The use of oil palm fruits waste brickets and manure in relationship as groundwater resistance materials to increase plant growth in critical land

The catchment area of Lake Toba geologically has soil properties that are sensitive to erosion because the land is hilly or mountainous with very steep slopes, very shallow soil solum (< 30 cm) to shallow (30-60 cm). Even though the level of rainfall in this area is quite high, the slope of the land causes the soil to easily lose ground water by the earth's gravity. Similarly, the level of erodibility is also high. The purpose of this research is to take advantage of the high potential of oil palm bunches waste which allows it to be used as a water retaining material compared to manure. To facilitate transportation, these two types of organic water retaining materials are used as briquettes. The study was structured using a non-factorial Randomized Block Design (RAK). Where each type of organic matter used 6 treatments with 6 replications, namely without using briquettes (P0) Doses of 0.25 kg, 0.50 kg, 0.75 kg, 1.00 kg and 1.25 kg, with 6 replications. The results shows that the waste briquettes of oil palm fruit bunches have the ability to hold water and increase the growth of Macadamia integrifolia plants which is the same as the ability to use manure.