Judul: Model Lintas Transformasi Unsur Fosfor Tanah Kaolinitik dan Smektitik
Abstrak: Phosphorus (P) is one of essentials needed in a sufficient amount to normal plant growth. The objective of this research was to path modelling caolinitic and smectitic soils P transformations. Path diagrams were able to describe soil P transformations, Its elaboration resulted in structural equation models which were P transformations path models. The models parameters estimated using Partial Least Square (PLS). Bartlett's test and KMO showed not all variables used had multicolinearity. Only P-uptake (X1), Po-NaHCO3 (X5), Pi-NaHCO3 (X6), Pi-NaOH (X7), P-occluded (X8), P-HCl (X9) from caolinitic and P-uptake (X1), Po-NaHCO3 (X5), Pi-NaHCO3 (X6), Pi-NaOH (X7), P-HCl (X9) from smectitic which included in path modelling.
Keyword: smectitic soils, phosphorus transformations, path analysis, partial least square, caolinitic soils

Judul: Perubahan Fraksi Fosfor Lambat Tersedia pada Tanah Tergenang yang Diameliorasi Bahan Organik
Abstrak: The low availability and easily fixed phosphorus (P) in soil resulted in heavy and continuous P fertilization by farmers, leading to accumulation of residue-P in soil. In such condition, further P fertilization will not result in higher plant productivity known as leveling off. One way to increase the availability of residual P in soil is to add organic matter. There are various forms of P in the soil, from soluble to unavailable phosphorus can also be differenciated as inorganic and organic forms, where the sum of both referred as total-P. The objective of this research was to study the changes of slow-available phosphorus fraction in a submerged soil ameliorated with organic matter effect of organic matter (extracted with 0.1 M NaOH). Research unit was 200 g (oven-dry, 105°C) in a 10 cm pot. The soil was treated with 0, 500, 750, 1000, 2000, and 5000 kg/ha, and submerged for 5 weeks. Every week for 5 weeks, subsample of each research unit was extracted for determination of NaOH-P following Tiessen and Moir 1993 procedure. The results showed that in general NaOH-Pi, NaOH-Po, and NaOH-Pt increase with increasing organic matter treatments. There was a dynamic pattern of NaOH-Pt, NaOH-Pi, and NaOH-Po with the time of submersion, in which in general NaOH-P initially decreased, increased, then finally decreased.
Keyword: Bogor Agricultural University (IPB), Submerged Soil., Organic Matter, NaOH-Pt, NaOH-Po, NaOH-Pi

Judul: Penekanan Kekebalan Akibat Infectious Bursal Disease Pada Ayam dan Kerentanannya Terhadap Infeksi Virus New Castle Disease
Abstrak: Ayam yang terinfeksi dengan virus Gumboro pada umur dini (0 sampai 21 hari), dapat menderita imunosupresi atau penekanan kekebalan, sehingga ayam akan menjadi lebih rentan terhadap infeksi penyakit lain, serta respon terhadap vaksinasi sangat menurun. Adanya penekanan kekebalan tersebut dapat diketahui dengan menggunakan respon serologis ayam terhadap Brucella abortus str. 19, yang diobservasi selama 7 minggu, Percobaan ini bertujuan untuk mengetahui tingkat penekanan kekebalan yang disebabkan oleh dua vaksin virus Gumboro pada ayam yang berumur satu hari. Satu dari vaksin tersebut dapat menyebabkan kerusakan bursa fabricius, sedangkan vaksin yang lain mengakibatkan kerusakan bursa yang tidak berarti. Vaksin ini dapat menyebabkan terjadinya penekanan kekebalan yang cukup parah, yang dapat diketahui dengan menggunakan respon serologis melalui inokulasi B. abortus str. 19. (Thornton et al., 1979).
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