Effects of improved saline-alkaline soil with coal gangue on potato growth

Cultivated land resources are seriously insufficient in China, where the per capita cultivated land area is only 1/3 of the world average. The improved saline-alkali soil can be expected to plant food crops, in order to alleviate the shortage of cultivated land resources. However, saline-alkaline soil has poor physical structure and a low plant survival rate. Fortunately, coal gangue has the potential to improve the physical structure and chemical properties of saline-alkali soil. It is a high demand to apply the coal gangue into the saline-alkali land for the better recycling of waste coal gangue resources with the improvement of saline-alkali land. In this study, a pot experiment was conducted to investigate the effect of coal gangue on the saline-alkali soil and potato cultivation. Coal gangues with different application rates (0, 15%, 30%, and 50%) were applied to the saline-alkali soil, marked as the treatment of CK, CL15, CL30 and CL50, respectively. Three potato varieties JZ-12, WT-5 and DF-10 were planted during the experiment. 12 replicates were set for each treatment, because the planting potatoes was not conducive to sampling and testing soil bulk density indicators. Among them, three varieties of potato were planted for nine repetitions (three repetitions for each variety), and the remaining three repetitions were used to determine the soil physicochemical properties with the applied coal gangue. A systematic analysis was made to clarify the effects of coal gangue on the soil physical and chemical properties of saline-alkali soil, potato plant growth, photosynthetic characteristics, malondialdehyde content, antioxidant enzyme activity, potato yield and quality. The results showed as follows: 1) The addition of coal gangue affected the soil's physicochemical properties, and then improved the poor and hardened quality of the saline-alkali soil. The soil pH value, salt concentration, and bulk density decreased gradually, whereas, the soil structure tended to be stable. At the same time, there was a significant increase in the content of organic matter, total nitrogen, total phosphorus, total potassium, hydrolytic nitrogen, and available potassium in the soil (P<0.05), with increases of 15.2%-447.2%, 11.7%-27.6%, 0.5%-29.5%, 43.3%-225.8%, 16.6%-216.1%, and 3.6%-34.9%, respectively. 2) There were some differences in the effects of different amounts of coal gangue on the growth, photosynthesis, and stress resistance of potato plants. The growth physiological and stress resistance indicators of plants at different stages showed a trend of first increasing and then decreasing, as the amount of coal gangue increased. CL30 treatment shared the best performance to promote potato growth, while CL50 showed a certain inhibitory. The above-ground biomass of the three potato varieties under different treatments after harvest was ranked as CL30, CL50, and CL15. 3) In the CK group, all potato plants died during the seedling stage, while planting potatoes with different treatments of coal gangue completed the growth cycle and produced potatoes. The weight of tuber per plant was the highest under CL30 treatment, ranging from 252.37-424.10 g. The highest content of starch, protein, and vitamin C in tubers also ranged from 90.0-110.3, 13.3-14.1, and 99.0-164.0 mg/kg, respectively. However, there was still a quality gap, compared with the commercial potatoes, where the starch, protein, and vitamin C content were 21.2%-35.7%, 45.8%-48.8%, and 7.9%-44.4% lower than commercial potatoes, respectively. In summary, the coal gangue can be used for the saline-alkali soil improvement. 30% coal gangue can be expected to effectively improve the saline-alkali soil environment suitable for planting potatoes. Therefore, the finding can provide application prospects in the field of saline-alkali soil improvement and food security.