I’m currently working on a paper about yield gaps in oil palm, and I actually think the topic is very fascinating, which is why I decided to write about it in this blog.
A yield gap is basically the difference between how much farmers could produce in theory, and how much they are actually producing. If the yield gap is small, then the farmers are producing large yields, and there isn’t much scope for producing even more. This is the case for many crops in western Europe, such as wheat and potatoes. If the yield gap is large, then for some reason, and usually for several, the farmers are not producing nearly as much as they could in theory. This is the case in many small farms in Africa, for example, but also in most of the oil palm plantations around the world.
In theory, the latest oil palm planting material, produced by specialised breeders, could produce 35-40 tonnes of fruit bunches per hectare per year, or eight to ten tonnes of oil. But most oil palm farmers and plantations don’t reach such yields at all. Malaysia and Guatemala produce the best yields, on average: around 24 tonnes per hectare, or five tonnes of oil. And these yields could probably be improved even more.
Is it a problem when there are large yield gaps? The answer to that question is much debated, both by scientists and by the wider public. Some people don’t think closing yield gaps is such a priority. Many are actually in favour of ‘low external input agriculture’, more popular known as ‘agroecology’. This is a type of agriculture where the use of fertilisers and pesticides is minimised and much attention is given to ecosystem services such as biodiversity, clean water, and soil health. It often involves the cultivation of different crops on the same field at the same time (‘intercropping’) or in sequence (‘crop rotation’), the integration of animals into the system, and the closing of nutrient cycles where possible by using manure and compost. Such practices can lead to very efficient, healthy, and beautiful agriculture, which does no or little harm to the environment. Intensive agriculture on the other hand often has many negative side effects such as water pollution, loss of biodiversity, the spill of pesticides into the environment, and farmers getting in debt to buy seeds and fertilisers. All of these problems are very real, and also occur in oil palm. So, should we try to close the yield gap in oil palm plantations (‘intensification’) or should we focus on mixed cropping, animal integration, and nutrient cycles?
Personally, I don’t think one solution is enough to solve the issue of ‘feeding the world in a sustainable way’, which is essentially what agriculture should be all about. Extensive agriculture is usually a healthy, sustainable way of farming, and can actually be very productive as well, if it is done in a smart way. But intensive agriculture also has its benefits, especially in cropping systems such as oil palm plantations. Why? Because land, unlike other inputs (water, fertilisers, pesticides) can never be renewable and cannot be replaced by alternative sources, so it’s the most scarce thing we have. The more land we can set aside for nature, such as rainforests, the better, but that means we need to produce high yields from the agricultural land that has already been converted. Most farmers only have limited land available and therefore their income depends on the productivity of that land, with better yields usually meaning better income.
Intensive and sustainable do not necessarily have to oppose each other. There are multiple ways of making oil palm plantations more sustainable. Growing oil palms together with other crops is unfortunately quite difficult, unless in the first three years after planting when the trees are still very young. The problem is that oil palms need a lot of sunshine, so if you grow them with other trees, the productivity will be bad because of the shade. The palms also have a very dense canopy, so growing other crops under the oil palm is more or less impossible, unless there are open spaces where palms died or were cut down. Crop rotation is not very practical either because the palms stay in the field for 25 years, and farmers usually want to get their income back as soon as possible after replanting. An option would be to plant the palms less close together, but this might mean that the farmers will lose some income, so unless this is compensated by growing profitable other crops, it is perhaps not very attractive to farmers. Some interesting research is on the way to see how oil palm could be grown in combination with other crops. Integrating animals in plantations has been done for a long time already, and cattle and oil palm go well together, as long as the cattle population doesn’t get too large. Because cattle are heavy and have small hooves, they can destroy the soil structure by making it more dense, so the oil palm roots can’t grow anymore, which is why it is important not to put too many animals in the plantation. But they can eat the weeds, drop their dung, provide a source of income, and even act as a sort of natural grass mowers, so they really have benefits as well.
Even with cattle, closing the nutrient cycles in oil palm plantations without fertilisers is difficult. After all, cattle don’t make nutrients, they only recycle what was already there. And oil palm is a really hungry crop. It needs about 150 kilos of nitrogen, 250 kilos of potassium, 40 kilos of phosphate, and 60 kilos of magnesium per hectare per year, and it beats all other crops in terms of fertiliser use. As an alternative to chemical fertilisers, the empty bunches can be put back in the field after the oil is removed in the mill, but there are not enough empty bunches to fertilise all the plantations all the time, so fertilisers remain important.
To me, it seems clear that we need to go towards a type of agriculture which is so healthy and smart that 100 years from now we have cleaner water, more biodiversity, and larger forests than we do now. I think it is important to stop thinking in terms of ‘industrial’ and ‘organic’ and to move towards ‘smart and sustainable agriculture’ which takes full advantage of technology and innovation while having a positive effect on the environment. This may seem ambitious, but why not? Some examples that come to my mind for oil palm are:
- Keeping a good cover of weeds under the oil palm to conserve the soil health
- Leaving the dead leaves in the plantation to maintain the organic matter in the soil
- Planting legumes, which can fix atmospheric nitrogen, as a natural fertiliser
- Using sufficient amounts of fertilisers in the right balance, so that little is lost
- Putting a few cows in the plantation (but not too many)
- Using all the empty bunches from the mill as a fertiliser
- Using excellent soil conservation techniques to prevent all erosion
- Planting flowering shrubs that attract natural enemies of oil palm pests
- Making nest boxes for barn owls, to keep the rat population under control
All these things can make an oil palm plantation intensive and sustainable at the same time. But if we really want to close nutrient cycles, then we need to think beyond the plantations. We really have to start re-using our sewage, so that we stop flushing all those valuable nutrients into the environment. Let the Netherlands, or Europe, or all the other rich developed countries, with their excellent sewage and other infrastructure, take a lead in producing fertiliser from poop, and then we can start recycling nutrients on a country scale instead of on a field scale!