Full Inversion Tillage (FIT) during pasture renewal as a potential management strategy for enhanced carbon sequestration and storage in Irish grassland soils

The potential to increase grassland soil C stocks by extending reseeding intervals is dependent on soil texture and depth

Grasslands account for ∼30% of global terrestrial carbon (C), of which most is stored in soils and provide important ecosystem services including livestock and forage production. Reseeding of temporary grasslands on a 5-year cycle is a common management practice to rejuvenate sward productivity and reduce soil compaction, but is physically disruptive and may reduce soil organic carbon (SOC) stocks. However, research to date is limited, which impacts on the ability to optimise grassland management for climate change mitigation. To determine whether extending the time interval up to 20 years between grassland reseeding can increase stable SOC stocks, a soil survey was conducted across three UK grassland chrono-sequences comprising 24 fields on contrasting soil types. We found that grassland SOC stocks (39.8-114.8 Mg C ha^-1) were higher than co-located fields in arable rotations (29.3-83.2 Mg C ha^-1) and the relationship with grassland age followed a curvilinear relationship with rapid SOC stock accumulation in the year following reseeding (2.69-18.3 Mg C ha^-1 yr^-1) followed by progressively slower SOC accumulation up to 20 years. Contrary to expectation, all grasslands had similar soil bulk densities and sward composition questioning the need for traditional 5-year reseeding cycles. Fractionation of soils into stable mineral associated fractions revealed that coarse textured grassland topsoils (0-15 cm) were near-saturated in C irrespective of grassland age whilst loam soils reached saturation ∼10 years after reseeding. Fine-textured topsoils and subsoils (15-30 cm) of all textures were under saturated and thus appear to hold the most potential to accrue additional stable C. However, the lack of a relationship between C saturation deficit and grassland age in subsoils suggests that more innovative management to promote SOC redistribution to depth, such as a switch to diverse leys or full inversion tillage may be required to maximise subsoil SOC stocks. Taken together our findings suggest that extending the time between grassland reseeding could temporarily increase SOC stocks without compromising sward composition or soil structure. However, detailed monitoring of the trade-offs with grassland productivity are required. Fine textured soils and subsoils (15-30 cm) have the greatest potential to accrue additional stable C due to under saturation of fine mineral pools.

Assessing spatial variability of selected soil properties in Upper Kabete Campus coffee farm, University of Nairobi, Kenya

This study aimed to evaluate spatial variability of selected soil parameters as a smart agricultural technology guide to precise fertilizer application. A farm designated as Field 3 which is under Arabica coffee within a bigger Soil Mapping Unit (SMU) was selected for a more detailed soil observation at a scale of 1:5000. Soil samples were taken at depths of 0–15 and 15–30 cm across 20 sample locations in grids and selected properties analysed in the laboratory. Kriging interpolation method was used to estimate the accuracy of interpolation through cross-validation of the top soil parameters. In 0 to 15 and 15–30 cm depth, soil reaction, percentage organic carbon and percent nitrogen showed low variability of 5.1% and 5.8%, 10.4% and 12.7%, 14.5% and 17.6% respectively. Phosphorus was deficient in both depths and showed moderate variability of 36.2% and 42.3% in 0–15 and 15–30 cm respectively. Calcium and Magnesium ranged from sufficient to rich and showed moderate and low variability in top and bottom depths, respectively. All micronutrients were sufficient in the soil. The soils were classified as Mollic Nitisols. Results showed that soil parameters varied spatially within the field therefore, there is need for variable input application depending on the levels of these elements and purchasing of fertilizer blends that are suitable for nutrient deficiencies. Precision agriculture is highly recommended in the field to capitalize on soil heterogeneity.

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There is need for variable agricultural input application in farms.

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Field spatial variability is a panacea to economically sound soil management.

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Precision agriculture is recommended for profits and environmental protection.

Plant Nutrition under Climate Change and Soil Carbon Sequestration

The climate is one of the key elements impacting several cycles connected to soil and plant systems, as well as plant production, soil quality, and environmental quality. Due to heightened human activity, the rate of CO2 is rising in the atmosphere. Changing climatic conditions (such as temperature, CO2, and precipitation) influence plant nutrition in a range of ways, comprising mineralization, decomposition, leaching, and losing nutrients in the soil. Soil carbon sequestration plays an essential function—not only in climate change mitigation but also in plant nutrient accessibility and soil fertility. As a result, there is a significant interest globally in soil carbon capture from atmospheric CO2 and sequestration in the soil via plants. Adopting effective management methods and increasing soil carbon inputs over outputs will consequently play a crucial role in soil carbon sequestration (SCseq) and plant nutrition. As a result, boosting agricultural yield is necessary for food security, notoriously in developing countries. Several unanswered problems remain regarding climate change and its impacts on plant nutrition and global food output, which will be elucidated over time. This review provides several remarkable pieces of information about the influence of changing climatic variables on plant nutrients (availability and uptake). Additionally, it addresses the effect of soil carbon sequestration, as one of climate change mitigations, on plant nutrition and how relevant management practices can positively influence this.