Sequestration of Soil Organic Carbon Pools under Diverse Tillage Practices and Cover Crops in Northern Guinea Savanna, Nigeria.

Abstract

Sequestration of soil organic carbon (SOC) is vital to increase soil quality and carbon stock, decrease soil erosion, and
mitigate climate change. This study evaluated effects of tillage and cover crops on the sequestration of different pools of
SOC. Three years field trials were conducted at Institute for Agricultural Research farm, Zaria, Nigeria. Three tillage
practices [no-till (NT), reduced till (RT), and conventional till (CT)] formed the main treatment while four cover crops
[Glycine max (GM), Centrosema pascuorum (CP), Macrotyloma uniflorum (MU) and Cucurbita maxima (CM)], and a
control, without cover crop (NC) formed the sub treatment. After harvesting of test crop each year, soil samples were
collected from depths 0-5, 5-10, 10-15, and 15-20 cm. Organic carbon sequestered in soil aggregate fractions [Fine
particulate organic carbon (FPOC) intra aggregate particulate organic carbon (IPOC), and silt plus clay associated carbon],
bulk soil (total organic carbon, TOC), and dissolved organic carbon (DOC) were determined. Conservation tillage (NT and
RT) surpassed CT in Carbon sequestration in both bulk soil and aggregate fractions. No-till soil had 34, 29, and 25 % more
st nd, rd
TOC than the conventionally tilled soil in the 1 , 2 and 3 years respectively. Similarly, the use of cover crops improved
TOC, FPOC, IPOC, silt plus clay associated C and DOC relative to the soil without cover crop, the significance of DOC
was in the order of CP > GM > MU > CM > NC. The soil under CP had 50 % more DOC than soil without cover crops. Soil
tillage disrupts soil aggregates, increases macroaggregate turnover, and releases C into the atmosphere, resulting in low
formation of microaggregates within macroaggregates and low stabilization of SOC. Conservation tillage and cover
cropping have great po