Variations of Light Interception and Biomass Prediction Model of Red Spinach (Amaranthus gangeticus) in Plant-Factory System

Artificial lighting given in plant-factory planting system is inseparable from uniformity problem. Spatial variation in the catch of light (radiation) will occur due to the position of the plant against the lamp. The purpose of this research was; a) to determine the relationship between biomass growth and the intensity of artificial irradiation in plant-factory systems, and b) to apply the mechanical model of plant growth based on radiation interception and temperature. Six boxes containing red spinach plants were placed on plant factory system in the form of two racks (each rack is placed 3 boxes). In each box, intercepted light was measured and then converted to radiation value. The air temperature in plant-factory space was measured during growth to harvest. Observations showed that there was a difference in light interception in plantfactory growing spaces that caused variations in plant biomass growth. Mathematical models were used to predict the relationship between light interception and biomass growth. This research concludes that the variation of light occurring in plant-factory planting cannot be ignored, as this leads to markedly different plant-end biomass differences. Modeling can be applied to design optimal lighting to improve plant biomass. Abstrak Pencahayaan buatan yang diberikan dalam sistem penanaman dalam ruang (plant factory) tidak terlepas dari masalah keseragaman. Variasi spasial dalam tangkapan cahaya (radiasi) akan terjadi karena posisi tanaman terhadap lampu. Tujuan dari penelitian ini adalah; a) untuk mengetahui hubungan antara pertumbuhan biomassa dan intensitas penyinaran buatan dalam sistem plant-factory, dan b) menerapkan model mekanik pertumbuhan tanaman berdasarkan intersepsi radiasi dan temperatur. Enam buah kotak berisi tanaman bayam merah diletakkan pada sistem plant factory berupa dua buah rak (masing-masing rak ditempatkan 3 buah kotak). Pada masing-masing kotak diukur cahaya terintersepsi yang kemudian dikonversi menjadi nilai radiasi. Suhu udara dalam ruang plant-factory diukur selama pertumbuhan hingga panen. Pengamatan menunjukkan bahwa dalam ruang tumbuh plant-factory terdapat perbedaan intersepsi cahaya yang menyebabkan adanya variasi pada pertumbuhan biomassa tanaman. Model matematika digunakan untuk memprediksi hubungan antara intersepsi cahaya dan pertumbuhan biomassa. Kesimpulan menunjukkan bahwa variasi cahaya yang terjadi dalam penanaman sistem plant-factory tidak dapat diabaikan, karena menyebabkan terjadinya perbedaan biomassa akhir tanaman yang cukup tajam. Permodelan dapat diterapkan untuk merancang pemberian cahaya yang optimal untuk meningkatkan biomassa tanaman.