Displays

The characterization of spatial variations in soil properties and crop performance within precision agriculture, and particularly the delineation of management zones (MZ) and sampling schemes, are complex assignments currently far from being resolved. Considerable advances have been achieved regarding the analysis of spatial data, but less attention has been devoted to assess the temporal asymmetry associated with variable crop×year interactions. In this case-study of a 9 ha field located in Spain, we captured interactions between both spatial and temporal variations for two contrasting seasons of remotely sensed crop data (NDVI) combined with several geomorphological properties (i.e., elevation, slope orientation, soil apparent electrical conductivity - ECa, %Clay, %Sand, pH). We developed an algorithm combining Principal Component Analysis (PCA) and clustering k-means and succeeded to delineate four MZ’s with a satisfactory fragmentation degree, each one associated with a different Elevation×ECa×NDVI combination. Simulated yield maps were generated using NDVI maps correlated to ground cover to establish initial conditions in simulation settings with a crop model. Yield maps were spatially correlated but fitted into variograms with irregular spatial structure. Both CV and spatial patterns did not show consistency from year to year. The results indicate that MZ’s temporal instability is an important issue for site-specific management as agronomic implications varied greatly with crop×year setting. We observed differences, not only regarding NDVI patterns but also in yield response to the combination of Elevation×ECa (and Texture) depending on the seasonal rainfall. A reduction of 14% of the ’Goodness of Variance Fit’ was observed for simulated yield from the first to the second crop×year, highlighting the difficulties in the delineation of MZ’s with persistent confidence. The interpretation of MZ×Yield associations was not straight forward from the metrics selected here as it also depended on agronomic knowledge. We believe that precision agriculture will benefit greatly from improved protocols for MZ delineation and sampling schemes. However, the uncertainty associated with temporal asymmetry of yield clustering and MZ’s interpretation reveals that ‘automated digital agricultural systems’ are still far from reality.

How to cite: Tenreiro, T. R., García-Vila, M., Gómez, J. A., and Fereres, E.: Uncertainties associated with the delineation of management zones in precision agriculture, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5709, https://doi.org/10.5194/egusphere-egu2020-5709, 2020.

Topsoils on the arable fields are usually considered as spatially uniform layers, especially just after the cultivation when the seedbed conditions are present. Nevertheless, there are features, resulting from the agricultural machinery operations or memory effects from the previous growing season, that cause spatially non-uniform soil infiltration characteristics even on a small scale. Examples of such features are the wheel tracks, wrinkles from the ploughing or the non-uniform morphology of the compacted subsoil. Surface runoff and soil loss are affected by the direction of the agro-operations. Wheel tracks act as an obstacle for the surface flow if the orientation is perpendicular to the slope and as the main draining flow path if the orientation is in slope wise direction. Ploughing changes the soil structure in the shallow part of the soil profile, creates sharp delineation between topsoil and compacted subsoil and subsequently alters the natural infiltration and may create lateral subsurface runoff. Plot scale artificial rainfall / runoff experiments were designed to study the ploughing and wheel track compaction effect on the surface runoff and soil loss. Several experiments were carried out at mildly declined slopes (slope ca 10 %) at 16 m2 plots located at an experimental site in the central part of the Czech Republic utilizing Norton Ladder Rainfall Simulator. Experiments were replicated at (1) a plot without wheel track (noWT), (2) a plot with wheel track oriented slope wise (swWT) and (3) a plot with wheel track oriented perpendicularly to the slope (psWT). Artificial rainfall experiments were supplemented with a detailed soil water regime monitoring, geophysical measurement and measurement of penetration resistance. Wheel track at the swWT plot caused faster runoff and soil loss response to the rainfall and increased the total runoff volume and soil loss mass. Wheel track at the psWT plot disconnected the upper and lower part of the plot. The psWT plot was entirely connected when surface depressions were connected which increased the time lag of the runoff and soil loss response. It was concluded that the surface topography and possibly impact of raindrops are the first order control factors of the surface runoff and soil loss formation. Filling and consequent interconnection of the surface depressions together, to the bottom of the plot or to the wheel track, triggers the surface runoff and soil loss. The compacted subsoil, which exhibited high penetration resistance and electrical resistivity, did not exhibit any lateral subsurface runoff in the shallow soil profile suggesting high hydraulic conductivity of both the topsoil and the subsoil when the soil is fully saturated. The experiments were carried out within a scope of projects 773903 “SHui - Soil Hydrology research platform underpinning innovation to manage water scarcity in European and Chinese cropping systems” and LTC18030  “The effect of land-use changes on soil erosion, sediment transport, water quality and rainfall-runoff balance”.

How to cite: Zumr, D., Jeřábek, J., Krása, J., and Dostál, T.: Plot-scale experiments to assess the effects of surface spatial heterogeneity on runoff and soil loss, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7424, https://doi.org/10.5194/egusphere-egu2020-7424, 2020.

Gully erosion is a soil degradation process widely present across the world. Permanent gully erosion has usually soil erosion rates one order of magnitude higher than hillslope water erosion in conventional agriculture, e.g. 2.1 vs 0.6 mm year^-1 (Castillo and Gómez, 2016). It remains a major process of soil degradation worldwide.

This work attempts to investigate recent trends of published research on gully erosion in relation to gully erosion control since 2000. A review in Web of Science (core collection, 2000-19 by title) reported 401 documents, produced mainly in the European Union (52.1%), China (22.7%), USA (16.0%) and Australia (8.7%). Approximately 17% of all these articles covered restoration or control of gully erosion as their main topic. When screened most of these 68 articles deal with specific situations and techniques with a limited number devoted to a comparative review of effectiveness of different techniques, one of the few exceptions was Liu et al. (2019a). To provide perspective, there were a similar proportion of articles devoted to the study of gully erosion processes, a and a much larger number of articles devoted to the description of gully development and erosion rates in specific situations. It is apparent that the subject of gully erosion control is not a dominant one in the scientific indexed literature. This review was complemented with an analysis in WOCAT (WOCAT, 2019), a comprehensive international databases of soil conservation technologies. It showed with 27 entries of gully erosion restoration techniques over a total of 1098 descriptions (2.5% approximately). This might be explained, partially, because most of the information on gully erosion control appears in documents outside scientific, or technical, international databases, many times in local languages. Overall, two of the major barriers frequently noted by stakeholders, particularly farmers, for effective gully erosion control, their high costs and the complexity of controlling expansion of very large gullies (e.g. Liu et al.2019b) are not major major subjects  in the international scientific literature on gullies in the last decades.

It is apparent that there is the need for a more comprehensive comparative analysis of the effectiveness and cost of different strategies of gully erosion control techniques, particularly oriented to reduce the investment cost of their implementation, especially in very large gullies where compex slope instability processes might play a dominant role. This communication presents a comprehensive analysis on the available information on international scientific literature on gully erosion research to suggest key lines and strategies for future research.

References

Castillo, C., Gómez, J.A. 2016 A century of gully erosion research: Urgency, complexity and study approaches Earth-Science Reviews 160: 300–319

Liu, X., et al. 2019a. Gully Erosion Control Practices in Northeast China: A Review. Sustainability 11: 5065, doi:10.3390/su11185065

Liu, H., et al. 2019b. Using 3D scanner to study gully evolution and its hydrological analysis in the deep weathering of southern China. Catena 183. https://doi.org/10.1016/j.catena.2019.104218

WOCAT. 2020. World Overview of Conservation Approaches and Technologies. https://www.wocat.net/en/

How to cite: Gomez, J. A., Zhao, G., Liu, H., Yang, Y., Lopez, J., and Xie, Y.: Research challenges on gully erosion control in EU and China, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7888, https://doi.org/10.5194/egusphere-egu2020-7888, 2020.

Knowledge and quantification of water fluxes within the soil-vegetation-atmosphere continuum is fundamental to understand ecohydrological systems. It is also essential to further develop water management practices and irrigation systems in times of increasing needs for water and rising water scarcity. A major component in this regard is evapotranspiration (ET) as it links the energy balance and the water balance. Evapotranspiration can be fractionated into productive water fluxes through plants’ stomata (transpiration) and non-productive water loss from soil surface (evaporation). Determination and understanding of factors influencing this ratio are assumed to help improving water use efficiency through best management practices in agriculture, especially in water limited environments. Aim of this study was to adapt a stable isotope mass balance method for determining evapotranspiration and its components transpiration and evaporation for soybeans under natural conditions.

The study site was in Groß-Enzersdorf, east of Vienna, Austria (48°12’ N, 16°34’ E; 157 m elevation a.s.l.). The study period covered the vegetation period of soybeans in 2019. Crop evapotranspiration was determined using a weighing lysimeter with 1.8 m diameter. For the fractionation, a stable isotope mass balance method from literature was adapted and further developed for soybeans under natural (stressed) climatic conditions. The underlying principle of isotope fractionation is that different physical properties of naturally occurring stable isotopes in water cause shifts in the isotopic composition due to evaporation. Therefore, evaporation causes enrichment of heavier stable isotopes in the near surface soil water, whereas water uptake by plant roots does not cause considerable partitioning in soil water. This allows determination of both fractions, assuming all other water balance components are known. Soil samples for the stable isotope mass balance were taken near a weighing lysimeter (1.8 m diameter). Evapotranspiration determined by the lysimeter provided the basis for the mass balance fractionation calculations. Monitoring throughout the soybeans vegetation period included weekly analyses of isotopic composition of soil samples, measurements of water content over the soil profile in 10 cm steps down to 80 cm, weather data, and crop growing stages.

Results reveal a plausible course of soybean evapotranspiration and its components. The preliminary designed method of soil water sampling could be adequately adapted to determine representative isotopic soil profiles for water balance determination under the given conditions. Water extraction from the soil samples worked well under moist as well as very dry soil conditions. Further data analysis was done to assess applicability of the modified method to determine fractionation ratios for different plant development stages. The available results encourage further experiments to test and investigate the versatility of this method with respect to different soil cultivation methods for a water use efficiency review.

How to cite: Liebhard, G., Klik, A., Strauß, P., and Nolz, R.: Partitioning evapotranspiration into transpiration and evaporation by use of isotope balance calculation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8805, https://doi.org/10.5194/egusphere-egu2020-8805, 2020.

AquaCrop is considered a reliable simulation model to predict crop yield. AquaCrop is supported by the FAO and seems to provide reasonable balance between accuracy and simplicity. While AquaCrop handles crop response to conditions of salinity, there have been few studies evaluating its accuracy to this parameter. We evaluated AquaCrop for its ability to simulate crop growth, transpiration and yield under conditions of irrigation-induced salinity using an experimental database of tomato grown during different meteorological conditions and demands under highly varied conditions of irrigation water salinity and irrigation amounts.

Field and lysimeter experiments were carried out in the Southern Arava Valley in Israel in fall and spring seasons. Tomato (Lycopersicon esculentum Mill. cultivar ‘5656’) was grown. Irrigation in the field was managed with treatments of 30, 60, 100, and 130% of reference evapotranspiration (ET₀) of Class A pan with irrigation water salinity (EC_I = electrical conductivity of irrigation water) of 3 dS m^-1. Irrigation treatments in the lysimeters were six EC_I levels from 1 to 11 dS m^-1 all at 130% of ET₀ and five irrigation levels of 30, 60, 100, 130 and 160 % of ET₀ all at EC_I of 3 dS m^-1. EC_I was regulated adding 1:1 Molar concentrations NaCl and CaCl₂. Irrigation was applied via drippers from soil surface covered with polyethylene mulch to reduce evaporative losses to a minimum. AquaCrop was run to calculate yield and transpiration in fall and spring. The datasets of meteorological, crop, management, and soil data were obtained from field-measured results.

Predicted biomass at the end of both growing periods agreed relatively well with measured biomass. Patterns of accumulated transpiration were different in the two seasons, with gradual increase to a stable maximum in the fall and continued increase in the spring. Irrigation level and salinity were found to effect biomass, transpiration and yield alternatively, with irrigation dominant at low EC_I levels and salinity dominant when irrigation application was relatively high. Transpiration was simulated well, showing similar trends of the measured data in lysimeters in both fall and spring. The biomass in fall and spring was predicted relatively well. Following these results, AquaCrop appears applicable for simulation of salinity effects on yield and transpiration, at least under conditions similar to those of the current study.

How to cite: Ito, Y. and Ben-Gal, A.: Evaluating AquaCrop for simulating response of tomato to irrigation induced salinity, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9459, https://doi.org/10.5194/egusphere-egu2020-9459, 2020.

In last decades several trends have been visible in agricultural land use in the Czech Republic. Among all oil rape production was raised (mainly in last 10 years) and maize production was enlarged in some regions where bio-fuel stations have been newly built. As a row crop, maize without proper management control leads to accelerated water erosion and sediment transport. Oil rape is generally considered as a relatively soil preserving crop, supporting also infiltration by a root system. But seeding period of oil rape in the Czech Republic starts in August still in the peak period of erosive rainstorms. Recent risks associated with both crops will be presented by data from field rainfall-runoff simulations, targeted on developing actual crop protection factor (C-factor) of USLE for Czech conditions. The second source of the data for presenting risk trends is Czech soil erosion monitoring database of State Land Office (https://me.vumop.cz/), where many occurrences of erosion damages were identified on both crops. Finally, study focused on bare soil remote sensing via Landsat 8 and Sentinel 2 in recent years showed link between erosion risks and the two above mentioned crops.

National implementation of European cross compliance policy in the Czech Republic targeted the protection also to fight these risky trends, but the power of the agricultural policy, as will be presented, is limited in this scope. We see similar threats in other European countries and we were able to visit North East China regions with intensive corn production where soil erosion by water is causing serious soil and water degradation. Therefore, shared knowledge on strategies how to prevent risky soil managements could lead to benefits in both European and Chinese conditions.

The contribution was prepared in the frame of projects No. QK1920224 (Possibilities of anti-erosion protection on farms to avoid the use of glyphosate), and H2020 SHUi (Soil Hydrology research platform underpinning innovation to manage water scarcity in European and Chinese cropping systems).

How to cite: Krasa, J., Dostal, T., Zumr, D., Tejkl, A., and Bauer, M.: Recent trends in crop rotation in the Czech Republic and associated soil erosion risks, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10964, https://doi.org/10.5194/egusphere-egu2020-10964, 2020.

In arid and semi-arid regions, restriction on water for agriculture is fostering the search of alternative water resources, such as the reuse of reclaimed water (RW), and water-saving techniques, such as regulated deficit irrigation (RDI) strategies to cope with forecasted food production requirements. Two long-term experiments carried out by the CEBAS-CSIC team offer two scenarios: 1) Intensive cultivation of citrus in coastal areas and 2) extensive grape production for wine making in inland areas of Spain. Experiments in the Murcia Region (Spain) studied the physiological and agronomic effects of irrigating a young commercial grapefruit orchard with two water sources (saline RW versus conventional water). Water transferred from an irrigation canal (TW; electrical conductivity, EC≈1.3 dS m⁻¹) and RW from a wastewater treatment plant (EC≈3.0 dS m⁻¹) were compared, with control irrigation supplying 100% of the crop evapotranspiration (ETc) while the RDI treatment was irrigated at 50% of ETc during the 2^nd stage of fruit growth Although the RDI treatment decreased annual irrigation volume by 13.2%, soil salinity substantially increased in summer in the RDI treatment While these treatments did not negatively affect vegetative growth, yield and fruit quality, trial duration (2008-2010) was short in relation to the commercial life of a citrus grove, requiring further research over a longer term. This highlights the need for a longer-term socio-economic analysis that is possible within projects of SHui’s duration (2018-2021). In grapevines research initiated in 2012 continues within SHui, to explore the effects of applying two different strategies: a) RDI in comparison with rainfed conditions and a full irrigation control. During the first three seasons (2012-2014), SDI was the preferred strategy to substantially improve yield (by 49%) compared to the rainfed regime, thereby significantly increasing water use efficiency (calculated considering both precipitation and irrigation). However, yield increments at 100% ETc were offset by detrimental effects that full irrigation had on grape composition. In this case, 8 years of these irrigation treatments produced similar results to the first three seasons of water application, suggesting cost benefit analyses of different deficit irrigation treatments over 3 may provide useful results to inform farmer choice

How to cite: Intrigliolo, D., Nicolas, E., Pedrero, F., Nortes, P., and Alarcón, J. J.: Deficit irrigation and the reuse of reclaimed water as strategies to cope with water scarcity in perennial crops. A summary of long-term trials within the H2020 SHUI project, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21244, https://doi.org/10.5194/egusphere-egu2020-21244, 2020.

Aiming to evaluate the effect of agricultural management practices in the environmental footprint, this study develops scenarios of future farm and soil management systems for improved productivity and enhanced soil quality. The analysis is at the continental scale in Europe and China. The evaluation has two components: (1) A multi-actor approach is used to develop the policy scenarios; and (2) An upscalling model is used to evaluate the effect of the scenarios at the continental scale. The results are presented in a series of maps with a 10 x 10 km resolutions, that allow comparison of strategies relevant to agricultural policy development. Three scenarios are evaluated: The Expected scenario maintains the observed tendency in the implementation of beneficial agricultural management practices. The Regional Targets assumes the same rate of implementation of agricultural management practices, but considers that policy efforts are focused on areas where soil threats are more active and soil quality indicators are poorer. The emphasis, therefore, is place on targeting the regions that where the practices would be more beneficial. The Towards 2050 scenario assumes an intensification on the rate of implementation of agricultural management practices as a result of public policies. The scenarios are necessarily a simplification of the complex policy processes that influences farmer choices at the local and regional levels. The content of the study is based on the results of the iSQAPER (http://www.isqaper-project.eu/) H2020 project.

How to cite: Martín-Candilejo, A., Santillan, D., Garrote, L., and Iglesias, A.: Policy scenarios for agriculture that enhance soil ecosystem services in Europe and China, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21825, https://doi.org/10.5194/egusphere-egu2020-21825, 2020.

SEW-REAP (Addressing food Security, Environmental stress and Water by promoting multidisciplinary Research EU And China Partnerships in science and business) was a European Union funded project (2016-2019) that placed European environmental researchers at Chinese institutions, in contrast to the more typical model of China Scholarship Council-funded visits of Chinese PhD students to the EU. These EU students were registered for their PhDs in European institutions, but conducted most of their research (18-24 months) in China. Since Chinese government policy is to become more self-sufficient in soya (Glycine max) production, and this crop provides a well-studied model system with significant genomic resources, two European students (PC and PMM) investigated variation in environmental stress responses (water deficit and phosphorus deficiency respectively) of diverse Chinese soya germplasm. PC identified significant variation in soya stomatal sensitivity to drying soil, which was related to variation in root-shoot signalling of the stress hormone ABA. PMM identified significant variation in soya root growth sensitivity to lack of phosphorus, which was related to variation in root accumulation of the stress hormone ABA. Whether variation in stomatal closure affects phosphorus transport to the shoot, and whether phosphorus-mediated changes in root growth affect root-to-shoot signalling of water deficit, needs to be investigated as different genotypic strategies may have antagonistic or complementary effects in multi-stress environments. Regardless of the physiological mechanisms involved in plant responses, SEW-REAP early career researchers have accessed complementary expertise across two continents to embrace a unique training opportunity and develop new scientific networks.

How to cite: Dodd, I., Castro, P., Martinez-Melgarejo, P., Perez-Alfocea, F., Tian, J., Lam, H.-M., Zhang, J., and Tyfield, D.: SEW-REAP: planting the seeds of early career soil-soya research in China, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21981, https://doi.org/10.5194/egusphere-egu2020-21981, 2020.