Livestock Research for Rural Development 17 (10) 2005 Guidelines to authors LRRD News Citation of this paper Effect on yield and composition of water spinach (Ipomoea aquatica), and on soil fertility, of fertilization with worm 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 or urea. The biomass yield response to fertilizer N was positive and curvilinear and was greater for the earthworm 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, 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
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 compared with the original manure (Nguyen Quang Suc et al 2000). The objective of this study was to compare 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 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 was analysed for total nitrogen (N) and ammonia-n (NH 3 -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, 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 Table 1: Effect of different levels of nitrogen, from urea or worm, 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 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 25.1 a 26.9 a 27.6 a Worm 19.6 21.3 23.6 24.9 26.0 b 27.4 b 28.3 b SEM 0.12 0.14 0.29 0.33 0.18 0.23 0.19 Yield, tonnes DM/ha Urea 0.67 1.13 1.85 a 2.11 a 2.24 a 2.44 a 2.49 a Worm 0.64 1.27 1.96 b 2.34 b 2.54 b 2.74 b 2.85 b 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 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 over urea also increased with increasing level of application of the fertilizers. The latter effect is to be expected as worm 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 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 14.1 a 15.4 a 17.4 a 21.7 a Worm 11.6 12.3 14.2 17.6 b 22.6 b 25.9 b 28.8 b 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 (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 Figure 6: Response of total N in soils fertilized with increasing levels of N from urea or earthworm Figure 7: Response of K 2 O in soils fertilized with increasing levels of N from urea or earthworm Figure 8: Response of P2O 5 in soils fertilized with increasing levels of N from urea or earthworm Table 3:Mean values for chemical characteristics of soils fertilized with increasing levels of N from urea or worm Parameter At kg N/ha beginning 0 10 20 30 40 50 60 Urea 5.13 5.12 5.15 5.08 5.11 5.15 5.17 5.09 ph Worm 5.14 5.14 5.15 5.16 5.16 5.18 5.19 5.18 Urea 4.50 4.39 4.25 a 4.38 a 4.38 a 4.29 a 4.32 a 4.30 a OM Worm 4.53 4.27 4.40 b 4.50 b 4.66 b 4.87 b 4.95 b 5.30 b SEM - 0.12 0.09 0.02 0.07 0.09 0.1 0.12 Urea 0.187 0.134 0.167 0.179 0.188 0.190 0.196 a 0.202 a N total Worm 0.179 0.121 0.187 0.189 0.192 0.198 0.210 b 0.240 b SEM - 0.011 0.009 0.008 0.007 0.005 0.004 0.008 Urea 0.073 0.067 0.071 0.068 0.074 0.075 a 0.083 a 0.075 a P 0 2 5 Worm 0.081 0.075 0.075 0.078 0.087 0.096 b 0.103 b 0.109 b SEM 0.0006 0.0007 0.0006 0.0008 0.0009 0.0007 0.0007 0.0008 Urea 0.51 0.27 0.26 a 0.26 a 0.23 a 0.24 a 0.27 a 0.26 a K 2 0 Worm 0.51 0.24 0.36 b 0.39 b 0.45 b 0.54 b 0.63 b 0.68 b 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 was superior to urea in promoting biomass growth and crude protein content of water spinach. In contrast to use of urea, application of worm 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 AOAC 1990 Official methods of analysis. Association of Official Analytical Chemists. 15 th edition. Arlington pp1290 Arancon N Q, Lee S, Edwards C A and Atiyeh R 2004 Effects of humic acids derived from cattle, food and paper-waste vermis 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 AFRIS 2005 Animal Feed Resources Information System, FAO, Rome. Retrieved June 7, 2005, from http://www.fao.org/ag/aga/agap/frg/afris/default.htm Chhay Ty and Preston T R 2005: Effect of water spinach and fresh cassava leaves on intake, digestibility and N retention in growing pigs. Livestock Research for Rural Development. Vol. 17, Art. #23. Retrieved June 7, 2005, from http://www.cipav.org.co/lrrd/lrrd17/2/chha17023.htm Hongthong Phimmmasan, Siton Kongvongxay, Chhay Ty and Preston T R 2004: Water spinach (Ipomoea aquatica) and Stylo 184 (Stylosanthes guianensis CIAT 184) as basal diets for growing rabbits. Livestock Research for Rural Development. Vol. 16, Art. #34. Retrieved, from http://www.cipav.org.co/lrrd/lrrd16/5/hong16034.htm
Le Ha Chau 1998a Biodigester effluent versus manure from pigs or cattle as fertilizer for production of cassava foliage (Manihot esculenta). Livestock Research for Rural Development. Volume 10, Number 3, December 1998. Retrieved June 7, 2005 from http://www.cipav.org.co/lrrd/lrrd10/3/chau1.htm Le Ha Chau 1998b Biodigester effluent versus manure, from pigs or cattle, as fertilizer for duckweed (Lemna spp.) Livestock Research for Rural Development. Volume 10, Number 3, December 1998. Retrieved June 7, 2005 from http://www.cipav.org.co/lrrd/lrrd10/3/chau2.htm Ly Thi Luyen and Preston T R 2004: Effect of level of urea fertilizer on biomass production of water spinach (Ipomoea aquatica) grown in soil and in water. Livestock Research for Rural Development. Vol. 16, Art. #81. Retrieved June 7, 2005, from http://www.cipav.org.co/lrrd/lrrd16/10/luye16081.htm Kean Sophea and Preston T R 2001 Comparison of biodigester effluent and urea as fertilizer for water spinach vegetable. Livestock Research for Rural Development 13 (6). Retrieved June 7, 2005 from, http://www.cipav.org.co/lrrd/lrrd13/6/kean136.htm