Building a Pankar-huyu

Adaptation from Noel Velasco's teaching manual on procedures for building an underground greenhouse, called a Pankar-huyu

 

To build and maintain a pankar-huyu is an easy task, the process can be divided into seven simple steps.

• Choose an appropriate site for building. Ideally, the location should be within 30 meters of a water source to facilitate irrigation. The best location is on a small hill or rise so that the pankar-huyu does not become flooded. A location with loamy soil is superior to one with sandy or clay soil.

Benson Institute staff works to construct a Pnakar-huyu in Bolivia.

• Excavate the hole. Because of the angle of the sun in Bolivia, the pankar-huyu will receive more light if the long side runs east-west. The hole should measure about 1.30 meters wide, 3.00 meters long and 0.80 meters deep. The top 20 centimeters of soil is the most fertile and should be set aside near the hole. The remaining soil (0.60 meters deep) can be piled separately. It will be used later to make mounds around the hole on which the cover will sit. The stability and durability of the walls of the pankar-huyu depend on careful excavation. Two men can normally excavate the hole in two working days.

• Prepare the floor of the pankar-huyu for planting. The ground must be leveled; then 10 wheelbarrow loads of rocks or gravel are poured in. Gravel is found throughout the Altiplano in dry streambeds and can be collected at no cost. The gravel allows excess irrigation water to drain so that the plants do not drown. The topsoil which was saved to one side is then mixed with an equal amount of dry sheep manure collected from the family’s animals. This mixture is poured on top of the gravel in the pankar-huyu. Before planting, this mixture should be deeply watered. This will initiate a heat-producing reaction in the soil resulting in homogenous soil with high chemical fertility.

• Construct the cover. The frame is built from 4 boards nailed together. It should be 3.3 meters long by 1.6 meters wide. Polyethylene is readily available in the Altiplano under the commercial name of "Agrofilm." A large piece of polyethylene (3.5 meters by 2 meters) should be stretched tightly over the frame and nailed down every 10 centimeters around its perimeter. Small pieces of rubber (which can be cut from old tires) should be placed between the nails and the polyethylene to prevent ripping. When the polyethylene is placed on the frame, an extra flap should be left along one of the long sides. This piece will hang into the trench along the north of the pankar-huyu to allow rainwater to drain away from the hole.

• Install the cover. Since Bolivia is in the southern hemisphere, the sun is to the north; a cover that slants down to the north allows the maximum amount of light to enter. Thus, the ground on the south edge of the pankar-huyu must be raised. If quality adobe bricks are available, they can be stacked in two layers along the south edge. If not, clay mud can be made from the soil remaining from the excavation of the hole and used to make a mound along the south edge. Also, 50 centimeters from the edge of the hole, a 15-centimeter-wide by 15-centimeter-deep trench should be dug around the entire perimeter of the hole. This trench will prevent rainwater from flooding the hole or ruining the walls. The cover is now placed over the hole so that the cover slopes down to the north and the extra fold of polyethylene falls into the trench on the north; this allows rainwater to drain into the trench. More bricks and mud must then be used to build mounds along the shorter east and west edges of the hole so that when the cover of the pankar-huyu is closed the inside of the hole is completely protected from outside air. The cover and mounds should be checked for firmness and stability; the stability and durability of the walls depends on these mounds preventing water damage. The entire pankar-huyu can usually be constructed in four days.

• Plant the pankar-huyu with the desired crops. Planting is often done by the mother or children, leaving the father free to continue his normal work. Seeds of some of the plants can be planted directly in the pankar-huyu. Others grow better if they are first germinated and then transplanted to the pankar-huyu. Besides weeding and watering, the main requirement after planting is to open and close the cover daily. Because of the strength of the sun, if the pankar-huyu is left closed throughout the day, the temperature inside can grow too hot for the plants. The south side of the cover is raised around 30 or 40 centimeters (an angle of about 12º), though this aperture can be changed depending on outside temperatures. The cover can be held open with stakes driven into the ground 15 centimeters from the edge of the hole. At dusk, the cover must be closed securely to prevent heat loss and frost damage.

• Maintain the pankar-huyu. The trenches must be kept clear of mud and the mounds must be maintained so that water does not seep in and cause the walls to crumble. The polyethylene must be stretched on the frame once a year, adding more nails if necessary. If this is not done, the cover will sag and develop holes as water falls on it and pools. Silicone patches can be placed over any holes. With proper care, one piece of polyethylene will last three years, and one pankar-huyu will last about six years.

Drawing of a Pankar-huyu