Soil & Nutrient Management
Roughly half of all agricultural GHG emissions in the U.S. come from soil-management practices such as tillage, fertilization, and irrigation. However, numerous scientific studies show that management systems designed to improve soil health can also aid carbon sequestration and reduce GHG emissions.
At the same time, they provide important environmental co-benefits: they can improve water quality, suppress pathogens, and support safer pollinator habitats and biodiversity in general. They can also benefit farmers and ranchers by increasing a soil’s available water-holding capacity and nutrient availability, improving drought resilience, reducing input costs, and mitigating erosion.
Scaling up these practices can increase carbon sequestration and reduce GHG emissions across the agricultural sector and result in significant air and water quality improvements that can directly benefit agricultural workers.
Soils have different carbon-sequestration potential. Calculating the actual sequestration potential for different practices in each soil or group of similar soils will help provide farmers and ranchers with accurate carbon management recommendations. This will require integrating new and affordable soil carbon measurement technologies with digital soil mapping and simulation modeling.
At the same time, in order to improve nitrogen use efficiency (NUE) and therefore reduce losses from sources of essential agronomic nitrogen such as fertilizers, soil organic matter, crop residues, cover crops, and animal manures, we need a better understanding of how soil nitrogen availability and plant nitrogen demand change over time and space. Foundational research that integrates the dynamics of nitrogen availability (regulated by soil processes, weather, and other variables) with the dynamics of plants’ nitrogen demand would enable better nitrogen management and recovery.
High Costs for Measurement Technologies
We need credible and transparent mechanisms for verifying the quantity of carbon sequestered in soil to confirm that practices are successful in capturing and storing atmospheric CO2. Current technologies that calculate carbon stocks by measuring soil carbon and soil bulk density are time consuming and expensive. Consequently, developing soil-carbon testing technology that is economical, accurate, and standardized is fundamental to scaling soil-carbon sequestration. Further modeling is also needed for nitrogen management and systems level assessment at watershed-to-regional scale so that conservation practices can be quantitatively evaluated. Without low-cost methods of estimating sequestration potential on individual farms, many researchers and policymakers continue to rely on average sequestration estimates.
Economic Incentives and Market Demand
The costs and benefits of adopting carbon reduction practices are often unclear to farmers and agricultural producers. Many of these uncertainties are due to a lack of standardized scientific measurement of sequestration and understanding of carbon saturation, the heterogeneity in soil sequestration levels, and the variability in implementation across farms. Even if better estimates existed, potentially high upfront costs also limit adoption rates.
Reducing GHG from the agriculture sector is further complicated by the current nature of commodity cropping systems, which are dominated by monocrops and rely on commercial inputs. For example, the livestock industry has consolidated to put downward pressure on production costs and the fertilizer industry is increasingly concentrated in order to maximize profits through market scale. If these consolidated producers do not see the business case for soil management practices and technologies, GHG reductions may not occur at scale.
Technology Innovation Examples
Crops and soil can sequester larger amounts of carbon. High carbon-input crop phenotyping, for example, can be achieved by genetically modifying crops or by perennializing grain, seed, and other crops to keep their root residues in the soil. Another approach is to apply biochar (plant matter turned to charcoal) or compost to cropland, which can improve soil health.
Feeding a growing and increasingly affluent global population without extensive changes in land use will require dramatic growth in agronomic yields. These yields must rise despite growing pressure from climate-change–induced variability, reduced soil quality, and pests.
To make this happen, we need technological solutions to rapidly transform crops, improve climate resiliency, and use new modes of production. For the greatest impact, producers should apply these innovations to the large-acreage crops, including wheat, soy, rice, and maize, that underpin the global food system.
We need accurate, low-cost, and efficient technologies to quantify soil carbon and nitrogen stocks in the field. Current technologies to measure soil carbon and bulk density are time-consuming and expensive. Developing remote-sensing soil-carbon technology that is economical, accurate, and standardized is fundamental to quantifying and scaling soil carbon sequestration.
Nitrogen measurement technologies also have the potential to significantly improve nitrogen use efficiency, thereby reducing nitrogen losses to the atmosphere (as nitrous oxide) and to water (as nitrate).
While nitrous oxide (N2O) emissions tied to nitrogen fixation and decomposition of crop residues are particularly challenging to mitigate, there is substantial potential to reduce emissions arising from fertilizer application and manufacture. Development and adoption of technologies such as enhanced efficiency fertilizers and microbial fertilizers could reduce the need for synthetic or organic fertilizer and reduce N2O emissions. Developing ammonia for use in fertilizer is also highly emissions-intensive and can be made cleaner through direct electrochemical and solar conversion processes, in addition to processes that could provide low-cost green hydrogen to traditional ammonia production.