Influence of lime and gypsum application on soil properties and yield of cassava (Manihot esculenta Crantz.) in a degraded Ultisol in Agbani, Enugu Southeastern Nigeria

• Degraded Ultisols are characterized by low fertility and high acidity.
• Poor soil quality is an attribute of long term effect of natural and man-made factors.
• Lime and gypsum were used to ameliorate soil quality for crop production.
• Soil physical quality control soil functions with reference to crop production.
• Crops respond to changes in edaphic conditions in their growth environment.

The experiment was carried out to examine the influence of lime and gypsum on soil physicochemical properties in a degraded Typic paleusult during 2013 and 2014 rainy season in Agbani, Enugu Southeastern Nigeria (6°29′N and 7°54′E). A Randomized Complete Block Design (RCBD) using lime and gypsum as treatments at the rate of 5000 kg ha−1 lime, 2500 kg ha−1 gypsum, 5000 kg ha−1 lime + 2500 kg ha−1 gypsum and a control without lime and gypsum treatments, replicated five (5) times using cassava (TMS 0304) as test crop was used for the experiment. Soil pH in plots amended with 5000 kg ha−1 lime (5.7 and 5.4) increased relative to the control by between 16 and 17% for both planting seasons. Soils amended with 2500 kg ha−1 of gypsum had lower pH relative to plots amended with 5000 kg ha−1 lime. However, Soil application of a combination of 5000 kg ha−1 of lime and 2500 kg ha−1 of gypsum increased soil pH by 19–20% when compared to the control for both seasons. Soil application of a combination of 5000 kg ha−1 of lime and 2500 kg ha−1 of gypsum increased soil exchangeable Ca2+ by 57% when compared to the control for both seasons. Soil percent base saturation was significantly improved from 72.8% to 93.0% relative to control when 5000 kg ha−1 lime + 2500 kg ha−1 gypsum was applied to the soil. Results showed that at 90 DAP in both seasons, soil dry bulk density in plots amended with 5000 kg ha−1 lime (1.58 and 1.62 Mg m−3) decreased relative to the control by between 5 and 7% for both planting seasons. Soil application of a combination of 5000 kg ha−1 of lime and 2500 kg ha−1 of gypsum reduced soil dry bulk density by about 17% when compared to the control for both seasons. The highest soil total porosity (46.4%) was found in plots with a combination of lime and gypsum at 5000 kg ha−1 and 2500 kg ha−1 respectively. The result also showed that soil water transmissivity improved from about 31.85 cm3 h−1 in the control plots to 37.60 cm3 h−1 in plots treated with 2500 kg ha−1 gypsum and up to 35.7 cm3 h−1 in treated with 5000 kg ha−1 lime then to 41.40 cm3 h−1 in plots treated with 5000 kg ha−1 lime + 2500 kg ha−1 gypsum. At 90 DAP the highest mean plant height of cassava (86–92 cm) was found in plots treated with 5000 kg ha−1 lime + 2500 kg ha−1 gypsum. This was followed by plots treated 2500 Kg ha −1 gypsum (59–62 cm) and those treated with 5000 kg ha−1 lime (61–66 cm) whereas the untreated (control plots) had a plant height of 61–64 cm. Plots treated with 5000 kg ha−1 lime + 2500 kg ha−1 gypsum had the highest mean fresh tuber yield of 9.5 Mg ha−1. This was followed by plots treated with 2500 kg ha−1 gypsum which gave a mean fresh tuber yield of 7.2 Mg ha−1, plots treated with 5000 kg ha−1 lime followed with 6.8 Mg ha−1 while the lowest tuber yield was found in untreated plots which had 6.1 Mg ha−1. The significant treatment differences on soil physical and chemical properties of the study soil due to effect of the treatments could be attributed to the ability of Ca2+ applied via lime and gypsum to flocculate soil particles thereby creating an enabling soil physical condition for better nutrient uptake, proper infiltration and aeration, increased P availability and optimum pH for proper growth of cassava.