Loamy sandChemical characteristics — —pH 8.4 7.8Electric conductivity (EC) (1:5) (dSm−1) 0.14 0.41Organic matter (%) 1.7 2.2Total calcium carbonate (%) 33.9 24.11Active calcium carbonate (%) 5.3 3.5Phosphorous, sodium bicarbonate (ppm) 258 179Potassium, ammonium acetate (ppm) 382 443

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(all in mM): NO−3 , 14.0; H2PO−

4 , 1.0; SO2−4 , 2.45; Kþ, 6.0; Ca2þ,

4.0; Mg2þ, 2.0; micronutrient concentrations (all in μM): Fe2þ, 15;Mn2þ, 10; Zn2þ, 5; B3þ, 30; Cu2þ, 0.75; Mo6þ, 0.5], applied up to3.12 gm−2 of N, during the first two weeks of July through theirrigation system.

In DI plots, the authors irrigated the plants by a single lateral lineper plant row using a turbulent flow dripline (AZUDRIP Compact,Sistema Azud S.A., Murcia, Spain) with emitters (2.2 L h−1)spaced 0.25 m apart. They continuously monitored the VSWC withcapacitance probes. In a ridge, they used a multidepth capacitanceprobe (Cprobe, Agrilink, Adelaide, Australia). The multidepthcapacitance probe had sensors whose midpoints were placed atdepths of 10, 20, and 30 cm, and each was connected to a radiotelemetry unit, which read the value of each sensor every 5 minand stored the average 15 min value, as reported in Hussein-Mounzer et al. (2008). Stored raw data were sent by radio througha relay station and then to a gateway connected to a computer fordata analysis with the addVANTAGE software from ADCONtelemetry GMbH (Vienna, Austria) (Vera et al. 2009). The authorscalibrated sensors by the gravimetric method (Ministerio deAgricultura, Pesca y Alimentación 1986). They used an open ringholder auger (Eijkelkcamp, Giesbeek, The Netherlands) to collectundisturbed soil samples at different depths. Then, they dried thesoil samples at 105°C in a forced-air oven (Model 297, JP Selecta,Barcelona, Spain) to obtain the sample water content (m3 m−3),which was compared with the corresponding value obtained byeach sensor in voltage units. They used variations of VSWC todetermine the in situ values corresponding to field capacity (FC)(Veihmeyer and Hendrickson 1931). Because it was previously re-ported that the maximum root density and water uptake by chufaplants occurred at a depth of 10 cm (Pascual-Seva 2011), theymaintained the irrigation schedule by maintaining the soil watercontent between FC and RP at 10 cm depth.

The RP corresponded to the moment when the VSWC values inR decreased to 80% of the FC value. The amount applied at eachirrigation event for the 2007 experiment was 14.7 mm (60 min),whereas in 2008 the irrigation management was automated suchthat each event was stopped when the sum of values of the VSWCat 10, 20, and 30 cm reached the corresponding FC value. Theauthors recorded the total rainfall and the emitter flow rate byusing automatic tipping bucket gauges connected to the radiotelemetry unit.

In FI plots, the authors continuously gauged the flow of water bya sensor (ISCO 2150 area velocity flow module, Teledyne ISCO,Lincoln, NE). They measured and stored discharge data at 1 minintervals. For each PS, they placed a capacitance sensor,ECH2OEC-5 with software ECH2O Utility at a depth of 10 cmin a ridge in the central line of a B2 bed and in the central rowof a B3 bed in the middle point of the plot and connected to adata-logger Em50 to monitor the VSWC, which was provided inm3 m−3 (factory calibration provides �3% accuracy for mineralsoils) and was therefore used directly. They scheduled the irrigationso that the RP corresponded to the moment when the VSWC at asoil depth of 10 cm in R reached 60% of the FC, considering thatwater delivery was restricted to a three-day on/three-day off sched-ule. They chose the RP values for both DI and FI on the basis ofprevious studies on the productive response of chufa crop (Pascual-Seva 2011). With both IS, they irrigated the beds and ridges simul-taneously and for the same duration.

The authors periodically sampled plants within 1 m of eachplant row from each experimental plot. They divided the plants intothree parts and analyzed them separately: (1) shoots with all of theirleaves (in this paper, referred to as leaves); (2) roots and rhizomesas a whole because of the difficulty of separating them (in this

paper, referred to as roots); and (3) tubers. They measured the plantheight with shoots and tubers counted at each sampling. Afterwashing, they dried each sampled plant part (leaves, roots, ortubers) at 65°C in a forced-air oven for four days; then, they mea-sured the DW and tuber dry-matter content. At harvest, they deter-mined the yield obtained in each experimental plot and took asample of approximately 500 ml from the tubers to determinethe fresh average tuber weight (ATW). They calculated the IWUEby using yield and IWA values. Immediately prior to harvest, andconsequently with no sieving process, they sampled 1 m from eachof the planting rows (N, C, and S in B3; N and S in B2) for yieldand ATW to detect potential differences between row.

The authors established a split-plot design with three replica-tions, with IS as main plot and PS as the subplot. Each replicatecombination consisted of two flat raised beds (for B2 and B3)or four ridges. Each experimental plot was surrounded by a similarplot to eliminate border effects. The authors analyzed the data by amultifactorial analysis of variance using the statistical programStatgraphics Plus 5.1 (Statistical Graphics, Rockville, MD).

Fig. 1. VSWC at 10 cm soil depth for FI in different PS and dailyrainfall (vertical bars) during each growing season

Fig. 2.VSWC at 10 cm soil depth (darker solid line) and sum of valuesof the VSWC at 10, 20, and 30 cm (lighter solid line) soil depth inridges for DI and daily rainfall (vertical bars) during each growing season

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They compared the differences between the means by using theLSD test at P ≤ 0.05.

Results and Discussion

The FC value, at 10 cm depth, for DI was 0.20 m3 m−3 in 2007 and0.17 m3 m−3 in 2008, whereas for FI it was 0.25 m3 m−3 in bothyears. Figs. 1 and 2 show the VSWC during the vegetative growthstage for the two IS and the daily rainfall in 2007 and 2008, respec-tively. Fig. 1 indicates the ridges (R) by a darker solid line, the flatraised bed with two plant rows (B2) by a lighter solid line, and theflat raised bed with three plant rows (B3) by a dotted line. With FItreatments, although water delivery was restricted to the three-day

on/three-day off schedule, the start of each irrigation event wasclose to the scheduled irrigation program. The 2008 spring rainfalldelayed the first irrigation event, reducing the number of irrigationevents in this growing season and the corresponding seasonal IWA(Table 2). There were 10 irrigation events in 2007 and 8 irrigationevents in 2008. In the second irrigation event of 2007, water did notreach the central row in B3, because the application time was tooshort. After adjusting the application time for the subsequent irri-gation events, the application times for B3 (and also for B2) wereadequate to increase the VSWC to levels similar to that of R. In2007, the VSWC values for R, B2, and B3 were similar throughoutthe growth period, whereas in 2008, the values for R were lowerthan those for B2 and B3 until the middle of August.

For the DI system in 2008, the authors observed that irrigationevents were more frequent because of the lower IWA each time, aconsequence of the automation of irrigation management. For bothGS, VSWC ranged between 0.14 and 0.23 m3 m−3 (except for therainfall events).

Table 2 shows the seasonal IWA values, being registered thehighest and the lowest values in R, ranging between 375 (DI for2008) and 1,149 mm (FI for 2007). The seasonal rainfall water in-put was 498 and 438 mm in 2007 and 2008, respectively. Figs. 3and 4 show the average plant biomass, tuber biomass, and harvestindex (HI) values for 2007 and 2008, respectively. Figs. 3 and 4indicate RDI by a darker solid line, B2DI by a darker dashed line,

Table 2. Irrigation Water Applied (mm) for FI and DI in Different PSduring Each Growing Season

Irrigation and PS 2007 2008

FI, R 1,149 994FI, B2 861 745FI, B3 574 497DI, R 504 375DI, B2 756 563DI, B3 756 563

Fig. 3. Average values in the different PS for FI and DI in 2007: (a) plant biomass: (b) tuber biomass accumulation; (c) harvest index

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B3DI by a darker dotted line, RFI by a lighter solid line, B2FI by alighter dashed line, and B3FI by a lighter dotted line. Plant biomassincreased during the cultivation phases to 2.3 kgm−2; the maxi-mum value obtained corresponded to B3 with DI in 2008. Initially,the aboveground biomass accounted for most of the plant biomass(HI < 0.5), but starting in August, the tuber biomass (HI > 0.5) ex-ceeded the aboveground biomass because of translocation to thetubers and leaf senescence. Figs. 3 and 4 show that, in general,DI led to higher plant and tuber biomass than FI, and flat raisedbeds resulted in higher plant and tuber biomass than R, whichagrees with the results obtained at harvest time. The GS had a largeimpact on biomass and tuber accumulation. Pascual-Seva et al.(2013) reported that differences among biomass and yield obtainedin different GS are typical in the traditional chufa cultivation,mainly because of different climatic conditions during the first partof the cultivation cycle.

Table 3 provides yield, ATW, and IWUE corresponding to thecommercial harvest period. GS (P ≤ 0.01), IS (P ≤ 0.01), and PS(P ≤ 0.05) significantly affected tuber yield, and the authors ob-served no significant interaction (P ≤ 0.05) between these factors.The highest tuber yields were obtained in 2007 (2.30 kgm−2), withDI (2.33 kgm−2) and with flat raised beds (B2: 2.30 kgm−2; notsignificantly different than B3: 2.21 kgm−2). The lowest yield wasobtained in 2008 with the combination of R and FI (1.91 kgm−2),which measured consistently lower VSWC than the flat raised beds

Fig. 4. Average values in the different PS for FI and DI in 2008: (a) plant biomass; (b) tuber biomass accumulation; (c) harvest index

Table 3. Influence of GS, IS, and PS on Yield, ATW, and IWUE

FactorsYield

(Kgm−2) ATW (g)IWUE

(Kgm−3)GS 2007 2.30a 0.67a 3.22a

GS 2008 2.10a 0.59a 3.70a

IS furrow 2.07a 0.59a 2.78a

IS drip 2.33a 0.67a 4.13a

PS ridges 2.09a 0.63 3.39a

PS beds with two plant rows 2.30a 0.63 3.24a

PS beds with three plant rows 2.21a 0.61 3.74a

ANOVAParameters (degrees of freedom) Sum of squares (%)GS (1) 15.8b 26.9b 5.6b

IS (1) 26.6b 27.5b 43.2b

PS (2) 11.9b 1.3c 4.1b

GS × IS (1) 1.1c 0.3c 3.8b

GS × PS (2) 4.1c 0.9c 0.6c

IS × PS (2) 6.5c 1.0c 37.2b

GS × IS × PS (2) 4.9c 0.4c 0.6c

Residuals (24) 29.9 38.2 4.8Standard deviation 0.17 0.06 0.27aMean values with significant differences at P ≤ 0.05 using the LSD test.bSignificant differences at P ≤ 0.05 (P ≤ 0.01).cNo significant difference.

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until the middle of August. Pascual-Seva et al. (2013) reported thatmaintaining a higher VSWC would increase chufa yield.

The greater yield obtained with DI relative to FI agrees with theresults of Pascual-Seva et al. (2010), who also reported a positivelinear increase in yield with IWA by DI. The PS results alsoagree with those obtained by Pascual-Seva et al. (2012), albeitwith slightly different distances from bed center-to-center in B2(90 cm) and, therefore, different plant densities. They reportedhigher yield in B2 than in R, and a significant interaction betweenGS and PS, with the significant differences between B2 and B3 andbetween B3 and R dependent on the GS (Pascual-Seva et al. 2012).Potato studies by Caliskan et al. (2009) also agree that the optimi-zation of plant density is of great importance in maximizing thetuber yield, because increasing plant density per unit area normallyresults in a competition between plants for production inputssuch as solar radiation, water, and nutrients, whereas supraoptimaldensities lead to wasting of these inputs. The yield increase withincreasing plant density up to a certain threshold may have hap-pened in the Pascual-Seva et al. (2012) study and has been observedin other root and tuber crops [i.e., potato (Caliskan et al. 2009) andonion (Brewster and Salter 1980)] and in other fruiting crops[i.e., strawberry (López-Medina et al. 2001; González and Acuña2009)]. In the present paper, with the same plant density in B2 andB3, only the yield of B2 was significantly higher (P ≤ 0.05) thanthat of R, with no significant differences (P ≤ 0.05) observed be-tween B2 and B3 or B3 and R because of the competition amongthe plants as previously mentioned.

Besides plant density, yield may be influenced by plant row dis-tribution. In potatoes, Essah and Honeycutt (2004) reported highertotal yields and marketable yields for raised beds using green-sprouted seed tubers, but this was not observed for nonsproutedseed tubers. In sweet potatoes, another tuber crop, Nasare et al.(2009) reported no significant increase in tuber yield when broadbed furrows were used rather than ridges and furrows. In straw-berries, Ram et al. (2009) reported higher yields in a row plantsystem compared with flat beds with the same plant density; never-theless, López-Medina et al. (2001) performed their experiments ina double hill system, and González and Acuña (2009) used a raisedbed with two or four rows of plants. In the present paper, althoughboth B2 and B3 produced higher yields than R, the differences wereonly significant (P ≤ 0.05) for B2. In accordance with those results,the technique of using raised beds appears promising if the properequipment (adapted to the bed dimensions) is available to growers(Mundy et al. 1999).

Both the GS and IS affected the ATW (P ≤ 0.01), with the high-est values found in 2007 (0.67 g) and with DI (0.67 g), but PS didnot affect the ATW (P ≤ 0.05). Results agree with those obtained inthe flat raised bed in the FI study: 0.61–0.64 g (Pascual-Seva et al.2012). The three factors considered in this paper (GS, IS, and PS)influenced (P ≤ 0.01) IWUE, with the highest efficiencies obtainedin 2008 (3.70 kgm−3), DI (4.13 kgm−3), and B3 (3.74 kgm−3),although two interactions (GS-IS and IS-PS) were also significant(Table 3). In 2008, the DI management was automated, stoppingeach session as a function of the VSWC, reducing IWA (375 mm)relative to 2007 (504 mm) and increasing IWUE. For DI, the averageIWUE value obtained with R (4.88 kgm−3) was higher (P ≤ 0.05)than with B2 or B3 (3.82 and 3.70 kgm−3, respectively), but theauthors observed the opposite behavior for FI (P ≤ 0.05), withthe lowest IWUE obtained with R (1.91 kgm−3), the highest withB3 (3.78 kgm−3), and an intermediate value with B2 (2.66 kgm−3).Within each IS, IWUE differences were mainly because of differen-ces in IWA. In DI, there was a single lateral line per plant row,16,667 mha−1 for R and 25,000 mha−1 for B2 and B3; conse-quently, the IWA value for R was 66.7% of the corresponding B2

and B3 values. In FI, the furrow number per unit surface of B3was the 50% that of R and 66.7% that of B2, consequently theIWA values represent 50% and 66.7%, respectively.

When comparing the different planting rows in B3 (Table 4),both IS and PRP affected the yield (P ≤ 0.01), but their interactionwas not significant (P ≤ 0.05). The highest tuber yields wereobtained with DI (1,009 g · m−1) similar to results obtained atplot-level (Table 3) and in the S row (1,028 gm−1), differing(P ≤ 0.05) from C (938 gm−1), which, in turn, differed(P ≤ 0.05) from N (892 gm−1). Similar results were found forB2 (Table 4), with the highest (P ≤ 0.05) tuber yield obtainedin DI (954 gm−1) and in the S row (952 gm−1). None of theconsidered factors (GS, IS, and PRP) influenced (P ≤ 0.05)ATW, neither for B2 nor for B3. Against the general viewpoint,the C row did not produce a lower yield (than the N row) or smallertubers. These results agree with the results from Mundy et al.’s(1999) study with potatoes; no differences in marketable and totalyields were found among the three rows in beds.

Conclusions

Planting in flat raised beds is advisable, because it leads to anincreased yield, particularly in beds with two plant rows, withoutdiminishing the average tuber size. In beds, tubers produced in thedifferent plant rows reach similar ATW. In surface irrigation, oneobtains important water savings by using beds compared with usingthe traditional ridge planting system. Research studies are currentlycarried out for analyzing different irrigation schedules to improveirrigation water use efficiency in flat raised beds.

References

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Table 4. Influence of GS, IS, and Plant Row Position (PRP) on Yield andATW in Beds with Three (B3) and Two (B2) Plant Rows

Factors

B3 B2

Yield(gm−1)

ATW(g)

Yield(gm−1)

ATW(g)

GS 2007 939.4 0.54 927.4 0.58GS 2008 966.0 0.58 901.7 0.57IS furrow 896.0a 0.54 875.5a 0.60IS drip 1,009.3a 0.58 953.6a 0.55PRP north 892.4a 0.56 887.0a 0.57PRP central 937.6a 0.56 — —PRP south 1,028.0a 0.55 952.1a 0.59ANOVAParameters (degrees of freedom)b Sum of squares (%)GS (1;1) 1.9c 4.6c 3.3c 0.0c

IS (1;1) 33.7d 4.4c 60.5d 4.5c

PRP (2;1) 33.4d 0.2c 28.2d 1.0c

GS × IS (1;1) 0.5c 0.1c 0.0c 6.8c

GS × PRP (2;1) 5.1c 6.3c 7.4c 0.0c

IS × PRP (2;1) 2.9c 3.8c 0.3c 0.0c

GS × IS × PRP (2;1) 3.1c 5.7c 0.7c 0.3c

Residuals (24;16) 19.4 74.8 29.7 87.4Standard deviation 52.59 0.10 47.25 0.12aMean values indicate significant differences at P ≤ 0.05 using the LSDtest.bIndicates the degrees of freedom (i; j) on B3 and B2 analyses,respectively.cIndicates no significant difference.dIndicates significant differences at P ≤ 0.01.

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