Increasing corn and soybean yields by arranging the plant spacing and NPK fertilizer dosages in intercropping system
Corn and soybean are food crops which are ranked on the second and third position as the main crops with the highest yield in Indonesia. Based on data of 2012, corn and soybean harvested areas amounted 3,956 ha and 597.65 ha with the productivity of 48.99 tons/ha and 843.15 tons/ha, these areas increased up to 4,388 ha (corn) and 589.42 ha (soybeans) which lead an increase in corn and soybean production by 52.85 tons/ha and 887.54 tons/ha. However, increasing crop productivity, especially for corn and soybeans, cannot continuously use land expansion because the land area of Indonesia that is suitable for agriculture is only 94.07 million ha from 188.20 million of total land area. Thus, the solution to overcome this issue is by arranging the plant spacing and providing proper nutrients. Plant spacing in intercropping systems can minimize competition between plants to provide a well-grown of both plants. This research aimed to determine the increase in productivity of corn and soybean plants using intercropping systems through a combination of plant spacing and a combination of NPK fertilizer dosages. This study used a factorial experimental method that planted crops on the land with 2 factors with split-plot design of 4 × 3 factorial and 3 replications. The first factor is the combination of plant spacing with 4 levels, they were plant spacing of corn; 50 cm × 40 cm (J1), 75 cm × 40 cm (J2), 100 cm × 40 cm (J3), 125 cm × 40 cm (J4) and plant spacing of soybean; 40 cm × 20 cm. The second factor is 3 levels of NPK fertilizer dosages combination, they were 0% NPK fertilizer dose of the recommendation (0 g/m2) (D1), 50% NPK fertilizer dose of the recommendation (198.5 g/m2) (D2), 100% of NPK fertilizer dose of the recommendation (397 g/m2) (D3), with 3 replications. DMRT test (Duncan, Multiple Range Test) was performed with a confidence level of 95% when the results between treatments were significantly different.