Evaluation of maize-soybean intercropping systems and fertilizer rates on maize grain yield using competitive indices
Field trials were conducted in savanna ecologies of Nigeria during the 2015 and 2016 seasons using maize (PVA8) and soybean (TGX 1448-2E) intercropping systems with different fertilizer rates to evaluate the yield of maize and assess the best intercropping system for resource management. Single plant stands and two plants/stand and 2 arrangements of rows (one row on a ridge and two rows on a ridge) were used to impose maize plant densities evaluated in strip inter-crop with soybean. The trial was factorial, laid out in a randomized complete block design and replicated three times. Thus, 8 maize-soybean strip cropping systems and application of 3 NPK rates were evaluated at Saki-Oyo, Ilorin, and Nasarawa (southern Guinea savanna), Kaduna in the northern Guinea savanna, Funtua (Katsina) and Gusau (Zamfara) located within Sudan savanna ecologies of Nigeria. Data on yields and yield components were collected. The intercropping systems were assessed using existing intercropping indices such as Land Equivalent Ratio (LER), Relative Crowding Coefficient (K), Aggressivity (A), Competitive Ratio (CR), Actual Yield Loss (AYL), Intercropping Advantage (IA) and Monetary Advantage Index (MAI). The result showed that Nasarawa and Kaduna were most ideal locations for maize production in the Nigeria savannas. The highest grain yield of 4.04 tons/ha maize and 1.36 tons/ha soybean were obtained from seeding 1 plant/stand in 2-rows per ridge x 4 ridges of maize alternated with 2 rows of soybean with the application of NPK at 100:50:50. The LER was 1.11, AYL (1.10) and MAI (208) gave a profit of ₦312,102.00 (US$990.80) ha-1 with a benefit-cost ratio of 2.38 and production efficiency of 29.56%. The study concluded that, seeding 80% maize and 20% soybean per ha will lead to sustainable maize crop production with limited use of fertilizer. It can be adopted by the farmers in Nigeria savannas as a relatively profitable intercropping system.
Keywords: Maize production, Ideal location, Fertilizer rate, Competitive indices, Savanna ecologies, Nigeria