José A. Gómez

Effects of tillage method on soil physical properties, infiltration and yield in an olive orchard

The long-term effects of two different tillage systems, conventional (CT) and no tillage (NT), were studied in an olive orchard in Santaella (Southern Spain) for 15 years. In both tillage systems, two distinct zones developed in the orchard in relation to soil physical properties; one underneath the tree canopy, and the other in the rows between trees. Surface soil organic matter content, bulk density, cone index, macroscopic capillary length and hydraulic conductivity showed significant differences between tillage systems and positions. After 15 years, the NT treatment achieved greater bulk density and cone index values than CT. This compaction reduced the infiltration rate of NT soil with respect to CT, particularly in the rows between trees. Despite that reduction, the NT soil retained a moderate infiltration potential. That may be explained by the high infiltration rates and macroporosity of the zone beneath the tree, the temporary effects of tillage on infiltration and probably by the self-repair of soil structure in the Vertisol studied. Yield was not affected by tillage except in one year with very low precipitation, where NT significantly yielded more than CT. The reduction in infiltration in NT must have been compensated by unknown factors that improve the tree water supply in drought years.

Sediment tracers in water erosion studies : current approaches and challenges

IntroductionInterest in the use of sediment tracers as a tool to complement traditional water erosion or deposition measurements has increased due to the additional information they provide, such as sediment source identification, tracking of sediment movement across the landscape at various temporal and spatial scales, and estimation of soil erosion rates. For these reasons, the utility and robustness of sediment tracing approaches using a wide range of substances and soil properties have been evaluated in numerous studies.ConclusionsA review of established tracing approaches identified five distinct groups of tracing approaches: fallout radionuclides, rare earth elements, soil magnetism and magnetic substances, other tracers, and sediment fingerprinting techniques. This paper describes the basic theory of each tracing approach in assessing soil erosion and sediment redistribution, describing their methodology and main applications, and summarizing the commonalities and differences between the approaches. It also identifies research gaps and future trends.

Analysis of sources of variability of runoff volume in a 40 plot experiment using a numerical model

Abstract Runoff volumes from field plots can be quite variable, but the reasons for this variability are not completely understood. Such variations can be important for understanding the hydrologic system, and for evaluating the effectiveness of infiltration, runoff and sediment models. In this study, we investigated the sources of variability among 40 replications in a previously reported experiment on fallow plots located on a claypan soil in Missouri, USA. A numerical model was calibrated using data from the experiment and from other published data on the variability of soil properties. The results describe qualitatively the trend in the observed relationship between the coefficient of variation (CV) and mean runoff volume per event, as well as the lack of stability in time of the relative differences in runoff volume among plots. Quantitatively, approximately 50% of the observed coefficients of variation among the replicated plots were explained by the spatial variability of Ks, surface storage, and the depth to claypan. The remaining 50% may be due to the variability in rainfall among plots, measurement error in runoff, the fact that some published rather than site specific information was used in the analyses, and simplifications introduced in the modeling process. Our results suggested that changes in the relative differences in runoff volumes between plots during the season might be explained by the modification of the spatial distribution of Ks and surface storage which occurs during tillage. The introduction of these sources of variability in the model formulation produced a realistic description of the variance of the observed values of runoff volume, as well as a relatively clear delineation between the explained and unexplained variability. The results may also serve as an index of model performance in predicting observed data.

Soil factors involved in the diversity and structure of soil bacterial communities in commercial organic olive orchards in Southern Spain

Nowadays, there is a tendency in olive production systems to reduce tillage or keep a vegetative cover to reduce soil erosion and degradation. However, there is scarce information on the effects of different soil management systems (SMS) in soil bacterial community composition of olive groves. In this study, we have evaluated the effects of soil type and different SMS implemented to control weeds in the structure and diversity of bacterial communities of 58 soils in the two geographic areas that best represent the organic olive production systems in Spain. Bacterial community composition assessed by frequency and intensity of occurrence of terminal restriction profiles (TRFs) derived from terminal restriction fragment length polymorphism (T-RFLP) analysis of amplified 16S ribosomal deoxyribonucleic acid were strongly correlated with soil type/field site (Eutric/Calcaric) that differed mainly in soil particle size distribution and soil pH, followed by a strong effect of SMS, in that order. Canonical discriminant (CD) analysis of TRFs properly classified all of the olive orchard soils as belonging to their respective soil type or SMS. Furthermore, only a small set of TRFs were enough to clearly and significantly differentiate soil samples according to soil type or SMS. Those specific TRFs could be used as bioindicators to assess the effect of changes in SMS aimed to enhance soil quality in olive production systems.

Curve Numbers for Olive Orchard Catchments: Case Study in Southern Spain

AbstractThe curve number (CN) method is widely applied around the world to estimate direct runoff and the corresponding hydrograph of a rainfall event. However, there is no information on its performance in olive orchards on the catchment scale. In this work, the CN method was applied in three small catchments in southern Spain with different soil types, topography, and management. A rainfall-runoff data set of six years was used to test the usefulness of the method and the accuracy of its reference parameterization (CNs) and of the initial abstraction (Ia). CN medians in the catchments were between 83 and 87. Classical equations based on the use of the 10th, 50th, and 90th CN percentiles for determining the antecedent moisture content (AMC) provided very good results in two of the catchments. In the third catchment, with the most arid hydrological pattern (annual rainfall <400  mm) and the most impervious areas of parental material, very poor performance was achieved. In addition, cumulative precipitatio...

Herbicide monitoring in soil, runoff waters and sediments in an olive orchard

Occurrences of surface water contamination by herbicides in areas where olive orchards are established reveal a need to understand soil processes affecting herbicide fate at field scale for this popular Mediterranean crop. A monitoring study with two herbicides (terbuthylazine and oxyfluorfen) in the first 2cm of soil, runoff waters, and sediments, was carried out after under natural rainfall conditions following winter herbicide application. At the end of the 107day field experiment, no residues of the soil applied terbuthylazine were recovered, whereas 42% of the oxyfluorfen applied remained in the top soil. Very low levels of both herbicides were measured in runoff waters; however, concentrations were slightly higher for terbuthylazine (0.53% of applied) than for oxyfluorfen (0.03% of applied), relating to their respective water solubilities. Congruent with soil residue data, 38.15% of the applied oxyfluorfen was found in runoff-sediment, compared to only 0.46% for terbuthylazine. Accordingly, the herbicide soil distribution coefficients measured within runoff field tanks was much greater for oxyfluorfen (Kd=3098) than for terbuthylazine (Kd=1.57). The herbicide oxyfluorfen is co-transported with sediment in runoff, remaining trapped and/or adsorbed to soil particle aggregates, due in part to its low water solubility. In contrast, terbuthylazine soil dissipation may be associated more so with leaching processes, favored by its high water solubility, low sorption, and slow degradation. By comparing these two herbicides, our results reaffirm the importance of herbicide physico-chemical properties in dictating their behavior in soil and also suggest that herbicides with low solubility, as seen in the case oxyfluorfen, remain susceptible to offsite transport associated with sediments.

Comment on "Rainfall erosivity in Europe" by Panagos et al. (Sci. Total Environ., 511, 801-814, 2015)

Recently a rainfall erosivity map has been published. We show that the values of this map contain considerable bias because (i) the temporal resolution of the rain data was insufficient, which likely underestimates rain erosivity by about 20%, (ii) no attempt had been included to account for the different time periods that were used for different countries, which can modify rain erosivity by more than 50%, (iii) and likely precipitation data had been used instead of rain data and thus rain erosivity is overestimated in areas with significant snowfall. Furthermore, the seasonal distribution of rain erosivity is not provided, which does not allow using the erosivity map for erosion prediction in many cases. Although a rain erosivity map for Europe would be highly desirable, we recommend using the national erosivity maps until these problems have been solved. Such maps are available for many European countries.

Rainfall erosion resistance and stability of various composts

Compost use in landscaping and erosion control applications has become widespread. Various types of composts have been utilized on highway embankments for soil conservation and runoff reduction. Different compost materials could have different erosion control effects. The objective of this study is to investigate the erosion resistance of three commonly used composts and their effects on slope stability. Bench-scale experiments were conducted to test the erosion of three natural base soils (sand, silt, and clayey sand). Rainfall simulators were constructed to simulate a rainfall intensity of 3.1 in h-1 (7.9 cm hr-1). Soil boxes were designed and built to simulate an inclined embankment. The soils were tested under one hour of rainfall. Significant soil solid losses—over 100 g (0.22 lb) on a 0.91 × 0.30 m (35.8 × 11.8 in) plot area—were observed in all base soil erosion tests, and the silt slope slid during the test. Repeated rainfall erosion tests were performed on the three base soils, respectively, with three types of compost covers (green compost, manure compost, and co-compost made of biosolid and green compost). Both manure compost and co-compost retained slope stability and reduced soil erosion. Green compost reduced solids loss of the silt and sand slopes, but it induced more solids loss of the clayey sand slope, which was stable without a compost cover. Mechanisms of the soil erosion of the three composts on the three base soils were investigated. It is concluded that different composts, when possessing different properties such as density, particle size distribution, and organic matter content, may vary significantly in erosion control resistance. An erodible compost cover can trigger the slope failure (sliding) of an embankment that is stable without a compost cover. Metal concentrations, biochemical oxygen demand, and coliform bacteria in the runoff were analyzed, and it was found that composts reduced the concentrations of some heavy metals in the runoff.

Effects of vegetation management intensity on biodiversity and ecosystem services in vineyards: A meta‐analysis

Abstract At the global scale, vineyards are usually managed intensively to optimize wine production without considering possible negative impacts on biodiversity and ecosystem services (ES) such as high soil erosion rates, degradation of soil fertility or contamination of groundwater. Winegrowers regulate competition for water and nutrients between the vines and inter‐row vegetation by tilling, mulching and/or herbicide application. Strategies for more sustainable viticulture recommend maintaining vegetation cover in inter‐rows, however, there is a lack of knowledge as to what extent this less intensive inter‐row management affects biodiversity and associated ES. We performed a hierarchical meta‐analysis to quantify the effects of extensive vineyard inter‐row vegetation management in comparison to more intensive management (like soil tillage or herbicide use) on biodiversity and ES from 74 studies covering four continents and 13 wine‐producing countries. Overall, extensive vegetation management increased above‐ and below‐ground biodiversity and ecosystem service provision by 20% in comparison to intensive management. Organic management together with management without herbicides showed a stronger positive effect on ES and biodiversity provision than inter‐row soil tillage. Soil loss parameters showed the largest positive response to inter‐row vegetation cover. The second highest positive response was observed for biodiversity variables, followed by carbon sequestration, pest control and soil fertility. We found no trade‐off between grape yield and quality vs. biodiversity or other ES. Synthesis and applications. Our meta‐analysis concludes that vegetation cover in inter‐rows contributes to biodiversity conservation and provides multiple ecosystem services. However, in drier climates grape yield might decrease without irrigation and careful vegetation management. Agri‐environmental policies should therefore focus on granting subsidies for the establishment of locally adapted diverse vegetation cover in vineyard inter‐rows. Future studies should focus on analysing the combined effects of local vineyard management and landscape composition and advance research in wine‐growing regions in Asia and in the southern hemisphere.

The Soil. Physical, Chemical and Biological Properties

This chapter provides a basic description of soil properties and processes, stressing the concept that the soil is a dynamic entity where complex interactions among its biological, chemical and physical components take place. All these components and properties determine the functioning of the soil for different purposes; this functioning is included in the concept of “soil quality”. One of the most used definitions of soil quality is the capacity of a soil to function within ecosystem boundaries to sustain biological productivity, maintain environmental quality, and promote plant and animal health (https://www.soils.org/publications/soils-glossary). Land use and management can have a profound impact on many soil properties, thus indirectly affecting soil quality which can result in improvements or constraints for productivity of agricultural lands and for agricultural sustainability in the long term.