Microbes population and activities of Inceptisol in the highland date palm plantation of Karo Regency based on different varieties and soil depth

Abstract The productivity of Inceptisol as a highland date cultivation area in Karo Regency is limited by the low availability of nutrients and low levels of organic matter. Organic matter is a very important factor in the activities of various microorganisms in the soil. The aim of this research was to calculate the population and assess microbial activity in Inceptisol soil in highland date palm plantations in Karo Regency based on different date palm varieties. This research was conducted using a survey method. The sampling technique was carried out using purposive random sampling. Sampling is differentiated based on the Ajwa and Barhee date palm varieties in some soil dephts, there are 0-20cm, 20-40cm, and 40-60cm. Observations carried out in the laboratory include calculating the total population of bacteria and fungi (CFU/ml) and microorganism activity including respiration of microorganisms (mg CO 2 /100 g soil/day) and biomass C of microorganisms (mg C/mg soil). The results showed that date palm varieties and Inceptisol soil depth in highland date palm fields had differences in microbial populations (bacteria and fungi) and microbial activity (respiration and microbial biomass). The Ajwa variety has the highest microbial population and microbial activity at the topsoil depth (0-20 cm) compared to the Barhee variety. Soil depth also influences the population and activity of microbes which are closely related to the availability of food sources for energy, namely organic material which is usually abundant in the topsoil of the soil.