studies (Bowman et al., 1990; Bres and Weston, 1993), in which hydrogels did not bring about a ... Bowman, D.C, Evans, R.Y. and Paul, J.L. 1990. Fertilizer salts ...
Performance of a New Superabsorbent Polymer on Seedling and Post Planting Growth and Water Use Pattern of Chrysanthemum Grown under Controlled Environment Anupama, M.C. Singh, R. Kumar and B.S. Parmar Indian Agricultural Research Institute New Delhi India
A. Kumar Indian Agricultural Statistics Research Institute New Delhi India
Keywords: chrysanthemum cv. Yellow Bouque, crosslinked hydrogel, soilless medium, self rooted cuttings, nursery, consumptive water use Abstract Water plays a critical role in nurseries for vegetative propagation of plants under greenhouse conditions. In view of the low water use efficiency in the growing medium, leaching of nutrients and hassles of frequent irrigation, an experiment was conducted to evaluate the performance of a newly developed eco-friendly crosslinked hydrogel. Observations were made on seedling growth, post planting behaviour and water use pattern of self rooted cuttings of chrysanthemum cv. Yellow Bouque grown under greenhouse conditions in soilless medium (mixture of coir husk, vermiculite and perlite in ratio of 6:1:1) amended with four rates of hydrogel (0.5%, 1.0%, 1.5% and 2.0% wt/wt). Medium amended with 0.5% hydrogel took minimum time of 18 days as compared to control (28 days), 1.0% (20 days), 1.5% (22 days) and 2.0% (22 days) to produce better quality seedlings. In terms of growth parameters of the established seedlings, 0.5% treatment produced maximum mean plant height (19.5 cm), root area (38.2 cm2), fresh root weight (5.6 g/plant) and fresh shoot weight (11.5 g/plant). After transplantation in soil, the growth behaviour of established seedlings showed similar trend with 0.5% treatment exhibiting most prominent growth with plant height (84.0 cm), stem diameter (1.1 cm), number of lateral branches (4.8), number of leaves/plant (102.6), number of flowers/plant (13.6), and flower size (20.6 cm2) as compared to control. Frequency of fertigation was effectively reduced to 4 in 0.5% and 1.0% amendments as compared to 10 irrigations in control, to raise nursery of healthy seedlings. INTRODUCTION Raising nursery of high value vegetable and flowering crops under greenhouse conditions and their marketing are gaining importance in modern intensive agriculture in India to obtain superior quality produce and higher profits. The quality of nursery grown plug plants is dependent on the physical and chemical composition of the growing medium, growing environment and most importantly water and nutrient management (Lamont et al., 1987). The physical composition of the growing medium bears a profound effect on the supply of water and nutrients to the plant and on the wetting properties of dried out medium (Beardsell et al., 1979 a,b; Beardsell and Nichols, 1982). Raising a nursery of superior produce requires frequent fertigations to keep the growing medium sufficiently wet. In view of poor water and nutrient use efficiency, there is a need to explore alternative water holding technologies, especially in India’s hot tropical climate, where water demand is higher when compared to supply. During the past two decades, headway has been made to promote the use of hydrophilic polymers such as hydrogels agriculture, with considerable success (Huttermann et al., 1990; Blodgett et al., 1993; Al-Mana and Bettie, 1996). A new generation of crosslinked hydrogels commonly termed as smart hydrogels, possesses remarkable water holding properties and has high sensitivity to temperature, pH, ionic strength of swelling solution. Performance of these materials depends on their tolerance to ionic solution, the tensions at which they bind water and their longevity in soil. Suitably Proc. Int. Conf. & Exhibition on Soilless Culture Ed. K.K. Chow Acta Hort. 742, ISHS 2007
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designed hydrogels are known to reduce the moisture stress in plug plants (Callaghan et al., 1988). A novel smart hydrogel has been recently developed in our laboratory (Anupama et al., 2005). Under laboratory conditions, it showed approximately 1800019000% water holding capacity at 50°C. When exposed to nutrient solution, it showed only 10-30% reduction in its swelling potential and remained stable in soil beyond two months. The objective of this work is to evaluate the performance of this hydrogel on seedling growth, post planting behaviour and water use economics of self rooted cutting of chrysanthemum cv. Yellow Bouque grown in soilless medium under greenhouse conditions. MATERIALS AND METHODS Soilless medium (cocopeat, perlite, vermiculite mixed in 6:1:1) was oven dried at 50°C till constant weight. It was amended with four rates of hydrogel (0.5%, 1.0%, 1.5% and 2.0% on w/w basis), filled in 3” dia. plastic pots (35 g/pot), in five replications per treatment including control. Measured volumes of nutrient solution containing NPK (19:19:19), computed on the basis of water holding capacity of unamended medium plus that of the hydrogel in respective amendment treatments, was added to each pot and kept overnight. The drained water was measured and the effective nutrient solution holding capacity of each treatment was determined by difference. Terminal cuttings of chrysanthemum (3-5 leaf) were planted in each pot (3 cuttings/pot) after treating the lower tip with rooting hormone (IBA) powder. The environmental conditions in the greenhouse were maintained at average day/night temperatures (24/18°C), relative humidity (60%) and evaporation rate (7 mm/day). The critical moisture limit of the medium for watering was standardized at 20% of its water holding capacity. Pots were daily weighed to determine the rate of water loss and compensated when required. RESULTS AND DISCUSSION Absorption Capacity of Hydrogel A comparison of the swelling of the hydrogel in distilled water and nutrient solution showed that as compared to the control, hydrogel amended medium absorbed more distilled water as well as nutrient solution (Table 1). The performance of 0.5% and 1.0% were superior to the application at 1.5% and 2.0%. Comparatively poor performance at higher rates may be due to lack of availability of sufficient space for the hydrogel to swell to its maximum, resulting in competition with the medium for space. Time for Seedling Establishment Seedling growth in each treatment at transplantable stage showed that at 0.5% gel, they grew the fastest and reached the transplantable stage in 18 days as compared to control (28 days) (Table 2). Seedlings grown in 1.0% treatment took 20 days while those at 1.5% and 2.0% treatments, required 22 days each for comparable growth. Seedling Growth Parameters Growth parameters of seedlings were compared on completion of the third week in all the treatments (Table 2). In all the gel treatments, plant height was significantly more than the control (13.1 cm) though the treatments did not differ significantly (Fig. 1). Similarly, seedlings in all the treatments except 0.2% amendment showed prominent root growth. Root area was significantly more than the control (15.9 cm2/plant) in all treatments except 0.2%. Maximum root area was obtained in 0.5% amendment (38.2 cm2/plant), significantly more than other treatments. A similar trend was observed in fresh root and shoot weight/plant. No significant variation was observed in leaf and stem growth of treated seedlings as compared to the control. Scanty root growth in 2.0% treatment may be attributed to water logging due to high quantity of polymer resulting in 44
less aeration and space competition between swollen polymer and the developing roots (Fig. 2). Post Planting Growth and Flowering The nursery raised seedlings were transplanted in pots after four weeks of growth. The plants raised in all the treatments except 2.0% exhibited significantly more plant height, stem diameter, number of lateral branches and number of leaves per plant as compared to the control. In terms of the days taken to flowering, number of flowers/plant and flower size, all the gel treatments performed better than the control (Table 3). No significant difference was observed in all the parameters except plant height, which was significantly more in 0.5% treatment (83.9 cm). The flowering was significantly delayed at 75 days after transplantation for control plants. The favourable effects on the use of hydrogel-amended medium on rooting enabled the plants to grow more vigorously and flower more abundantly as compared to the control (Fig. 3). Frequency of Fertigation The most conspicuous effect of the hydrogel application was observed with the reduction in frequency of fertigation as compared to the control. It is evident from Table 4 that treated medium required a smaller number of fertigations. The 0.5 and 1.0% treatments performed the best and each required only 4 fertigations as compared to 10 in the control. These were followed by 1.5 and 2.0% treatments, with each requiring 6 fertigations. Larger quantity of hydrogel requires more space to swell to its equilibration stage, which in 1.5% and 2.0%, owing to the competition for space among medium, polymer and developing roots, an increase in fertigation frequency was observed. All the treatments required a smaller number of irrigations as compared to the control. Treatment 0.5% required 5 irrigations as compared to 10 in the control while treatments 1.0, 1.5 and 2.0% required 5, 5 and 4 fertigations respectively. Better performance of 2.0% treatment in soil may be due to the sufficient space available for its swelling. Consumptive Water Use It is clear that the consumptive water use (total water applied/pot) was lower in all the treatments compared to that of the control (414.2 ml/pot) (Table 5). The 0.5 and 1.0% gel treated amendments registered a remarkable reduction of 60.8% and 58.4% in the consumptive water use per pot as compared to the control. The treatments 2.0% and 1.5% gave almost similar results exhibiting a reduction of 36.1% and 37.8%, respectively. CONCLUSION Significant improvement in the chrysanthemum seedling growth and establishment in reduced period with reduced transplant shock, was apparent with lower application rates of hydrogel. These observations are in contrast to some of the earlier studies (Bowman et al., 1990; Bres and Weston, 1993), in which hydrogels did not bring about a noticeable improvement. The test hydrogel showed best response in terms of efficient water and ion holding capacity at low rates of application. Comparatively poor response of hydrogel at higher rates may be attributed to the lack of sufficient space for swelling in the pots used in the studies. It is possible that 1.5 and 2.0% levels may perform better if larger sized pots are used. This observation is supported by earlier reports (Fonteno and Bilderback, 1993). However, in view of the cost of such materials, lower application rates will be highly desirable. The present study underlines the importance of specific hydrogel amended medium in nursery production to save not only water and nutrients, but also time and energy in nursery production.
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Literature Cited Al-Mana, F.A. and Beattie, D.G. 1996. Effects of hormone charged hydrogels on root regeneration in red oak and black gum transplants. Acta Hort. 429:459-466. Anupama, Kumar, R. and Parmar, B.S. 2005. Novel superabsorbent/s hydrogels and method of obtaining the same. Indian Patent Application (submitted). Beardsell, D.V., Nichols, D.G. and Jones, D.L. 1979a. Physical properties of nursery potting mixtures. Scientia Hort. 11:1-8. Beardsell, D.V., Nichols, D.G. and Jones, D.L. 1979b. Water relations of nursery potting medium. Scientia Hort. 11:9-17. Beardsell, D.V. and Nichols, D.G. 1982. Wetting properties of dried out nursery container medium. Scientia Hort.17:49-59. Blodgett, A.M., Beattie, D.J., White, J.W. and Elliot, G.C. 1993. Hydrophilic polymers and wetting agents affect absorption and evaporative water loss. Hort Sci. 28(6):633635. Bowman, D.C, Evans, R.Y. and Paul, J.L. 1990. Fertilizer salts reduce hydration of polyacrylamide gels and affect physical properties of gel-amended container medium. J. Amer. Soc. Hort. Sci. 115:382-386. Bres, W. and Weston, L.A. 1993. influence of gel additives on nitrate, ammonium and water retention and tomato growth in a soilless medium. Hort Sci. 8(10):1005-1007. Callaghan, T.V., Abdelnour, H. and Lindley, D.K. 1988. The environmental crisis in the Sudan: the effect of water absorbing synthetic polymers on tree germination and early survival. J. Arid Environ. 14:301-317. Fonteno, W.C. and Bilderback, T.E. 1993. Impact of hydrogel on physical properties of coarse structured horticultural substrates. J. Amer. Soc. Hort. Sci. 118(2):217-222. Huttermann, A., Zommorodi, M. and Reise, K. 1990. Addition of hydrogels to soil for prolonging the survival of Pinus halepensis seedlings subjected to drought. Soil and Tillage Res. 50:295-304. Lamont, G.P. and O’Connell, M.A. 1987. Shelf-life of bedding plants as influenced by potting medium and hydrogels. Scientia Hort. 31:141-149.
Tables
Table 1. Effects of nutrient solution on swelling potential of hydrogel. Hydrogel rate (% w/w) Control 0.5% 1.0% 1.5% 2.0% SE(mean) CD
Calc. absorption capacity (ml) 120 150 180 210 240
Mean volume of solution absorbed (ml) Distilled water Nutrient solution 120 115 150 135 170 162 172 168 170 168 5.6 5.4 3.9 3.7
Note: 35 g media amended with different rates of hydrogel was taken/pot and hydrated with calculated quantity of water
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Table 2. Effects of hydrogel amended medium on establishment and growth of self rooted cuttings of chrysanthemum. Number of days taken to Plant Treatment attain the height seedling stage (cm) T0 28 13.1 T1 18 19.5 T2 20 18.8 T3 22 18.9 T4 22 17.6 SE (mean) __ 0.8 CD 3.1
No. of leaves/ plant 11.6 14.2 12.6 11.8 11.6 0.8 ---
Growth parameters Stem Root area Fresh 2 dia. (cm / root wt. (cm) plant) (g/plant) 0.2 15.9 2.9 0.2 38.2 5.7 0.2 36.7 4.1 0.2 34.8 3.7 0.2 21.1 3.4 0.2 1.6 0.2 --6.5 0.8
Fresh shoot wt. (g/plant) 7.4 11.5 9.0 8.1 7.8 0.2 0.7
Table 3. Effects of hydrogels on plant growth and flower parameters in chrysanthemum after transplanting. Plant growth and flower yield parameters Treatment T0 T1 T2 T3 T4 SE (mean) CD
Plant height (cm)
Stem dia. (cm)
No. of lateral branches/ plant
No. of leaves/ plant
No. of days to flowering
No. of flowers/ plant
56.0 83.9 76.2 73.2 59.8 1.1 4.7
0.8 1.1 1.0 1.0 0.9 0.0 0.1
2.4 4.8 4.4 3.2 3.0 0.4 1.6
71.6 102.6 92.8 86.0 81.0 2.7 11.3
75.0 64.0 61.0 64.0 65.4 0.9 3.7
8.6 13.6 13.2 12.6 11.8 0.7 2.7
Flower size Vase (LXW) life 2 (cm ) (day)
17.6 20.7 20.2 19.4 19.0 0.3 1.1
10.4 15.2 12.4 12.2 11.0 0.4 1.5
Table 4. Effects of hydrogel application on frequency of irrigation. Fertigation applied (days after Fertigation applied Irrigation planting of cutting in nursery) (days after transplanting) number Control 0.5% 1.0% 1.5% 2.0% Control 0.5% 1.0% 1.5% gel gel gel gel gel gel gel 1 5 7 7 7 6 6 7 7 7 2 9 11 12 10 11 12 22 20 20 3 12 14 16 12 14 18 32 29 29 4 15 18 20 16 16 24 40 36 38 5 19 18 20 29 46 41 42 6 22 22 22 33 7 24 37 8 25 41 9 26 44 10 28 47
2.0% gel 9 25 35 45
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Table 5. Effects of hydrogel application on consumptive water use. Irrigation number 1 2 3 4 5 6 7 8 9 10 Total water use/pot (ml)
Control 33.8 33.1 36.3 41.9 36.0 42.9 47.6 48.0 47.3 47.5 414.2
Water applied/pot (ml) 0.5% gel 1.0% gel 1.5% gel 37.7 40.7 37.6 39.6 44.6 46.6 42.4 42.6 46.7 42.9 44.2 46.7 52.7 52.7
162.5
172.5
264.9
2.0% gel 38.1 38.0 43.6 41.2 42.4 47.8
257.9
Figurese
2.0%
1.5%
1.0%
0.5%
control
Fig. 1. Growth profile of seedlings grown in media amended with different rates of hydrogel.
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2.0%
1.5%
1.0%
0.5%
control
Fig. 2. Differential root growth as affected by media amended with different gel concentrations.
2.0%
1.5%
1.0%
0.5%
control
Fig. 3. Effects of hydrogel application on post planting growth of chrysanthemum seedlings.
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