Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Designing Technosols to reduce salinity and water stress of crops growing under arid conditions

Auteur : Kong Chao

Université de soutenance : Massey University

Grade : Doctor of Philosophy of Applied Science 2021

Résumé partiel
Salt- and plant-water stress are widely considered to be major abiotic stresses threatening crop production in dry areas. Innovative methods to alleviate salt and plant-water stress that are both practical and economically efficient are in great demand. While the most common reclamation strategy for salt-affected soils is to flush the salts out of the root zone with low salinity/sodicity water, this is challenged by the fact that water is commonly scarce in areas affected by salt stress. The use of specific soil amendments or a combination of them in such areas may well solve some of these problems. Biochar has, in fact, been shown that, in some instances, it is able to effectively reduce salt stress to plants. Other porous materials, such as pumice, have not yet been considered although pumice has been reported to contribute to water retention under arid conditions. Further potential amendments include organic residues, as they can produce beneficial impacts on plant growth by improving soil functions. To date, however, limited research has attempted to unravel (and compare) the effects of either pumice and/or biochar in alleviating salt and plant-water stress. There is also scant information on (i) how to minimise the impact of biochar on the salinity of soils in dry regions ; (ii) the underlying mechanisms explaining how the use of either pumice or biochar amendments can decrease soil salinity under arid conditions ; and (iii) whether individual or combined additions of either pumice and/or an organic amendment, algae, to a sandy soil alleviates salt and water-stress on plant growth. Therefore, my objective in this study is to investigate whether these amendments can be used in the formulation of Technosols specifically designed to reduce salinity and water-stress of crops growing under arid environments. A quantitative review of the literature was carried out to evaluate what type of biochar and under what conditions its use is suitable in dryland soils. For this, a meta-analysis of 40 studies published between 2013 and 2020 using pairwise comparisons was carried out to evaluate the short-term effect of biochar on the salinity using electrical conductivity (EC) as the proxy for soils under dry environments (Mediterranean, arid, semi-arid climates, or under simulated dry and saline conditions). The results indicated that in terms of the risk of biochar increasing soil salinity, (i) biochars made from high-ash material should not be applied to soils in dry regions ; and (ii) the addition of biochars made from relatively low-ash ligneous material at application rates ≤ 20 t ha-1 is suitable as an amendment to soils under dry environments.

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