Arancon N Q, Lee S, Edwards C A and Atiyeh R 2004 Effects of humic acids derived from cattle, food and paper-waste vermicomposts on growth of greenhouse plants. Pedobiologia, January 2004, vol. 47, no. 5-6, pp. 741-744(4) Retrieved June 7, 2005, from http://www.ingentaconnect.com/content/urban/281/2004/00000047/F0020005/art00051
Effect on yield and composition of water spinach (Ipomoea aquatica), and on soil fertility, of fertilization with worm compost or urea
Tran Hoang Chat, Ngo Tien Dung, Dinh Van Binh and T R Preston*
Goat and Rabbit Research Centre, Sontay, Hatay, Vietnam
binhbavi@netnam.vn
*UTA, TOSOLY, AA #48, Socorro, Santander, Colombia
trpreston@mekarn.org
Abstract
This trial was conducted at the Goat and Rabbit Research Centre, Sontay, Hatay, Vietnam from April to December 2004. The aim was to evaluate the response of water spinach to fertilization with increasing levels of nitrogen (0, 10, 20, 30, 40, 50, 60 kg N/ha over 28 days) in the form of earthworm compost or urea.
The biomass yield response to fertilizer N was positive and curvilinear and was greater for the earthworm compost at the higher levels of application of N. Increasing application of fertilizer N provoked linear responses in DM content, which decreased, and in crude protein content, which increased. Soil fertility was improved by the worm compost, but not by urea, as measured by the organic matter, phosphorus and potassium contents of the soil at the end of the trial.
It appears that the most economical level of N is 40 kg/ha applied over the 28 day growth period.
Key words: biomass, fertilization, urea, water spinach, worm compost
Introduction
Water spinach (Ipomoea aquatica) is a variable water and marsh plant, rich in protein, that is traditionally planted as a vegetable in many tropical countries (AFRIS 2005). Recent research has shown that it has a high potential as a replacement for soya bean meal in pig diets (Chhay Ty and Preston 2004) and as a complete feed for rabbits (Hongthong Phimmmasan et al 2004). Yield of water spinach biomass showed a linear response to application of biodigester effluent up to 140 kg N/ha over a 28 day period, reaching a production of 24 tonnes fresh matter/ha (Kean Sophea and Preston 2003). By contrast, the maximum response to application of urea was 12 tonnes/ha, and there was no advantage from applying more than 40 kg N/ha in a growth cycle of 21 days (Li Thi Luyen and Preston 2004). Recycling pig or cattle manure through biodigesters gives rise to an effluent which was shown to be superior in fertilizer value to the original manure when these sources of plant nutrients were applied to cassava and duckweed (Le Ha Cha (1998a,b). Recycling manure through earthworms also improves the fertilizer value. Maize plants grew at twice the rate on worm compost compared with the original manure (Nguyen Quang Suc et al 2000).
The objective of this study was to compare compost from earthworms with urea as fertilizer for water spinach.
Materials and methods
Location
The research was conducted at the Goat and Rabbit Research Centre, Sontay, Hatay province, North Vietnam in 2004-2005
Design and treatments
The experiment was laid out in a completely randomized block design with 8 replications. The treatments were arranged in a 2*6 split-plot design. The main plots were levels of nitrogen (0, 10, 20, 30, 40, 50, 60 kg N/ha). The split-plots were earthworm compost or urea.
Land preparation, planting, fertilizing and irrigation
The soil was cultivated two times by hoe, and a raised bed prepared, which was 12-15 cm high. The water spinach was planted from seed in rows across the bed, with spacing between seeds of 1-2 cm at 2-3 cm depth. The distance between rows was 20 cm. The distance between plots was 50 cm. The fertilizers were applied 3 times in the growing period, the quantities being 10, 40 and 50% of the total allowance at 7, 14 and 21 days, respectively. A watering can was used to apply water twice a day (morning and afternoon) at the rate of 3 to 4 litres/m². On rainy days no water was applied.
Measurements
The first harvest was made at 28 days after planting. All plants in individual plots were weighed. Leaf and stem samples were collected at random and analysed for DM, N, ash and ADF (AOAC 1990) and NDF (Van Soest 1991). The compost was analysed for total nitrogen (N) and ammonia-N (NH3-N). Samples of soil were taken from each plot before planting and after harvest for determination of pH, OM, N, P, K. Before planting and after harvesting the water spinach, two samples of soil (2 kg) were taken from the 0 - 20 cm layer in each plot and put into plastic bags. Five seeds of maize were planted in each plastic bag and watered every day. One week after planting the number of maize plants was reduced to three per bag for the growing test. After 30 days the height to the growing point was recorded and the biomass harvested and weighed fresh.
Results and discussion
The response of biomass DM yield to fertilizer N was curvilinear (Figure 1) for both urea and earthworm compost, and was higher for the latter at the higher levels of application of N (Table 2). The optimum level of application of N would appear to be about 40 kg/ha. The response to 40 kg N/ha over the control (0 kg N) was an increase of 1.66 tonnes of DM while applying a further 20 kg N (from 40 to 60 kg N/ha) increased yield by only 0.11 tonnes/ha (Figure 1).
Figure 1: Response in biomass yield of water
spinach fertilized
with increasing levels of N from urea or earthworm compost
Table 1: Effect of different levels of nitrogen, from urea or worm compost, on DM and crude protein content, and biomass yield of water spinach |
|||||||
|
|
kg N/ha |
||||||
0 |
10 |
20 |
30 |
40 |
50 |
60 |
|
DM, % |
|
|
|
|
|
|
|
Urea |
17.8 |
15.7 |
14.2 |
13.1 |
12.7 |
11.6 |
10.5 |
Worm compost |
17.6 |
15.8 |
14.5 |
14.2 |
13.1 |
12.1 |
10.9 |
SEM |
0.09 |
0.11 |
0.21 |
0.42 |
0.31 |
0.37 |
0.36 |
Crude protein, % of DM |
|||||||
Urea |
19.5 |
21.7 |
23.1 |
24.6 |
25.1a |
26.9a |
27.6a |
Worm compost |
19.6 |
21.3 |
23.6 |
24.9 |
26.0b |
27.4b |
28.3b |
SEM |
0.12 |
0.14 |
0.29 |
0.33 |
0.18 |
0.23 |
0.19 |
Yield, tonnes DM/ha |
|
|
|
|
|
|
|
Urea |
0.67 |
1.13 |
1.85a |
2.11a |
2.24a |
2.44a |
2.49a |
Worm compost |
0.64 |
1.27 |
1.96b |
2.34b |
2.54b |
2.74b |
2.85b |
SEM |
0.021 |
0.095 |
0.020 |
0.051 |
0.034 |
0.046 |
0.039 |
|
a, b Means within criteria, within columns,, without common superscript differ at (P<0.05) |
|||||||
Increasing application of fertilizer N provoked linear responses in DM content, which decreased (Figure 2), and in crude protein content, which increased (Figure 3). Similar responses in the composition of water spinach were recorded by Kean Sophea and Preston (2003), with application of biodigester effluent, and by Li Thi Luyen and Preston (2004) with urea.
 |
 |
|
Figure 2: Relationship between level of fertilizer N and the DM content of the biomass |
Figure 3: Relationship between level of fertilizer N and the crude protein content of the biomass |
There was a marked improvement in soil fertility in response to the application of urea and worm compost as measured by the maize biotest (Figure 4 and Table 2). The rate of improvement appeared to increase more rapidly at the higher levels of fertilizer application; the advantages of worm compost over urea also increased with increasing level of application of the fertilizers. The latter effect is to be expected as worm compost supplies other essential plant nutrients as well as N and also can be expected to bring about benefits in plant growth through the presence of humic acids which are known to enhance soil fertility (Arancon et al 2004).
Figure 4: Response in biomass yield of maize plants grown on soils fertilized with
increasing levels of N from urea or earthworm compost
|
Table 2: Weight of combined root and green biomass of maize plants grown for 30 days in soil from the experimental plots |
|||||||
|
|
0 |
10 |
20 |
30 |
40 |
50 |
60 |
|
Urea |
11.2 |
12.1 |
13.9 |
14.1a |
15.4a |
17.4a |
21.7a |
|
Worm compost |
11.6 |
12.3 |
14.2 |
17.6b |
22.6b |
25.9b |
28.8b |
|
SEM |
0.21 |
0.25 |
0.32 |
0.57 |
0.98 |
1.12 |
1.2 |
|
a, b Means within columns without common superscript differ at (P<0.05) |
|||||||
Levels of organic matter, nitrogen, phosphorus and potassium in the soils all showed marked improvements as a result of fertilization with worm compost (Figures 5 to 8; Table 3). With the exception of N in soil, fertilization with urea had no effect on these parameters.
 |
 |
| Figure 5: Response of organic matter in soils fertilized with increasing levels of N from urea or earthworm compost |
Figure 6: Response of total N in soils fertilized with increasing levels of N from urea or earthworm compost |
 |
 |
| Figure 7: Response of K2O in soils fertilized with increasing levels of N from urea or earthworm compost |
Figure 8: Response of P2O5 in soils fertilized with increasing levels of N from urea or earthworm compost |
|
Table 3:Mean values for chemical characteristics of soils fertilized with increasing levels of N from urea or worm compost |
|||||||||
|
Parameter |
At beginning |
kg N/ha |
|||||||
|
0 |
10 |
20 |
30 |
40 |
50 |
60 |
|||
|
pH |
Urea |
5.13 |
5.12 |
5.15 |
5.08 |
5.11 |
5.15 |
5.17 |
5.09 |
|
Worm compost |
5.14 |
5.14 |
5.15 |
5.16 |
5.16 |
5.18 |
5.19 |
5.18 |
|
|
OM |
Urea |
4.50 |
4.39 |
4.25a |
4.38a |
4.38a |
4.29a |
4.32a |
4.30a |
|
Worm compost |
4.53 |
4.27 |
4.40b |
4.50b |
4.66b |
4.87b |
4.95b |
5.30b |
|
|
SEM |
- |
0.12 |
0.09 |
0.02 |
0.07 |
0.09 |
0.1 |
0.12 |
|
|
Ntotal |
Urea |
0.187 |
0.134 |
0.167 |
0.179 |
0.188 |
0.190 |
0.196a |
0.202a |
|
Worm compost |
0.179 |
0.121 |
0.187 |
0.189 |
0.192 |
0.198 |
0.210b |
0.240b |
|
|
SEM |
- |
0.011 |
0.009 |
0.008 |
0.007 |
0.005 |
0.004 |
0.008 |
|
|
P205 |
Urea |
0.073 |
0.067 |
0.071 |
0.068 |
0.074 |
0.075a |
0.083a |
0.075a |
|
Worm compost |
0.081 |
0.075 |
0.075 |
0.078 |
0.087 |
0.096b |
0.103b |
0.109b |
|
|
SEM |
0.0006 |
0.0007 |
0.0006 |
0.0008 |
0.0009 |
0.0007 |
0.0007 |
0.0008 |
|
|
K20 |
Urea |
0.51 |
0.27 |
0.26a |
0.26a |
0.23a |
0.24a |
0.27a |
0.26a |
|
Worm compost |
0.51 |
0.24 |
0.36b |
0.39b |
0.45b |
0.54b |
0.63b |
0.68b |
|
|
SEM |
0.01 |
0.009 |
0.011 |
0.012 |
0.009 |
0.014 |
0.021 |
0.023 |
|
|
a, b Means within columns without common superscript differ at P<0.05 |
|||||||||
Conclusion
-
Earthworm compost was superior to urea in promoting
biomass growth and crude protein content of water spinach.
- In contrast to use of urea, application of worm compost had beneficial effects on soil fertility when this was measured biologically and chemically.
Acknowledgments
The authors wish to thank the MEKARN project, financed by Sida/SAREC for supporting this research.
References
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