Soil salinity and its associated effects on soil microorganisms, greenhouse gas emissions, crop yield, biodiversity and desertification: A review.

Significant research has been conducted on the effects of soil salinity issue on agricultural productivity. However, limited consideration has been given to its critical effects on soil biogeochemistry (e.g., soil microorganisms, soil organic carbon and greenhouse gas (GHG) emissions), land desertification, and biodiversity loss. This article is based on synthesis of information in 238 articles published between 1989 and 2022 on these effects of soil salinity. Principal findings are as follows: (1) salinity affects microbial community composition and soil enzyme activities due to changes in osmotic pressure and ion effects; (2) soil salinity reduces soil organic carbon (SOC) content and alters GHG emissions, which is a serious issue under intensifying agriculture and global warming scenarios; (3) soil salinity can reduce crop yield up to 58 %; (4) soil salinity, even at low levels, can cause profound alteration in soil biodiversity; (5) due to severe soil salinity, some soils are reaching critical desertification status; (6) innovate mitigation strategies of soil salinity need to be approached in a way that should support the United Nations Sustainable Development Goals (UN-SDGs). Knowledge gaps still exist mainly in the effects of salinity especially, responses of GHG emissions and biodiversity. Previous experiences quantifying soil salinity effects remained small-scale, and inappropriate research methods were sometimes applied for investigating soil salinity effects. Therefore, further studies are urgently required to improve our understanding on the effects of salinity, address salinity effects in larger-scale, and develop innovative research methods.

Soil salinisation and irrigation management of date palms in a Saharan environment.

The continuance of agricultural production in regions of the world with chronic water shortages depends upon understanding how soil salinity is impacted by irrigation practises such as water salinity, irrigation frequency and amount of irrigation. A two-year field study was conducted in a Saharan oasis of Tunisia (Lazala Oasis) to determine how the soil electrical conductivity was affected by irrigation of date palms with high saline water. The study area lacked a saline shallow water table. Field results indicate that, under current irrigation practises, soil electrical conductivity can build up to levels which exceed the salt tolerance of date palm trees. The effects of irrigation practises on the soil electrical conductivity were also evaluated using model simulations (HYDRUS-1D) of various irrigation regimes with different frequencies, different amounts of added water and different water salinities. The comparison between the simulated and observed results demonstrated that the model gave an acceptable estimation of water and salt dynamics in the soil profile, as indicated by the small values of root mean square error (RMSE) and the high values of the Nash-Sutcliffe model efficiency coefficient (NSE). The simulations demonstrated that, under field conditions without saline shallow groundwater, saline irrigation water can be used to maintain soil electrical conductivity and soil water content at safe levels (soil electrical conductivity <4 dS m(-1) and soil water content >0.04 cm(3) cm(-3)) if frequent irrigations with small amounts of water (90 % of the evapotranspiration requirements) were applied throughout the year.