Effect of Desiccants and Packaging Materials on Seed Storability in Soybean [Glycine max (L.) Merrill]

Soybean [Glycine max (L.) Merrill] is one of the most important oilseed crops in the world and is a cheaper source of quality protein and edible oil. In the total edible oil production of the world, 30 per cent is contributed by soybean (Assefa, 2008). Soybean seed contains about 40-45% protein, 20-22% oil, 20-26% carbohydrate and a high amount of Ca, P and vitamins (Rahman et al., 2011).

High quality seed that provides adequate plant stand is the basis for profitable production and expansion of soybean crop. Loss of viability and vigour under high temperature and RH conditions is a common phenomenon in many crop seeds but it is well marked in soybean. The problems of maintaining the soybean seed viability in storage have always been an important concern; and retention of high viability over a long period is necessary for crop production. Many factors determine the longevity of seeds during storage. These includes seed moisture content, temperature, relative humidity, initial viability, stage of maturity at harvest, storage gas and initial moisture content of seed entering into storage (Tatipata, 2009). Soybean seed losses its viability in very short period of storage even when stored in good nonporous container (Woodruff, 1998).

The principle of drying using a desiccant is that the dry desiccant will take up moisture from the wet seed until the two come to equilibrium. How much water the desiccant adsorbs from the seed and how quickly it does so depends on number of factors, including the ratio of desiccant to seeds, temperature and the affinity of the desiccant for water. It may also be necessary to refresh the desiccant to ensure that seeds reach the target moisture content. Aluminium silicate ceramics are a type of molecular sieve with very small, uniform pores where water molecules can be adsorbed. Small balls of this molecular sieve material are being marketed as seed ‘Drying Beads ®’ with professed advantages over other desiccants including greater affinity for water, particularly at low humidity; more rapid drying; and no hysteresis effect, which reduces the amount of water that can be adsorbed following regeneration. The beads can be regenerated by heating to 200°C for 3-4 hours (Hay et al., 2012).

Selection of containers for storing the seeds is one of the important techniques to extend shelf life of seed according to the prevailing climatic conditions of particular area. Grain Pro Super bag (Introduced by Grain Pro Agro Pvt. Ltd, Israel is multilayered polythene bag consist inert gas in between two layer) was exploited for safe storage of seeds / dry grains of several crops. Super grain bags help in extending seed storability, most importantly, they control insect pest without any insecticides. Rice seeds stored in Super grain bag maintained its viability up to 12 months under ambient conditions (Rickman, 2004).

Proper seed treatment with fungicide will improve the germination of poor quality seed if the low quality is due to fungal infection. A fungicide treatment also protects the seeds and young seedlings from many seed borne and soil borne pathogens (Taylor et al., 1998). With this background, a study was undertaken to determine the effect of desiccants and packaging materials on vigour and viability of soybean seeds treated with Vitavax 200, a broad spectrum dual action (systemic and contact) polymer formulated fungicide as pre-storage seed treatment as shown in Fig1.

The experiment was conducted on freshly harvested each 10 kilograms of soybean cv. JS 335 seeds treated with Vitavax 200 (2 g/kg of seed) and stored in Super grain bag with CaCl2 (T₁):  Super grain bag with silica gel (T₂): Super grain bag with drying beads (Zeolites-drying beads @ 1:0.035)  (T₃): Super grain bag without desiccants (T₄): cloth bag with CaCl₂ (T₅): cloth bag with silica gel  (T₆): cloth bag with drying beads (T₇):  cloth bag without desiccants (T₈) under ambient conditions at Pandit Jawaharlal Nehru College of Agriculture and Research Institute, Karaikal, the coastal district of Puducherry (UT), India during 2018-19. Seed samples were drawn at three months interval and evaluated for seed moisture content (%), seed germination (%), shoot and root length of seedlings (cm), dry weight of seedlings (g/10 seedlings), vigour index I and II up to nine months by ISTA rules (Anonymous, 2016).The analysis and interpretation of the experimental data were done as suggested by Panse and Sukhatme (1967) with level of significance used as P = 0.05.

Seed moisture content
 
Several factors may affect the quality of seeds in storage, however, the most critical among them is high seed moisture content (OHare et al., 2001). In the present study, the seed moisture content was significantly influenced by the period of storage and packaging materials used (Table 1). An initial seed moisture content of 8.40 per cent was enhanced to 11.45 per cent at 6th month of storage in cloth bags; while, it was almost maintained in the Super grain bags throughout the storage. The overall mean seed moisture content between the packaging materials indicated that nearly 2 per cent higher seed moisture content was observed in cloth bags as compared to super grain bags during storage. However, treatments with desiccants didn’t differ with seed moisture content during storage.  Irrespective of desiccants, a steep increase in seed moisture content was observed in cloth bags at 6th month of storage and thereafter it declined. Thus, it was found that seeds stored in cloth bags had higher moisture content than super grain bags due to moisture pervious nature of cloth bags. Similar results were observed by Baskin et al., (1987) and Kurdikeri (1991). These findings are also in agreement with studies of Ravi Hunje et al., (2007) and Barua et al., (2009) in Chilli. Tiwana et al., (2021) also opined that Super Grain bag was the only storage system that kept grain moisture content stable along the storage period.


 
Seed germination
 
Seed germination was also significantly influenced by the period of storage and packaging materials used in the present study (Fig 2). However, treatments with desiccants didn’t differ in seed germination during storage. Though the germination was well above the Indian Minimum Seed Certification Standard for germination (70%) in all the treatments at 6^th month of storage, a drastic reduction to the tune of 41 per cent was noticed in seeds stored in cloth bags (42.75%) at 9th month of storage. The overall mean seed germination between the packaging materials also indicated that nearly 11 per cent higher seed germination was recorded in super grain bags (86.69%) as compared to cloth bags (75.69%). Seed germination decreased with increase in storage period, as seen by Mandal and Basu (1986) in wheat; Dharmalingam (1995); Hussaini et al. (1988) and Ramamoorthy et al. (1989) in maize due to natural ageing process. Singh and Dadlani (2003) also opined that the germination per cent was affected by packaging materials during storage. Meena et al., (2017) also observed that seeds stored in vacuum packed bags maintained the seed quality with least deterioration with respect to all the seed quality parameters compared to seeds stored in gunny bags and high density polythene bags. Chin and Kieu (2006) concluded that hermetically sealed storage system using poly-ethylene bag reduced insect population in the stock of rice seeds and increases germination percentage of rice seeds as compared to the traditional method of aerobic storage by farmers.


 
Shoot and root length of seedlings
 
Seedling growth is considered as the important tool that can be used for assessing the magnitude of deterioration (Toole et al., 1957). The seedling vigour in terms of shoot and root length was also influenced by the period of storage and packaging materials used (Table 1). The initial shoot and root lengths of 21.44 cm and 25.83 cm were reduced to 14.19 cm and 15.13 cm, respectively at 9th month of storage. Significant reduction in shoot and root lengths to the tune of 56 per cent and 68 per cent were observed in cloth bag; while it was 11.3 per cent and 12.9 per cent, respectively in Super grain bag at 9^th month of storage. Further, the shoot and root lengths in super grain bags were almost two and three fold higher than cloth bags at 9thmonth of storage. The overall mean shoot and root length of seedlings between the packaging materials indicated that nearly 2 and 4 cm longer shoot and root lengths were recorded in super grain bags (86.69%) compared to cloth bags (75.69%), respectively. Similar results were observed by Akter et al., (2014) in soybean and reported that storage container had significant effect on root length and shoot length; which decreased with the increase in storage period. Seeds in tin container gave the highest seedling length than cloth bags.
 
Dry weight of seedlings
 
The deterioration of seed, which is a progressive process accompanied by accumulation of metabolites, which progressively depress germination and growth of seedling with increased age (Floris, 1970), ultimately reducing the dry matter and vigour of soybean seed during storage. The dry weight of seedling an important measure of seed vigour was significantly influenced by packaging materials used (Table 2). Between packaging materials, seeds stored in super grain bags registered nearly 31 % higher dry weight of seedlings than cloth bags and indicated its superiority in the maintenance of seed vigour during storage.


 
Vigour indices
 
The computed vigour indices I and II were also significantly differed due to period of storage and packaging materials used (Table 3). A reduced vigour index I to the tune of 81 per cent was observed in cloth bag as against only 12 per cent in super grain bags. Interestingly, the super grain bags didn’t show any reduction in vigour index II while it was nearly 60 per cent in cloth bags.  Similar results with polythene bags of 700 gauge were reported by Tammanagouda (2002); Arati (2000); Dwivedi and Shukla (1990) in Pulses. Kurdikeri et al. (1996) reported that the seed germination and seedling vigour declined with increasing storage period. Chuansin et al. (2006) reported that prolonged storage life of soybean seed without the use of chemical could be attained by the use of different kinds of packaging materials.



Thus, the seeds stored in super grain bag recorded significantly higher germination (83.25%), shoot length (20.42 cm), root length (21.96 cm), seedling dry weight (0.382 g) seedling vigour index I (3397) and vigour index II (31.85) as compared to the seeds stored in cloth bag (43%, 9.46 cm, 8.30 cm, 0.263 g, 756 and 11.24, respectively) after nine months of storage (Fig  2). Significantly higher seed quality parameters observed in the seeds stored in super grain bag might be due to constant seed moisture content, reduced respiration rate of seeds stored due to hermetic condition inside the bag and the cushion effect exerted by the inert gas filled in between the two layers of polythene bag protects the seeds from the influence of environment. Similar observation was made by Rickman (2004) in Rice. Wilson and McDonald (1992) observed that Polyethylene and aluminium foil materials were moderately effective in preventing moisture uptake and maintaining seed viability, while paper and cloth containers were least effective. Seeds stored in any air tight containers could retain viability for a longer period of time. Sealed plastic pot and polythene bag are more effective storage containers than cloth bag or jute bag and earthen pot, etc. (Rahman et al., 2010). High moisture content and presence of oxygen were the main causes for lipid autoxidation in soybean to lead rapidly seed deterioration and the quality decline (Chang et al., 2004). Akter et al., (2014) opined that the soybean seeds stored in tin container showed maximum germination capacity with high germination index, highest seedling growth, seedling dry weight per plant and vigour index. The result revealed that all the seed quality parameters under study were significantly influenced by storage materials. Ramanadane and Rettinassababady (2008) opined that rice seed quality declined with storage period, the rate of seed deterioration was higher at high moisture level and the storability differed with type of storage container. Rice seeds with low moisture content stored in super bags or poly-lined cloth bags performed better in storability under coastal area with high relative humidity. Bista et al., (2022) also observed that PICS bag followed by super grain bag was found to be superior in terms of seed moisture content, germination percentage and seed health throughout the storage period in rice.

Soybean seeds treated with vitavax 200 and stored in Super grain bags exhibited the highest seed germination, seedling length, seedling dry weight, vigour index-I and II than cloth bags after nine months of storage. The loss in seed vigour (VI-I) during storage was only 12 per cent in Super grain bags as compared to 81 per cent in cloth bags indicated that Super grain bag has the potential to effectively contain the influence of environment on seeds stored in it. Hence, it is suggested that the vigour and viability of soybean seeds could be very well prolonged by storing fungicide treated seed in Super grain bag instead of cloth bags under coastal environment.

The authors gratefully acknowledge the financial assistance extended by the ICAR-Indian Institute of Seed Science, Mau for conducting the research experiments under AICRP on Seed (Crops) at PAJANCOA and RI, Karaikal.

All authors declared that there is no conflict of interest.