Utilisation of some Erythrina species and biomass production of Erythrina variegata

Daovy Kongmanila, Jan Bertilsson*, Inger Ledin* and Ewa Wredle*

Faculty of Agriculture, National University of Laos, Vientiane, Lao PDR
daovyk@yahoo.com
* Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences,
Box 7024, SE-750 07, Uppsala, Sweden

Abstract

Utilisation of three Erythrina species, E. indica, E. subumbrans and E. variegata, was studied in three different areas of Lao PDR (centre, north and south). Many farmers used both E. indica and E. variegata for fencing and as a shade tree and E. variegata leaves were also used as a traditional food and medicine. Erythrina subumbrans was commonly used as a shade plant and as fertiliser for Arabica coffee plants. Erythrina foliage was to some extent used as a feed supplement for cattle, goats, buffaloes and horses.

In the biomass experiment, E. variegata was tested with two different fertilisers, cow manure and mineral fertiliser, and a control treatment (no fertiliser). Branch cuttings were used as planting material. The foliages were harvested six months after establishment. Dry matter (DM) yields were recorded and nutritive values of the foliage analysed. Fertilisers significantly decreased the mortality of shoots and increased the height of shoots and fresh and crude protein (CP) yield. Total DM foliage yields were 194, 363 and 326 kg/ha and CP yields 29, 55 and 48 kg/ha for control, cow manure and mineral fertiliser, respectively. There were no significant differences in nutritive value of the foliage between treatments. The mean values over treatments in E. variegata were 200 g CP/kg DM in the leaves, and 7.6 g Ca, 2.0 g P and 8.4 g condensed tannins/kg DM in leaves plus petioles.  

Key words: cow manure, foliage, Lao PDR, mineral fertiliser, nutritive value, yield

Introduction

Legume trees offer a renewable and cheap source of feed protein for ruminant animals in smallholder farms in tropical regions. Erythrina species belong to a legume family that can be found throughout the tropics and even in warm temperate areas such as South East Asia, South Africa and the southern United States (Whistler and Elevitch 2006). Although species vary with region, the general uses of Erythrina are principally as a shade and support tree, for windbreaks, as live fence posts and as wood or medicinal plants (Speedy and Pugliese 1991). The juice of fresh leaves from some Erythrina species is used in traditional medicine, where it is considered to be a sedative and an analgesic (Ratnasooriya and Dharmasiri 1999; Deb et al 2009). Erythrina subumbrans is more commonly used as a shade tree planted among coffee or cocoa trees (Whistler and Elevitch 2006). Erythrina variegata foliage has high crude protein (CP) content, 19 to 22% in  dry matter (DM), and can be an excellent feed for most livestock (Kibria et al 1994; Aregheore and Perera 2004; Kongmanila and Ledin 2009).  

Some information is available on the forage biomass production of some Erythrina spp., e.g. E. caffra trees are reported to yield 15 tonnes/ha/year of fresh leafy biomass (Jaenicke and Owino 1993) and E. poeppigiana trees from 5 tonnes/ha/year of DM leafy biomass (Borel and Benavides 1993). Although E. variegata is well known, easy to grow and has multiple uses, the cultivation of this tree is limited in Lao PDR and data on growth rate and biomass yield are not available.  

The aim of this study was to investigate the use of Erythrina species in different parts of Lao PDR and to measure foliage yield and the effect of fertilisation on the foliage yield from E. variegata. The hypothesis was that more than one Erythrina species is grown in different areas and that the utilisation differs depending on species and locations. Using cow manure as a fertiliser when cultivating E. variegata will give higher foliage yield than mineral fertiliser.

Materials and methods

Utilisation of Erythrina species

The utilisation of Erythrina species was investigated in five provinces in three different areas of Lao PDR: Vientiane capital and province in the centre of the country, Luang Prabang province in the north and Champasack and Salavanh provinces in the south. The study areas in the centre, north and south of Lao PDR, at 200, 400 and >700 masl, respectively, were selected as being locations where Erythrina trees are grown or cultivated based on the geography of the area, soil characteristics and some informal information about Erythrina species used. In general, the central area has poor quality soils that are acid hydromorphic, with low organic matter (OM) and nutrient content, while more fertile basaltic soils, with high OM and good physical properties, are found in the south (Kashio and White 1996). On the Bolovens plateau in the south, Erythrina trees have long been cultivated to provide shade and fertiliser for Arabica coffee plants.     

Data were obtained from primary sources using two techniques: informal interviews and a formal questionnaire. The informal interviews were carried out by advisory officers at province and district level. The objective of these informal interviews was to identify the specific locations where Erythrina trees are cultivated and the general reasons for cultivating Erythrina.    

The formal survey used a structured questionnaire and a total of 50 households in the three areas were surveyed. Some of the information obtained was general, such as number of Erythrina species cultivated, the general reasons for their cultivation, cutting regime and end uses, but more specific information was sought on animal feeding, mainly when the foliage was available and the feeding system used.    

Biomass production of Erythrina variegata

Experimental design and management

The biomass experiment was carried out at the Faculty of Agriculture, National University of Laos during early June to December, 2009. The climate in this area is tropical monsoon, with a dry season between November and April and a rainy season from May to October. Average annual rainfall in this area is 2000 mm/year and the highest rainfall occurs in June to August. The soil is a clay loam (42.9, 25.0 and 32.2% of sand, silt and clay, respectively), with pH 4.7, 41.2 g OM/kg DM soil, 8.3g N/kg DM soil, 40.4 mg/kg DM soil of available P and 0.17 meq/100 g DM soil of available K (Kaensombath and Frankow-Lindberg 2012).  

The experiment was a randomised complete block design (RCBD) with three treatments, control (no fertilisation), cow manure and mineral fertiliser. There were 36 plots (12 plots per block and 4 plots per treatment and block). The experiment was established in a field of 2,400 m² of which 1,152 m² were allocated for planting Erythrina stems and 1,248 m² were the border areas between the plots and blocks. The experimental area was previously used for experiments on taro (Colocasia esculenta. (L.) Schott) and stylo (Stylosanthes guianensis (Aubl.) Sw. var. guianensis).  

The soil was ploughed by a tractor-drawn 7-furrow plough to about 15-20 cm depth in the middle of May and was then left to dry for 2 weeks to control weeds. The soil was then harrowed with a disc harrow, resulting in clods 3-5 cm in diameter. The experimental plots were demarcated and finally prepared by hand, using hoes to break large soil particles before planting.  

Erythrina variegata branches 3-4 cm in diameter were collected from planted areas near the research unit, cut into 35-40 cm pieces and planted on the same day. Twenty-five Erythrina stem cuttings were used in each plot (32 m²) with 1 m between plants and 2 m between rows, giving 5 rows with 5 plants in each plot. Each plot was planted manually with one cutting per hole in an upright position and the bottom end was covered with soil to about 15 cm depth.  

Cow manure and mineral fertiliser were applied to give similar amounts (respectively) of N (38.9 and 38.7 kg/ha), P (18.2 and 18.5 kg/ha) and K (4.1 and 4.5 kg/ha). The total amount of mineral fertiliser supplied was 150 kg/ha (30, 70 and 50 kg of compound fertiliser NPK 15:15:15, NPK 16:20:00 and urea, respectively). Dry cow manure was applied in an amount of 2430 kg/ha. Before fertilisation, samples of cow manure were taken for DM, N, P and K analyses. Half the total amount of cow manure and mineral fertiliser was applied 2 weeks after planting and the remaining half  3 months later. 

The experiment was carried out during the rainy season and watering was carried out as necessary. Weeding was performed manually three times during the experimental period by light slashing with a bush knife. Weeding was also carried out along the walkways and borders of the experimental plots.  

 Data collection and chemical analyses

Number and height of shoots were measured 6 months after planting. The total height of the plant was measured by gathering all shoots together and was considered to be the distance from the soil at the base of the plant to the highest tip of the leaves. On each plot, mortality was calculated as the number of plants that had died 6 months after establishment, divided by the number of live plants at the beginning of the experiment.  

The fresh foliage yield and the proportion of leaves, petioles and stems were determined by cutting 50% of each shoot on the 9 plants inside each plot. Each proportion was taken from each plot for DM determination and chemical analyses. 

The samples were analysed for DM (drying at 100˚C for 24 hours), ash (burning at 550˚C for 3 hours) and N (copper catalyst Kjeldahl method) according to AOAC (1990). Neutral detergent fibre (NDF) and acid detergent fibre (ADF) were assayed without heat-stable amylase and expressed inclusive of residual ash using the procedure of Van Soest et al (1991). Condensed tannins (CT) were analysed using the vanillin-HCl method (Burns 1971). Mineral contents were determined by plasma emission spectroscopy (Spectro Analytical Instruments GmbH & Co., Kleve, Germany) with the samples extracted with HNO₃ according to Bahlsberg-Pålsson (1990).  

Statistical analysis

 For data from the interviews, only descriptive statistics were used. The biomass data were analysed using the GLM procedure of Minitab Software, version 16.1 (Minitab 2010). Tukey’s pair-wise comparisons were used to determine differences between treatment means at P<0.05. The statistical model used was:
Y_ij = µ + F_i + B_j + F_i*B_j + e_ij,
where Y_ij is the dependent variable, µ is the overall mean, F_i is the effect of treatment (fertiliser), B_j is the effect of block, F_i*B_j is the effect of interaction between treatment and block and e_ij is the random error effect. There were no significant effects of the interaction between treatments and blocks and it was therefore excluded in the final model.

Results and discussion

Utilisation of Erythrina species

Three different Erythrina species (E. indica, E. subumbrans and E. variegata) were found in different locations and their utilisation is shown in Table 1. Many of the farmers interviewed used Erythrina in a similar way as in many previous studies, e.g. as a multipurpose tree (Speedy and Pugliese 1991). E. variegata and E. indica were used for fencing around the houses or crop fields, due to the sharp prickles on their stems, and E. variegata leaves were also used as a food or as traditional medicine for humans, as reported previously (Ratnasooriya and Dharmasiri 1999; Deb et al 2009). In both the north and south of Lao PDR, E. subumbrans was cultivated and used mainly as a shade tree and as a fertiliser for Arabica coffee plants, as reported previously by Whistler and Elevitch (2006). The E. subumbrans plant was selected by the farmers as a shade tree because it has no thorns.

Erythrina foliage was also fed to animals. Cattle and goats were fed Erythrina foliage as a supplement in some cases in all three areas, while in the south other animals such as buffaloes and horses were fed this foliage. However, use of Erythrina foliage as an animal feed seemed to be less common in the north and centre of the country, even though this foliage has good nutritive value, with high protein content that could have had a positive influence on feed intake and performance (Daovy et al 2008). Feeding systems based on free-range grazing, native grasses or forages and no feed supplementation are commonly practised in these regions (Phengsavanh 2003). This was also confirmed by farmers interviewed in the present study. In addition, competition from other uses, e.g. shade or green manure, could be another reason why only a small number of the farmers interviewed used Erythrina foliage as an animal feed.  

Cutting foliage from E. variegata and E. subumbrans only once per year was a common method (Table 2). This system is also practised in Sri Lanka (Powell and Westley 1993). There was no information about cutting time for E. indica. In both the centre and the north, Erythrina foliage was available during the period May-October, whereas foliage of E. subumbrans in the south was available for a longer period, May-December, since there is precipitation in this area almost all year round.

Biomass production of Erythrina variegata 

Plant mortality, the height of the Erythrina shoots, total fresh yield, DM yield and CP yield six months after planting were similar between the plots fertilised with cow manure or mineral fertiliser (Table 3). Approximately 30-60 cm height of shoots or re-growth of branches is common for Erythrina spp. 5-6 months after pruning (Powell and Westley 1993; Paterson 1994). The fresh foliage yield of the E. variegata trees, 750 to 1480 kg/ha, found in the present study was lower than the yield obtained by Jaenicke and Owino (1993) for E. caffra trees, which was 15 tonnes/ha/year of fresh leafy yield. Different species, older trees, four pruning times per year and higher amount of fertiliser (64 kg N/ha and 164 kg P₂0₅/ha) in the latter study resulted in these differences.

Higher yields of DM and CP have been reported in many previous studies with other species of Erythrina, e.g. E. fusca trees yielded 3.4 tonnes of DM of leaves/ha/year (Muschler 1993), E. poeppigiana trees yielded from 5 tonnes of DM and 450 kg of N per ha/year (Borel and Benavides 1993), and E. lanceolata yielded 350 kg of N in biomass (Frank and Eduardo 2003). Different species, 2-3 years after planting and 4-6 pruning times per year could be the reasons for higher yields in many previous studies compared with the present study. The lowest number of shoots and yield occur with pruning during the 4-6 months after planting, but higher yields can be obtained by starting pruning at 9-12 months, as recommended by Nygren (1996). However, periods longer than 6 months could not be measured in this study, since Erythrina leaves drop during the dry season and many Erythrina trees were damaged by termites. This short period is a limitation of this study, which makes it difficult to compare with other published papers. .  

Nutritive value of Erythrina variegata

The differences in nutritive value of the foliage among the three treatments (no fertiliser, cow manure and mineral fertiliser) were not statistically significant (Table 4). As a mean over treatments, the stems were generally low in CP (59 g/kg DM) and had higher NDF (737 g/kg DM) compared with petioles (91 and 639 g/kg DM, respectively) or leaves (199 and 546 g/kg DM, respectively), as also reported by Kongmanila and Ledin (2009). The CP content of leaves in the present study fell within the 193-213 g/kg DM range reported in previous studies (Kibria et al 1994; Aregheore and Perera 2004; Ngamsaeng et al 2006). Factors such as differences in age of the trees or the shoots or stage of maturity of the leaves could be the reason for the differences between reported values. 

The amount of condensed tannins (CT) in the leaves plus petioles for the treatment without fertiliser was 10.1 g/kg DM. According to the analytical method used for CT determination (Terrill et al 1992), the value in this study was soluble CT (Mupangwa et al 2000). It was lower than the total CT value obtained by Kongmanila and Ledin (2009) for the same Erythrina species under similar conditions (51 g/kg DM). In ruminant nutrition studies, a range of 60-100 g total CT/kg DM has been shown to reduce voluntary feed intake, digestibility and growth (Waghorn et al 1987; Min et al 2003). The interaction of tannins with saliva and mucus protein in the mouth might be a factor reducing the palatability of tannin-rich diets (Landau et al 2000). The content of CT found in the present study was below the level considered harmful and may not be negative for intake or animal performance.

In general, forage legumes are rich sources of K but poor in Na (NRC 2007). Similar results were found in out study, with contents of 0.2 and 11.3 g/kg DM of Na and K, respectively, in the leaves plus petioles of E. variegata.

The Ca and P contents found in this study (7.6 and 2.0 g/kg DM, respectively) were lower than the 19.2 and 4.4 g/kg DM of E. variegata leaves reported by Ibrahim et al (1998), the 19.1 and 3.0 g/kg DM of E. abyssinica leaves (Anthofer et al 1998) and the 17.5 and 2.2 g/kg DM of E. indica leaves (Amanullah et al 2006). In the present study, the petioles were included, which could be the reason for the lower results.

Conclusions

• Three different Erythrina species were found in the north, centre and south of Lao PDR. They were mainly used for fencing, shade and green manure and only to a limited degree as a feed.

• Under the conditions of this experiment, E. variegata was easily established using the branch cuttings, but cow manure or a mineral fertiliser should be supplied for more effective establishment.

• Cow manure and mineral fertiliser gave similar results for shoot height and foliage yield.

• Average foliage biomass yield was about 300 kg DM/ha for the three treatments at 6 months after establishment.Erythrina variegata contained 200 g crude protein/kg DM in the leaves, and 7.6 g Ca, 2.0 g P and 8.4 g condensed tannin/kg DM in the leaves plus petioles.

• E. variagata can thus be promoted as a sole or supplementary feed for ruminants, especially in free-grazing systems with poor pasture.

Acknowledgements

The authors gratefully acknowledge the Swedish International Development Agency/Department for Research Cooperation with Developing Countries (Sida/SAREC) for financial support for this research, and two BSc and five HD students at the Faculty of Agriculture, National University of Laos, for collecting data during the survey and biomass experiment.

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Received 31 May 2012; Accepted 15 July 2012; Published 1 August 2012

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