Judul: Soil Testing to Establish Phosphorus Critical Level for Potato (Solanum Tuberosum L.) in Andisol of Lembang
Abstrak: Evaluation of fertility status of the soil based on its capacity to supply nutrients can help to improve productivity and increase fertilizer efficiency. Soil testing is a method of evaluation of soil fertility status in order to know the level of nutrient availability for a certain crop in a given soil type. Soil test phosphorus (STP) is a measure of plant available phosphorus (P) in a soil extracted by various extractant later the STP calibrated with crop response in order to determine P fertilizer requirement. The basic aim of soil testing is to assess nutrient status, thereby identifying current and potential need for fertilization. In Lembang district, Indonesia Andisol covers appreciable area, and defined taxonomically its andic properties and contains high allophanic materials. However, in volcanic ash soil P is strongly sorbed by non-crystalline aluminum and iron materials, it lowers P availability for plant uptake. Hence, inadequate P concentration in soil can restrain plant growth in the district and low P fertilizer efficiency reduces farm profitability. This study, soil testing to establish P critical level for potato (Solanum Tuberosum L.) in Andisol was conducted in Lembang district, west Java, Indonesia in greenhouse from February – June 2018 at Indonesian Agricultural Technologies Research Center (BPTP) in Lembang. In the study area farmers grow intensively agricultural crops including potato. However, the farmers apply blanket method of P fertilizer to grow potato is commonly practiced. The blanket method of fertilizer application does not consider the spatial and temporal soil fertility variations and farmers apply the same P fertilizer rate to their fields regardless of fertility difference. As a result profitability of potato production can be restrained by low P fertilizer efficiency. Therefore, the objective of this study was soil testing to establish P critical level for potato in Andisol of Lembang by graphical approach in order to increase P fertilizer use efficiency. Hence, soil P tests are useful to identify soils deficient in P and provide a guide to determine P requirement as to the magnitude of the crop's response to applied P. In turn, it allows for the growers more efficient utilization of P fertilizer. For the selection of representative soil across the area 30 soil samples (0- 15cm depth) were collected before the onset of the trial. Selected soil physical and chemical properties such as soil texture, organic carbon, Cation Exchange Capacity, exchangeable basic cations, total nitrogen, and available P were analyzed by respective methods. Soil test P was extracted by Olsen extraction method and the soil categorized in to low P (soils with P concentration <25 mg kg-1) and high P (Soils with P concentration >46 mg kg-1) using standard rating of Olsen extraction method. The number of treatments were 7 rates of phosphorus fertilizer (0, 25, 50, 75, 100, 125, and 150 kg P ha-1), replicated thrice for both low P and high P soil. Total number of pots were 42 (21 pots for low P soil and 21 pots for high P soil). After three weeks of planting soil samples taken from each pots (5cm depth) in order to analyze
Keyword: Andisol, Critical level, Fertilizer, Phosphorus, Potato, Soil test

Judul: Development of soil test of phosphorus and potassium for fertilizer recommendation of tomato
Abstrak: The best management practices for fertilizer application on vegetable crop in Indonesia are not available at present. Environmentally friendliness in fertilizer recommendation based on soil analysis has been adopted by many developed countries for crop production. Soil testing using single-nutrient soil analysis in Indonesia has been developed since 1970. However, due to limited research fund, soil testing has not been programmed continuously and recommendation for fertilization of specific location based on soil family has not been established yet. Therefore, this research developed the basic model of P and K fertilizer efficiency and recommendation based on soil analysis for tomato in Inceptisols. This model will be adopted for other vegetable crops and different soil type in the future. Tomato is a vegetable growing well on Inceptisols soil type, which generally has low pH and high P-fixation. Research was done in greenhouse and open field of Cikabayan, UF, IPB, from March 2010 to December 2011. The objective of this research was to develop the best management practice for P fertilizer and K fertilizer recommendation based on soil analysis on Inceptisols for tomato. The study was designed in two years. The first year was to build recommendation for P and the second year for K fertilizer. Each study consisted of three experiments. First experiment was correlation study that aimed at finding out the best extraction method. The second experiment was calibration study that aimed at developing soil response category. The third experiment was recommendation study that aimed at building P and K fertilizer recommendation for each soil category on Inceptisols for tomato. Treatments were phosphorus and potassium rates i.e. 0X, ¼ X ½ X ¾ X and 1X, where X was 368.6 P2O5 kg ha-1 and was 608.6 K2O kg ha-1. Correlation of soil P and K test with tomato growth was conducted in the greenhouse through media obtained from soil incubation processes. Soil P test used five extraction methods i.e. Bray I, Bray II, Mehlich I, Morgan Wolf and Truog. Soil K test also used five extraction methods i.e. Mehlich I, Morgan Vanema, Truog, HCl 25% and NH4OAc 1 M pH 7. Calibration test was arranged in a completely randomized design with two factors. The treatment consisted of several soil P status (levels) ranging from very low to very high. Fertilizer dosage i.e. X, ¾ X, ½ X, ¼ X, and 0X was the second factor, where X was 368.6 P2O5 kg ha-1 for P and was 608.6 kg ha-1 K2O for K. Results showed that there were significant differences among P and K fertilizer treatments on plant height, stem diameter, leaf number, fresh biomass and dry biomass for both correlation test and calibration test. The correlation test showed that the best extraction reagent was Mehlich I for P and Truog for K. Fertilizer recommendation criteria for “very low-nutrient status” was 183.3 P2O5 kg ha-1 and 281.3 K2O kg ha-1. Fertilizer recommendation for “low-nutrient” status was 71.4 P2O5 kg ha-1 and 178.6 K2O kg ha-1.
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Judul: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
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