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The transferability of excess wasted organic materials, such as agricultural and forestry residues into materials like biochar and compost, to be used as a nutrient-rich organic soil amendment for food production has been viewed as an ecological approach to enhance soil ecosystem services. In this dissertation a variety of research techniques and experiments were used to investigate the effects of different locally produced biochar and also biochar dairy manure co-composts on soil hydrological properties, GHG emissions, nitrogen leaching, and crop productivity. The dissertation is divided into three main research chapters. In the first chapter, we generated moisture retention curves for seven biochar derived from wasted orchard materials e.g. almond shell, walnut shell, and almond pruning, using a mobile pyrolizer unit. More specifically, we used the water sorption film approach to determine specific surface area for the different biochar and incorporated the data into a model to assess its influence on soil moisture content. Additionally, three of the biochar (one from each feedstock) were also selected and used in two 109 days incubation studies to investigate biochar influence on soil respiration under different moisture levels. In the second chapter, numerical simulation was performed (5-years impact) on the three selected biochar to assess its impacts on soil hydrological properties and plant uptake dynamic for common cropping systems with dissimilar irrigation practices. Lastly, in the third chapter the three selected biochar were co-composted with fresh dairy manure for 45 days then used as soil amendment in a 133 day outdoor soil-tomato column study. Leaf chlorophyll content, canopy coverage, and GHG measurements were taken throughout the season as proxy for crop productivity and soil emissions as influenced by soil treatments. Results from chapter one show that walnut shell biochar has the greatest surface area while almond shell derived biochar has the most positive effect on moisture retention and soil respiration. Next, our 5-years numerical simulation shows that application of biochar at 5% enhanced water conservation by reducing seasonal soil evaporation loss and allowing for more root water uptake. However this positive effect varied between cropping systems and is substantially greater in the rainfed compared to irrigated system. In the last chapter, results from our soil-tomato study show greater positive effect on soil ecosystem services e.g. nitrogen retention and crop productivity, from biochar-dairy manure co-compost soil treatments compared to the control. However crop yield was constrained by external factors such as plant water stress.

Progress in sensor technologies has allowed real-time monitoring of soil water. It is a challenge to model soil water content based on remote sensing data. Here, we retrieved and modeled surface soil moisture (SSM) at the U.S. Climate Reference Network (USCRN) stations using Sentinel-1 backscatter data from 2016 to 2018 and ancillary data. Empirical machine learning models were established between soil water content measured at the USCRN stations with Sentinel-1 data from 2016 to 2017, the National Land Cover Dataset, terrain parameters, and Polaris soil data, and were evaluated in 2018 at the same USCRN stations. The Cubist model performed better than the multiple linear regression (MLR) and Random Forest (RF) model (R2 = 0.68 and RMSE = 0.06 m3 m-3 for validation). The Cubist model performed best in Shrub/Scrub, followed by Herbaceous and Cultivated Crops but poorly in Hay/Pasture. The success of SSM retrieval was mostly attributed to soil properties, followed by Sentinel-1 backscatter data, terrain parameters, and land cover. The approach shows the potential for retrieving SSM using Sentinel-1 data in a combination of high-resolution ancillary data across the conterminous United States (CONUS). Future work is required to improve the model performance by including more SSM network measurements, assimilating Sentinel-1 data with other microwave, optical and thermal remote sensing products. There is also a need to improve the spatial resolution and accuracy of land surface parameter products (e.g., soil properties and terrain parameters) at the regional and global scales.

Poor soil fertility status due to erosion, intensive farming, and leaching of nutrients causes food insecurity in Ethiopia. Hence, estimating soil fertility status using different measurements is very essential to secure food insecurity. The aim of this study was to determine the effects of land management on soil fertility using a nutrient balance approach at Kecha and Laguna micro watersheds in 2016. Plant nutrient losses were estimated through measuring discharge and sediment loads coming from the treated (Kecha) and untreated (Laguna) catchments. A total of 40 bulk sediment and water samples were collected on a monthly basis. The inputs used in the two catchments, inorganic fertilizer and organic manure, were quantified through interviews using a semi-structured questionnaire. Plant samples were collected from 92 plots for determining grain yield (OUT1) and straw biomass (OUT2). Other inputs and outputs were calculated using a transfer function. From sediment, grain and straw samples, NPK contents were determined. The nutrient balances were found to be −89.37, −23.66 and −124.75 NPK kg/ha, and −112.41, −20.62 and −130.26 NPK for Kecha and Laguna, respectively. The main paths for these negative balances were residue removal and soil losses. Higher nutrient losses were observed in Laguna than Kecha watershed; this may be due to lack of soil management practices, crop rotation and planting of leguminous plants. Therefore, soil management practices should be done to reduce these higher losses of plant nutrients, and maintain crop residues in the farm so that nutrient recycling and better soil fertility can be achieved.

Soil erosion is affected by rainfall temporal patterns and intensity variability. In vineyards, machine traffic is implemented with particular intensity from late spring to harvest, and it is responsible for soil compaction, which likely affects soil hydraulic properties, runoff, and soil erosion. Additionally, the hydraulic and physical properties of soil are highly influenced by vineyards&rsquo, inter-rows soil management. The effects on soil compaction and both hydrological and erosional processes of machine traffic were investigated on a sloping vineyard with different inter-row soil managements (tillage and permanent grass cover) in the Alto Monferrato area (Piedmont, NW Italy). During the investigation (November 2016&ndash, October 2018), soil water content, rainfall, runoff, and soil erosion were continuously monitored. Field-saturated hydraulic conductivity, soil penetration resistance, and bulk density were recorded periodically in portions of inter-rows affected and not affected by the machine traffic. Very different yearly precipitation characterized the observed period, leading to higher bulk density and lower infiltration rates in the wetter year, especially in the tilled vineyard, whereas soil penetration resistance was generally higher in the grassed plot and in drier conditions. In the wet year, management with grass cover considerably reduced runoff (&minus, 76%) and soil loss (&minus, 83%) compared to tillage and in the dry season. Those results highlight the need to limit the tractor traffic, in order to reduce negative effects due to soil compaction, especially in tilled inter-rows.

Erosional processes are highly affected by seasonal climatic fluctuations and soil management practices. Controlled grass cover is one of the most used soil conservation practices adopted in temperate climates, even if the protective effect of grass cover may decrease according to seasonal pattern. This technique is effective and, thus, widely adopted in the inter-rows of orchards such as olives, citrus or vineyards. This study reports the erosive events recorded in two different rain-fed hillslope vineyards with different rows orientation located in the Monferrato region, NW Italy. The study is addressed at compare the effects of different inter-row managements and rainfall characteristics on runoff and soil loss in hillslope vineyards (average slope from 15% to 35%). Rainfall, runoff and erosion variables were monitored in hydraulically bounded vineyard plots, where the inter-rows were managed with tillage and grass cover. Seventy-two erosive events were recorded in the period 1992–1996 in two vineyard plots with rows along the contour lines while 86 erosive events were recorded in two plots with rows up-and-down the slope from 2000 to 2014 (158 erosive events and four plots in total). Events were classified according to rainfall characteristics as “long-lasting”, “intense” and “normal”. In plots with rows along the contour lines, “intense” events were responsible for the highest mean soil loss in tilled plots (0.7 Mg ha−1) with very high erosion rates (12.3 Mg ha−1) observed during a single storm. In plots with rows up-and-down the slope the highest erosion rates, 21.2 and 3.4 Mg ha−1, were recorded during fall “long-lasting” events in the tilled and grass cover plots respectively. The grass cover proved to be effective in decreasing runoff and soil losses during most of the events (at least 68% and 61% of the occurrences, respectively) reducing soil losses especially during summer storms when most of the “intense” events occured. Furthermore, the results show the fundamental role of contour-slope row orientation in reducing runoff and soil losses, disregarding the inter-rows soil management that is adopted.

The definitive version is available at: http://www.sciencedirect.com/science/journal/01671987, In Central Aragon, winter cereal is sown in the autumn (November–December), commonly after a 16–18 months fallow period aimed at conserving soil water. This paper uses the Simple Soil–Plant–Atmosphere Transfer (SiSPAT) model, in conjunction with field data, to study the effect of long fallowing on the soil water balance under three tillage management systems (conventional tillage, CT; reduced tillage, RT; and no-tillage, NT). This was on the assumption that soil properties would remain unchanged during the entire fallow season. Once the model was validated with data obtained before primary tillage implementation, the differences between simulated and observed soil water losses for the CT and RT treatments could be interpreted as the direct effect of the soil tillage system. The model was calibrated and validated in a long-term tillage experiment using data from three contrasting long-fallow seasons over the period 1999–2002, where special attention was paid to predicting soil hydraulic properties in the pre-tillage conditions. The capacity of the model to simulate the soil water balance and its components over long fallowing was demonstrated. Both the fallow rainfall pattern and the tillage management system affected the soil water budget and components predicted by the model. The model predicted that about 81% of fallow seasonal rainfall is lost by evaporation in long-fallow periods with both a dry autumn in the first year of fallow and a rainfall above normal in spring. Whereas, when the fallow season is characterised by a wet autumn during the first year of fallow the model predicted a decrease in soil water evaporation and an increase in water storage and deep drainage components. In this case, the predicted water lost by evaporation was higher under NT (64%) than under RT (56%) and CT (44%). The comparison between measured and simulated soil water loss showed that the practice of tillage decreased soil water conservation in the short term. The long-term analysis of the soil water balance showed that, in fallow periods with a wet autumn during the first year of fallow, the soil water loss measured under CT and RT was moderately greater than that predicted by the model., This research was supported by the Comisión Interministerial de Ciencia y Tecnología of Spain (grants AGF98-0261-CO2-02 and AGL2001-2238-CO2-01 and PNFPI pre-doctoral fellowship awarded to the first author) and the European Union (FEDER funds).