Subsurface Drainage Impact Assessment-in Ibshan, Egypt

This paper aims to mitigate the impacts of subsurface drainage system in Ibshan, Egypt on the environment. For studying and analyzing these impacts, data are collected concerning before and after the installation of the subsurface drainage system. The environmental impacts are set to be crops yields, salinity, and water table depth. Concerning crops yields, five crops are identified to study the effect of the subsurface drainage system on their productivity. Regarding salinity, the saline areas are investigated pre and post the subsurface drainage system. For the water table depth, the ground water table depths are reviewed before and after the subsurface drainage system. Also, the DRA1NMOD-S computer program is employed to determine the effect of the subsurface drainage system on the water table depth. It is concluded that the environmental impacts of the subsurface drainage system in Ibshan area are very good. The yields of five crops increased from 7% to 38%, 16.4% of saline areas are improved, and the ground water table depth is reduced by 10%. Also, an equation is obtained to predict the percentage decrease of ground water table depth according to the laterals spacing of the subsurface drainage system.

Effect of Combined Application of Subsurface Drainage and Mineral Fertilization on Iron-Reducing Bacterial Populations’ Developments and Fe2+ Uptake by Two Rice Varieties in an Iron Toxic Paddy Soil of Burkina Faso (West Africa)

Rice is one of the staple crops in Burkina Faso. However, the local production covers only 47% of the population demands. One of the main reasons of the poor productivity in Burkina Faso is iron toxicity which is related mainly to the activity of Iron Reducing Bacteria in the rice field’s ecosystems. In order to control the harmful effects of Iron Reducing Bacterial populations and to improve rice productivity, a pots experiment was conducted at the experimental site of the University Ouaga I Pr. Joseph KI-ZERBO. An iron toxic soil from Kou Valley (West of Burkina Faso) and two rice varieties, BOUAKE-189 and ROK-5, sensitive and tolerant to iron toxicity, respectively, were used for the experiment. The pots were drained for 14 days (D2) and amended with chemical fertilizers (NPK + Urea and NPK + Urea + Ca + Mg + Zn complexes). Control pots without drainage and fertilization (D0/NF) were prepared similarly. The kinetics of Iron Reducing Bacterial populations and ferrous iron content in soil near rice roots were monitored throughout the cultural cycle using MPN and colorimetric methods, respectively. The total iron content was evaluated in rice plant using a spectrometric method. Data obtained were analyzed in relation to drainage and fertilization mode, rice growth stage and rice yield using the Student’s t-test and XLSTAT 2014 statistical software. The experiment showed that the combined application of subsurface drainage and NPK + Urea + Ca + Mg + Zn fertilization, reduced significantly the number of IRB in the soil near rice roots for both rice varieties (p = 0.050 and p = 0.020) increased the leaf tissue tolerance to excess amounts of Fe, and rice yield.

Comparative investigation on soil salinity leaching under subsurface drainage and ditch drainage in Xinjiang arid region

This study was carried out to explore the effects of leaching salinity under subsurface drainage and mulched drip irrigation on saline and alkaline land from the year 2012 to 2014 in Xinjiang Region of China.Three sampled points were both set up in the subsurface drainage and ditch drainage areas.Soil samples were obtained at varied depths.Through observing the underground water table under each sampled point and measuring the electrical conductivity(EC)of the soil extracts,the following results were obtained:(1)after draining,the underground water table ranged from 1.6 m to 2.2 m in the ditch drainage area,and ranged from 1.5 m to 2.2 m in the subsurface drainage area.Thus,both irrigations could control underground water table below 1.5 m which is deeper than the main water-absorbing layers of crop root systems;(2)for subsurface drainage,the closer to the pipe,the better to leach salinity;decreased from the initial 13.54-22.95 g/kg to 8.20-11.47 g/kg;(3)compared with the amounts in 2012,soil total salt at each sampling point at depths of 0-200 cm in subsurface drainage area decreased by 42.99%,36.84%and 24.41%respectively in 2014;and in ditch drainage area decreased by 46.85%,38.12%and 30.80%respectively in 2014.The results showed both ditch and subsurface drainage could leach salinity effectively.

Soil Drainage as an Active Agent of Recent Soil Evolution: A Review

While research on pedogenesis mainly focuses on long-term soil formation and most often neglects recent soil evolution in response to human practices or climate changes, this article reviews the impact of artificial subsurface drainage on soil evolution. Artificial drainage is considered as an example of the impact of recent changes in water fluxes on soil evolution over time scales of decades to a century. Results from various classical studies on artificial drainage including hydrological and environmental studies are reviewed and collated with rare studies dealing explicitly with soil morphology changes, in response to artificial drainage. We deduce that soil should react to the perturbations associated with subsurface drainage over time scales that do not exceeding a few decades. Subsurface drainage decreases the intensity of erosion and must i) increase the intensity of the lixiviation and eluviation processes, ii) affect iron and manganese dynamics, and iii) induce heterogeneities in soil evolution at the ten meter scale. Such recent soil evolutions can no longer be neglected as they are mostly irreversible and will probably have unknown, but expectable, feedbacks on crucial soil functions such as the sequestration of soil organic matter or the water available capacity.