Effect of Bioslurry from Fixed Dome and Tubular (Flexi) Biodigesters on Selected Soil Chemical Properties, Maize (Zea mays) Growth, Yield and Quality

Agricultural utilization of bioslurry plays a critical role in soil conditioning and hence crop production. It also reduces greenhouse gas emissions thus mitigating climate change. Although the effect of bioslurry on growth and yields is well researched, that of different biodigester types is under-researched. Therefore, a study was carried out in Waruhiu Agricultural Training Centre, Githunguri sub-county, Kiambu county in Kenya, to investigate the effect of bioslurry from flexi and dome biodigesters on soil chemical properties, maize growth, yield and grain quality. Treatments were laid out in a Randomized Complete Block Design (RCBD) and replicated three times. The treatments were bioslurry from both Fixed Dome and Flexi biodigesters, applied separately at a rate of 400mls per hill as basal and top dress fertilizer. Planting was done during the 2019 short and 2020 long rains, using Duma 43 maize variety. The agronomic (germination percentage, number of leaves, leaf width, leaf length, plant height) and productivity data (stalk, stovers, grain yields and grain quality) were subjected to analysis of variance (ANOVA) through Proc general linear model (GLM) procedures. Mean separation was done using least square means (LS-Means). Results showed an increase in soil pH, total N and OC, exchangeable P, K, Mn and Na in both biodigester types. Total N and OC were higher in Dome treated soils by 38.89% and 37.00%, while in Flexi, it was 16.67% and 16.00% respectively. Exchangeable P and K was higher in Flexi treated soils with a 38.57% and 50.00% increase while in Dome it 37.86% and 47.22% respectively. Magnesium and Zn decreased after treatment by 34.30% and 22.59% in Dome while Flexi had 33.23% and 31.79% increase. Exchangeable Fe and acidity decreased in Dome but increased in Flexi treated soils. No statistical differences were observed on growth and yield parameters but Dome registered higher grain yields by 9.4% and 6.3% for short and long rains respectively. Flexi treated soils registered higher values in most grain nutrient content such as K, Fe, Cu, Mn and Zn in short rains and P, Ca, Fe, Cu, Mn and Zn in the long rains. Bioslurry from both biodigester types variably increased the evaluated soil chemical properties but decreased Mg and Zn. Despite the numerical differences noted between bioslurry from both biodigester types on maize growth and yield, there was no significant difference (p≤.05). However, Dome bioslurry increased N, OC and maize grain yield more while exchangeable P and K and most of the grain nutrient content were higher in Flexi treated soils. Therefore, bioslurry from either biodigester type can be used in enhancing soil conditions, growth, yield and quality of maize. However, a long-term experiment is required validate the findings.