China 
Africa 
Explore chapters and articles related to this topic
Sodic Soils: Properties
Published in Brian D. Fath, Sven E. Jørgensen, Megan Cole, Managing Soils and Terrestrial Systems, 2020
Soils with sodic subsoils are characterized by moderate to high exchangeable sodium and, in many cases, with high pH (>8.5) where carbonate and bicarbonate minerals are present. Subsoil sodicity restricts drainage beyond the root zone and as a result salts accumulate in this zone. The concentration of accumulated salts fluctuates with rainfall pattern, input of salt from agronomic practices, and soil weathering, as schematically explained in Figure 2. Dryland salinity or “seepage salinity” in many countries is associated with rising saline groundwater tables. However, the extent of subsoil salinity, also called “transient salinity,” not associated with saline groundwater is large in many landscapes dominated by subsoil sodicity. A relationship between rainfall, subsoil ESP, and ECe for northeastern Australian soils has been reported.[7] In dryland regions with annual rainfall between 250 and 600 mm, sodic subsoils have an ECe between 2 and 20 that can dramatically affect crop production through osmotic effects during dry periods. Laboratory measured ECe will increase several folds under field conditions as the soil layers dry in between rainy days. The combination of poor water storage and osmotic stress enhance water stress to crops under dryland cropping.
Soil Degradation: Global Assessment
Published in Yeqiao Wang, Landscape and Land Capacity, 2020
Part of the excess salinity in Australia is of primary origin and was retained in the subsoil by trees, which have now been cleared to create soil surfaces for cropping and pastures, allowing penetration of water to the saline subsoil, then followed by abstraction from the water table, thus leading to the ultimate disaster. About 30% of Australia’s agricultural land is sodic, creating poor physical conditions and impeded productivity. This problem can only be alleviated by massive revegetation programs and by taking extra care of the water table and plant cover. Despite the introduction of costly conventional measures for reclamation, salinity levels continue to increase across Australia in the dry and irrigated soils. The dryland salinity in the continent affects about 5 million ha of farmland and is expanding at a rate of 3–5% per year.[30]
Combating Strategies
Published in Ajai, Rimjhim Bhatnagar, Desertification and Land Degradation, 2022
Practices like the use of salt-tolerant varieties are feasible steps to handle salinization. Better irrigation practices such as drip or micro-jet irrigation can help in optimized water use. The plantation of deep-rooted perennial plants helps in reducing the spread of dryland salinity. This is because they restore the balance between rainfall and water use and prevent the rising of water tables and the movement of salt to the soil surface.
The spatial distribution and determinants of irrigators’ price choices for water entitlement trading
Published in Australasian Journal of Water Resources, 2022
Results for the spatial variables depicting poorer resource areas show an association with price choices for buying and selling water entitlements. Specifically, irrigators growing on sandier soils and affected by dryland salinity are likely to buy water entitlements for higher prices, potentially because of the need to maintain the soil by leaching. This indicates that irrigators’ values for their water are impacted by lower resource areas. Model results further showed that lower final seasonal allocation levels over the previous five years increased irrigators’ price choices selling water entitlements. As a result, areas affected by increased water scarcity led irrigators to value their water entitlements more. Other studies also concluded that water scarcity is a major driver of water entitlement values (e.g. Seidl, Wheeler, and Zuo 2020a; Zuo, Qiu, and Wheeler 2019).