Effects of Individual Applications of Corncob Biochar and Calcium Carbonate on Soil pH and Soybean (Glycine max L.) Yield in Ferralsols

Published: 12 August 2026| Version 1 | DOI: 10.17632/83jrp97zm4.1
Contributor:
William Koliie

Description

i. H01: Soil pH on Ferralsols vary by location. ii. H02: Different rates of CaCO3 and biochar increase soil pH by their magnitude. iii. H03: Application of different quantities of CaCO3 and biochar under field conditions raise the soil pH, increase plant nutrients, and improve crop performance on Ferralsols. Data were analyzed using GenStat 16th edition and declared significant at p<0.05 using the statistical model as described by Gomez and Gomez (1984). Mean separation was done using the Duncan’s Multiple Range Test (DMRT) and conclusions made at p<0.001 and 0.05 levels of significance.

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Soil samples were collected from the experimental sites at a depth of 0–20 cm using an auger and thoroughly mixed to form composite samples. The samples were placed in plastic bags, labeled, and transported to Les Rams Consultant, Water Quality, Soil and Plant Analysis Laboratory, located on Apollo Kaggwa Road, Bwaise, Kampala, Uganda. The samples were air-dried and ground to pass through a 2-mm sieve, then analyzed for pH, exchangeable aluminum, exchangeable hydrogen, active acidity, cation exchange capacity, and soil bulk density following protocols recommended by Okalebo et al. (2002). These analyses served as baseline data for the field before treatments were applied. A greenhouse soil-lime incubation study was set up at the Uganda Martyrs University (UMU) farm in Nkozi to determine the lime requirement. Soils were air-dried and processed using a 2-mm sieve. Thereafter, 2 kg of soil was weighed, placed in separate containers, and thoroughly mixed with different rates (0, 1, 3, and 5 t ha⁻¹) of CaCO₃ and corncob biochar, based on work by Delfim et al. (2020). The soils were moistened with distilled water and allowed to react over time. A 100-g subsample was collected biweekly from each container to monitor pH response to liming using the procedure recommended by Trans and Van Lierop (1981), until the pH stabilized. The same rates (0, 1, 3, and 5 t ha⁻¹) of CaCO₃ and biochar used in the greenhouse study were applied in the field. The only difference was the amount of soil, which corresponded to an 8 m² plot in the field. See calculations below: Weight of soil in 8m2 plot = 2000000 kg x 0.15 x 8 = 240 kg 10000 m2 The 240 kg of soil in the field divided by the 2 kg of soil used in the greenhouse amounts to 120 kg. Therefore, 1 g x 120 kg of soil = 120 g; 3 g x 120 kg of soil = 360 g; 5 g x 120 kg of soil = 600 g respectively. At full maturity, four soybean plants were randomly selected and harvested from a 1 m² area within the three central rows of each subplot. Yield in kg ha⁻¹ was calculated by scaling the average weight of the four plants from 1 m² to one hectare: yield = (average weight per plant × plants per hectare) / 1,000.

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Agricultural Soil, Agriculture

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