Open Journal of Forestry
2014. Vol.4, No.1, 34-37
Published Online January 2014 in SciRes (http://www.scirp.org/journal/ojf) http://dx.doi.org/10.4236/ojf.2014.41006
34
Effects of Hydrogels on Soil Moisture and Growth of Cajanus
cajan in Semi Arid Zone of Kongelai, West Pokot County
Cheruiyot Gilbert1*, Sirmah Peter1, Ng’etich Wilson2, Mengich Edward1,3
Mburu Fr ancis1, K imaiyo Sylvester1, Bett Eric k 4
1School of Natural Resource Management, University of Eldoret, Eldoret, Kenya
2School of Agriculture, University of Eldoret, Eldoret, Kenya
3Kenya Forestry Research Institute, Londiani, Kenya
4School of Science, University of Eldoret, Eldoret, Kenya
Received September 8th, 2013; revised October 21st, 2013; accepted November 9th, 2013
Copyright © 2014 Cheruiyot Gilbert et al. This is an open access article distributed under the Creative Com-
mons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, pro-
vided the original work is properly cited. In accordance of the Creative Commons Attribution License all Copy-
rights © 2014 are reserved for SCIRP and the owner of the intellectual property Cheruiyot Gilbert et al. All
Copyright © 2014 are guarded by law and by SCIRP as a guardian.
Studies on the effects of hydrogels on soil amendments, moisture conservation and grow th of Cajanus
cajan in arid and se mi-arid lands were carried out. Seedlings of C. cajan wer e established both in the
nursery and in the field with and without hydrogels. In the field, three replications were used with three
levels of hydrogels concentration (7 g, 11 g, and 15 g). Control seedlings were established in soils without
hydrogels. In the nursery, root collar diameters and heights were measured every two weeks up to eight
weeks. Seedlings established without hydrogels in the nursery were transplanted into field soils with none,
7 g, 11 g and 15 g of hydrogels. Root collar diameters and heights were again measured every month for
three months. In addition, s oil was collected randomly once every month from the base of each seedling
and analyzed for soil moisture using standard laboratory procedures. All data were subjected to analysis
of variance. The results show that growth in both the height and root collar diameter of the species was
significantly different at the three levels of hydrogels. This suggests that use of hydrogels retards plant
growth in nursery soils but improves growth in the field. Hydrogels increased soil moisture volume from
8.3% to 10% in H15g level of hydrogels under C. cajan after transplanting. It was concluded that hydrogels
do not contribute to growth of seedlings in the nursery but they do so after transplanting. Hydrogels in-
crease soil moisture in the soil, so they are recommended for use in semi-arid lands to boost the survival
and growth of seedlings.
Keywords: Hydrogels; Moisture; Growth; Semi-Arid Lands
Introduction
Keny a is a developing country striving to achieve vision
2030 (Muchiri et al., 2009). One way of a chieving the goals of
Vision 2030 is by improving the livelihoods of people living in
arid and semi arid lands through introduction of appropriate
agroforestry technologies and practices to mitigate aridity
(Okorie, 2003). Forest cover in Kenya is currently standing at
1.7% way bel ow the internationally accepted minimum of 10%
(IPCC, 2008), t hus there is need to support the development of
forestry practices to increase forest cover towards the required
minimum percentage. On the basis of moisture availability for
plant growth, Ke nya is classified as 88% a rid and se mi -arid
with a population of over 10 million, many of whom are pasto-
ralists and agro-pastoralists (GoK, 2010). Similarly, moisture
retention in the soil is important for the growth of agroforestry
tree species. Soil water affects plant growth direct ly because it
influences ae r ation, temperature, nutrient transport, uptake and
transformation (Luo et al., 2011).
Hydrogels are networks of polymer chains that are hydro-
philic and highly absorbent to water molecules (Abedi-Koupai,
2008). The addition of hydrogels to soil can improve water
holding capacity, decrease evapotranspiration and allow plants
to mitigate the drought stress (Chirino et al., 2008).
This study therefore aimed at investigating the effects of hy-
drogels on soil water availability and growth of C. cajan seedl-
ings in the nursery and during early establishment in the field. It
was carried out in the arid and semi-arid areas of Kongelai.
Materials and Methods
Location and Climate of Study Area
This study was carried out at Kongelai, West Pokot County,
Keny a (Figure 1; 1.47˚71'S, 35.02 ˚07'E). The study area lies be-
tween 1500 m and 2100 m above sea level, and is characterized by
a bimodal type of rainfall with the long rains between April and
August and short rains between October and February. The area is
characterized by great variations in temperature with 30˚C in the
lowlands and 15˚C in the highlands.
The hydrogels used was “Belsap” manufactured by Bell
*Corresponding a uthor.

C. GILBERT ET AL.
35
Figure 1.
Map of study ar ea, West Pokot County (County Commissioner’s Office, 2013).
Industries limited in Nairobi Kenya.
Potting soil was obtained from Kapolet Forest Station within
the county.
Procedures in the Nursery
Seeds of C. cajan were directly sown into polythene tubes
measuring 4 × 6 inches containing 800 g of forest soil and at
different levels of hydrogels. A total of 4 treatments of different
levels of hydrogels: 0, 7, 11 and 15 g were prepared. Each con-
sisted of 42 seedlings and replicated thrice. Treatments were
randomized within the blocks. All polythene tubes were labeled
for identification purposes. Once the seedlings germinated, root
collar diameter and height were measured every two weeks for
two months. A Randomized Complete Block Design (RCBD)
was used in this experiment.
Procedures in the Field
After two months in the nursery, control seedlings were
de-potted and transplanted into pre-tested soil samples in a field
within the same region. Seedlings treated with hydrogels were
not transplanted. In the field, the same levels of hydrogels as in
the nursery were applied in the planting holes and mixe d with
soil. Thirty seedlings were used for each treatment. Once a
month for two months, RCD and height of seedlings were
measured. In addition soil samples were collect ed from the base
of each growing seedling for moisture analysis.
Determination of Soil Moisture
50 g soil from 0 - 10 cm horizons were collected in the field
under Cajanus cajan seedlings using a soil auger seedlings.
Initial weight was determined and the sample oven-dried at
100˚C. Oven dry weight was determined and soil moisture
content determined.
The data collecte d were analyzed using Microsoft Excel;
Analysis Toolpak, a computer package for data analysis. F-test
was used to test the level of significance.
Results and Discussion
Effects of Hydrogels on the Growth of Seedlings in
the Nursery
Cajanus cajan seedlings established in soils with no hydro-
gels gave higher height growth than those in soils treated with
hydrogels (Figure 2). Soils treated with the higher amount of
hydrogels (H15 g) gave the least growth in height of the seedl-
ings. Analy sis of variance for the hei gh t of Cajanus cajan
seedlings showed that {F0.05(1) [3,15] = 3.6182 > F c rit i cal
(3.4903)} implying t hat hydrogels application had a significant
effect on the height growth.
Cajanus cajan seedlings established in soils with no hy dro-
gels gave higher RCD growth compared to those established in
soils treated with hydrogels (Figure 3). Analysis of variance
showed that {F0.05(1) [3,15] = 6.9127 > F critic al (6.2913)}
implying that hydrogels appl ic at ion had a significant effe ct on
the root collar diameter growth.
Increasing levels of hydrogels had a negative effect on the
growth of seedlings in the nursery both in height and RCD
(Figures 2 and 3). Hydrogels also absorb water and fi ll the soil
pores causing flooding in the po l ythene tubes therefore retard-
ing the growth of seedlings (Del Campo et al., 2011; Korsaeth,
2012).
Effects of Hydrogels on the Growth of Seedlings in
the Field
Cajanus cajan seedlings grown in soils with no hydrogels
gained lower growth in height than those in soils treated with
hydrogels (Figure 4). Analysis of variance for the height of

C. GILBERT ET AL.
36
0
2
4
6
8
10
12
14
0
2
4
6
8
Height (cm)
Time (weeks)
H0
H7g
H11g
H15g
Figure 2.
Effects of hydrogels on height of Cajanus cajan seedlings in the nur-
sery.
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0
2
4
6
8
RCD ( cm )
Time (weeks )
H0
H7 g
H11g
H15g
Figure 3.
Effects of hydrogels on RCD of Cajanus cajan seedlings in the nursery.
0
10
20
30
40
50
60
70
80
During
transplanting
1st
2nd
3rd
Height (cm)
Time (Months)
H0
H7 g
H11g
H15g
Figure 4.
Effects of hydrogels on height of transplanted seedlings after 3 months.
Cajanus cajan showed that {F0.05(1) [3,15] = 144.8962 > F
critic al (3.4903)}. This showed that hydrogels had a significant
effect on the growth of transplanted seedlings hence use of
hydrogels to amend soils in the field had a positive impact on
height growth.
Cajanus cajan seedlings grown in soils with no hydrogels
gained least growth in RCD compared with those in soils treated
with hydrogels (Figure 5). Analysis of variance for the height
of Cajanus caj an showed that {F0.05(1) [3,15] = 138.89 > F
critic al (3.4903)}. This showed that hydrogels had a significant
effect on the growth of transplanted seedlings hence use of hy-
drogels in soils in the field has a positive impact on RCD growth.
Hydrogels is used in arid and semi -arid areas to improve the
growth of agroforestry tree species. They absorb water, im-
proving growth of transplanted seedlings under arid conditions
(Chen et al., 2010). The results of Chen et al. (2010) confirm
that changes in soil nu trie nt st a tus were influenced by the ap-
plication of hydrogels which led to the increase in soil fertility
and hence the differences in growth rate.
Effects of Hydrogels on Soil Moisture
Soil moisture contents we re determined in subplots under the
species. Results are presented in Figure 6. In the arid and semi
arid climate, hydrogels had an impact on soil moisture content
in the soil af t er transplanting. Anal ysi s of variance showed that;
F0.05(1) > F critical, implying that hydrogels had a significant
effect on the growth of transplanted seedlings in the field.
Landis (2012) reported that hydrogels improved soil moisture
content and provided water to the plants during dry seasons.
This was experienced in soils treate d with hydrogels that gained
more soil moisture as compared to controls.
Conclusion
Hydrogels reta rd ed growth of seedlings in the nursery but
improve the same after transplanting. They increase soil moisture
content under arid and semi-arid conditions, therefore increasing
seedlings survival after transplanting.
Further studies need to be done to compare the effects of hy-
drogels on a range of soil types using a wide range of tree species.
0
0.1
0.2
0.3
0.4
0.5
0.6
During
transplanting
1st
2nd
3rd
RCD (cm)
Time (months)
H0
H7 g
H11g
H15g
Figure 5.
Effects of hydrogels on height of transplante d seedlings after 3 months.
Figure 6.
Effects of hydrogels on soil moisture after transplanting.

C. GILBERT ET AL.
37
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