Corn yield response to irrigation interval and the resultant savings in water and other overheads

The aim of this project was to conduct research into the effect of irrigation interval, using drip irrigation, on the depletion of available soil moisture and on corn yield, and the possible savings it might bring about in water, manpower, energy and
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  CORN YIELD RESPONSE TO IRRIGATION INTERVAL AND THE RESULTANTSAVINGS IN WATER AND OTHER OVERHEADS y PASCHALIS S. DIOUDIS 1 , AGATHOS T. FILINTAS 1 AND ARISTOTELIS H. PAPADOPOULOS 2 * 1 Technological Educational Institute of Larissa, Faculty of Agriculture, Department of Agricultural Engineering and Irrigation, Larissa, Greece 2  NAGREF/ Soil Science Institute, Thermi, Thessaloniki, Greece ABSTRACTThe aim of this project was to conduct research into the effect of irrigation interval, using drip irrigation, on thedepletion of available soil moisture and on corn yield, and the possible savings it might bring about in water,manpower, energy and other overheads. The experiments were carried out between 2000 and 2001 in the plain of Thessaly, central Greece. The experimental field had a complete randomized block design and consisted of threetreatments (i.e. irrigation every 2, 5 and 9 days) for four replicates. Daily measurements were taken of the soilmoisture content using the time domain reflectrometry (TDR) method and the depletion of available soil moisturewas calculated. The amount of water used in each irrigation session was equal to the cumulativeevapotranspirationbetween two successive irrigation sessions as measured using evaporation pan type A.Results showed that irrigation could be carried out every nine days instead of every two or even five days, thusbringing about substantial savings in the consumption of water. In addition, other overheads such as manpower,energy, etc. could be cut down with no statistically significant difference in crop yield. Copyright # 2008 JohnWiley & Sons, Ltd. key words : corn yield; irrigation scheduling; drip irrigation; TDR; available soil moisture; water savings  Received 22 November 2006; Revised 28 November 2007; Accepted 3 December 2007  RE´SUME´Lebutdecetravaile´taitdeconduireunerecherchesurl’effetdel’allongementdel’intervalleentreirrigations(maı¨sirrigue´ au goutte a` goutte) sur la diminution de la re´serve en eau du sol et sur le rendement, ainsi que les e´conomiespossibles sur l’eau, la main d’œuvre, l’e´nergie et les autres charges ge´ne´rales. Les expe´rimentations ont e´te´conduites en 2000 et en 2001 dans la plaine de Thessalie en Gre`ce centrale. Le terrain expe´rimental comportait unbloc complet randomise´ avec trois traitements (soit une irrigation tous les 2, 5 et 9 jours) et quatre re´pe´titions. Desmesures ont e´te´ faites quotidiennement sur l’humidite´ du sol selon la me´thode TDR (temps, domaine, re´flectome´-trie) et la diminution de la re´serve en eau du sol a e´te´ calcule´e. Le volume de chaque irrigation e´tait e´gal a`l’e´vapotranspiration cumule´e entre deux irrigations successives telle que mesure´e a` l’aide d’un e´vaporome`tre detype A.Les re´sultats ont montre´ que l’irrigation peut eˆtre re´alise´e tous les 9 jours au lieu de 5 ou de 2, conduisant ainsi a`de substantielles e´conomies d’eau. En outre d’autres charges telles que main d’œuvre, e´nergie, etc., ont pu eˆtree´conomise´e sans diffe´rence significative de rendement. Copyright # 2008 John Wiley & Sons, Ltd. mots cle´s : rendement du maı¨s; pilotage de l’irrigation; irrigation au goutte a` goutte; TDR; re´serve en eau du sol disponible; e´conomie d’eau IRRIGATION AND DRAINAGE  Irrig. and Drain.  58 : 96–104 (2009)Published online 29 May 2008 in Wiley InterScience (  DOI : 10.1002/ird.395*Correspondence to: Dr Aristotelis H. Papadopoulos, NAGREF/Soil Science Institute of Thessaloniki, P.O. BOX 60435, 570 01 Thermi,Thessaloniki, Greece. E-mail: y Rendement du maı¨s et espacement des irrigations, effet sur l’e´conomie d’eau et d’autres charges. Copyright # 2008 John Wiley & Sons, Ltd.  INTRODUCTION Corn(  ZeamaysL  .)iscultivatedinareas lyingbetween58 8 Nand40 8 Sfromsealeveluptoanaltitudeof3800m.Itis a crop which is irrigated worldwide (Musick   et al ., 1990; Filintas, 2003), the main corn-producing country beingthe USA (Filintas, 2003).In Greece, 266700ha are given over to corn cultivation (Greek National Statistical Organization, 2002), i.e. 5%of the country’s total cultivated area. In the years 2000 and 2001, according to data issued by the Ministry of Agriculture, the average corn yield in Greece was 9477 and 9676kgha  1 , respectively (Filintas, 2003).According to Musick and Dusek (1980), corn requires large quantities of water seasonally if it is to yield a largecrop. Panoras  et al . (1997) reached the same conclusion and observed that restricting water quantities in cornirrigation (replenishing only 65–66% of the water deficit) during an experiment conducted in the plain of Thessaloniki reduced the crop yield by 37%.Gill etal .(1996)conductedresearch,oncoarse soil,intotheeffectoftilling,theincorporationornotofmulch,and irrigation on crop yield. The aforementioned researchers observed that corn production was increased with acombination of deep tillage and the incorporation of hay deposits in mulch, together with a general increase incrop irrigation. Various other research scientists – Storchshnabel (1965), Klapp (1967), Mpountonas andKaralazos (1968), Zarogiannis (1979), Danalatos (1992), Dioudis  et al . (2003a, b), Filintas (2003), Filintas  et al .(2006, 2007), who have made an extensive study of irrigation in the cultivation of corn – drew the same conclusion, i.e. that irrigation is of the utmost importance, from the appearance of the first silk strands until themilky stage in the maturation of the kernels on the cob. Once the milky stage has occurred, the appearance of black layer development on 50% of the corn kernels is a sign that the crop has fully ripened, according to Renchand Shaw (1971) and also Danalatos (1992) who carried out research in an experimental field in Greece. Theaforementioned criterion was used in the experimental plots for the total irrigation process. In Greece, irrigationtakes place from June until the ripening stage mentioned above, which usually occurs some time around themiddle to the end of August (Danalatos, 1992; Dioudis  et al ., 2003a, b; Filintas, 2003) but which may evenextend into the first two weeks of September (Danalatos, 1992; Filintas, 2003; Dioudis  et al ., 2003a; Filintas et al ., 2006, 2007). Most research projects on this particular subject refer to the effect of irrigation on corn yield using sprinkler orfurrow irrigation. In contrast, only a few studies have been made on corn cultivation using drip irrigation (Danalatos,1992; Dioudis  etal .,2003a,b;Filintas,2003; Filintas  etal .,2006, 2007).Inthese studies the evaporation pan method was used to calculate the amount of water needed for irrigation. The evaporation pan method was also used inEngland, in 2001, for an irrigation schedule which was applied to 45% of the irrigated areas of the country (outdoorcultivation, not in greenhouses) (Weatherhead and Danert, 2002).The aim of this project was to carry out research on the effect of irrigation interval on the depletion of availablesoil moisture and its effect on the corn yield irrigated with drip irrigation, thus bringing about substantial savings inthe consumption of water and other overheads such as manpower, energy, etc. MATERIALS AND METHODS  Description of installation The project was carried out during the cultivation season of the years 2000 and 2001 on the farm of theTechnological Educational Institute of Larissa in the plain of Thessaly, central Greece.A drip irrigation system was installed and the effect of irrigation interval (2, 5 and 9 days) on the corn yield wasstudied and evaluated. Soil moisture content was also studied and evaluated daily.The irrigation system (Figure 1) consisted of: (a) an irrigation head unit (filter, hydrocyclone, hydro fertilizer,etc.); (b) a primary conduit, made of metal (diameter, 89mm); (c) secondary conduits, made of polyethylene (PE40mm/6.08 bar); (d) drip laterals. The drip laterals were made of low density polyethylene (PELD), (externaldiameter 20mm) with internal spiral-line drippers achieving a flow (nominal discharge) of 4lh  1 for a nominalpressure of 1.215 bar and the space between drippers being 0.50m. Copyright # 2008 John Wiley & Sons, Ltd.  Irrig. and Drain.  58 : 96–104 (2009)DOI: 10.1002/irdCORN YIELD RESPONSE TO IRRIGATION INTERVAL  97  Experimental design The experiments were conducted during the years 2000 and 2001 in an experimental field with a completerandomized block design layout consisting of three treatments, for four replicates. The three treatments were,according to their respectiveirrigation interval {E}, everytwodays {E2}, every fivedays {E5} and every nine days{E9}, for four replicates. The experimental design layout and the drip irrigation system layout are shown inFigure 1.Each experimental plot was 10m wide (the width was at right angles to the seed rows) and 12m long (the lengthwas parallel to the seed rows). The distance between the corn rows was 0.75m.  Methodology Measurements were taken of the dripper discharge and were seen to be within the limits set down by themanufacturer (Figure 2).Measurements were also taken daily of the soil moisture volume in the experimental plots, throughout the entireirrigation season, using the TDR (time domain reflectrometry) method. The TDR method is a non-radioactive onewhich has been proved to be quick and reliable, irrespective of soil type (ESI Environmental Sensors Inc., 1997;Filintas, 2003; Dioudis  et al ., 2003a; Filintas  et al ., 2007). ATDR device from the ESI company was used, whichwas tested and calibrated using laboratory measurements at the beginning of each cultivation season. Testing thesoil moisture content is a very complex process and the placing of a sensor at the root level of the crop is, in themajority of cases, not sufficient for a satisfactory performance of the test. As a solution to this problem, quite anumber of researchers, Filintas (2005), Campbell and Campbell (1982) and Cary and Fisher (1983), recommendusing two or more sensors at various depths, so that a greater area of the root level is covered.In order to do this andto ensure greater accuracy, soil moisture probes with five sensors each were used and lay permanently installed inthe 12 experimental plots, where they were in continuous contact with the soil. Each probe had sensors whichmeasured the soil moisture content at five different depths: 0–15, 15–30, 30–45, 45–60 and 60–75cm. From themeasurements taken at each position, the average value was calculated from the five depths for each treatment Figure 1. Layout of the experimental plots (treatment E2, E5, E9 are irrigation intervals every 2, 5 and 9 days, respectively) and of the dripirrigation systemCopyright # 2008 John Wiley & Sons, Ltd.  Irrig. and Drain.  58 : 96–104 (2009)DOI: 10.1002/ird 98  P. S. DIOUDIS  ET AL.  (irrigation interval of 2, 5 and 9 days). Moreover, from the daily soil moisture content testing, the available soilmoisture depletion (ASMD) for each treatment was calculated and the results can be seen in Figure 3.The volume of irrigation water used, for each treatment, was equal to the cumulative evapotranspiration (ETc)betweentwoconsecutiveirrigationsessionsasestimatedwiththeaidofanevaporationpantypeA,correctedbytherespective coefficient  K  p  of the evaporation pan.It has been observed that the root development, at deeper levels, is greater in dry areas, due to the roots’ need toseek moisture at a deeper level. For this reason, the first irrigation was delayed (until after sowing) so that the rootsystem could develop at a deeper level.At the end of each cultivation period, once the crop had fully ripened with the appearance of black layerdevelopment on 50% of the corn kernels, which is the sign of crop maturation (Rench and Shaw, 1971; Danalatos,1992), the corn crop was harvested. Then the cobs were separated from the corn ears, the kernels from eachexperimental plot were removed from the cobs and weighed. In this way, the corn yield from each treatment wasaccurately determined. RESULTS AND DISCUSSION The soil of the experimental field was a heavy one with 28.5% sand, 25.5% silt and 46.0% clay. The field capacityon a dry weight basis was 31.2%, the permanent wilting point 17.1% and the bulk density 1.42gcm  3 . Thesaturated hydraulic conductivity,measured using a Guelph permeameter, was found tobe 3.0  10  5 cms  1 for thefirst 15cm of the soil and 3.2  10  5 cms  1 at a depth of 45cm. Finally, the pH of the soil was found to be 7.5.From the soil moisture content measurements (the averageofthe total measurements atthe fivedifferent depths),the depletion of available moisture was calculated daily and a chart drawn up of the available soil moisturedepletion in relation to each irrigation interval (Figure 3). The negativevalues which appear in Figure 3 apparentlycorrespond to soil moisture values greater than the field capacity and they may be attributed to rainfall (Figure 4).It is reported (Doorenbos and Kassam, 1986) that for the cultivation of maize, soil water depletion up to 55% of available soil water, has a non-statistically significant effect on corn yield (  p ¼ 0.55). Moreover, it is recommended(Doorenbos and Kassam, 1986), that in order to meet full water seasonal requirements, the water depletion levelshouldrangebetween55and65%duringthevariousperiods(vegetative,flowering,yieldformation)andupto80%during the ripening period. Figure 2. Chart of pressure versus dripper discharge from the measurements taken (a) by the manufacturer and (b) in the laboratoryCopyright # 2008 John Wiley & Sons, Ltd.  Irrig. and Drain.  58 : 96–104 (2009)DOI: 10.1002/irdCORN YIELD RESPONSE TO IRRIGATION INTERVAL  99  Table I shows the maximum and mean peak values of ASMD for the two years and for each irrigation interval.The mean peak depletionvalues of ASM for both years were 25.7% for an irrigation interval of 2 days (E2), 44.0%for an irrigation interval of 5 days (E5), 62.5% for an irrigation interval of 9 days (E9). These values of ASMD areconsistent with the peak depletion values recommended above (Doorenbos and Kassam, 1986).The results of the corn yield for the years 2000 and 2001 of the three treatments are shown in Figure 5. Thestatistical analysis (Table II) of the two years’ corn yields shows that the yield variation for each irrigation interval Figure 3. Chart of available soil moisture depletion versus time, for the three treatments (E2, E5 and E9) for the years 2000 and 2001Copyright # 2008 John Wiley & Sons, Ltd.  Irrig. and Drain.  58 : 96–104 (2009)DOI: 10.1002/ird 100  P. S. DIOUDIS  ET AL.

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