Legume: Mucuna Bracteata

Mucuna bracteata -a cover crop and living green manure (Dr. Chee Kheng Hoy FISP)

Note: This article is written by Dr. Chee in mandarin and published by Agroworld, Issue No. 188, February 2007, Kuala Lumpur: 30-34. Agroworld is a Chinese magazine for farmers. Please read the original article. To subscribe Agroworld, please email or contact Agroworld Enterprise, No. 10, Jalan 3/18D, Taman Mastiara, Off Jalan Ipoh Bt 5 1/2, 51200 Kuala Lumpur, Malaysia. Tel: 603-62500975 / 0972 / 0915

(Translated by Soon, S.H.)

A new leguminous cover crop – Mucuna bracteata is planted in the interrows of rubber and oil palm. The desirable characteristic of this cover that attracts much attention is its ability to produce three to four times more biomass than conventional leguminous cover. Furthermore, it helps to prevent the invasion of pest and diseases in the fields. Many estate managers are unwilling to spend extra money on planting leguminous cover crop. In fact, after the conventional leguminous cover crop grows under open condition for two and a half years, the remaining litter mulch can effectively provide nitrogen for oil palm replanting.

Mucuna bracteata Seminar was held at Sg. Tekam Plantations Resort, Pahang at the end of 2006 (29 November). During this 2-day seminar, ten papers on Mucuna bracteata M. bracteata ) were discussed on the first day while a well-known soil scientist from Malaysia, Dr. S. Paramananthan led us on the identification of different soil profiles on the second day. Param is regarded as an “old friend” to planters from all over the world.

A group photo of the seminar participants who are interested in soil survey. The man in red shirt is Dr. Param, in blue shirt beside him is K.J. Goh, in yellow shirt is C.T. Lee.

Advantages of leguminous cover crop

The seminar ended successfully. Besides the efforts of committee members, we appreciated FELDA support on funds and manpower. The facilities and research programmes of FELDA Sungai Tekam research station as well as the large-scale FELDA oil palm plantations definitely added much charm to the seminar.

The inspiration to organize the seminar comes from my ex-colleague, Mr. Chiu Sheng Bin. Many from the plantation industry know the agronomist, S.B. Chiu. He graduated from Harvard University. He worked as an electrical engineer before he furthered his studies in agriculture. Mr. Chiu and I were invited by agronomist, Lee Chin Tui from FELDA to visit M. bracteata , a leguminous cover crop planted by FELDA on a large scale. Young palms grow in between very well.

Mr. Chiu felt that we should promote the advantages of leguminous cover crop. Unfortunately, he spends most of the time working overseas. When I mentioned about the organization of a cover crop seminar again, besides Lee, Param and Goh Kah Joo also gave their full support to us. Goh was elected as chairman of the seminar. He is Deputy Director of Research of AAR, an associate company of Boustead Plantations Berhad and Kuala Lumpur Kepong Berhad and graduated from University of York with biological computation specialisation. Five of us as committee members (Goh, Param, Lee, Chiu, Chee) had dinner and meeting at the same time at a chinese restaurant in Petaling Jaya twice. We also exchanged opinions through emails.

A senior estate manager, C. Matthews, from Golden Hope imported 2 kg of M. bracteata seeds from India in 1991. This new legume was planted between sapling lines in the rubber plantation in India at that time. Before M. bracteata reached Malaysia, I was already involved in research and development. At that time, I traveled not so far from my work place to a M. bracteata experimental site-Golden Hope Plantation Berhad, North Labis Estate, Johor (please refer to Agroworld magazine Issue No. 114, “New legume produces living green manure”).

Beginning with the new M. bracteata legume at North Labis Estate, Golden Hope Plantations Berhad has now planted 30,000 ha. of this cover crop. Golden Hope is the first plantation company to plant M. bracteata in Sabah. The first company to plant M. bracteata in Indonesia is Lyman Agro. In the early 90’s, Mr. Chiu Sheng Bin and I were doing research and development on oil palm, rubber and forestry in this chinese company. We introduced M. bracteata to Indonesia.

From left : C. Matthews (who is the first to import M. bracteata from India), Z.H. Shamsudin (UPM professor), C.F. Chee (seed supplier), K.J. Goh (seminar chairman), Dr. Chee Kheng Hoy, C.T. Lee (FELDA agronomist), S.B. Chiu (oil palm consultant).

Prevent young palm from invasion of weeds and pests

Many estate managers are unwilling to spend extra money on planting leguminous cover crop. Somehow the cover crop cannot survive under shaded condition after growing for one to two years. In fact, after the conventional leguminous cover crop eg. Pueraria javanica grows under open conditions for two and a half years, the remaining litter mulch can effectively provide nitrogen for the oil palm replant over the following two and a half years.

M. bracteata cover crop can be found in newly planted or replanted oil palm plantations in Malaysia, Indonesia and Colombia, South America today. The desirable characteristic of this cover that attracts much attention is its ability to produce three to four times more biomass (green manure) than conventional leguminous cover. Apart from that, it grows luxuriantly and also has the habit to smother weeds: lallang, shrubs and ferns included.

Rhinoceros beetle damages young palm. The conventional leguminous cover crop can prevent 65% damage while M. bracteata can prevent 93% damage. The thick M. bracteata can physically prevent the invasion of beetle towards the remaining organic residues after oil palm replanting. On the other hand, it provides a moist environment for oil palm residues to decompose faster.

In addition, M. bracteata also interrupts the activities of rat and therefore reduces the rat damage to oil palm.

The seminar participants testify that M. bracteata enhances the oil palm growth at FELDA plantation.

The mulch is beneficial to barren soil

M. bracteata is most impressive as it forms a thick pure cover under oil palm, often 1 m thick with 40 cm of litter mulch below. Even under the shade of 10 years old palms, it still maintains 50 mm of litter mulch below the thick cover of M. bracteata . It produces large amounts of organic matter through its litter mulch and thus rebuilds poor, degraded soils by enriching them with mulch.

M. bracteata seeds do not come cheap. It is about RM 300 per kg, all imported from India. M. bracteata originates from Tripura, Northeast India in the Himalaya range. This area is also known as the northeastern hill region of India and it lies between 21.5-29.5° N latitude and 85.5-97.5° E longitude. Temperature varies between 10 and 35° Celsius and average annual rainfall between 2855 mm and 1811 mm. The day length can be as high as 13.6 hours. Fruits are covered by stinging hairs and turn blackish when ripe during winter only.

From botanical record, Bangladesh, China, Hainan, Laos, Myanmar, Thailand, Vietnam and Andaman Island have M. bracteata growing naturally but there is no record of whether these places produce mucuna seeds.

We had tried to plant M. bracteata in areas with different latitudes and temperature, for instance “Penang Hill” in Penang and highland in Laos. It has flowered but has not seeded yet. The flower emits a stinking smell of rotting meat to attract insects. It is said that one type of insect pollinators that visits the flowers is the hornet.

M. bracteata flowered under a special environment locally. This is the research result of S.B. Chiu. Although it has flowered, but research is still needed on how to make it produces seed.

We need workers to harvest the seed pods produced by M. bracteata planted in our experiment. This task is not easy because seed pods are covered with sharp, needle-like hairs that cause great irritation when touched as they penetrate the skin easily. Perhaps, because of this reason, the workers in India only harvest the seed pods before noon. The weather becomes hot in the afternoon and they return home to “heal their wound”.

To judge the seed quality by condition

One of the papers in the seminar is about the seed quality. The seed quality can be judged by its condition: a well formed seed is big and round, about 4700 seeds per kg, germination rate up to 80%; a slightly undesirable seed is big and flat, has about 7400 seeds per kg, germination rate only 5%; small and round seed contains 11600 seeds per kg, germination rate is about 32%; undesirable seed is small and flat, has about 12000 seeds per kg, germination rate nearly 0%.

A mixture of seeds from the four seed categories above is about 6700 seeds per kg, germination rate is approximately 68%. Briefly, good quality seed should not exceed 7000 seeds per kg, germination rate ranges from 60 to 70%.

The seeds of M. bracteata are similar to another cover crop which will die within a year- Mucuna pruriens . So, planters may easily mistake M. pruriens seeds for those of M. bracteata when purchasing M. bracteata seeds.

There is another type of Mucuna called M. cochinchinensis which is among the various types of leguminous cover crop that are already planted in the estate for a long time. The size of M. cochinchinensis seed is two to three times bigger than M. bracteata . The leaves are somewhat similar but bigger than M. bracteata M. cochinchinensis is an annual lasting six to seven months. On the other hand, M. bracteata is a perennial although it only grows vigorously after planting for nine to ten months.

M. bracteata grows luxuriantly and vigorously under oil palm shade.

A special edition of the papers that was full of pictures, charts and articles was distributed at the seminar. Some uncommon data and opinions were mentioned. This will be published as a book shortly.

In estates planted with M. bracteata , the soil fertility within 30 cm from the topsoil will be maintained. On the other hand, the soil fertility will decrease continuously in areas full of weeds. This is due to the deep-rooted nature of M. bracteata which might possibly extract nutrients from the deeper layers of the soil and transport it to the vines and leaves and deposit them on the surface in the form of mulch or organic matter after that.

M. bracteata was firstly planted as a cover crop in rubber plantation in India. Larger numbers of bacteria and fungi were counted under M. bracteata compared with under P. javanica in rubber plantation in India. These bacteria included N fixing bacteria and phosphate solubilising microorganisms. Hence, M. bracteata improves soil fertility.

M. bracteata produces large amounts of organic matter through its litter mulch. It becomes an extra source of manure for oil palm.

Planting methods

The total number of participants for this seminar was about 200 which was more than the expected number. They included planters from Indonesia and East Malaysia. We did not expect that some of them are from estate top management.

According to a participant from Sabah, the rooting depth of M. bracteata is 9 feet and thus it is drought tolerance. After the gardener frequently mowed M. bracteata that was planted at the backyard of his house by using a lawnmower, new leaves grew again after some time. Although the survival rate of M. bracteata is good, it still can be killed by herbicides.

A participant who has been selling M. bracteata seeds for many years and with full of experience in planting M. bracteata mentioned that seed handling method for M. bracteata is different. It should not be soaked in water in order to enhance the germination rate. If the seed is soaked in water before germination, the germination rate will drop to 10%. The soil medium that is used in the nursery should be sandy loam soil to avoid stagnant water. After sowing, he suggested to put up a plastic cover with the main intention of controlling rainwater. Watering is required once daily.

M. bracteata that was planted in FELDA nursery. These seedlings can be transplanted to the field at any time.

The quantity of seeds to purchase depends on the number of seedlings of M. bracteata to be planted within one hectare of oil palm. According to FELDA, the M. bracteata seedlings were planted in the interrows at 4 m apart giving a density of 300 seedlings per ha, reaching full ground coverage after nine months. We planted two seedlings in the interrows at 8 m apart in Indonesia. In fact, every estate has their own planting density, between 130 seedlings per hectare and 680 seedlings per ha (5 seedlings of M. bracteata per palm).

Rhizobium bacteria provide nitrogen indirectly

One of the characteristics of legume is that the root nodules are infected by rhizobium bacteria. It is able to fix N from the atmosphere and provide nitrogen to the plant indirectly.

There are many strains of rhizobium bacteria. Which strains is the most suitable for research on M. bracteata was acknowledged in the seminar. The experiment was conducted in Universiti Putra Malaysia to screen Bradyrhizobium strains that can effectively nodulate M. bracteata . FiveBradyrhizobium strains were tested for effectiveness as legume inocula. From the experiment, M. bracteata inoculated with isolate UPMR51 achieved the highest growth rate and produced the largest nodule number with the greatest N concentration.

AAR showed that M. bracteata can fix 70% of nitrogen for its own consumption. From the analysis and calculation, absorbing one unit of nitrogen is equivalent to releasing two units of nitrogen to the soil.

Rhizobium bacteria provides nitrogen to M. bracteata and the rich biomass of M. bracteata produces green manure. Can young palm rely on M. bracteata to provide all or most of the nitrogen? Agronomists have been doing research on this.

Some smallholders in Indonesia cannot afford to buy chemical fertilizers resulting in decreasing oil palm yields. We helped to plant M. bracteata in these poor oil palm gardens in order to know how much of the cost of chemical fertilizers we could save for smallholders by planting M. bracteata.

From the experiment in EPA oil palm plantations in Johor, after planting for two years, M. bracteata dry vine weight was 5.7 tonne per ha, root and root nodules were 2.5 tonne, stem and leaf were 3.0 tonne, total biomass was 11.02 tonne. Excluding leaf litter, the total biomass contained P(19kg), K(153 kg), Mg(18 kg). According to the current price of fertilizer, the biomass is equivalent to RM 1066.

Less plant disease problem

According to the Golden Hope research report, the dry weight of M. bracteata was 17.2 tonne per ha while the conventional leguminous cover crop only 5.7 tonne per ha. But, the age of M. bracteata and the soil types were not reported. By using basaltic soil, dry matter production is up to 19 tonne (11 tonne from vine, 8 tonne from leaf litter).

M. bracteata has less plant disease problem. This may due to its high concentration of phenol, thus it is able to avoid being attack by other creatures. However, young plants (less than 6 months old) are palatable to cattle but not goats.

If we walk in between M. bracteata , the fluid from the broken vines may leave some stubborn stain on our pants. It is very difficult to remove the stubborn stain and the pant may have to be thrown away.

The seminar was held successfully. We should carry on our effort. In my opinion, I felt that the title of the next seminar may be “Analysis of oil palm planting materials”. FELDA is an ideal place to hold this seminar because FELDA produced 17,300,000 oil palm seeds in 2006, 22,000,000 oil palm seeds in 2005, 23,000,000 oil palm seeds in 2004, and has 26.3% market share. If smallholders have a chance to take part in the seminar (English medium), they can know more about the process of seed production and it helps in choosing good planting materials.

At the moment, M. bracteata is already well known in the plantation industry. It has proven to be an useful cover crop.