No abstract

In recent years biochar has been demonstrated to be a useful amendment to sequester carbon and reduce greenhouse gas emission from the soil to the atmosphere. Hence it can help to mitigate global environment change. Some studies have shown that biochar addition to agricultural soils increases crop production. The mechanisms involved are: increased soil aeration and water-holding capacity, enhanced microbial activity and plant nutrient status in soil, and alteration of some important soil chemical properties. This review provides an in-depth consideration of the production, characterization and agricultural use of different biochars. Biochar is a complex organic material and its characteristics vary with production conditions and the feedstock used. The agronomic benefits of biochar solely depend upon the use of particular types of biochar with proper field application rate under appropriate soil types and conditions. © 2016 Society of Chemical Industry.

The addition of fast pyrolysis biochar made from pine sawdust improved the quality of Kubuqi Desert soil and enhanced plant growth. Hence, it can be used for desert modification.

We report a laboratory study in a model sand-tank to investigate improvements using partial ponding over the common method of leaching salts from soils by flooding the entire area above equally spaced subsurface drains. The physical basis of the theory developed by E. G. Youngs and P. B. Leeds-Harrison was demonstrated in the model. We traced the streamline patterns for complete ponding and 3 situations of partial ponding of the soil surface to demonstrate the flow paths. We also leached saline water, initially uniformly distributed in the sand, with sweet water and recorded the breakthrough curves of the leaching water for the same situations of complete and partial ponding. The results demonstrate that partial ponding is more effective than complete ponding in that it requires less time to carry solute towards the drain and saves water of good quality needed to leach salts through drains. They also confirm the theoretical findings that more uniform leaching with less water can be achieved by constraining the infiltrating area with bunds, initially flooding only the region midway between the drains and then progressively increasing the flooded area until the entire surface above the drains is ponded.

This paper examines an efficient method of removing salts through progressive flooding of surface strips between subsurface drains. The method has been tested in the laboratory using a sand tank model experiment. The work extends earlier theoretical investigations by Youngs and Leeds-Harrison (2000) which suggest that more uniform leaching with less water can be obtained by constraining the infiltrating area with the use of bunds, initially flooding only the region midway between the drains and then progressively increasing the flooded area towards the drains until the whole area between the drains is flooded.Streamlines were traced to determine flow pattern and solute movement under complete and partial flooding. The tracing results suggest that partial flooding is more effective than complete flooding as the streamlines move faster and require less time to carry the salt towards the drain. The results have been further supported by the pore volumes of solute and salt loads leached under partial and complete flooding. The quarter flooding situation was extremely efficient followed by half and three-quarter situations where solute leaching towards drains was higher than complete flooding. Results show that 59% superfluous good quality water is required to desalinise the area midway between drains with complete flooding, as compared to quarter area of flooding. Similarly, half and three-quarter flooding situations require 21 and 37% additional good quality water, respectively, to leach the same amount of salts from the area midway between drains. RÉ SUMÉCet article examine une méthode efficace pour enlever les sels par une submersion progressive des bandes entre les drains enterrés. La méthode a été testée en laboratoire en utilisant une expérience sur réservoir de sable. Ce travail prolonge les premières recherches théoriques de Youngs et Leeds-Harrison (2000) qui suggèrent qu'un lessivage plus uniforme avec moins d'eau peut être obtenu en contraignant l'infiltration, en submergeant seulement la zone entre les drains puis en étendant progressivement la zone submergée jusqu'aux drains.Des profils ont été tracés pour déterminer le modèle d'écoulement et le mouvement des solutés sous une submersion complète et partielle. Les résultats suggèrent que la submersion partielle est plus efficace que la submersion totale car le profil se déplace plus rapidement et moins de temps est nécessaire pour transporter les solutés jusqu'aux drains. La submersion au ¼ est extrêmement efficace suivie des submersions au ½ et au où les solutés lessivés vers les drains sont supérieurs qu'en situation de submersion totale. Les résultats prouvent qu'un surplus d'eau de bonne qualité de 59% est nécessaire pour désaliniser la zone entre drains par submersion complète IRRIGATION AND DRAINAGE par rapport à une submersion au ¼. De même, les submersions au ½ et au demandent un surplus d'eau de bonne qualité de 21 et de 37% respectivement pour lessiver la même quantité de sels dans la zone entre les drains.