Judul: Analsis Status Hara Fosfor Pada Berbagai Lahan Pertanian Pangan di Pulau Jawa
Abstrak: Indonesia is an agricultural country that has the fourth largest population in the world with 237,6 million people and growth rate of 1,49%. One program that made by the government to fulfill the demands of food is agricultural intensification program. While using the improved varieties, fertilizing is one of the most important input to succed this program. In Indonesia, P fertilizer is the second most important after N fertilizer, especially on up land. Availability of phosphorus in the soil becomes very important because it has many roles in plants. However, in the soil, their availability relatively low because of binding by Al, Mn and Fe in acid soils, or by Ca, Mg in alkaline soil. Since it is easily fixed and the presence of P in the soil is limited but needed in large quantities, the role of P fertilizer is critical in maintaining the availability of P nutrient for plant growth. The phenomenon levelling off, which is the rate of increase in soil productivity is not in line with the rate of fertilizer is the main reason to evaluate the status of the current P nutrient in agricultural soils in Java. This study aimed to evaluate the status of the current P nutrient (available-P and potential-P) in agricultural lands in Java, and their association with some other soil chemical properties. There are 43 samples (locations) were taken from the island of Java, which consists of 23 samples of paddy field and 20 samples of up land agriculture. The methods that used to measure the potential-P is HCl 25% extraction and the available-P is Bray 1. The results based on the available criteria show that from 23 samples of paddy field, 19 samples have very high status of potential-P, two samples have high status and two other samples have low status of potential-P. In the paddy field available-P there are 21 samples that have very high status and two other samples that have high and low status of available-P. On up land agriculture, from 20 samples, 15 samples have very high status of potential-P, four samples have high status and one other sample have medium status. Available-P in up land agriculture entirely have very high status. For paddy field there are positive correlations between available-P with exch-Ca, and pH, meanwhile on up land agriculture, potential-P has positive correlations with total-C, total-N, and EC. From this study, it is concluded that the status of P in agricultural soil in Java is in general very high. In the future, it is worthed to consider how to harvest especially the potential-P for plant growth.
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Judul: Evaluasi Status Hara Kalium Pada Tanah Sawah di Pulau Jawa
Abstrak: It was reported in 1975 by Research Centre for Soil and Agroclimate that the content of potassium (K) determined by HCl 25 % on paddy field in Java island ranged from low to high. Another report published in 2000 by above institution showed that most of paddy field in eighteen (18) provinces in Indonesia contained K in high status determined by HCl 25%, and most of them were located in Java island. The high content of K in paddy field especially in Java Island was due to application of K fertilizer in long periode. This long periode of K fertilizer application was supposed to cause unbalance soil nutrients status. The latter was one of the factors causing the leveling off in rice production. Therefore it is necessary to reevaluate the status of K in Java island to have good management and to maintain high rice production. The objectives of this research were to evaluate exchangeable K status on paddy field in Java island determined by 1 N NH4OAc pH 7, non exchangeable K and total K. Moreover the effect of location and soil order to the amount of exchangeable K, non exchangeable K and total K were also evaluated. Soil samples amounted to 23 samples from paddy field in Java island were collected. It consisted of 7 samples from West Java, 11 samples from Central Java and 5 samples from East java. Those soil samples were analysed for exchangeable K, non exchangeable K and total K. The results showed the content of exchangeable K, non exchangeable K and total K varied among locations and soil orders. For exchangeable K status in those samples varied from low to high status judged by criteria published by Research Centre for Soil and Agroclimate (1992). From 23 locations in Java Island, 9 locations were low status, 8 locations were medium status and 6 locations were high status. West Java consisted of 7 locations. From 7 locations in West Java, 2 locations were low status, 3 locations were medium status and 2 locations were high status. Central Java consisted of 11 locations. From 11 locations in Central Java, 4 locations were low status, 4 locations were medium status and 3 locations were high status. East java consisted of 5 locations. From 5 locations in East Java, 3 locations were low status, 1 location was medium status and 1 location was high status. Comparison of the mean values of exchangeable K among the provinces showed that all the provinces were in medium status. Locations and soil orders did not statistically significantly affected the differences of exchangeable K, non exchangeable and total K values. However this research revealed that Central Java contained the highest mean value of exchageable K and non exchangeable K and East Java contained the lowest mean values of those forms of K. As for total K, West Java contained the highest value of total K and East Java contained the lowest value of total K. Inceptisols contained the highest mean values of exchangeable K and total K, while Vertisols contained the highest mean values of
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Judul: Konstruksi aritmetika kurva eliptik F(2m) supersingular dan non-supersingular untuk skema kunci publik ElGamal
Abstrak: Algoritme ElGamal adalah salah satu algoritme kunci publik dengan aritmetik modular p yang mempunyai struktur grip siklik Z(p). Tingkat keanaman algoritme ini terletak pada pemecahan masalah logaritme diskret dari Z(p). Akan tetapi, tingkat keamanan tadi tahun ke tahun semakin menurun yang disebabkan kemampuan pemecahan algoritme diskret semakin meningkat. Untuk memenuhi tingkat keamanan yang memadai dibutuhkan p yang cukup besar yang menyebabkan proses enkripsi dan dekripsi menjadi lambat.
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