물의 잠재력 탐구

Stakeholders in our workshops expressed eagerness to know more about the potential of land use alternatives to protect or increase soil carbon and improve greenhouse gas (GHG) mitigation for croplands. This interest stems both from concern that land idling could exacerbate carbon loss from soil—with knock-on effects for soil fertility, structure, and infiltration—as well as the possibility that maintaining crops on land that would otherwise lie fallow could accrue soil carbon and allow for participation in carbon- and GHG-based incentive programs.Nori and ESMC) have emerged that aim to compensate farmers and land managers for management practices that sequester carbon in the soil." Available information on this question is scant, but it suggests that the soil carbon and GHG benefits of water-limited cropping would probably lie somewhere in between a bare (tilled) fallow and a summer irrigated crop managed with carbon-friendly practices such as low tillage and residue retention./p>

The picture becomes more complex when considering elements of the system's GHG balance beyond soil carbon. Agriculture emits CO2 and other GHGs through fuel and energy use for tractors, irrigation, and other operations, as well as nitrogen fertilizer additions. While atmospheric CO2 can be stored in aboveground biomass—especially woody biomass such as orchard tree trunks—this carbon can still be a source of emissions depending on how biomass is managed at the end of an orchard's lifespan (Marvinney and Kendall 2021). More potent GHGs such as nitrous oxide (N2O) and other gases with negative environmental implications, such as ammonia, can also be emitted from soil, whether directly from soil microbial processes or indirectly through volatilization or leaching of fertilizer nitrogen (Velthof and Rietra 2018).4) is emitted in highly anaerobic, or low oxygen, conditions (Smartt et al. 2016), making it of limited importance for many cropping systems outside of flooded rice or when biomass burning occurs. Methane is a more important emissions source in livestock systems due to enteric fermentation from animals and anaerobic digestion of manure." Depending on the level of fuel and energy use for crop production, N2O can be a large component of an agricultural system's overall GHG emissions./p>

But these opportunities are constrained by logistical challenges, including the up-front costs of installing fencing and water access for livestock. And, similarly to water-limited crops, fragmentation of agricultural land uses in the valley—which causes these and other costs to be spread across fewer acres—may inhibit the expansion of rangeland enterprises because low margins require operating on a larger land base to ensure adequate returns. But creative business structures, such as the contracting arrangements mentioned above for integrated systems, could leverage more of the opportunity. Coordinating habitat restoration efforts with grazing has seen some interest, as demonstrated by plans to restore and fence riparian corridors on working or retired lands to achieve the multiple benefits of flood protection, ease of movement for wildlife, and improved forage management for grazing herds.One example of this concept was developed by the former Westside Resource Conservation District and mapped for Valley Greenprint." On the whole, rangeland establishment as an alternative to fallowing may be most feasible where strategically retired cropland can adjoin existing rangeland operations or multi-use conservation areas, or where livestock management can be outsourced or performed in partnership with an experienced livestock manager./p>

Providing water credits for limited irrigation is one programmatic way to provide support. Programs could also take the form of grants, tax benefits, cost shares, crop insurance or low-interest loan programs, corporate responsibility or sustainability initiatives, and emerging marketplaces for carbon and other ecosystem services (see note 23), among others. Existing federal and state programs could integrate water-limited winter cover crops or crop production into their protocols.Conservation Stewardship Program (CSP) and Environmental Quality Incentives Program (EQIP), California Department of Food and Agriculture programs such as the State Water Efficiency and Enhancement Program (SWEEP), Fertilizer Research and Education Program (FREP), and Healthy Soils Program (HSP), and the California Strategic Growth Council's Sustainable Agricultural Lands Conservation (SALC) program." And new programs—such as the Department of Conservation's Multibenefit Land Repurposing Program—could support minimal irrigation to increase the scope for dryland range and crop repurposing proposals. Making sure that wildlife-friendly farms, including rangelands and water-limited cropping operations, are included in the California 30×30 plan would be another way to stack benefits from public programs geared toward land repurposing and conservation. Recognizing working lands as potential habitat and enabling management systems that support this benefit would go further towards meeting objectives of multi-functionality for repurposed lands—and might enable speedier progress towards conservation goals than targeting habitat areas alone./p>