Judul: Pemberian kotoran sapi pada pertanaman jagung (Zea mays) perubahan beberapa sifat kimia dan fraksi fosfor inorganik pada ultisol Gunung Sindur
Abstrak: Indonesia has wide area for acid upland soils. This upland soils are potential to develop as agricultural land. Soil order which dominantly occupied these acid upland is Ultisols. The Ultisols occupied about 24.3 % of the total acid upland soils. Acid upland soils in Indonesia have some limiting factors chemically and physically. Chemically, they have very low nutrient status and deficient in phosphorus (P), so that P fertilizer is recommended. Application of organic matter such as cow dung was expected to improve some chemical properties and P availability on acid upland soils. This reasearch was conducted in acid upland soil situated at Gunung Sindur District, Bogor Regency Cibadung Village. Analyses of soil chemical properties and the P inorganic fractions were held in the Laboratory of Chemistry and Soil Fertility, Department of Soil Science and Land Resource, Faculty of Agriculture, Bogor Agricultural University. The objectives of this research were to evaluate the effect of cow dung on the changes of some chemical properties and inorganic phosphorus fractions under maize cultivation. The rates of cow dung applied were 0, 10, 20, and 40 tons ha-1. The soil samples used were collected at the time before planting as initial soil properties, two weeks after incubation of manure application and harvest time in the rhizosphere area and between the plant rows The Application of cow dung increased soil pH significantly on two weeks after incubation and after harvest in rhizosphere area. These increases soil pH were followed by the decreases of exchangeable Aluminum. The Application of cow dung increased cation exchange capacity (CEC) significantly on two weeks after incubation but not significantly on that of after harvest in rhizosphere area and between plant rows as well. The application of cow dung increased soil organic carbon (C) on two weeks after incubation and on after harvest in rhizosphere area. The application of cow dung increased base saturation of the soil on two weeks after incubation and after harvest in rhizosphere area and between plant rows as well. The Application of cow dung increased resin-Pi and NaHCO3-Pi fractions on two weeks after incubation and on after harvest in the rhizosphere area and between plant rows as well. As for NaOH-Pi fraction, the application of cow dung only increased this P fraction on two weeks after incubation. Analyses of the P fraction changes (the content of the P fraction after harvest - two weeks after incubation) showed that the resin-Pi was negative values both in rhizosphere and between planting rows. This suggested the resin-Pi contents partly were transformed into other P fraction. The changes NaHCO3-Pi after harvest in rhiszosphere area and between plant rows were positive values. It suggested that partly resin-Pi contents were transformed into this fraction. From the evaluation of the changes on NaOH-Pi fraction which were interpreted as Al-P and Fe-P, the 3 contents of this P fraction of some samples decreased. This suggested that the NaOH-Pi fraction was not stable because it transformed to replenish if available P in soil solution depleted. Dynamics of P fractions that occurred after harvest were related to plant activities.
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Judul: The Application of Cow Dung on Corn (Zea Mays) Cultivation: The Dynamic of Changes in Organic Carbon and Available Nitrogen Content in Ultisol Gunung Sindur.
Abstrak: The research entitled The application of Cow Dung on Corn (Zea Mays) Cultivation: The Dynamic of Changes in Organic Carbon (C) and Available Nitrogen (N) Content in Ultisol Gunung Sindur was conducted in Cibadung village, Gunung Sindur, West Java. Chemical Analyses were conducted in Laboratory of Soil Chemistry and Fertility Department of Soil Science and Land Resource, Faculty of Agriculture, Bogor Agricultural University. The objectives of this research were to evaluate the dynamic of changes in Organic C and available N (ammonium and nitrate) in Ultisol Gunung Sindur treated by cow dung on corn cultivation. The treatments were 0 ton ha-1 (control plot) and 20 ton ha-1 of cow dung in air air-dried condition. The soil samples collection were conducted at 1st, 2nd, 3th, 4th, 6th, 8th, 10th and 14th week after planting in root zone. Organic C content in plot treated by 20 ton ha-1 of cow dung increased with time of soil samples collection and their values were always higher than those of control plot up to 6th week. The equilibrium where the content of organic C of control and plot treated by 20 ton ha-1 of cow dung were similar and constant, occured at 14th week after planting. Ammonium content in plot treated by 20 ton ha-1 of cow dung increased with time of soil samples collection and their values were always higher than those of control plot up to 14th week. Similar to organic C content, the equilibrium was reached at 14th week after planting. The first order kinetic equation coud not be used to simulate the data of ammonium. The Nitrate content increased with time of soil samples collection. The nitrate contents in control plot and plot treated with 20 ton ha-1 of cow dung as well, were always higher than those of ammonium in all time of soil samples collection. The first order kinetic equation revealed that in control plot N which was potential to mineralize to be nitrate was 494 mg kg-1 with rate constant 0.61 week-1 while in plot treated with 20 ton ha-1 of cow dung, N which was potential to mineralize to be nitrate was 620 mg kg-1 with rate constant 0.41 week-1. As for availabe N (ammonium + nitrate), N which was potential to mineralize to be available N in control plot was 538 mg kg-1 with rate constant 0.63 week-1 while in plot treated with 20 ton ha-1 of cow dung N which was potential to mineralize to be available N was 665 mg kg-1 with rate constant 0.46 week-1. The first order kinetic equation also revealed that N from 20 ton ha-1 will fully mineralize to be nitrate and available N at 14th week after planting. The results suggested that equilibrium of application of 20 ton ha-1 cow dung on corn plantation in Ultisol Gunung Sindur for organic C, amonium, nitrate and available N occured at 14th week. N mineralization to be nitrate and available N was simulated well by first order kinetic equation.
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Judul: Cycle Hamilton pada Graf Lengkap, Graf Regular, dan Graf 2-Connected 4-Regular Berorder Kurang dari Sepuluh
Abstrak: Suatu graf disebut graf Hamilton apabila graf tersebut memuat cycle Hamilton, yaitu cycle yang melewati setiap vertex tepat satu kali. Menentukan keberadaan cycle Hamilton pada suatu graf dapat menggunakan syarat cukup yang berupa teorema-teorema yang telah diperkenalkan sejak tahun 1950-an. Beberapa syarat cukup yang dibahas dalam karya ilmiah ini adalah syarat cukup yang berhubungan dengan graf lengkap dan graf regular. Suatu graf lengkap berorder 𝑛������ ≥ 3 dan graf r-regular berorder 𝑛������ ≤ 2𝑟������ + 1 merupakan graf Hamilton, Karena kedua graf tersebut memuat cycle Hamilton. Selanjutnya, syarat cukup tersebut digunakan untuk menentukan keberadaan cycle Hamilton pada graf 2-connected 4- regular berorder kurang dari 10.
Keyword: graf Hamilton, graf regular, graf lengkap, graf 2-connected 4-regular