597 research outputs found
No-till durum wheat yield success probability in semi arid climate : A methodological framework
No full textThe aim of this study is to develop a framework for the evaluation of no-till (NT) yield success probability as a decision tool for farmers or decision makers. The effect of soil management on durum wheat yield has been tested on many long-term field experiments. Results of these researches were collected in a unique dataset to evaluate the success of NT management in comparison to conventional tillage (CT) as influenced by the aridity index, crop residue management and cropping system. A total of 519 observations of long-term experiments (>3years) regarding durum wheat in a number of areas with semi arid climate were included in the present study. The relative ratio of yield under NT and CT was correlated to the aridity index (Ai) for different cropping systems and residue management strategies. No-till performed better with lower values of the Ai. When NT and CT yields were the same, the Ai value was defined as the Ai threshold, and this value resulted as being strongly dependent upon crop management. The developed framework, in any given site, allows us (i) to know the threshold for different managements tecniques, (ii) to estimate the probability of success in adopting NT and CT soil management techniques; (iii) to predict the best management with reference to Ai variation
Soilwater conservation : Dynamics and impact
No full textHuman needs like food and clean water are directly related to good maintenance of healthy and productive soils. A good understanding of human impact on the natural environment is therefore necessary to preserve and manage soil and water resources. This knowledge is particularly important in semi-arid and arid regions, where the increasing demands on limited water supplies require urgent efforts to improve water quality and water use efficiency. It is important to keep in mind that both soil and water are limited resources. Thus, wise use of these natural resources is a fundamental prerequisite for the sustainability of human societies. This Special Issue collects 15 original contributions addressing the state of the art of soil and water conservation research. Contributions cover a wide range of topics, including (1) recovery of soil hydraulic properties; (2) erosion risk; (3) novel modeling, monitoring and experimental approaches for soil hydraulic characterization; (4) improvement of crop yields; (5) water availability; and (6) soil salinity. The collection of manuscripts presented in this Special Issue provides more insights into conservation strategies for effective and sustainable soil and water management
Coping with drought for food security in Tigray, Ethiopia
No full text Agricultural production in drylands suffers from drought and in sub-Saharan Africa, only about 15% of the terrestrial rainwater is used by plants for food, fodder and fiber. Drought was the major cause of crop failure and food insecurity for the last three decades in the semi-arid northern Ethiopia. Information from field experiments, farmers and FAO’s AquaCrop model were used to understand and evaluate characteristics of the local climate in relation to drought and its mitigation. Farmers often have a different perception of drought than scientists. This gap was solved with an improved analysis of rainfall data that focuses on drought. Drought in semi-arid north Ethiopia can be due to (1) a too short growing season due to late start and/or early cessation of rains, (2) a too long dry spell at critical growth stage or (3) due to total failure of rain. Different types of drought have different coping strategies. Coping strategies for drought are adaption of sowing date, in-situ water conservation and water harvesting for deficient irrigation. Physical water conservation structures need to account for extreme variations in rainfall typical for most drylands. Ridging is most promising while mulching is no longer promoted. Agronomic measures such as the use of quick maturing and drought resistant crops are often more attainable than adoption of water conservation practices. Crop failure is often more due to water scarcity than to lack of fertility. However, when agricultural production increases, water and nutrients often alternate as production limiting factors. The strong water-nutrient synergy in drylands requires precision fertilization and plant density adjustment. Farmers also have a different opinion about climate change; farmers’ climate change has more to do with desertification. Experimental results showed that drought alleviation strategies have the potential to reduce the risk of crop failure and drought in the semi-arid northern Ethiopia.</p
Testing simple scaling in soil erosion processes at plot scale
No full textExplaining scale effects for runoff and erosion improves our understanding and simulation ability of hydrological and erosion processes. In this paper, plot scale effects on event runoff per unit area (Qe), sediment concentration (Ce) and soil loss per unit area (SLe) were checked at El Teularet-Sierra de Enguera experimental site in Eastern Spain. The measurements were carried out for 31 events occurring in the years 2005 and 2007 in bare ploughed plots ranging from 1 to 48 m2. The analysis established the scaling relationship by dimensional analysis and self-similarity theory, and tested this relationship at different temporal scales ranging from event to annual scale. The dimensional analysis and the incomplete self-similarity condition allowed us to establish a power scaling relationship which was found to also be usable for the moments of k (1, 2, 3, 4) order. The power scaling relationship was theoretically deduced applying a boundary condition which is based on the hypothesis that sediment delivery processes do not occur at the selected plot scale. The simple scaling invariance condition was always verified (i.e. for each temporal horizon) for runoff and soil loss while the same hypothesis was not perfectly acceptable for sediment concentration. The analysis of the scaling relationships at event temporal scale showed that the spatial scale effects were less frequent for the composite variable (soil loss = sediment concentration × runoff) than the constituting variables. For 48% of the events, a statistically significant scale effect was detected for all tested variables. With reference to the statistically significant relationships, both runoff and soil loss always decreased and sediment concentration always increased in the passage from the reference area (1 m2) to the largest one (48 m2). The analysis at aggregated temporal scales suggested that annual scale effects for soil loss per unit area should be temporally more stable than those for both runoff and sediment concentration. Finally, at mean event scale the three investigated variables have a similar behaviour in terms of simple scaling invariance
Interplay between river dynamics and international borders: The Hirmand River between Iran and Afghanistan
No full textFluvial dynamics in riverine borders can play an important role in political relationships between countries. Rivers
move and evolve under the influence of natural processes and external drivers (e.g. land use change in river
catchments). The Hirmand River is an important riverine border between Iran and Afghanistan. The present
study shows the evolution and lateral shifting of the Hirmand River along the international border (25.6 km)
over a period of 6 decades (1955–2015). Seven data series of aerial photos, topographic maps and Landsat images
were used to analyze land cover and channel changes in the study reach. The land cover has changed dramatically
on both sides of the border during the last 6 decades, especially in the Afghan part. Overall, 49% of all land surface
changed its cover type, especially the area of agriculture and residential land contributed to that, with an increase
in surface area of about 4931 ha and 561 ha, respectively. On the other hand, the natural cover and water bodies
decreased to 38% and 63%, respectively. The impact of these land use changes on the morphological evolution of
Hirmand River was investigated in 5 sub-reaches. We found an average decrease of the active channel width of
53% during 60 years and the average River Network Change Index for the whole study reach during 60 yearswas
−1.25 m/year. Deposition and narrowing turned out to be the main processes occurring within the study reach.
Furthermore, due to natural riverine processes the Hirmand River has moved towards Afghanistan (37m on average)
and lateral shifting was found to be up to 1900 m in some sections
The immediate effectiveness of barley straw mulch in reducing soil erodibility and surface runoff generation in Mediterranean vineyards
No full textSoil and water loss in agriculture is a major problem throughout the world, and especially in Mediterranean areas. Non-conservation agricultural practices have further aggravated the situation, especially in vineyards, which are affected by one of the highest rates of soil loss among cultivated lands. Therefore, it is necessary to find the right soil practices for more sustainable viticulture. In this regard, straw mulching has proven to be effective in other crop and fire affected soils, but, nonetheless, little research has been carried out in vineyards. This research tests the effect of barley straw mulching on soil erosion and surface runoff on vineyards in Eastern Spain where the soil and water losses are non-sustainable. An experiment was setup using rainfall simulation tests at 55 mm h(-1) over 1 h on forty paired plots of 0.24m(2): twenty bare and twenty straw covered. Straw cover varied from 48 to 90% with a median value of 59% as a result of the application of 75 g of straw per m(2). The use of straw mulch resulted in delayed ponding and runoff generation and, as a consequence, the median water loss decreased from 52.59 to 39.27% of the total rainfall. The straw cover reduced the median sediment concentration in runoff from 9.8 to 3.0 g L-1 and the median total sediment detached from 70.34 to 15.62 g per experiment. The median soil erosion rate decreased from 2.81 to 0.63 Mg ha(-1) h(-1) due to the straw mulch protection. Straw mulch is very effective in reducing soil erodibility and surface runoff, and this benefit was achieved immediately after the application of the straw
Lateral saturated hydraulic conductivity of soil horizons evaluated in large-volume soil monoliths
No full textEvaluating the lateral saturated hydraulic conductivity, Ks,l, of soil horizons is crucial for understanding and modelling the subsurface flow dynamics in many shallow hill soils. A Ks,l measurement method should be able to catch the effects of soil heterogeneities governing hydrological processes at the scale of interest, in order to yield Ks,l representative values over large spatial scales. This study aims to develop a field technique to determine spatially representative Ks,l values of soil horizons of an experimental hillslope. Drainage experiments were performed on soil monoliths of about 0.12 m3 volume, encased in situ with polyurethane foam. Median Ks,l of 2450 mm·h-1 and 552 mm·h-1 were estimated in the A and B horizon, respectively. In the upper part of the B horizon, the median Ks,l was 490 mm·h-1, whereas it mostly halved near the underlying restricting layer. The decline of Ks,l values with depth was consistent with the water-table dynamics observed at the same site in previous studies. Moreover, the Ks,l from the monoliths were in line with large spatial-scale Ks,l values reported from the hillslope in a prior investigation based on drain data analysis. This indicated that the large-scale hydrological effects of the macropore network were well represented in the investigated soil blocks. Our findings suggest that performing drainage experiments on large-volume monoliths is a promising method for characterizing lateral conductivities over large spatial scales. This information could improve our understanding of hydrological processes and can be used to parameterize runoff-generation models at hillslope and catchment scale
Effects of an extreme flood on river morphology (case study : Karoon River, Iran)
No full textAn extreme flood occurred on 14 April 2016 in the Karoon River, Iran. The occurred flood discharge was the highest discharge recorded over the last 60 years in the Karoon River. Using the OLI Landsat images taken on 8 April 2016 (before the flood) and 24 April 2016 (after the flood) the geomorphic effects were detected in different land cover types within the 155-km-long study reach. The results show that the flood significantly affected the channel width and the main effect was high mobilization of channel sediments and severe bank erosion in the meandering reaches. According to field surveys, the flood occupied the channel corridor and even the floodplain parts. However, the channel pattern was not significantly altered, although the results show that the average channel width increased from 192 to 256 m. Statistical results indicate a significant change for active channel width and sinuosity index at 99% confidence level for both indexes. The flood-induced morphological changes varied significantly for different land cover types along the Karoon River. Specifically, the channel has widened less in residential areas than in other land cover types because of the occurrence of bank protection structures. However, the value of bank retreat in residential and protected sides of the Karoon River is more than what we expected during the study of extreme flood
Using Beerkan experiments to estimate hydraulic conductivity of a crusted loamy soil in a Mediterranean vineyard
No full text In bare soils of semi-arid areas, surface crusting is a rather common phenomenon due to the impact of raindrops. Water infiltration measurements under ponding conditions are becoming largely applied techniques for an approximate characterization of crusted soils. In this study, the impact of crusting on soil hydraulic conductivity was assessed in a Mediterranean vineyard (western Sicily, Italy) under conventional tillage. The BEST (Beerkan Estimation of Soil Transfer parameters) algorithm was applied to the infiltration data to obtain the hydraulic conductivity of crusted and uncrusted soils. Soil hydraulic conductivity was found to vary during the year and also spatially (i.e., rows vs. inter-rows) due to crusting, tillage and vegetation cover. A 55 mm rainfall event resulted in a decrease of the saturated soil hydraulic conductivity, K s , by a factor of 1.6 in the inter-row areas, due to the formation of a crusted layer at the surface. The same rainfall event did not determine a K s reduction in the row areas (i.e., K s decreased by a non-significant factor of 1.05) because the vegetation cover intercepted the raindrops and therefore prevented alteration of the soil surface. The developed ring insertion methodology on crusted soil, implying pre-moistening through the periphery of the sampled surface, together with the very small insertion depth of the ring (0.01 m), prevented visible fractures. Consequently, Beerkan tests carried out along and between the vine-rows and data analysis by the BEST algorithm allowed to assess crusting-dependent reductions in hydraulic conductivity with extemporaneous measurements alone. The reliability of the tested technique was also confirmed by the results of the numerical simulation of the infiltration process in a crusted soil. Testing the Beerkan infiltration run in other crusted soils and establishing comparisons with other experimental methodologies appear advisable to increase confidence on the reliability of the method that seems suitable for simple characterization of crusted soils. </p
Actual provision as an alternative criterion to improve the efficiency of payments for ecosystem services for C sequestration in semiarid vineyards
No full textThe aim of this paper is to evaluate the efficiency of the PES scheme actually used in the Sicilian rural development program, based on an egalitarian criterion, and proposing an alternative scheme in order to guarantee a greater equity and fairness of premium distribution in relation to soil carbon (C) sequestration potential. We, first, assessed the ecosystem services (ES) provided by agri-environmental measures (AEM) in terms of SOC stock increase in Sicilian vineyards. Based on these data we evaluated the efficiency of agro-environmental payments according to an egalitarian criterion and simulated the effects of the actual provision criterion adoption. Results showed that the adoption of an egalitarian criterion generates an inequitable distribution of agri-environmental payments, which could potentially be mitigated by a scheme such as actual provision. The latter, indeed, leads to a greater efficiency in the distribution of financial resources among land users and offers a higher premium to land users that, by adopting an agro-environmental practice, contribute to increase soil C sequestration.</p
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