Can “Mulberry Plot-Fish Ponds” Help to Achieve Sustainable Agriculture?
C+S 2020 students are blogging about topics that interest them for Applications in Climate and Society, a core spring class.
Integrated agriculture can play an important role in addressing hunger as well as mitigating climate change and environmental problems. There is a sustainable agriculture model that is very popular in southern China called mulberry plot fish ponds, which integrates mulberry cultivation, sericulture, and fish farming to fully exploit the production potentials for food while limiting other wasted resources and its impact on the climate.
This type of agriculture is important because it reuses waste as a resource. For example, fish excrement is used in this model as the fertilizer for mulberry plants. This model isn’t just a farm, but a successful ecosystem itself so that farmers do not need to follow a carbon-intensive path to produce food. Lastly, it increases agricultural efficiency. This model produces multiple farm products such as fish, mulberry and silkworm in the same farm, ensuring farmers' income and causing less environmental harm.
For mulberry cultivation, the main nutrient source is mud or humus from the fish ponds. After the fish harvest in winter each year, the pond mud is collected and used later as fertilizer for mulberry plants. Meanwhile, liquid humus is saved during summer and autumn every year. At the end of each year, the so-called “base soil” that came from pond mud and the humus of the mulberry plants has increased to a thick layer. The base soil not only acts as a source of fertilizer but also resists drought and prevents the growth of weeds. That means that especially during high temperatures in summer and drought, the addition of pond humus can significantly increase the production of mulberry leaves. With the nutrients from base soil, the mulberry plants can produce mulberries and provide food.
The mulberry plants also provide food and habitat for silkworms whose cocoons can be used to make silk. Meanwhile, worm feces and shed silkworm skin, as well as any fallen and rotting mulberry, can be used to fertilize fish ponds or as food for the fish. What isn’t used by the fish is deposited on the pond bottom where it eventually merges with the pond mud that’s recycled to help grow the mulberry plants.
Due to the variation in climate and other natural conditions such as humidity, the amount of products this integrated agriculture system produces vary in different places. For example, integrated fish farms produce around 2500 kilograms of mulberry leaves per mu (a Chinese unit measure equal to 0.165 acre), which is sufficient to feed 9 cycles of the silkworm in Pearl River Delta. In the Taihu basin, integrated agriculture can produce up to1500 kilograms of mulberry leaves per mu, which is sufficient to feed 4 -5 cycles of silkworms. Regardless, conventional agriculture is less profitable and efficient compared to integrated agriculture because conventional farms need to grow each part of the integrated model separately, producing more waste and pollution.
The system produces fish and mulberries that can be sold as food and silk that can be sold as raw material to make clothes. The silkworms can also serve as a snack for people. And if fish are kept in the ponds, they can be an entertaining place for people who love fishing.
This system also has environmental benefits. It minimizes the amount of land used to produce food. Farmers also have an incentive to maximize the use of what would normally be waste and byproducts to increase their profits. For example, the pond mud and fish excrement can be used as fertilizers instead of producing more waste that is dumped into the environment from traditional fish farming. The soil will also remain fertilized for a longer time, and the system will be more stable than regular farms due to the right use of waste and byproducts.
Integrated farm models are popular in China but also being used in other countries. This model can improve the efficiency of agriculture by producing multiple commercial products at the same time while reducing the land use and causing less waste and pollution.