Impact of Cropping Ratios of Maize (Zea mays)-Egusi Melon (Colocynthis citrullus) and NPK Fertilizer on Soil Productivity Rating of an Ultisol of Edo State in Nigeria

Three separate field studies were conducted at the Research Farm of University of Benin in Nigeria to determine soil productivity index rating for ultisol in which seven cropping ratios of maize (MA) and egusi-melon (EM) Viz 1:0, 0:1, 1:1, 2:1, 3:1, 1:2 and 1:3) were tested using four rates (0, 200, 400, 600 kg/ha) of NPK 20:10:10 fertilizer for experiments 1 and 2 and six rates (0, 200, 400, 600, 800, 1000 kg/ha) of the fertilizer in experiment 3. The design of the experiment was factorial randomized complete block replicated three times. The soil productivity index rating (PI) was determined to measure the status of the soil for further productivity purposes after consecutive cultivations and harvests. The results showed that the highest nutrient depletion (with negative soil productivity rating) occurred in sole maize where no fertilizer was applied as opposed to maize plots treated with the fertilizer at the end of experiment 2. While in experiment 3, the highest nutrient rate was obtained in maize in ratios of 1:2 and 1:3 with egusi melon. Soil productivity ratings were all positive, either sole or intercropped with maize under the various cropping ratios, thus suggesting no nutrient depletion. It further suggests that egusi melon in mixture with maize does not require as much nutrient as maize does.