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African Journal of Agricultural Marketing ISSN 2375-1061 Vol. 8 (10), pp. 001-007, October, 2020. Available online at 
www.internationalscholarsjournals.org © International Scholars Journals 

 

Author(s) retain the copyright of this article. 
 
 

Full Length Research Paper 

 

Effects of low cost drying methods on seed 

quality of Sorghum bicolor (L.) Monech 
 

Ali Zakaria Babiker1, Mohammad Ehsan Dulloo2*, M. A. Mustafa El Balla3 and El Tahir 
Ibrahim1

 
 

1
Plant Genetic Resources Unit, Agricultural Research Corporation, Sudan. 

2
Bioversity International, Rome, Italy.  

3
Department of Horticulture, Faculty of Agriculture, University of Khartoum, Sudan. 

 
Accepted 19 May, 2020 

 
The effect of low cost drying methods on the seed quality of different genotypes of sorghum was investigated. Fresh 
seeds from five genotypes were subjected to three drying regimes, namely sun, shade and silica gel, and were 
compared to the standard recommended drying condition using a seed dryer (Munter seed dryer Model M120) as 
control. The effects of the drying regimes on seed moisture content, viability and quality were studied. All the drying 
methods were able to dry seeds to safe seed moisture contents levels (range of 5.6 - 7.5%) for conservation. None of 
the alternative drying methods examined proved to be better than drying in a seed dryer. Seeds dried with the seed 
dryer gave the highest germination percentage compared to those dried using silica gel, or under shade and sun. 
However, this study indicates that drying with silica gel and shade are good alternative methods. Sun drying is 
quicker, but is harmful to the seeds and affects long-term seed viability. 
 

Key words: Genebank, low cost drying, sorghum, seed storage, Sudan. 

 
INTRODUCTION 

 
It is well known that the most important factors influencing 
seed longevity are temperature, seed moisture content and 
relative humidity (Ellis and Roberts, 1980; Dickie et al., 
1990). It is also recognized that the extent to which potential 
longevity of a seed is maximised depends on the storage 
condition as well as on its initial quality (Roberts, 1992). 
Seeds are generally harvested at high moisture content and 
need to be dried before storage, and to do this, attention 
should be paid to the rate and extent of artificial post-harvest 
drying. If drying is too slow, there is a possibilty of reduction 
in seed quality during the drying process due to seed aging. 
On the other hand, if seeds are dried rapidly, a large 
proportion may be lost due to desiccation damage (Ellis and 
Roberts, 1980) . There is no fixed rule that applies to all 
species. Delay in drying or slow drying together with high 
temperature (above 25°C) will tend to reduce viability 
considerably in orthodox seeds. 

The recommended methods for safely drying seeds of 

germplasm collections to very low moisture content using  
 
 

 
*Corresponding author. E-mail: e.dulloo@cgiar.org. Tel: (39) 
066118206. Fax: (39) 0661979661. 

 
 
seed drying facilities, such as seed drying chambers, seed 
dryers, where the relative humidtiy of the drying environment 
is controlled (Ellis et al., 1985), may not be easily 
implemented in many developing countries due to the high 
cost of establishing, running and maintaining such facilities. 
Therefore, there is a need for low cost drying methods to be 
used as alternatives to such expensive seed drying 
equipment in genebanks within those countries. Ellis and 
Roberts (1991) recommended a variety of methods for seed 
drying such as shade, sun, vacuum, freeze and refrigeration 
drying with low relative humidity depending on species, the 
initial seed moisture content and the resources available. 
Several studies have demonstrated the potential of these 
low cost methods in reducing the seed moisture content to 
an acceptable levels for long term storage (Vodouhe et al., 
2008; Probert, 2003), but their impacts on seed quality has 

not been adequately studied. In a study on wild shrub, 
Millettia leucantha Vatke, endemic to east Africa, 
Muthoka (2003) showed that neither sun nor shade 
drying were detrimental to seed quality. In crop plants 
various desiccants have been used to dry seeds (Probert, 
2003).  

Sorghum bicolor (L.) Moench is a a major staple crop in 

sub-Saharan Africa, where it had orignated and was 

file:///C:\Users\user\Documents\REPUBLICATION\AGRICULTURAL%20SCIENCES\AppData\Local\Temp\www.internationalscholarsjournals.org


 
 
 

 

domesticated (De Wet and Harlan, 1971). Its primary 
centre of origin is located in north east Africa and has 
spread to other continents (Asia, Australia and America). 
India and China are considered as secondary centres of 
diversity. It is now considered to be one of the five top 
cereal crops and is an important part of the diets of many 
people in the world, it is also used as animal feed and a 
range of other products. Because it is such an important 
crop for food and agriculture, its diversity in genebank 
collections needs to be effectively conserved. A global 
strategy for sorghum developed with support from Global 
Crop Diversity Trust (GCDT) (GCDT, 2007) has identifed 
the major collections of sorghum in the world. The 
International Crops Research Institute for the Semi-Arid 
Tropics (ICRISAT) (India), and United States Department 
of Agriculture, Agricultural Research Service (USDA-
ARS) collection in USA, hold the highest number of 
accessions, but the strategy also recognises other key 
collections in Asia, America and Africa including India, 
China, Brazil, Ethiopia, Russia, Australia, Zimbabwe, and 
Sudan (GCDT, 2007).  

The objective of this study was to investigate the effect 
of sun, shade and silica gel as alternative drying 
procedures on seed quality of different sorghum 
genotypes (accessions) compared to the recommended 
drying procedure at low temperature and relative humidity 
using a conventional seed dryer. 
 

 
MATERIALS AND METHODS 
 
The study was carried out during the period 2000 - 2002 at the 
Plant Genetic Resources Unit of Agricultural Research Corporation 
(PGR/ARC) of Sudan. Five genotypes were used in this study 
including four accessions of Sudanese origin and one improved 
cultivar. The Sudanese sorghum accessions were PI 570120, PI 
570300, PI 570342 and PI 570356 representing four sorghum 
groups, namely Kafir, Milo, Feterita and Hegari, respectively, while 
the improved cultivar was Tabat, a variety officially released by 
ARC in the early nineties. Seeds of these accessions were obtained 
from genebank of the PGR/ARC and the Sorghum Research 
Programme of Agricultural Research Corporation. 

The accessions used in this study were first multiplied to bulk up 
the numbers of seeds in order to obtain adequate amounts for the 
study. Sowing was carried out in a sub-plot of five rows on ridges 3 
m long at spacing of 0.8 m between rows and 0.3 m within rows. 
One hunderd and fifty plants were established from each lot per 
sub-plot at the rate of three plants per hole. The multiplication 
process was conducted in the Farm of the Gezira Agricultural 
Research Station in Wad Medani, Sudan, which lies at latitude of 
14°24` N., longitude of 33° 29` E and altitude of 406.9 m above sea 
level (ASL). The climate of the area is hot semi-arid, the soil is 
vertisol with clay content (40 - 65%), pH value ranging from 8 to 9.6, 
less than 1% organic carbon, 300 ppm total nitrogen and 406 - 700 
ppm total phosphorus (Ishag and Said, 1985). Cultural practices 
including irrigation, nitrogen fertilization and weeding which followed 
the current practices at PGR/ARC for sorghum (Elash Abdelhi 
Elash, pers.com). The newly harvested seeds were then used for 
moisture content determination, viability testing, drying and storage. 
Seed moisture content and viability levels were assessed both 
before and after drying. Seed testing, drying and storage were 
undertaken in the laboratory of the PGR/ARC using the procedures 
as thus described. 

 
 
 
 

 
Determination of seed moisture content 
 
Moisture content of seeds was determined twice; immediately after 
harvesting and after drying to a constant weight. The moisture 
content was determined using high constant oven drying method, 
as recommended by Rao et al. (2006). Two replicate samples of 
ground seeds, five grams each, were dried at 130 -133°C for 2 h. 
Seed Moisture Content (SMC) was then calculated (using the mean 
of the two replicates) on fresh weight basis using the following 
formula: 
 
SMC = (Weight of fresh seeds – Weight of dry seeds) × 100% / 

Weight of fresh seeds 
 

 
Drying procedures 

 
After harvest, the seed samples from different genotypes were sub-
divided into four groups for drying, using four different drying 
regimes, namely: Sun, shade, silica gel and a seed dryer. Seed 
samples to be dried under sun and shade were spread evenly in a 
monolayer on mesh sieves, held above ground level. The sieves 
were placed in a bird-and rodent-proof structure, made up of 
wooden framework covered by a fine mesh wire netting, which 
would prevent the entry of these pests, while at the same time 
allowing free air movement. The mean ambient temperature over 
the drying period was 26°C with a range of 17 - 35°C and the mean 
Relative Humidity (RH) was 43%. The sun dried seed samples were 
kept under direct sun light for six hours each day, while shade dried 
samples were placed in a ventilated room with an ambient 
temperature of 22°C and similar RH as aforementioned. Changes in 
seed weight were monitored every 7 - 10 days until it reaches a 
constant weights. Each sun and shade dried sample was then 
packaged hermetically, sealed into a laminated aluminium foil 
packet of the type used in the long term storage of seeds at sub-
zero temperature in the genebank provided by International Plant 
Genetic Resources Institute (now Bioversity International) and 
stored in a room at temperature ranging between 20 and 25°C .  

Seed samples to be dried over silica gel were put inside porous 
cloth bags. They were placed over activated silica gel inside 
dessicators at the ratio of 2:1 (seeds : silica gel), and left inside a 
room at temperature ranging between 20 and 25°C. The silica gel 
was activated by heating an oven whenever the need arose. As a 
control treatment, seed samples were also dried using a Munters 
Rotaire M120 Dehumidifier and Refrigeration Packaged Seed 
Dryer, Serial Number F3/662 (from Munters Rotaire, England) 
adjusted at about 20°C and 15% relative humidity. Seed samples 
were spread evenly in a monolayer on mesh sieves and placed 
inside the seed dryer. Seed moisture contents of those samples 
dried over silica gel or inside the seed dryer were monitored 
regularly at 7 - 10 days intervals until reaching constant weights, 
then the samples were packaged hermetically in sealed laminated 
aluminum foil packets and stored in a room at temperature ranging 
between 20 and 25°C. 
 
 
Ageing assessment 
 
After drying, the different seed lots were subjected to accelerated 
ageing, based on methods described by Agrawal (1986) and 
Delouche and Baskin (1973) . A sample of four hundered seeds 
from each drying treatment was placed in small mesh containers 
supported above the water inside a tightly closed plastic pot in order 
to maintain a high relative humidity of about 100%. The whole pot 
was then placed into an oven adjusted at a temperature of 43°C for 
four days. At the end of the ageing period, the seeds were removed 
and immediately assessed for viability and vigour. 



 
 
 

 
Table 1. Mean percentage seed moisture contents (SMC %) (means of 2 replicates) of different Sorghum genotypes before 

and after drying. SDr = Seed dryer; SH= Shade drying; SG= Silica Gel; SN= Sun drying.  
 

 Before drying   After drying    

   Drying method     

Genotypes  SDr SH SG SN mean SD  

PI 570120 20.97 7.52 6.84 6.27 5.81 6.61 0.739  

PI 570300 18.65 7.29 6.5 6.1 5.64 6.38 0.7  

PI 570342 19.37 7.19 6.63 6.11 5.77 6.43 0.621  

PI 570356 19.52 7.36 6.79 6.03 5.98 6.54 0.66  

Tabat 19.30 7.48 6.73 6.14 5.99 6.59 0.677  

Mean  7.368 6.698 6.13 5.838    

 
 
 
 

Table 2. Effect of drying method and genotype on seed germination percentage before drying, after drying 

and after ageing.  
 

 Main effect Before drying After drying After aging 

 Drying method    

 Seed dryer 76.9 a 91.6 a 60.4 b 

 Shade 76.9 a 87.0 b 57.6 c 

 Silica gel 76.9 a 83.7 c 66.2 a 

 Sun 76.9 a 82.4 c 52.7 d 

 Genotype    
 PI 570120 80.0 b 93.0 a 71.0 b 

 PI 570300 85.9 a 82.9 c 39.6 e 

 PI 570342 80.6 b 88.1 b 75.0 a 

 PI 570356 77.2 c 83.5 c 65.7 c 

 Tabat 60.8 d 83.4 c 44.8 d 
 

*** Significant at 0.001 probability levels.  
Means followed by the same letter(s) within a column are not significantly different at 0.05 probability level 

according to the least significant difference test (LSD). 
 
 

 
Assessment of seeds for viability and vigour 
 
Seeds were assessed for viability and vigour using germination test. 
This was conducted at three different stages during the study; 
immediately after harvesting, drying and ageing. Seed samples 
assessed after drying were hydrated by holding the seeds in porous 
cloth bags that inside a dessicator over water for 24 h at room 
temperature ranging between 20 and 25°C (Ellis et al., 1985). The 
germination tests were conducted according to the recommen-
dations by ISTA (1999). A complete randomised design of four 
replications with 100 seeds per replication was used. Seeds were 
germinated on sand medium using plastic pots that were placed 
inside a dark room with temperature ranging between 25 and 30°C. 
Emerging normal seedlings, which had well developed shoot and 
root systems with green expanding primary leaves and well 
developed straight coleoptile (ISTA, 1999) were counted three 
times during the test (that is, four, seven and ten days after sowing). 
Viability was then expressed as germination percentage of the total 
normal seedlings.  

Seed vigor was evaluated on the normal seedlings at the end of 

the germination test. It was assessed as radicle length, shoot dry 

weight and germination speed. A sub-sample of ten seedlings was 

 
 
 

 
taken randomly for measuring their radicle lengths from which the 
average radicle length was calculated. Radicles were then 
removed, while the shoots were dried in an oven at 100°C for 2 h to 
obtain the shoot dry weight from which the average shoot dry 
weight per seedling was calculated. The germination speed was 
calculated using the following equation: 

 
MTG = (D x G)/N 
 
Where MTG is the mean germination time, D is the number of days 
after sowing, G is the number of seedlings which were counted as 
normally germinated seeds within D days, and N is the total number 
of seeds normally germinated at the end of test (Walters et al., 
1998). 
 

 
Statistical analysis 
 
The data were analysed using the computer statistical software 

(Mstat-c) and least significant difference (LSD) tests was used for 

comparison of means. 



 
 
 

 
Table 3. Effect of drying methods on seed vigour.  

 
Seed vigour parameter Drying method Before drying After drying After aging  

 
 

Radicle length (cm) 
 
 
 
 

 
Seedling shoot dry weight (mg) 

 
 
 
 

 
Mean time to germinate (days)  

  
 

Seed dryer  17.9 a  17.5 a  13.1 a 

Shade  17.9 a  15.5 b  12.2 b 

Silica gel  17.9 a  13.7 c  13.2 a 

Sun  17.9 a  13.7 c  10.8 c 

Seed dryer  7.100 a  6.367b  4.605 b 

Shade  7.100 a  6.250 b  4.417 b 

Silica gel  7.100 a  6.667 a  4.817 a 

Sun  7.100 a  6.000 c  4.133 c 

Seed dryer  6.3 a  4.2 b  5.5 ab 

Shade  6.3 a  4.1 c  5.3 b 

Silica gel  6.3 a  4.2 b  5.7 a 

Sun  6.3 a  4.5 a  5.5 b 
 

 

 

RESULTS 

 

Effect of drying method and genotype on seed 

moisture content 
 
The data in Table 1 showed that among all the 
genotypes, sun drying consistently produced the lowest 
moisture content, followed by silica gel, shade and seed 
dryer, respectively. A simple one-way ANOVA test on 
drying methods, indicated a significant difference 
between drying methods (p < 0.001). However, there was 
no significant difference among genotypes, the mean 
percentage moisture contents of the seeds among 
genotypes before and after drying varied between 18.7 
and 21% among all the different drying methods (Table 
1). 
 

 

Effect of drying method and genotype on seed 

viability 
 
Seed viability as represented by germination percentage 

was significantly affected by the seed drying method, 

irrespective of the genotype. The highest germination 

percentage after drying (91.6%) was observed in the seeds 

that were dried in the seed dryer, which was significantly 

different from those dried under shade (87%) (p < 0.001) . 

On the other hand, seeds dried over silica gel and under sun 

had the lowest germination percentages (83.7 and 82.4%, 

respectively) (Table 2, Figure 1).  
The result on seed germination also showed 

differences among genotypes when tested before drying, 
and after drying. The highest germination percentage 
before drying (85.9%) was recorded in the accession PI 
570300, while the lowest (60.8%) was recorded in the 
cultivar Tabat. Irrespective of the drying method, the 

 
 

 

highest germination level after drying (93.0%) was 
recorded by the accession PI 570120, which was 
significantly different from the others; whereas, the lowest 
germination levels of 83.5, 83.4 and 82.9% were recorded 
in the genotypes PI 570356, cultivar Tabat and PI 570300, 
respectively (Table 2 and Figure 2). However, it was 
interesting to observe a general trend of increase in the 
germination percentages after seed drying, compared with 
those recorded before drying.  

When seeds of the different treatments were subjected 
to accelerated aging, the germination levels differed 
significantly from each other (p < 0.001). Drying using 
silica gel resulted in the highest germination percentage 
(66.2%), followed by the seed dryer (60.4%) and shade  
(57.6%), whereas, the lowest germination level was given 
by sun drying (52.7%). After accelerated ageing, the 
accession PI 570342 gave the highest germination 
percentage (75%), while the lowest (39.6%) was obtained 
by the accession PI 570300, indicating different 
responses among genotypes (Table 2). 
 

 

Effect of drying methods on seed vigour 
 
The effect of drying method on seed vigour was assessed 
in the form of radicle length, shoot dry weight and 
germination speed. Radicle length was significantly 
affected by the drying methods. Irrespective of genotype, 
the longest radicle length (17.5 cm) was obtained in the 
seeds dried with the seed dryer, followed by those dried 
under shade (15.5 cm) with the radicle length significantly 
different from each other (Table 3). Both drying methods 
(that is, seed dryer and shade drying) also resulted in 
radicle lengths that were significantly different from those 
of the seeds dried over silica gel or under sun, which in 
effect have the same radicle length (13.7 cm). 



 
 
 

 

 100   
 

p
e

rc
e

n
ta

g
e

 90   
 

80   
 

70   
 

60  
Seed dryer 

 

   

G
e

rm
in

a
ti

o
n

 

50 
 

 

 
Shade 

 

40 
 

 

  
 

30 
 Silica gel 

 

  
 

20 
 Sun 

 

  
 

   
 

 10   
 

 4 7 10 
  

 

Time (days) 

 
Figure 1. Effect of drying methods on germination percentage. 

 
 

 

 100   
 

p
e

rc
e

n
ta

g
e

 

90   
 

80   
 

70 

 
PI 570342 

 

G
e

rm
in

a
ti

o
n

  
 

 

PI 570356 
 

  
 

60  PI 570120 
 

  PI 570300 
 

50  Tab at 
 

   
 

 40   
 

 4 7 10 
  

 

Time (days) 
 

Figure 2. Effect of drying on germination percentage among genotypes. 
 
 

 

After ageing, highly significant differences were also 
observed between the different drying methods. The 
silica gel and seed dryer gave the longest radicles (13.2 
and 13.1 cm) and the differences between the two were 
not significant (p = 0.05). Shade and sun drying resulted 
in the shortest radicles of 12.2 and 10.8 cm, respectively, 
which were significantly different between the two and 

 
 
 

 

also from those obtained with silica gel and seed dryer. 
The result on shoot dry weight showed that drying over  

silica gel gave seedlings with the highest shoot dry weight 
(6.7 mg), which was significantly different from sun drying 
(6.0 mg) (p = 0.001 ) as well as those obtained from seed 
dryer and shade drying (Table 3). After ageing, the 
different drying methods resulted in the 



 
 
 

 

same trend of significance, where the silica gel gave the 
highest dry weight (4.8 mg), and sun drying resulted in 
the lowest dry weight (4.1 mg), while seed dryer and 
shade drying gave medium dry weights (4.6 and 4.4 mg, 
respectively) (Table 3).  

Drying methods also significantly affected the speed of 
germination. The quickest germination speed (4.0 days) 
was obtained by shade drying, while the slowest speed 
(4.5 days) was obtained by sun drying. Seeds dried in the 
seed dryer and over silica gel gave the same germination 
speeds (4.2 days) (Table 3). After ageing, no significant 
differences were observed between the different drying 
methods except for the silica gel, which gave the slowest 
germination speed that was significantly different from 
those of shade and sun drying (Table 3). 
 

 

DISCUSSION 

 

All drying methods used, including those under natural 
conditions, that is, shade and sun, achieved the seed 
moisture contents in the range of 5.6 - 7.5% that are safe 
for conservation of sorghum. Rao and Bramel (2000) 
recommend the drying of seeds down to 3 - 7% SMC for 
long-term storage (Base collection) and 8 - 10% SMC for 
medium term conservation, which is used for regene-
ration, distribution, characterization and evaluation. 
Although the result of this study showed that drying in the 
sun and by silica gel achieved the lowest moisture 
content, compared to seed dryer and shade drying, these 
drying methods adversely affected the seed quality in 
terms of the seed viability and seed vigour. Seed dryer 
and shade drying gave the highest seed viability for most 
of the genotypes tested (Table 2), indicating that they 
ensure high initial quality of the seeds at start of storage.  

This point is an important one, as Rao et al. (2006) 
suggest that high initial seed viability is a pre-requisite for 
improving seed longevity in genebanks that helps reduce 
regeneration loads. Many authors have also shown that 
the moisture content at which seeds were stored had a 
significant effect on seed longevity (Ellis et al., 1990; 
Nutile, 1964; Nakamura, 1975; Woodstock et al., 1983; 
Zheng, 1994). Differences in seed vigour (radicle length, 
seedling dry weight, and speed of germination) which are 
measures of seed quality were found between the 
different genotypes in the present study. The seed vigour 
test for all three parameters demonstrated that sun drying 
in particular, affects seed quality and we thus recommend 
that sun drying should not be used for sorghum seeds 
intended for long-term conservation. The results showed 
that drying in silica gel and seed dryer produce the best 
results in seed quality and they may be the most optimum 
drying methods to be used. The shorter drying time using 
the seed dryer for seeds to reach their lowest moisture 
content is attributed to air flow and low RH, inside the 
seed dryer. The high mean day temperature (26°C) also 
allowed seeds to dry faster under sun, whereas, the 

 
 
 
 

 

fluctuating day, night RH and the low mean day 
temperature (22°C) extended the period for seed dried 
under shade. Highly significant differences were also 
observed on seedling shoot dry weight; both after drying 
and aging. Accessions PI 570342 and PI 570120 
recorded the highest seed vigour and this could be 
attributed to the higher starch content found in the seeds 
of these genotypes, according to the information available 
in the genebank documentation system at PGR Unit of 
Sudan.  

Our study also showed that there were no significant 
differences in final seed viability when the seeds were 
dried by silica gel or under sun. Similarly, Kong and 
Zhang (1998) in their study on nine vegetables seeds 
using three methods of drying, namely: Freeze drying, 
heating at 50°C for two days and drying over silica gel, 
found that there was no difference in longevity when 
seeds were dried by either exposure to silica gel, freeze 
drying or heating to 50°C as long as the seeds were not 
over dried.  

Drying seeds improved the germination percentages in 
all drying cases (Table 2), which is a phenomenon 
demonstrated by many previous studies (Ellis et al., 1983; 
Kong and Zhang, 1998; Vodouhe et al., 2008). This is 
explained by the fact that newly harvested seeds show 
some type of innate dormancy, which can be broken by 
different external factors such as time, drying or storage 
conditions. Dormancy that occurs immediately after 
harvest in sorghum has been reported by many scientists 
(Goodsell, 1957). Chantoreau and Nicou (1994) stated 
that dormancy period in sorghum rarely exceeds three 
weeks to one month and is linked to the high level of 
tannin that occurs in grains of some varieties. Ellis et al. 
(1983) demonstrated that germination of Oryza glaberrima 
seed was improved after drying and attributed this to after-
ripening.  

In this study, different genotypes showed different 
levels of seed moisture content both, before and after 
drying, which could be explained by the differences in 
biochemical composition of seeds. The same variation 
could also be the reason behind the differences in the 
final seed viability after drying. Thus, accessions PI 
570342 and PI 570120 gave the highest germination 
percentage after drying and also after the accelerated 
ageing treatment, which could be attributed to the fact 
that these two genotypes had higher starch contents 
(completely starchy) compared to other genotypes with 
starch content ranging between intermediate to mostly 
corneous. Harrington (1972) also found some association 
between low starch level and poor storability among 
seeds with different starch levels.  

In conclusion, none of the alternative drying methods 
proved to be better than the seed dryer which is the 
recommended seed drying method. However, this study 
indicates that silica gel could be a good option, in cases 
when the optimum recommended facilities are not 
available. Thus, both viability and vigour of seeds dried 



 
 
 

 

over silica gel were affected to a lesser extents when 
compared with those dried using the other drying 
methods. Using silica gel could also be cheaper than the 
seed dryer when a limited number of seed samples are to 
be dried.  

The study indicated that shade drying could be the 
second best alternative method for drying sorghum seeds. 
According to Rao et al. (2006), shade drying can be an 
effective way of reducing seed moisture content in 
environment where the RH is low (less than 40%). Shade 
and sun are both natural low-cost methods. Although sun 
drying may be a quicker method of drying, the study 
shows that it has a harmful effect on the seed viability and 
thus should not be recommended. 
 

 

ACKNOWLEDGEMENTS 

 

The authors would like to thank the staff of the Plant 
Genetic Resources Unit of Agricultural Research 
Corporation (PGR/ARC) of Sudan for supporting the 
research activity as well as Bioversity international for 
their financial support. 
 

 
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