Simulation of Availability and Loss of Nutrient Elements in Land with Android-Based Fertilizing Applications Dian Pratama Putra Agrotechnology Department Institut Pertanian STIPER Yogyakarta dianswn@instiperjogja.ac.id M. Prasanto Bimantio Food and Agricultural Technology Department Institut Pertanian STIPER Yogyakarta bimantiomp@instiperjogja.ac.id Angga Ade Sahfitra Agrotechnology Department Universitas Medan Area Medan anggasahfitra@staff.uma.ac.id Teddy Suparyanto Bioinformatics & Data Science Research Center Bina Nusantara University Jakarta, Indonesia 11480 teddysup@binus.ac.id Bens Pardamean Computer Science Department, BINUS Graduate Program - Master of Computer Science Bina Nusantara University Jakarta, Indonesia 11480 bpardamean@binus.edu Abstract—The ability of land in the supply of technically sustainable nutrients for the growth and development of long- lived oil palm plants is very limited. The limited carrying capacity of land in the supply of nutrients must be balanced with the addition of nutrients through fertilization. Ideally, the application of fertilization is site specific, but it is unfortunate that the cost constraints cause location-specific fertilization doses cannot be obtained immediately. The purpose of this study is to develop an Android-based fertilizer application to simulate the availability and loss of nutrients in the care or cultivation of oil palm. The Hydrometer method was used to carry out soil structure analysis. Data on the amount of nutrients stored and released from fertilizer applications was modeled with the help of the stock and flow diagram method. The stock and flow diagram method was used to determine the effect of the amount of fertilizer introduced on nutrients stored in the main crop and the large amount of fertilizer that was evaporated, runoff, and deviated. Furthermore, this method was able to predict the amount of nutrition during fertilization (1 semester). The results of this study are in the form of an Android-based application which is compiled based on the calculation scheme obtained from the Stock and Flow Diagram. Keywords— soil, fertilizer loss, precision agriculture I. INTRODUCTION Precision Agriculture introduces the basic concepts or principles on time, right amount, right place, right source and right way in agriculture. Precision Agriculture relies on location-specific resource management or spatial data management so that the parameters that should be obtained are in the form of geographic positions using GPS (Global Positioning System) and Differential GPS, geographic information systems (GIS), and remote sensing (satellites, aircraft, non-aircraft manned/Unmanned aerial vehicles/ UAV). Agricultural land that is used is generally not uniform in terms of fertility, especially soil nutrients that affect agricultural production in the future. Oil palm (elaeis guineensis jacq) plantations in Indonesia are excellent commodities, because they have high economic value. The development of oil palm in Indonesia is very rapid, both through area expansion and increased production because it is supported by natural suitability, land availability and labor. Currently the human need for agricultural land is very high, coupled with the reduction in soil fertility, good cultivation is needed without damaging the soil and can restore the fertility of the land [1]. Palm oil plants are plants that have a production period of more than 1 year. Growth and development depends on the availability of nutrients. Nutrients have different properties where the nature is determined from the treatment and type of fertilizer itself, fertilizer itself also affects the C/N of land where C/N affects the process of nutrient mineralization available to plants [2]. Land as a nutrient provider has limited ability to meet the needs of plants. These limitations can be offset through fertilization. Fertilization is the activity of adding one or several nutrients to maintain the availability of these nutrients and increase soil fertility [3]. Fertilization can replace nutrients absorbed by plants or lost due to leaching and maintain ideal soil conditions for the growth and development of oil palm [4]. The type of fertilizer given can be organic or chemical fertilizer. Organic fertilizer can come from solid or liquid palm oil waste. Solid waste in the form of oil palm empty fruit bunches is used as organic fertilizer in the form of compost [5]. The use of fertilizer is currently considered less effective because around 40-60% of nutrients are wasted which causes economic losses, damage to soil structure, and pollutes ground and river water [6]. The kinetics of nutrient loss was tried to be improved by Bimantio (2017) in his research by modeling urea and KCl fertilizer with the addition of natural zeolites to resist the release of these nutrients [7]. From the results of the modeling results obtained that the nutrients in fertilizer can be absorbed and slowly released again as much as 30-50% of the absorbed. These results form the basis of the authors in calculating more precisely about nutritional loss information. This has led to the emergence of a type of slow release fertilizer that can be an alternative for farmers with a favorable value and a profitable application savings [8]. The physical and chemical nature of the soil can be a factor that causes loss of nutrients in the fertilization process that is