Judul: Disain dan pengujian metering device untuk unit pemupuk butiran laju variabel (variable rate granular fertilizer applicator)
Abstrak: Uniform rate of fertilizer applicator (URA) practice is disregarding the productive potential of the various areas within the field. Thus, some area is less fertilized and other is over fertilized. It is also an important issue recently that nitrogen from fertilizers may be subjected to lost into atmosphere or enters streams through surface or subsurface drainage (leaching). The place with overfertilization will be a potential source of pollution in the form of ammonia (NH3), nitrite (NO2) and nitrate (NO3) which may hazard people health. Therefore, a contemporary issue is how to give an effective dose at the accurate position and right time for optimum growth of crops while preserving the environment without causing economic losses. Variable rate of fertilizer applicator (VRA) is a solution to overcome the negative impact of URA. It can control the appropriate of fertilizer dosage and location of application in the field. The objective of this research is to design a metering device for variable rate granular fertilizer applicator. In this research, the metering device was equipped with two rotor, which could be operated as single rotor or double rotor. The dose of granular fertilizer could be controlled by the rotation of the rotor. The rotation of the rotor was controlled using digital PID algorithm. The result of variable rate fertilizer testing of the metering device using single rotor indicated that the rate of urea, SP- 36 and NPK are 0.84, 0.96 and 1.2 g/rotation respectively. The testing using double rotor indicated that the rate of urea, SP-36 and NPK are 1.14, 2.22 and 2.1 g/rotation respectively. All results showed that the prototype of metering device can control fertilizer dose of urea, SP-36 and NPK fertilizer precisely.
Keyword: 

Judul: Desain dan Pengujian Prototipe Mesin Pemupuk Butiran Laju Variabel Empat Baris untuk Pertanian Presisi
Abstrak: In conventional method, fertilizer is applied at a uniform dosage for all location of a field. However, each location within the field needs different amount of fertilizer according to the soil nutrient content and growth condition of crop. For that purpose, it is important to develop a fertilizer applicator that allows a prescribe rate of fertilizer to be applied at each location within the field, based on recommended dose. The objectives of this research were: 1) to design digital metering system to control the application rate of a variable rate granular fertilizer applicator, 2) to develop a prototype of 4 rows granular fertilizer applicator, that can provide prescribe application rate automatically, and 3) to obtain field performance data of the prototype. A prototype of the variable rate granular fertilizer applicator was designed and constructed.The metering device consisted of two fluted wheel type of rotors which was driven by controlled DC-motor. To provide a prescribe rate of fertilizer, a control system based on microcontroller DT-AVR ATmega128L modul was developed and set to control the speed of the rotor. The prototype then was tested using three types of granular fertilizers (Urea, SP-36 and NPK), on stationary test and field tests. The stationary test result showed that the PID controller could control and provided a proportional correlation between application rate and rotor speed. The field performance test result showed that the designed prototype could provide a proper predetermined application rate of fertilizers precisely. The average deviations of the application rate for 50, 100, 150, 200, 250 kg/ha dose of Urea were -1.67 , 3.33, 0.28, 2.71 and 1.33 % respectively. For SP-36 were -21.67, -5.42, -2.47, -2.71, and -1.67 %. respectively. For NPK were -18.33, -4.17, -4.17, -3.75 and -2.33 % respectively.
Keyword: 

Judul: Embriogenesis ikan buta (Astyanax fasciatus)
Abstrak: Ikan buta Astyanax fasciatus adalah spesies ikan unik dari famili Characidae yang menempati perairan dalam gua di Wilayah La Cueva Chica-San Luis Potasi-Mexico. Ikan ini memiliki mata yang tereduksi (Blind Cavefish) dan warna kulit merah muda, pucat serta mengkilap.
Keyword: