Soil potassium adsorption at several shallot center areas, Brebes Regency, Central Java Province

Brebes Regency, Central Java, is one of Indonesia's most important shallot production center implementing intensive agriculture. In the bulb production, K needed more than other nutrients. This study aimed to assess and describe adsorption characteristics on soils farming system in District, Java. Soil samples were collected at several locations areas Java Province. The observed soil properties included pH H<sub>2</sub>O, EC, texture, organic C, potential-K, exchangeable Ca, Mg, Na, K, CEC, Al H, water-soluble K. was simulated by Freundlich equation. proportion from low high retention energy studied had order, namely K<exchangeable K<potential-K. result showed that a capacity adsorb It indicated added accumulated soil. with continuous fertilization. research recommended increase efficiency fertilizer, it necessary introduce technology mine like bacteria capable dissolving or biofertilizers.