Effect of different water regimes on agronomical traits and irrigation efficiency in bread wheat (Triticum aestivum L.) grown in the Nile Delta

M. E. Ibrahim1, S. M. Abdel-Aal1, Mahmoud F. M. Seleiman1,2 Hamid Khazaei2 and Philippe Monneveux3

 

1 Department of Crop Science, Faculty of Agriculture, Minufiya University, Egypt

2 Department of Applied Biology, P. O. Box 27 , University of Helsinki , FIN-00014, Finland

3 Montpellier SupAgro 2, place Pierre Viala 34060 MONTPELLIER Cedex 01, France

Corresponding Author: Mahmoud F. Seleiman

E-mail: mahmoud.seleiman@yahoo.com

 

Abstract

Irrigation is the most important factor in determining bread wheat (Triticum aestivum L.) yield in Egypt. The effects of different water regimes were investigated during two years on growth and yield components of the cultivar Gemmeiza 9 cultivated under three and four irrigations at 30 days interval, and five and six irrigations at 25 days interval. Grain filling rate and effective grain filling period were also calculated for each treatment. Significant effects of the water regime were found on all measured traits. However, increasing the number of irrigations from five to six, keeping the same interval of time between irrigations, did not significantly increased grain yield, harvest index, number of tillers and spikes per m2, spike length and fertility, thousand kernel weight and grain weight per spike. The grain production obtained by irrigation (or irrigation efficiency) was similar under three and four irrigations at 30 days interval but drastically decreased under five and six irrigations at 25 days interval. For the number of tillers and spikes per m2 as well as for grain yield, gains decreased with each additional irrigation, up to three irrigations. Conversely, for the number of grain per spike and to a lesser extent for thousand kernel weight, the highest gains were noted when both the number and frequency of irrigation increased, i.e. when the crop was irrigated five times at 25 days interval, rather than four times at 30 days intervals. The study emphasizes the importance, for irrigated wheat, to define irrigation timing and frequency that allow maximal yield and optimal use of irrigation water.

Introduction

Wheat (Triticum aestivum L.) is one of the most important crops in Egypt. According to FAO (2009), wheat is cultivated on 1.2 million hectares with a production of 8 million tons. Egypt however still imports 6 million tons of wheat to cover its consumption. An important objective of the Egyptian government is consequently to reduce the dependence on imported wheat by enhancing grain yield and production (Kherallah et al. 2000). As most of the Egyptian wheat is produced under irrigated conditions, it is essential to determine the water regimes leading to highest yield and irrigation efficiency. Irrigated wheat is cultivated in Egypt under low rainfall and late heat stress conditions, especially with late sowing. These conditions correspond to wheat mega-environment 1 (ME1) as defined by Rajaram et al. (1995). Under ME1 conditions, Abd El-Gawad et al. (1994) found that increasing number of irrigation from two to four increased thousand kernel weight. Ibrahim et al. (1996) and Khatun et al. (2007) reported yield increase with the increase of irrigation frequency. Alderfasi et al. (1999) observed a significant increase of plant height, fertile tillering, thousand kernel weight and grain and biological yields with increased amount of irrigation. Dawood and Kheiralla (1994) and Bankar et al. (2008) observed that five irrigations at crown root initiation, tillering, jointing, flowering and milking stages, led to the highest yield. The present study was carried out to determine the water regime leading to highest yield in the case of the cultivar Gemmeiza 9 in the Nile Delta, and to analyze the differences for yield components and other agronomical traits in the different treatments. Efficiency of irrigation and gains obtained from each additional irrigation were also calculated under for yield and yield components.

Material and Methods

The experiments were conducted at the Experimental Farm of the Faculty of Agriculture, Minufiya University, Egypt, during the growing seasons 2004-2005 and 2005-2006 (thereafter referred as season 1 and 2) on the bread wheat (Triticum aestivum L.) cultivar Gemmeiza 9. The preceding crop was maize in both seasons. The soil texture was a clay loam with a pH of 7.8 and an organic matter concentration of 2.0%. Rainfall was low during the vegetative period (42 and 30 mm during the growing seasons 1 and 2, respectively), and nil during the reproductive period. Average maximal temperature during grain filling was around 32.5oC.

The experiment included four water regimes: 3 irrigations (I3) and 4 irrigations (I4) at 30 days intervals and 5 irrigations (I5) and 6 irrigations (I6) at 25 days intervals. The first irrigation was brought on December 15 for I3 and I4 and December 10 for I5 and I6. As a consequence of differences in the date of the first irrigation as well as in irrigation number and frequency in the different treatments, the last irrigation was done on February 13, March 15, March 20 and April 15 in I3, I4, I5 and I6 treatments, respectively. The four treatments were arranged in a randomized complete block design with four replications. The area of each experimental plot was 12 m2 (4*3 m). Calcium super phosphate (15.5% P2O5) was applied during soil preparation at the rate of 15.5 kg P2O5 by fed (i.e., 37 kg ha-1). Sowing was done on 15th November in both growing seasons. Seeding density was 350 seeds m-2 and row width was 20 cm. Total nitrogen fertilization was applied at a rate of 60 kg N by fed (i.e., around 140 kg ha-1) as urea (46.5%) in two equal doses, before the first and second irrigations.

Days from sowing date to heading and physiological maturity were recorded for each plot. At harvest one square meter was taken randomly from the middle area of each plot to determine plant height (cm), number of tillers and spikes per m2, spike length (cm), number of spikelets and grains per spike, thousand kernel weight (g) and grain yield per spike (g). Grain, straw and biological yield (t ha-1) were determined from the whole plot area. Harvest index was estimated as the ratio of grain yield to biological yield and was expressed in per cent.    

For estimating grain filling rate, five main spikes were collected from each plot at 14, 21, 28, 35 and 42 days after heading. 10 grains from the middle part of each of the 5 spikes were removed, oven dried at 80◦C for 24h and weighed. Grain filling rate was calculated as GFR = (wt+1 – wt)/[(t+1) – t] where wt+1 and wt represent grain dry weight per spike at time t+1 and t, respectively, and was expressed in mg spike-1 day-1. Effective grain filling period was estimated according to Daynard et al. (1971) as the ratio of the final grain weight per spike to the average grain filling rate. 

Data obtained were analyzed using Statistical Package for Social Science, version 10 (SPSS, 1999). Mean of values were compared at 5 % level of probability using Duncan's multiple range test.

Results and Discussion 

The different water regimes had a pronounced effect on the duration of the vegetative and reproductive periods, and on the growing cycle duration (Table 1). The shortest vegetative and reproductive periods were noted when plants were irrigated three times (I3). These results are in agreement with Alderfasi et al. (1999) who found that the number of days from sowing to flowering and maturity was increased by increasing the amount of irrigation from 2000 up to 7500 m3/ha.

Irrigations number and frequency also showed a significant effect on grain yield (Table 2). In both seasons, the highest grain yield was obtained when plants were irrigated six or five times at 25 days intervals compared with four or three times at 30 days intervals. Grain yield increases from I3 to I4, I3 to I5 and I3 to I6 were 33.0, 42.3 and 46.3%, respectively. Increasing the number and frequency of irrigations was also accompanied by a significant increase in straw and biological yields, as already reported by El-Monoufi and Harb (1994) and El-Barbary (1998). Straw and biological yields (averaged over the two seasons) in treatment I6 were 11.8 and 22.3% higher, respectively, than in treatment I3. Irrigating six times at 25 days interval (I6 treatment) allowed an increase of 6.5 and 7.7% of straw and biological yields over the I4 treatment and of 2.0 and 2.3% over the I5 treatment. Increase in grain yield with irrigation number and frequency being higher than increase in straw yield, harvest index increased significantly with water availability, as reported by Moursy (1999). Plant height also significantly increased with the number of irrigations. In treatments I4, I5 and I6, plant height was enhanced by 7.2, 9.9 and 13.3% in the first season and 7.0, 11.4 and 13.0% in the second season, respectively, compared to treatment I3. Plant height was also found to increase with irrigations number up to five times by El- Barbary (1998) and Moursy (1999) or six times by Dawood and Kheiralla (1994), El-Monoufi and Harb (1994) and El-Far and Allam (1995). Yield enhancement due to irrigation was associated to significant increases in number of tillers and spikes per m2, number of grain per spike and thousand kernel weight. Similar values were found, however, for number of tillers and spikes per m2 in treatments I5 and I6. The increase in the number of tillers and spikes per m2 in I6, compared to I3, was 6.0 and 8.1% in the first season and 6.8 and 8.4% in the second season. Number of grains per spike and thousand kernel weight was significantly higher in I5 and I6 treatments, compared to I3 and I4. Similarly, Abd El-All (1991), El-Monoufi and Harb (1994), El-Barbary (1998) and Moursy (1999) reported a significant increase of these components with additional irrigation. The increase in spike fertility was associated with an increase in spike length (r = 0.995, P>0.01 and r =0.996, P>0.01) and number of spikelets per spike (r = 0.994, P>0.01 and r=0.998, P<0.01).  As shown in other ME1 environments (Monneveux et al. 2005), the reduction in thousand kernel weight under limited irrigation is likely to be due to a reduction of photosynthesis associated to stomatal closure, exacerbated by the high temperature and evaporative demand that occur during grain filling (Monneveux et al. 2005). As a consequence of the increase in both number of grains per spike and thousand kernel weight, grain weight per spike was drastically enhanced by irrigation, as reported by Ibrahim et al. (1996) and Moursy (1999).

Mean values of grain filling rate and effective filling period are presented in Table 3. Grain filling rate was significantly lower under water limitation (I3) than under well-watered conditions (I6). However, no significant difference was noted between I5 and I6. Also, plants irrigated five or six times had a higher effective grain filling period compared with those irrigated three or four times.

In summary, both timing and frequency of irrigation increased yield and yield components and affected agronomical traits. However, increasing the number of irrigation from five to six, keeping the same interval of time between irrigations, did not significantly increased grain yield, harvest index, number of tillers and spikes per m2, spike length and fertility, thousand kernel weight and grain weight per spike. Similar results were obtained by El-Barbary (1998) and Moursy (1999). Moreover, the grain production obtained by irrigation (or irrigation efficiency) was similar in I3 and I4 (1.66 and 1.65 t ha-1), but drastically decreased in I5 (1.41 t ha-1) and I6 (1.21 t ha-1). As shown on Fig. 1, the highest gains obtained for each additional irrigation were noted for the number of grains per spike. Increasing the number of irrigations had more impact on the number of spikes per m2 than on the number of tillers per m2. For these two traits as well as for grain yield, gains decreased with each additional irrigation, up to three irrigations. Conversely, for the number of grain per spike and to a lesser extent for thousand kernel weight, the highest gains were noted when both the number and frequency of irrigation increased, i.e. when the crop was irrigated five times at 25 days interval, rather than four times at 30 days intervals.

These results show the importance of irrigation for wheat crop management in drought and heat prone environments. They also indicate that both irrigation timing and frequency are determining maximal agronomical and economical wheat yield in Egypt, and more generally in ME1 environments. Considering the increasing limitations of water resources, it appears essential to analyze also in details the impact of irrigation timing and frequency on water use efficiency, and more specifically on the efficiency of use of irrigation water. This would help in improving yield and production, while ensuring sustainability of wheat based systems  

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