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Effect of Soil Moisture Deficit on Root Growth of Upland Rice Cultivars

M. Sh. Islam
Agronomy Division, Regional Station, Bangladesh Rice Research Institute, Comilla

M. N. I. Miah
Bangabandhu Seikh Mujibur Rahman Agricultural University, Salna, Gazipur

M. M. Haque
Bangabandhu Seikh Mujibur Rahman Agricultural University, Salna, Gazipur

M. M. Kamal
Bangladesh Rice Research Institute, Gazipur

N. Ahmed
Bangladesh Rice Research Institute, Gazipur

Abstract/ Executive Summary:

An experiment was conducted in the plastic vinyl house at the Institute of Postgraduate Studies in Agriculture to evaluate the effects of soil moisture deficit on root growth of six selected upland rice cultivars. Water deficit was imposed at three crop growth stages, i.e. early vegetative, late vegetative, and reproductive. Water deficit during early and late vegetative stages significantly affected root penetrability but not during reproductive stage. Cultivar Hanumanjata had the highest and BR2 had the lowest root penetrability under both stress and control conditions. Generally, the root-shoot (A-S) ratio was higher under stress compared to control. Traditional cultivar Hanumanjata and Chantara had significantly higher root-shoot ratios than modern cultivars BA2 and BA24. Water deficits reduced root length density (RLD) in all the cultivars except Hanumanjata, which produced the highest AlD under both conditions. Reduction in root weight density was maximum when water deficit was applied in late vegetative stage followed by early vegetative stage. Significant and positive relationship between A-S ratio and grain yield we.re observed among the stressed plants.

Keywords: Root, Shoot, Soil, Moisture, Rice

Location: Gazipur

Start Date: 12-03-1997

End Date: 02-06-1997

Program Area: Crop-Soil-Water Management

Commodity: Rice

Objectives:

To explore the role of inherent root characters of different cultivars in drought resistance.

Methodology:

The experiment was carried out in the plastic vinyl house of the Institute of Postgraduate Studies in Agriculture (IPSA) during the Aus season, 1997. The study was laid out in factorial RCBD with six replications. Moisture deficits were imposed at 21-40, 41-60 and 61-80 days after emergence (DAE). These periods coincided with the early and late vegetative stages and the reproductive stage. Six Aus rice cultivars BR24, Chantara, Hasikalmi, Voira, Hanumanjata (drought resistant check) and BR2 (drought susceptible check) were used for this study. One set was sprinkled irrigation continuously, from seed to maturity and was designated as control. Rooting depth and R -S ratio was measured from the length of root volume and dry weight of root and shoot, respectively. Shoots were removed and roots of every plant were separated carefully from the soil of the pots by flushing with water. Root samples were preserved in the refrigerator and scanned by a root scanner (Delta-T Devices Ltd. Model : NV-M-12). After staining with methyl violet (1%) for 12 hr., 4-cm segments of roots were sprayed in root box of scanner and root length and area were measured in the laboratory. Root length density was determined by using the following formula : RLD where, RLD ARL/π r²h = ARL/πr²h = Root length density (m/m³) =Total root length (m) of the sample r= Radius of the pots (cm) π= 3.1416 h= Height of the pots (cm). Root weight density (RWO) was measured by using the following formula: RWD where, RWD = ARW /πr²h = Root weight density (gm/m³) ARW =Total root weight (g) r= Radius of the pots (cm) π = 3.1416 = Height of the pots (cm).

Source of Information: Bangladesh J. Agril. Sci. 28(1): 79-86, January, 2001

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

It was observed that when the stress was imposed at early vegetative stage, soil moisture depletion pattern was relatively slower compared to other. It might be due to less evapo-transpiration demo.nd of the low leaf surface area during this stage. As the growth advances, the soil moisture depletion pattern showed a sharp decline trend. In general, there were rapid declines up to 5 DAE in reproductive stress while early and late vegetative stress showed a slow depletion up to the same period. Cultivar Hanumanjata and Voira had the extreme soil moisture depletion due to their higher evapo-transpiration demand by their higher crop growth and leaf surface areas.In most cases, stressed plants showed significant deeper root penetration than control plants but the plants stressed during reproductive stage did not show significant change in rooting depth. During the reproductive stage the smaller difference in root penetration between stress and control plants might be attributed to less production of new roots due to limited soil mass and resistance from the bottom of the pots.Relationship between R-S ratio and grain yield: In this study it was observed that the R-S ratio significantly influenced grain yield among the rice cultivars. The data revealed that the higher R-S ratio of a cultivar was associated with a higher grain yield under stress condition; but this relationship was not substantial in case of control plant. which was significant at the 5% level. This might have been due to the soil moisture being held at field capacity throughout the growing season for control plants. The cultivar Hanumanjata, Voira and Chantara had higher R-S ratios, which were related to their high yielding ability under stress condition. It may be concluded that cultivars with higher rooting depth, high R-S ratios and high RLD are drought resistant.

Knowledge Management: Journal