Intercropping with Paulownia Trees

Backgrounder

Intercropping with Paulownia Trees
By growing trees with crops you can increase crop yields and harvest lumber, firewood, and livestock feed at the same time. In different parts of the world farmers are experimenting with different combinations of crops and trees. This is called intercropping.

What is intercropping?
Intercropping is growing different crops together in the same field. For example, you might plant corn in one row, beans in the next, and corn again in the next. This way you make better use of soil nutrients and harvest two crops instead of one.

You can also intercrop crops with trees. It is important to choose trees that are well adapted to local conditions and if possible, to use a variety of trees on your farm.
Intercropping with paulownia trees
In China, farmers increase yields by planting paulownia trees (Paulownia spp.) with grain crops such as corn, wheat, or millet. They space the trees in rows 5 metres apart with 30-50 metres between rows. This way they can plant 40 to 67 trees per hectare. In this system the farmers consider the food crop to be more important than the wood harvest.

Grain crops have a higher yield because trees can improve the climate around the crops. Trees reduce the damaging effect of dry winds and put moisture into the air. Trees also help to save soil.

The paulownia tree grows quickly. The Chinese people say that it looks like a pole after one year, like an umbrella at three years, and, after five or six years, it can be sawed down and cut into small boards. The branches can be used for fuelwood. A 10 year old tree produces 400 kilograms of branches per year. The roots go so deep into the soil that they do not compete with other crops for water and nutrients. In fact, paulownia roots can absorb water and nutrients deep in the soil that other plant roots cannot reach. This is useful especially during the dry season when paulownia absorbs the underground water and releases it into the air.

Products of paulownia
Paulownia is a useful tree in other ways too. The wood is lightweight yet strong. It dries easily. It has a beautiful grain and it does not crack or warp. It is easy to work with and is excellent for making musical instruments, furniture, and plywood.

The leaves and the flowers are good fodder for livestock because they are rich in protein, carbohydrates, and minerals. A ten year old tree produces 30 kilograms of fresh leaves each year. The leaves can also be dug into the soil as green manure.

Sweet potatoes and sesame seeds do not grow well with paulownia. Yields of these crops tend to decrease particularly when intercropped with trees more than five years old.

Generally, however, the Chinese farmers harvest more food when they grow trees with crops. They also harvest valuable livestock feed. And within ten to fifteen years they are harvesting enough lumber to produce an important extra income.

This is one example of how farmers grow trees to improve crops. There may be trees that farmers use to improve crops in your region.