Surface Soil Organic Content Research Articles

Soil and soil organic carbon effects on simulated Southern High Plains dryland Cotton production

The effect of increasing soil organic content (SOC) on the soil water retention and cotton yield productivity of two benchmark U.S. Southern High Plains (SHP) soils was estimated using pedotransfer functions and the CROPGRO-Cotton crop simulation model. Increasing plow layer (0−30 cm) SOC leads to increased wilting point (WP), field capacity (FC), and plant available water capacity (PAW = FC-WP) in both soils. The increase in a clay loam’s available water capacity is modest, with a 1% increase in SOC producing an additional 0.16 cm of PAW in the soil profile’s uppermost 30 cm. The fine sandy loam’s plow layer effect is twice that, with a 1% SOC increase producing a 0.32 cm PAW increase. These effect’s magnitudes were consistent with a recent meta-analysis of SOC on soil water retention, but considerably below those cited by national and regional extension services. As surface SOC levels in both soils were increased above baseline levels the fine sandy loam’s median simulated cotton lint yields were essentially unchanged, while clay loam yields decreased. The clay loam yield effect is attributed to increased soil evaporation rates. Conservation agriculture (CA) practices such as increased residue retention may compensate for these weak soil water retention effects, but cotton’s limited residue production would require winter cover crops or alternate crop rotations. As the success of terminated winter wheat – dryland cotton rotations is unclear in past SHP field studies, a CA sorghum-cotton rotation with periodic tillage is proposed as a SHP dryland production system.

Impacts of surface soil organic content on the soil thermal dynamics of alpine meadows in permafrost regions: data from field observations

The relationship between soil organic matter and soil temperature plays an important role in our understanding of the effect of climate change on the hydrological and carbon cycles in permafrost regions. Several studies have documented that the organic horizon thickness has profound buffering effects on soil temperature for both tundra and boreal forest ecosystems. In the present study, the alpine meadow ecosystem in the middle and low-latitude permafrost region of the Qinghai–Tibet Plateau (QTP) was selected to examine the impacts of surface soil organic matter on the thermal properties of deep soil. Based on the data obtained from more than 23 observation sites, the relationship between soil organic content and soil temperature dynamics in different seasons was determined. The findings indicate a strong positive exponential (in thawing period) and linear (in freezing period) relationship between surface soil organic content (SOC) and soil temperature dynamics in deep soil layers. The higher SOC at the surface soil layer is associated with a lower rate of soil temperature variation and a later onset time for the thaw–freeze transformation. In permafrost regions of the QTP, the greater lapse rate of soil temperature per 100m of increased elevation resulted in more significant modification of the SOC and soil thermal relationship in alpine meadows than that in tundra and boreal ecosystems. The coupled soil organic matter, soil thermal and water relationships play an important role in the resilience of permafrost during climate changes.