We aimed to investigate: the effects of different management practices on the soil microbial community, the relationship between soil physicochemical and biochemical properties and the microbial community structure, and the most sustainable management system to promote a more abundant microbial community. The application of oat straw to soil has increased the organic carbon content and, as a consequence, there is an important increase of the microbial biomass. The total PLFAs are highly correlated with the microbial biomass carbon, determined by the fumigation-extraction method. The correlation obtained in this research between these parameters is similar to that reported in previous works. Our results suggest a substantial level of differentiation in the microbial community structure, according to the management practices assessed, as has also been observed by other authors. These results corroborate the notion that the microbial community structure is a good indicator of soil quality, perturbations and the effects of different management practices, because the microorganisms respond against changes in soil management more rapidly than chemical or physical soil properties. The selected soil under wild forest coverage, not disturbed for long time, is used as high quality soil for reference,blueberry grow bag based on the fact that soils under wild and native vegetation that develop freely reach an equilibrium amongst their properties that leads to long-term stability.

The rest of treatments have been compared with this forest soil to assess which one supports a microbial community more similar to non-disturbed ecosystems, reference of high soil quality, since soil quality has been defined as “the capacity of a soil to function, within the limits imposed by the ecosystem, to preserve the biological productivity and environmental quality, and promote plant, animal and human health”. Since the WF system supports a more abundant and richer microbial community, those agroecosystems with more abundant and diverse community, are supposed to be indicative of increased soil quality. Increments in richness and biomass have been proposed as a basic objective in the management of degraded ecosystems. Multivariate analysis showed that the microbial community structures of the soil with wild forest coverage and the soil receiving oat straw treatment were influenced by soil organic matter content. Microorganisms likely responded to increases in organic matter levels in the soil, involving increases in carbon, aggregate stability, increases in the capacity for water retention and higher microbial activity. It is important to note that the microbial community structure in the OS treatment falls within the positive range of axis 1 in the RDA, similar to the soil under wild forest coverage. Thus, the application of organic residues is a suitable management practice that enhances organic matter, improves structure and increases microbial biomass and activity in soils. This practice also shifts soil microbial communities to respond to increases in organic carbon. The increment of fungal proportions is directly related to the microbial community composition in OS and WF soils, as fungal communities play a dominant role in fresh organic matter decomposition. The soil developed under wild forest coverage exhibited a community structure with higher values for both the C/N ratio and the metabolic quotient. This result may indicate a higher degree of stabilisation of soil organic matter, and microbial communities in this soil may need to use more recalcitrant carbon pools, compared to communities in the soil where oat straw was added, to remain at a steady state.

By contrast, the rest of the agricultural management practices shared a similar microbial community composition, bound to low contents of organic matter and characterised by low microbial size and activity and high proportions of bacteria and actinobacteria. found that the microbial community structure of abandoned agricultural lands was not explained by any physical or chemical soil property measured, suggesting that the abandonment of the perturbation caused by agricultural activity perse and the associated changes in vegetation rather than direct changes in soil properties led to shifts in the soil microbial community structure. In this study, we found that the qCO2 largely accounts for variation in LA soil microbial community structure, which may be related to differences in the quality of organic matter. Organic matter is more stabilised in LA than in the soils receiving other treatments, so microbial communities need to use more recalcitrant carbon pools to remain at a steady state. The high concentration of the fungal PLFA 18:1w9c within the LA system supports this hypothesis, as fungi use more recalcitrant sources of C than bacteria. Non-till management practices and the application of organic residues such as oat straw cause a consistent increase in the populations of fungi and Gram negative bacteria, and a significant decrease in the ratio of bacteria:fungi, as shown in previous reports. The relatively high fungi abundance in OS and LA plots, compared to the other treatments, renders the soils under these management practices more similar to the soil with wild forest coverage, as previously reported. Increments in the proportion of fungi are indicative of sustainable management practices since fungi are more sensitive to bacteria to perturbation. Apart from increases in organic matter, the lack of tillage has also likely contributed to increases in fungal populations because tillage promotes the breakage of hyphae. Bacteria are more abundant in the soils treated with herbicide and tillage, as they tend to dominate the decomposition and nutrient cycles in soils that are intensively managed, such as tilled, chemically fertilized, pesticides used, crop rotation, etc. The addition of herbicides can have toxic effects on microbial populations, thereby limiting the development of microorganisms. reported that repeated residual herbicide application significantly decreased microbial biomass carbon and fungal biomass, as shown in our results.

The carbon footprint is defined as a measurement of the total amount of carbon dioxide emission that is directly and indirectly caused by an activity or is accumulated over the lifetime of a product. Due to its impact on the environmental issues such as global warming, the carbon footprint is the hot topic in the field of environmental science. Virtual water trade refers to the hidden flow of water if food or other agricultural products are traded from one place to another. At the same time, virtual water is related to the carbon footprint directly and indirectly. Some studies have focused on the virtual water trade aiming to conserve water in the production of crops by increasing product export to areas with less water needs . In this effort, the research on virtual water of agricultural products has the potential to reduce economic costs, where water withdrawals may have greater impacts on water-lacking regions than on water-abundant regions. However,blueberry grow bag size few studies have analyzed the internal virtual water flow dynamics of the U.S. on a state or regional scale. And fewer have focused on the associated carbon footprint on a state or regional scale in the U.S. In this study, we calculated the carbon footprint of the exporting agricultural products of California to their destinations by firstly exploring the products’ water footprint. Previous virtual water quantification studies have identified the U.S. as the leading global virtual water exporter . Close examination indicates that California is the largest agricultural producer . Thus we hypothesize that California is the largest virtual water exporting state in the country. Accordingly we also hypothesize that California is releasing a great amount of carbon dioxide related to the embedded water of agricultural products. And in this research, we focus on the carbon footprint associated with energy cost by the embedded water in agricultural products exported from California to other regions of the world.Nowadays, carbon emission is a worldwide topic that hinders the development in many various sectors of human life. Every year, the United Nations would regulate the carbon budget for most of the countries. How to use the carbon budget efficiently is a mandatory issue to be managed. At the same time, water resources shortage is becoming an urgent problem all over the world, as energy deficiency is an equally critical problem. California is facing an unprecedented water crisis in history where water treatment is the largest energy use of the state taking up approximately 19 percent of the total annual electricity consumption . It will cost significant financial investment to keep the water supplies sufficient for next several decades. New regulations and court decisions have resulted in the reduction of water delivery from the Sacramento-San Joaquin Delta . In some areas of the state, the quantity of underground water and surface water supplies is experiencing rapid decrease .

The energy water relationship is particularly inseparable in the Southwestern arid and semi-arid regions of the United States, where significant amounts of energy are used to import water. California is exceptionally vulnerable because its water sector is the largest energy user in the state, estimated to account for 19 percent of the total electricity consumed annually . Another fact is that the annual water used in growing agricultural products in California is much greater than the total amount used by the other fields such as commercial and industrial applications . Less known is the amount of water embedded or embodied in agricultural products that are exported to other states and countries. For some certain kinds of agricultural products, California is dominating the supply of the whole U.S. market, such as almond, grape, strawberry, processed tomato, and lemon .Macrotunnel production has been increasing in coastal counties of California and is poised for expansion due to its recent adoption as a standard practice by the U.S. Department of Agriculture . In high tunnel production, crops are grown within plastic-covered structures to enhance crop performance, extend production seasons and to protect crop quality. While most caneberries, some strawberries, cut flowers, herbs and leafy greens are widely grown under plastic in California, contributing $1 billion to the state’s economy, in other states small fruits, melons and nuts are also grown in high tunnel systems. This interest in plasticulture tunnels is driven by many factors: increased production due to season expansion; reduced exposure to deleterious weather events; consumer demand for fresh, local produce; and national interest in reducing transportation-related greenhouse gas emissions, amongst other concerns. Unfortunately, it comes at a time when climate-induced weather pattern changes, particularly shorter-duration, higher-frequency storm events, are expected to become the norm . The plastic covering hoop structures can reduce the available permeable surface of a field’s production area by over 90%, which increases the volume of water likely to run off a field in a storm event . During rains, water intercepted by plastic covers is channeled into post rows , accelerating soil erosion, especially on slopes, which ultimately degrades surface water quality. In California, surface water quality is regulated by the State Water Resources Control Board through the Irrigated Lands Regulatory Program . To protect water quality, California regional water quality control boards have adopted different measures to regulate pollutants in water from agricultural operations, including implementation of best management practices . Typical pollutants in areas with exceedances of total maximum daily loads include nitrogen, sediment, phosphorus and pesticides, such as chlorpyrifos. Many surface water TMDL exceedances occur during the rainy season, indicating the need for practices that address storm water runoff. In some areas, management practices that reduce rain-induced leaching of soluble pollutants into groundwater may also be needed. In this project we compared treatment efficacies and costs of untreated tunnel post rows with rows treated under four different practices in plastic-covered raspberry operations at Somis and Santa Maria , California. Both sites were on moderate slopes , but the beds were planted on the contour to reduce runoff and were on a 1% slope at both sites. The post row treatments were selected based on previous work and potential feasibility for caneberry operations. Each treatment was applied to 6-foot-by-300-foot post rows in an experiment with randomized complete block design with three replications at both sites. Site conditions are described in table 1. The project focused on the rainy seasons of 2016–2017 and 2017–2018. The four treatments were as follows: A barley cover crop was seeded in 2016 at 500 pounds per acre with a seed spreader, lightly raked into the soil and established with sprinkler irrigation used for delivering overhead water to newly planted raspberry roots . At both locations we reseeded barley at the same rate during the second rainy period of the project to increase cover crop density in areas lacking ground cover.