Agroforestry and other multi-cultures increase productivity and sustainability Prof. Bob Orskov
In Asia, the pressures of population have presented particular challenges on how best to increase production in a sustainable manner; and that’s where agroforestry has shown the most surprising promise.
I first became involved with agro-forestry in a research project in Sri Lanka carried out in collaboration with the Coconut Research Institute in Lunawila. Large areas of Sri Lanka are covered with coconut plantations owned by large industries and by small farmers. Coconut trees do not form a dense canopy so it is always possible to grow other plants under the trees. Cattle are often seen grazing under the coconut trees, but the owners of the coconut trees are frequently not the owners of the cattle. The cattle belong to small poor farmers, and the owner of the coconut trees typically allows them to graze for free.
We set up an experiment to graze cattle under the coconut trees at a high stocking rate. In fact, the animals had much less food than they needed for maximum growth and reproduction (see Table 1) [1, 2].
The animals were old at calving, calving interval was long and milk yield was low. Supplementing the feed with imported rice straw improved the animals’ reproductive performance and when they were also given rice bran, performance was further increased so that the calving interval was normal at 13 months.
Table 1. Effect of grazing and supplement of female cattle under coconut
| Age at calving month | Calving interval | Milk yield kg/d | |
Grazing | 57 | 20 | 0.87 |
Grazing + rice straw | 47 | 18 | 1.53 |
Grazing + rice straw + rice bran | 40 | 13 | 2.36 |
These results may be expected, but the unexpected was the beneficial effect on coconut yield (see Table 2).
Table 2. Effect of grazing on annual coconut yield and soil water holding capacity [1]
Nuts/palm | Copra/palm (kg) | Water holding capacity (mm/m) | |
Non grazing | 41.1 | 11.1 | 16.9 |
Grazing | 47.9 | 13.3 | 18.3 |
Grazing + rice straw | 50.6 | 14.2 | 18.9 |
Grazing + rice straw + rice bran | 57.4 | 16.7 | 17.6 |
Grazing alone was sufficient to increase coconut yield by about 15%. No wonder the owners of the coconut trees were quite happy for the small farmers’ animals to graze under them! This was due to a rapid turnover of biomass and the effect on soil quality seen here as water holding capacity. Bringing nutrients for the cattle from outside further increased coconut yield, as a result of the N, P and K etc contained in the feed (see Table 3).
Table 3. Effect of grazing and supplement on coconut leaf composition after 6 years
| Content in coconut leaf (%) | |||
| N | P | K | |
| Non grazing | 1.89 | 0.15 | 1.21 |
| Grazing | 1.86 | 0.15 | 1.18 |
| Grazing + rice straw | 1.92 | 0.16 | 1.48 |
| Grazing + rice straw + rice bran | 2.23 | 0.18 | 1.76 |
The increased yield in coconut due to the animals is effectively an animal product; but that is often ignored. Since then, whenever I see animals grazing under trees or tied to trees I have often asked the question, what is the effect on production from the trees be it mango, coconut, durian or other fruit or on wood production e.g. teak. But there is seldom an answer.
The effect of grazing animals on socioeconomy became very apparent to me recently on a visit to an oil palm plantation in Bengkulu province of Sumatra, Indonesia. The Indonesian company owning the plantations employed workers to collect palm fruit bundles from the plantation and carry them to a road passable by trucks. The employers had taken the initiative to give to the workers a Bali cattle (Bos banteng), for pulling a small cart that could hold about 15 to 20 bundles instead of the one carried by the worker. This increased the capacity of a worker to attend to 15 rather than 10ha. The feed for the cattle was plants growing under the trees plus leaves and core from the palm fronds, which had to be cut down before a palm bundle could be cut off. At night, the cattle were also given some palm sludge from the factory. It soon transpired that there was much more feed than one animal could eat so the farm workers were allowed to take several animals with them during the working day in the plantation. At the moment, an average of six animals come with each worker in the morning. What is the possible stocking rate under palm oil trees? I was told maybe 2/ha even with full canopy. If so, many millions of cattle could be fed under oil palm trees in the world. These could provide a secure living for many families. Similar effects on oil palm production were observed some years ago [3] (see table 4).
Table 4. Effect of mixed cattle and goat grazing on annual yield of fresh fruits in oil-palm plantations in Malaysia [3]
| Year | Grazed area | Non-grazed area | Difference |
Fresh fruit bunches (metric t. /ha) | |||
| 1980 | 30.55 (C)* | 25.61 | 4.94 |
| 1981 | 17.69 (C)* | 15.87 | 1.82 |
| 1982 | 25.12 (C & G) | 22.97 | 2.15 |
| 1983 | 23.45 (C & G) | 18.29 | 5.16 |
*C = cattle: C & G = cattle and goats.
There were consistent increases in oil palm yield of some 15 to 20% as a result of grazing with cattle and goats in the plantation, probably a result of increasing turnover of biomass and soil water-holding capacity. The positive effects of livestock in agroforestry are not unique to the tropics. Recent work [4, 5] showed that productivity of sheep grazing under trees in Scotland was similar, and in dry years greater than sheep grazing a similar area in open land. Evidently the growth of the trees was a bonus and soil fertility improved.
In Indonesia where many forests have been illegally cut, the government is trying to re-establish the forests with the aid of small farmers living nearby. These farmers are given the right to cultivate and plant complementary crops between the trees, in this case teak and eucalyptus trees, until the full canopy has formed. One may question if the full canopy is necessary for optimal growth and quality of the trees. Less than full canopy could give small farmers continuous access to grazing and other complementary crops and maybe also to better quality trees. Interplanting with leguminous trees and bushes for animal feed could capture N also for the forest trees. The way silvopastoral systems should be developed or perhaps more precisely redeveloped will vary environmentally according to climate, type of trees, type of animals and socioeconomic circumstances. What’s important here is not always the maximum production of trees, but the best total production of all the components in the system. An added advantage is that such systems will be much more sustainable than monoculture tree systems and special animal systems. Chickens and pigs after all were forest animals and not designed for large intensive stall-fed and battery-fed systems. The trees will also accumulate carbon from atmospheric CO2 and therefore help in slowing down climate change. The relentless push to monoculture promoted recently by herbicide resistant GM crops cannot be the solution from environmental and socio-economic points of view.
In many tropical areas in developing countries, multi-culture has been used for many years particularly in densely populated areas. This involves both combinations of forests with arable crops or grazing animals and a mixture of arable crops. Often three crops are grown together. Leguminous crops such as groundnut, soya bean and peas are frequently grown together with non-leguminous crops such as maize, cassava and wheat. The nitrogen captured by leguminous plants can be used also by non-leguminous plants. These crops are not harvested at the same time. Cassava for instance is generally harvested only once a year while other plants that have a much shorter season can be replanted. Combine harvesters cannot be used in harvesting; but as labour is typically not a problem, labour-saving devices provide no solutions and often create unemployment and poverty. Multi-culture systems such as these are sustainable and help to maintain soil fertility and high yields of crops.
The negative effect of monoculture was recently demonstrated in rice production. Here herbicides had been recommended for use in the paddy fields; but instead of herbicides ducks were introduced (see Table 5) [6].
Table 5. Integrated system of rice, rice plus duck, rice plus fish, and rice plus fish and duck on net benefit for farmers (Mill.Vietnam Dong/ha)
Systems | Rice | Duck Rice | Fish Rice | Duck Fish Rice | Layer Duck Fish Rice |
Inputs: For rice | 6.62 | 3.92 | 7.36 | 3.92 | 3.92 |
For duck | - | 8.70 | - | 8.70 | 52.92 |
For fish | - | - | 15.58 | 13.90 | 13.90 |
Total | 6.62 | 12.62 | 22.94 | 26.52 | 70.74 |
Outputs: | |||||
From rice | 8.56 | 8.03 | 9.23 | 9.85 | 10.44 |
From duck | - | 14.50 | - | 14.50 | 68.02 |
From fish | - | - | 22.22 | 46.39 | 47.92 |
Total | 8.56 | 22.53 | 31.45 | 70.74 | 126.38 |
Net benefit | +1.94 | +9.91 | +8.51 | +44.22 | +55.64 |
The ducks ate the weeds and the insects and increased the yield of the paddy. As the young ducks were also fed at night they essentially brought some fertiliser to the paddy in the form of faeces. Now fish have also been introduced to consume the plankton grown in the paddy fields as a result of the ducks fertilising the paddy. The total income per ha increased by 50 times.
There are so many possibilities for increasing production in ways that are sustainable.
Prof. Bob Ørskov OBE is head of International Feed Resource Unit, Macaulay Institute, Aberdeen, Scotland, Fellow of the Royal Society of Edinburgh & Fellow of the Polish Academy of Science
Article first published 27/04/05
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