Soil Health

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Soil properties changes after seven years of ground mounted photovoltaic panels in Central Italy coastal area

Land use change is a major driver of soils’ properties variation and potential degradation. Solar photovoltaic plants installed on the ground represent a key to mitigating global climate change and greenhouse gas emissions. However, it could represent an emerging source of land consumption, although reversible, which prevents the use of soils for agricultural purposes and may affect crucial ecosystems services. Despite the large widespread deployment of photovoltaic plants, their potential effect on soil properties has been poorly investigated. The aim of this study was to assess changes of soil physical, chemical and biochemical properties seven years after the installation of the panels. For this purpose, the soil under photovoltaic panels was compared with the GAP area between the panels’ arrays and with an adjacent soil not affected by the plant. The main results showed that seven years of soil coverage modified soil fertility with the significant reduction of water holding capacity and soil temperature, while electrical conductivity (EC) and pH increased. Additionally, under the panels soil organic matter was dramatically reduced (-61% and -50% for TOC and TN, respectively compared to GAP area) inducing a parallel decrease of microbial activity assessed either as respiration or enzymatic activities. As for the effect of land use change, the installation of the power plant induced significant changes in soils’ physical, chemical and biochemical properties creating a striped pattern that may require some time to recover the necessary homogeneity of soil properties but shouldn’t compromise the future re-conversion to agricultural land use after power plant decommissioning.
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MN Research Shows Solar Grazing Improves Soil Quality

Solar energy is the fastest growing renewable energy source. It is predicted that 20-29% of global power will be sourced by solar by 2100. Solar energy requires larger land footprints and long-term commitments. Vegetation left under solar panels reduces soil degradation and opens up the potential for solar grazing as a dual income for farmers and vegetation management for solar utilities. Research conducted on multiple solar sites in Minnesota reveal there can be meaningful forage in 45% shade and 80% shade from solar panels. Furthermore, grazing sheep under solar panels produces both a higher content of carbon and nitrogen in the soil. Managed episodic grazing can be used as a strategy for carbon sequestration and vegetation management. Soil properties show an overall improvement and benefits depending on soil properties. Future work must be done to measure the long term soil carbon and hydrological properties.
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Solar park microclimate and vegetation management effects on grassland carbon cycling

Increasing energy demands and the drive towards low carbon (C) energy sources has prompted a rapid increase in ground-mounted solar parks across the world. This represents a significant global land use change with implications for the hosting ecosystems that are poorly understood. In order to investigate the effects of a typical solar park on the microclimate and ecosystem processes, we measured soil and air microclimate, vegetation and greenhouse gas emissions for twelve months under photovoltaic (PV) arrays, in gaps between PV arrays and in control areas at a UK solar park sited on species-rich grassland. Our results show that the PV arrays caused seasonal and diurnal variation in air and soil microclimate. Specifically, during the summer we observed cooling, of up to 5.2 °C, and drying under the PV arrays compared with gap and control areas. In contrast, during the winter gap areas were up to 1.7 °C cooler compared with under the PV arrays and control areas. Further, the diurnal variation in both temperature and humidity during the summer was reduced under the PV arrays. We found microclimate and vegetation management explained differences in the above ground plant biomass and species diversity, with both lower under the PV arrays. Photosynthesis and net ecosystem exchange in spring and winter were also lower under the PV arrays, explained by microclimate, soil and vegetation metrics. These data are a starting point to develop understanding of the effects of solar parks in other climates, and provide evidence to support the optimisation of solar park design and management to maximise the delivery of ecosystem services from this growing land use.
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Wind Farm and Solar Park Effects on Plant–Soil Carbon Cycling: Uncertain Impacts of Changes in Ground-Level Microclimate

Global energy demand is increasing as greenhouse gas driven climate change progresses, making renewable energy sources critical to future sustainable power provision. Land-based wind and solar electricity generation technologies are rapidly expanding, yet our understanding of their operational effects on biological carbon cycling in hosting ecosystems is limited. Wind turbines and photovoltaic panels can significantly change local ground-level climate by a magnitude that could affect the fundamental plant–soil processes that govern carbon dynamics. We believe that understanding the possible effects of changes in ground-level microclimates on these phenomena is crucial to reducing uncertainty of the true renewable energy carbon cost and to maximize beneficial effects. In this Opinions article, we examine the potential for the microclimatic effects of these land-based renewable energy sources to alter plant–soil carbon cycling, hypothesize likely effects and identify critical knowledge gaps for future carbon research. Land use change for land-based renewables (LBR) is global, widespread and predicted to increase. Understanding of microclimatic effects is growing, but currently incomplete, and subsequent effects on plant–soil C cycling, greenhouse gas (GHG) emissions and soil C stocks are unknown. We urge the scientific community to embrace this research area and work across disciplines, including plant–soil ecology, terrestrial biogeochemistry and atmospheric science, to ensure we are on the path to truly sustainable energy provision.
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Soil Health and Sustainable Agriculture

This review will discuss the external factors controlling the abundance of rhizosphere microbiota and the impact of crop management practices on soil health and their role in sustainable crop production.
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Soils and Sites for Organic Orchards and Vineyards

This publication discusses site selection and soil preparation for fruit plantings. It also describes cover crop and mulching options for orchards and vineyard floors, and discusses fertilization and the role of mycorrhizae in maintaining healthy fruit plants. A list of additional resources is included.
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Soil and Soil Water Relationships

This publication presents and discusses concepts that are fundamental to understanding soil, water, and plant relationships and the soil water balance.
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Nutrient Cycling in Pastures

This publication looks at the pathways and drivers that move nutrients into, out of, and within pasture systems. It attempts to provide a clear, holistic understanding of how nutrients cycle through pastures and what the producer can do to enhance the processes to create productive, regenerative, and resilient farm and ranch systems.
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Native Vegetation Performance Under a Solar PV Array at the National Wind Technology Center

Implications for vegetation growth when large opaque objects such as solar collectors are placed between the sun and ground-level vegetation across large portions of earth surface have received little attention to date. The present study seeks to address this void, advancing the state of knowledge of how constructed PV arrays affect ground-level environments, and to what degree plant cover, having acceptable characteristics within engineering constraints, can be re-established and thrive.
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Managing Soils for Water: How Five Principles of Soil Health Support Water Infiltration and Storage

Worldwide, water is becoming scarcer and more expensive due to the effects of climate change. Significant adaptation will be necessary to ensure adequate supply and efficient use of a diminishing resource. This reduction in the supply of water will affect agriculture and will require a change in focus from increasing productivity of land to increasing productivity per unit of water consumed.
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Agrivoltaics Provide Mutual Benefits Across the Food-Energy-Water Nexus in Drylands

The vulnerabilities of our food, energy, and water systems to projected climatic change make building resilience in renewable energy and food production a fundamental challenge. We investigate a novel approach to solve this problem by creating a hybrid of colocated agriculture and solar photovoltaic (PV) infrastructure.
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Agrivoltaics Provide Mutual Benefits Across the Food-Energy-Water Nexus in Drylands

Researchers present here a novel ecosystems approach—agrivoltaics—to bolster the resilience of renewable energy and food production security to a changing climate by creating a hybrid of colocated agriculture and solar PV infrastructure, where crops are grown in the partial shade of the solar infrastructure. They suggest that this energy- and food-generating ecosystem may become an important—but as yet quantitatively uninvestigated—mechanism for maximizing crop yields, efficiently delivering water to plants and generating renewable energy in dryland environments. We demonstrate proof of concept for agrivoltaics as a food–energy–water system approach in drylands by simultaneously monitoring the physical and biological dimensions of the novel ecosystem. We hypothesized that colocating solar and agricultural could yield several significant benefits to multiple ecosystem services, including (1) water: maximizing the efficiency of water used for plant irrigation by decreasing evaporation from soil and transpiration from crop canopies, and (2) food: preventing depression in photosynthesis due to heat and light stress, thus allowing for greater carbon uptake for growth and reproduction. An additional benefit might be (3) energy: transpirational cooling from the understorey crops lowering temperatures on the underside of the panels, which could improve PV efficiency. We focused on three common agricultural species that represent different adaptive niches for dryland environments: chiltepin pepper (Capsicum annuum var. glabriusculum), jalapeño (C. annuum var. annuum) and cherry tomato (Solanum lycopersicum var. cerasiforme). We created an agrivoltaic system by planting these species under a PV array—3.3m off the ground at the lowest end and at a tilt of 32°—to capture the physical and biological impacts of this approach. Throughout the average three-month summer growing season we monitored incoming light levels, air temperature and relative humidity continuously using sensors mounted 2.5m above the soil surface, and soil surface temperature and moisture at 5-cm depth. Both the traditional planting area (control) and agrivoltaic system received equal irrigation rates, and we tested two irrigation scenarios—daily irrigation and irrigation every 2d. The amount of incoming photosynthetically active radiation (PAR) was consistently greater in the traditional, open-sky planting area (control plot) than under the PV panels. This reduction in the amount of incoming energy under the PV panels yielded cooler daytime air temperatures, averaging 1.2+0.3 °C lower in the agrivoltaics system over the traditional setting. Night-time temperatures were 0.5+0.4 °C warmer in the agrivoltaics system over the traditional setting (Fig. 2b). Photosynthetic rates, and therefore growth and reproduction, are also regulated by atmospheric dryness, as represented by vapour pressure deficit (VPD) where lower VPD indicates more moisture in the air. VPD was consistently lower in the agrivoltaics system than in the traditional growing setting, averaging 0.52+0.15 kPa lower across the growing season. Having documented that an agrivoltaic installation can significantly reduce air temperatures, direct sunlight and atmospheric demand for water relative to nearby traditional agricultural settings, we address several questions regarding impacts of the food–energy–water nexus system.