Effect of varying Irrigation Frequencies on Growth, Yield and Quality ...

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342 I. Ashraf et al. Jan 13.5 12.5 58.1 67.4 8.2 0.0 Feb 20.3 15.5 52.4 67.1 14.6 55.9 Mar 21.4 19.4 40.7 47.0 37.0 41.3 Apr 29.2 28.9 23.4 35.1 0.0 0.0 May 34.8 32.2 23.9 25.0 24.0 0.0 Source: Crop Physiology Department, Meteorological Station, University <strong>of</strong> Agriculture, Faisalabad. RESULTS AND DISCUSSION Main stem length (cm) The data (Table 2) revealed that on the basis <strong>of</strong> two years average, both the cultivars performed significantly better in I 3 treatment (12 irrigations upto seed filling). Meteor had more main stem length (58.0 cm) than Climax (55.0 cm) in this treatment. Treatment I 4 (13 irrigations upto maturity) stood second in case <strong>of</strong> both cultivars (Climax 54.9 cm and Meteor 54.5 cm), while I 1 (8 irrigations upto flowering) produced the shortest stem length (Table 2). The data further showed that both cultivars produced higher stem length during second year <strong>of</strong> study i.e. 2006-07 (Meteor 58.0 cm and Climax 57.2cm) due to higher rainfall. Availability <strong>of</strong> moisture to plants during the year 2006-07 enhanced the plant health and vigour which resulted in more stem length. Similar findings have been reported by Hsio et al. (13) who observed that water stress was a limiting factor for proper plant growth. These results partially contradict the findings <strong>of</strong> Salter (23) who noted positive response <strong>of</strong> irrigation till flowering in peas. Number <strong>of</strong> leaves per plant Significantly maximum number <strong>of</strong> leaves per plant was recorded in treatment I 3 (irrigation upto seed filling stage) in case <strong>of</strong> both cultivars (Table 2). In this treatment Meteor had more number <strong>of</strong> leaves (67.1) than Climax (61.5) followed by treatment I 4 (irrigation upto seed maturity stage) (65.5 in Meteor and 60.8 Climax). As far as years effect is concerned both cultivars gave more number <strong>of</strong> leaves in the year 2005-06 (64.0) and stood at par. The results further revealed that irrigation upto flowering did not prove its worth. Vegetative growth was more sensitive to water stress than reproductive growth in peas. Peas are an indeterminate plant and flowering, pod filling and vegetative growth can occur simultaneously. There is competition for assimilate between these processes and the response <strong>of</strong> yield components will vary according to the relative strengths <strong>of</strong> the sources and sinks for assimilates. Salter (24) and Maurer et al (17) found excessive vegetative J. Agric. Res., 2011, 49(3)
<strong>Effect</strong> <strong>of</strong> irrigation frequencies on pea 343 growth where water stress was avoided. The present results are also in line with those <strong>of</strong> Hsio et al. (13) who reported that water stress during growing stage reduced the growth <strong>of</strong> pea plants. Leaf area (cm 2 ) Results <strong>of</strong> leaf area (cm 2 ) were found similar to those <strong>of</strong> number <strong>of</strong> leaves per plant. Maximum leaf area was observed in treatment I 3 in case <strong>of</strong> both cultivars. Meteor cultivar had comparatively more leaf area (246.0 cm 2 ) than Climax (241.0 cm 2 ) (Table 2). These results are similar to those <strong>of</strong> Hsio et al (13) who reported that water stress reduces growth via affection cell expansion. In experiments with two pea cultivars, Salter (23, 24) also observed a response to irrigation at flowering but not to application <strong>of</strong> water in dry conditions during the vegetative growth stage. Number <strong>of</strong> pods per plant In this trait also both cultivars produced more number <strong>of</strong> pods per plant (Meteor 25 and Climax 22.3) in I 3 i.e. irrigations upto seed filling stage followed by I 4 i.e . irrigations upto seed maturity in case <strong>of</strong> Meteor (23.5) and I 2 in case <strong>of</strong> Climax (21.5) (Table 3). For years effect, Climax gave more number <strong>of</strong> pods per plant during the year 2005-06 (22.1) than the year 2006- 07 (19.8). However, Meteor produced similar number <strong>of</strong> pods during both years (22.7) which was higher than Climax. <strong>Irrigation</strong> upto flowering (I 1 ) produced the lowest number <strong>of</strong> pods (17.2) during the year 2006-07. <strong>Irrigation</strong> at any growth stage increased the yield <strong>of</strong> Meteor. The highest yields for this cultivar were achieved where irrigation was applied throughout the season but these results did not differ significantly from other irrigation treatments where less water was applied. There was also a more effect <strong>of</strong> irrigation on Meteor cultivar than Climax. . As in the previous year, Meteor was also more responsive to irrigation at vegetative stage than Climax and overall. In this experiment, water stress might have a stronger effect on reducing the number <strong>of</strong> pods/unit area than on leaf area development. The low yields were associated with low number <strong>of</strong> pods, nodes/stem and pods/node and a slower increase in pod weight (19). Whether these changes would affect the balance between sources and sinks, is uncertain. The resulting source-sink relationships during the filling phase would then have been quite different for early and late drought plots experienced. Consequently, there may have surplus photosynthates to fill the peas in treatments with low pea numbers perunit area despite less J. Agric. Res., 2011, 49(3)
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