Effects of Application of a By-Product of the Two-Step Olive Oil Mill Process on Maize Yield

This study presents an account of soil quality parameters and maize (Zea mays L. cv. Tundra) yields as influenced by the application of a by-product of two-step olive oil mill process (BOM). Such information is desirable for finding out the suitability of renewable energy resources such as by-products of different industries as alternatives to synthetic fertilizers and amendments. For this purpose, the main objective of this work was to study in the field the effect of incorporating BOM on soil properties (chemical, physical, and biological) in the period between two maize crops. The second objective was to study the effect of BOM on the productivity and quality of maize crop and to evaluate the utility of the BOM for maize. A by-product of two-step olive oil mill process was applied at 0, 10, 20, 30, and 40 t ha⁻¹ rates, respectively, on a maize crop in Lora del Río (Andalusia, Spain) for 2 yr. The results indicated that BOM has a great soil amendment potential due to its organic matter and nutrient content. The application of BOM to the soil caused an increase in soil chemical, physical, and biological properties. Mineralization of organic matter produced higher contents of NO⁻ ₃–N in soil and increased NO⁻ ₃–N uptake by plants. Yield parameters of the second experimental season were better than those of the first experimental season due to the residual effect of the organic matter after application in the first season. In fact, application of the BOM gave a significant grain gross protein content of about 18 and 20% for each experimental season, a significant grain soluble carbohydrate content of about 25% for both experimental seasons, a significant number of grains per corncob of about 17 and 21% for each experimental season, and a significant maize yield of about 16 and 18% for each experimental season over the control.