## 4 Discussion
### Impacts of Soil Restoration on Plant Growth, Physiology and Yield  
In this study, growth and yield were significantly improved by the application of gypsum, both alone and in combination with organic amendments; similar improvements were reported by [PERSON], et al. [79]. All treatments showed an increase in germination, plant height, dry matter content and yield when compared to the respective control. [PERSON], et al. [80] observed that soil salinity can decrease crop growth, metabolism, and the quality of the produce, with salinity causing a decrease in root length of up to 36%, which significantly increased (up to 80%) when organic wastes were applied; similar findings were reported by [PERSON], et al. [81] and [PERSON], et al. [82]. Other authors observed that addition of gypsum and organic amendments compensated for deficiencies in both soil micro- and macronutrients during and after soil reclamation [66]. [PERSON], et al. [83] observed differences in nutrient absorption under different treatments that greatly influenced growth and yield potential. [PERSON], et al. [84] observed that compost applications improved all growth parameters measured, including crop yield. Many previous studies have shown that, with the application of organic wastes, soil nutrients and nutrient use efficiency are increased by providing the slow release of nutrients to plants [85]. Increases in crop yield with organic amendments were also reported by [33]. The addition of organic fertilizers increases N and P availability and enhances soil microbial activity [86], thus, contributing to improved plant nutrition and enhancing the root system of the crop [87].  
The fresh and dry weight of the crops also showed a significant increase with the gypsum and organic amendments. A similar increase in dry matter production with the application of gypsum was reported by [PERSON], et al. [88]; they suggested that gypsum increases the soil water and nutrient use efficiency, which ultimately increases the growth and yield of plants. It has been also reported that a 48.4% increase occurred in the plant biomass in a wheat crop after the application of rapeseed meal in saline soils in China [53]. Similarly, efficient use of all available resources may be further improved by the low and consistent supply of nutrients and increased water absorption associated with the applied organic manures [89].  
Plant physiology was also significantly improved through the application of gypsum and organic amendments. The crops were able to absorb a higher quantity of light, resulting in a significantly greater amount of vegetative development in all treatments compared to the control. This could be explained by the addition of N in the amendments, which is an integral constituent of the chlorophyll [90; 91]. As the chlorophyll content increased, the rate of photosynthesis also increased. The maximum increase recorded was 47% higher than the control treatment, as previous similar results were reported by [92]. Stomatal conductance also increased compared to the control, suggesting that the plant is better supplied with water associated with improved soil structure and water holding capacity. The higher stomatal conductance could also be attributed to the input of potassium in the manure,which is the key element in stomatal regulation [93]. Improved stomatal regulation will result in more efficient use of water resources by the plant.