Impact of soil tillage and soil amendment on soil carbon sequestration, Co2 emission and maize yield

Tillage practices and soil amendments are important technologies in crop production but their influence on yield and soil organic carbon dynamics are diverse with some findings seemingly controversial. A study was conducted at a site that had received same treatments for three years at the Agricultural Research Station of the Kwame Nkrumah University of Science and Technology (KNUST), Anwomaso. A 4x4 factorial experiment in a Split-plot design with three replications (blocks) was used. Four tillage practices: no-till (NT), hoe tillage (H), plough plant (PP) and plough and harrow tillage (PH) were the main plots and four soil amendments 3 t/ha poultry manure (PM), 60-40-40 NPK (NPK), 1.5 t/ha poultry manure plus 30-20-20 NPK (HR) and no amendment (NA) were the subplots. Soil samples were taken from the top soil (0-15 cm) and sub soil (15-30 cm) depths. Carbon stocks was determined within fractionated soil aggregates separated by wet sieving. The relative proportion of aggregate fractions and carbon stock per aggregate fraction was in the order of Large macroaggregates (LM) > small macroaggregates (SM) > Microaggregates (M) > Silt and clay fraction (S+C) within the 0-15 cm depth and small macroaggregates (SM) > Large macroaggregates (LM) > Microaggregates (M) > Silt and clay fraction (S+C) within the 15-30 cm depth. Tillage effect on carbon stocks (total stocks in all aggregate fractions) was in the order of NT (45.31 t C/ha) > H (37.13 t C/ha) > PP (31.10 t C/ha) > PH (14.73 t C/ha) in the topsoil (0-15 cm) and PP (31.38 t C/ha) > NT (31.15 t C/ha) > H (29.96 t C/ha) > PH (26.38 t C/ha) in the subsoil (15-30 cm). The most stable soil carbon stock which occurs in the microaggregate fraction (0.053 – 0.250 mm) was highest in PP (18.12 t C/ha) and was significantly different from NT (15.69 t C/ha), H (15.51 t C/ha) and PH (12.12 t C/ha) over 0-30 cm depth. NT and H were similar in the carbon stock in microaggregate but significantly different from PH. Soil amendment did not have significant effect on carbon stocks within the various soil aggregates. The tillage-soil amendment interactive effect on carbon storage in microaggregates was highest in PP/PM and was significantly higher than all other combinations except PP/NPK and PP/ HR. Carbon dioxide emission was significantly higher in NT plots (8.36 g C/m2/day) and NPK amended plots (8.11 g C/m2/day) than other tillage practices (PH=7.88 g C/m2/day, PP=7.67 g C/m2/day, H=7.23 g C/m2/day) and soil amendments (NA=7.86 g C/m2/day, PM=7.81 gC/m2/day, HR =7.36 g C/m2/day). The Combined effects H/ HR and PP/PM which recorded 6.28 and 6.42 g C/m2/day respectively, had significantly lower carbon dioxide emissions whereas NT/NPK (8.88 g C/m2/day) and NT/PM (8.66 g C/m2/day) had higher carbon dioxide emission. In the major season, tillage effect on maize grain yield was highest under No till (4.12 t/ha) followed by PH = 3.28 t/ha, PP = 2.85 t/ha and H = 2.33 t/ha. Soil amendments effect was highest under HR soil amendment (3.47 t/ha) followed by PM = 3.37 t/ha, NPK = 3.29 and NA = 2.46. Similar trend was observed in the minor season. Plough plant showed potential of sequestering.

Source: KNUST