Effect Of Water Stress At Different Periods On Growth And Yield Of Guar (Cyamopsis Tetragonoloba (L.) Taub.)

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Deng Manasseh Mac Anyang-Aluong
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University of khartoum
A field experiment was conducted for two consecutive seasons (2005 and 2006) to study the effect of water stress imposed at different growing periods on growth and yield of three guar lines (L12, L18, and L33). Three water regime treatments (withholding irrigation at 35, 50, and 65 DAS) were compared in relation to the control treatment. The treatments were laid out in a split-plot design with three replications. The water regimes were assigned to main plots while the lines were assigned to sub-plots. Vegetative growth attributes (plant height, number of main branches per plant, number of leaves per plant, leaf area index, shoot dry weight), days to 50 % flowering, yield and yield components, harvest index (HI), and some seed quality characteristics (seed moisture content, crude protein, ash, phosphorus, copper and zinc contents) were examined. Soil moisture content, leaf relative turgidity, water use efficiency (WUE); measured and estimated evapotranspiration were calculated in this study. Crop coefficients were also calculated based on estimates of pan evaporation, modified Penman’s formula, and Penman-Monteith equation. The results obtained indicated that withholding irrigation at any growing period reduced plant height, number of main branches per plant, number of leaves per plant, and leaf area index (LAI). However, the reduction was more pronounced when stress was imposed at 35 DAS, than at 50 and 65 DAS. On the other hand, the effect was not significant on the number of days to 50 % flowering, shoot dry weight, height of the first cluster pods from soil surface, number of pods per plant, 1000-seed weight, seed yield (t/ha), water use efficiency (WUE) and seed quality characteristics. In this study harvest index (HI) was reduced by withholding irrigation at all the periods, but was more clear at 35 and 50 DAS than at 65 DAS, due to the reduction effect of water stress on seed yield than on biological yield. The experiment indicated that genotypic differences among the three lines were significant on number of leaves per plant, LAI, days to 50 % flowering, number of pods per plant, 1000-seed weight, seed yield, HI, phosphorus content, and WUE. On the other hand lines were not significantly different regarding plant height, number of main branches per plant; shoot dry weight, height of the first cluster pods, seed moisture content, crude protein content, ash content, copper content, zinc content and leaf relative turgidity. However, line L12 performed best under soil water shortage than line L33, while line L18 was severely affected. The results also revealed that soil moisture contents at the top layers (0 -20cm) were reduced more than at the lower layers (20-40 and 40-60cm). High leaf relative turgidity was maintained under the control treatment, whereas it was reduced when irrigation water was withheld at all the periods. Measured crop evapotranspiration (ETc) was reduced when water stress was imposed at all the periods. However, the reduction was high when irrigation water was withheld at 65 DAS than at 35 DAS. Evaporation values recorded for pan were greater than those predicted with modified Penman’s estimate and Penman-Monteith method. This eventually resulted to the fact that, coefficient values based on Penman’s formula and Penman-Monteith equation were greater than those based on pan evaporation.
A Thesis Submitted to the University of Khartoum in Partial Fulfillment of the Requirements for the Degree of Ph.D. in Agriculture.
Water Stress Guar Cyamopsis tetragonoloba (L.) Taub. Agronomy University of Khartoum
Deng Manasseh Mac Anyang-Aluong, Effect of Water Stress at Different Periods on Growth and Yield of Guar (Cyamopsis tetragonoloba (L.) Taub.). – Khartoum : University of Khartoum, 2008. - 160 P. : illus., 28 cm., Ph.D.