RESPONSE OF PHYSIOLOGY, GROWTH AND YIELD OF SOYBEAN VARIETIES ON FERTILIZATION TREATMENT IN AGROFORESTRY SYSTEMS

In agroforestry system, magnitude of crops adaptive responses to shade depends on amount of shade. Hence, soybean may modify its growth to adapt to competition in agroforestry systems. The objective of this study was to describe the growth and yield of soybean varietes grown in intercropping under Mindi (Melia azedarach) with several doses of fertilization. This research has been conducted in Kwala Bekala Arboretum, Universitas Sumatera Utara using factorial design, consisting of soybean varieties (V) and fertilizing dosage (P). Variety factors are consisted of Anjasmoro; Burangrang, Dena-1, and Dena-2. Fertilization factor consisted of 50% of recommended dosage (urea 50 kg/ha, SP-36 100 kg/ha, KCl 50 kg/ha), recommended dose (urea 100 kg/ha, SP-36 200 kg/ha, KCl 100 kg/ha); and 150% of recommended dosage (urea 150 kg/ha, SP-36 300 kg/ha, KCl 150 kg/ha). The difference in growth response is closely related to environmental conditions such as light intensity, temperature and humidity levels received, that affects the plant height parameters, leaf chlorophyll, flowering age and yield components. In addition to shade, fertilization also has a significant effect, where under shaded conditions, to produce optimal growth, a dosage of 150% of the recommendations is required, with soybean Dena-2 variety the most adaptive variety.