Effect of Liquid Digestate on Agricultural Soil-II: Microbial Population Dynamics

Abstract

The aim of this study was to investigate the effect of liquid digestate (produced from anaerobic digestion of organic municipal solid waste) on the population dynamics of selected soil microbial groups during cultivation of maize plants. Maize seeds where subjected to various concentrations (between 0% to 72%) of the digestate with a total of ten (10) runs. One set of experimental runs were treated with one-time application of the corresponding digestate concentration (OTDA). Another set of experimental runs were treated with two-time application of the corresponding digestate concentration (TTDA). The first application of the digestate (for OTDA and TTDA) was conducted two weeks after sowing while the second application (for TTDA alone) was conducted three weeks after the first application. During the growth of maize plants, the populations of soil aerobic bacteria (AEB), strict anaerobic bacteria (SAB), ammonia oxidizing bacteria (AOB), nitrate reducing bacteria (NRB) and fungi (FUN) where monitored using standard cultural methods. In OTDA and TTDA treatments, the population of soil AEB, SAB, AOB, NRB and FUN ranged from 3.0 × 10 6 CFU/g to 50.2 × 10 6 CFU/g and 3.1 × 10 6 CFU/g to 78.6 × 10 6 CFU/g; 1.9 × 10 4 CFU/g to 7.2 × 10 5 CFU/g and 2.2 × 10 4 CFU/g to 2.53 × 10 5 CFU/g; 0MPN/g to 4.3 × 10 4 MPN/g and 0MPN/g to 3.9 × 10 5 MPN/g; 0 MPN/g to 4.4 × 10 5 MPN/g and 0 MPN/g to 1.4 × 10 5 MPN/g and 1.3 × 10 3 CFU/g to 2.6 × 10 4 CFU/g and 1.2 ×10 3 CFU/g to 9.4 × 10 3 CFU/g respectively before and 70 days after applying the digestate. Bacteria species isolated appear to belong to genera such as Arthrobacter, Azotobacter, Flavobacterium, Nocardia, Bacillus, Clostridium, Cellulomonas, Micrococcus and Pseudomonas. Fungi species isolated appear to belong to genera such as Aspergillus, Cladosporium, Fusarium, Geotrichum, Penicillium, Rhizopus and Trichoderma. Digestate application appears to have increased the population of soil microbes with time during the cultivation of maize plants.

Effect of Liquid Digestate on Agricultural Soil – I: Growth Dynamics of Zea mays Plant

“…Collection and characterisation of the liquid digestate and the loamy soil used for cultivation of the test plant (Zea mays) were carried out as described by [38]. The liquid digestate was obtained from a pilot-scale anaerobic digester (AD H ) treating organic municipal solid waste while the loamy soil was obtained from an agricultural field at the Nigerian Institute for Oil Palm Research (NIFOR) in Edo State, Nigeria.…”

“…The liquid digestate was obtained from a pilot-scale anaerobic digester (AD H ) treating organic municipal solid waste while the loamy soil was obtained from an agricultural field at the Nigerian Institute for Oil Palm Research (NIFOR) in Edo State, Nigeria. In order to model the effect of the liquid digestate on growth dynamics of Zea mays (the test plant), we subjected the Zea mays (TZESR-W; early maturing streak resistant white grain variety) to various concentrations (ranging from 0% to 72%) of the digestate using One-Factor Response Design (Design Expert version 9.0) as described by Ogbonna et al [38]. After completely loading the pots with the loamy soil, two seeds of the Zea mays were sown into the soil in each of the pots at a depth of 5cm per hole.…”

“…This was tagged "Two-time Digestate Application (TTDA)". The first application of the liquid digestate (for OTDA and TTDA) was conducted two weeks after sowing while the second application (for TTDA alone) was conducted three weeks after the first application [38]. The liquid digestate (as bio-fertiliser) was applied by spraying into the soil in the pots.…”

“…The properties of the liquid digestate and the loamy soil used to cultivate the maize plant are presented in [38]. This particular result showed that elements (or compounds) such as carbon (as total organic carbon), total nitrogen, ammonial nitrogen, phosphorus, potassium, calcium, magnesium, manganese, zinc, copper, nickel, cobalt, iron, and molybdenum, which are known to be beneficial for plant growth at the appropriate concentrations were higher in the digestate compared to the soil [40].…”

“…After the 70-day period, the plants were harvested for biomass estimation. In the soil set-ups treated with OTDA, crop growth rate (1.077cm/day) and biomass yield (22.37g/kg of digestate) of Zea mays plant peaked Stanley et al; JEAI, 31(5): 1-9, 2019; Article no.JEAI.42738 2 with 48% digestate after 70 days. In the soil set-ups treated TTDA, crop growth rate (1.321cm/day) and biomass yield (29.95g/kg) of Zea mays plant peaked with 72% digestate after the same period.…”