Abstract
Soil salinization is one of the major causes of land degradation. In Senegal, this phenomenon continues to grow, making soils unsuitable for agriculture. To rehabilitate salty lands, one of the recommended strategies is the use of salt-tolerant plants. Among them, plants of Casuarinaceae family form a relationship with symbiotic microorganisms such as arbuscular mycorrhizal fungi and nitrogen fixing bacteria. It has been shown that symbiotic microorganisms play an important role in the establishment of tolerant plants in saline conditions (Djighaly et al., 2018). They improve plant performance and reduce transplant shock under salt stress conditions (Diagne et al., 2014). These microorganisms can be used as biofertilizers. However, inocula containing symbiotic microorganisms are either too expensive or unavailable in many developing countries. The aim of this study is to test alternatively affordable and low-tech solutions to promote symbiotic interactions such as Casuarina crushed nodule, Casuarina rhizosphere soil and Casuarina leaves compost that may contain symbiotic microorganisms and also nutrients such as N and phosphorus. Two species of Casuarina (Casuarina equisetifolia L. and Casuarina obesa Miq.) were grown in the greenhouse on sterile soil to which an amendment was added (Casuarina crushed nodules, Casuarina Rhizospheric soil or Casuarina leaves compost). Plants were subjected to saline stress. After four months of cultivation, they were harvested and morphological and physiological parameters were determined. Results showed that inoculation with Casuarina crushed nodules, Casuarina rhizospheric soil and Casuarina leaves compost improved growth, total dry biomass, total chlorophyll and proline contents of C. equisetifolia and C. obesa plants in salt stress condition. These positive effects were more important in C. obesa plants amended with Casuarina leaves compost. This study shows that Casuarina leaves compost can play an important role in the rehabilitation of saline soils by improving Casuarina trees performance in saline conditions.
Highlights
IntroductionSalinization can be defined as a process of accumulating soluble salts in the soil at high levels that can negatively affect agricultural production or cause biodiversity degradation [2]
Salinity is a major abiotic stress affecting crop yield in the Sahel [1]
The aim of this study was to test alternative types of inocula such as crushed nodules containing nitrogen-fixing bacteria from adult Casuarina plants, C. equisetifolia canopy soil which may contain symbiotic microorganisms such as mycorrhizal fungi, nitrogen-fixing bacteria and Plant Growth Promoting Rhizobacteria (PGPR), and a compost derived from Casuarina leaves litter (Casuarina compost) which is commonly found in Senegal [13] and may contain beneficial microrganisms and nutrients that improve salt tolerance of C. equisetifolia and C. obesa
Summary
Salinization can be defined as a process of accumulating soluble salts in the soil at high levels that can negatively affect agricultural production or cause biodiversity degradation [2]. Lands affected by salinity are estimated worldwide at about 932.2 million hectares [3]. In Senegal, about 1,200,000 hectares of land are reported to be affected by salinization, representing nearly 6% of the country’s total area. In arid and semi-arid ecosystems, salinization results from high water evaporation and irregular and deficient rainfall [6]. This salinization leads to land degradation and adverse effects on soil fauna and plants, resulting in decreased soil fertility and lower agricultural yields [7]. Several methods have been used to rehabilitate saline soils, which include mechanical methods, chemical methods and biological methods
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