Reclamation and Utilization of Saline Soils in Arid Northwestern China: A Promising Halophyte Drip-Irrigation System

Abstract

W the context of arable land and fresh water limits and a large population, the ability of China’s agriculture to meet demands for food, fodder, and fuel presents a falling tendency. Therefore, it is crucial for China to find appropriate methods and effective technologies to solve the food security problem, to achieve agricultural stability and sustainable development. Saline agriculture is proposed as one of the best solutions to deal with this threat. Success stories in saline agriculture have been documented in India and Pakistan. Nearly 70% of the total area of China’s saline soils occur in arid or semiarid regions, so developing water-saving saline agriculture is perhaps an efficient method for the optimized matching of agricultural water and soil resources. As an advanced irrigation technique with water-saving advantages, drip-irrigation is widely used in traditional agriculture throughout China. Here, we propose that planting halophyte crops under drip-irrigation conditions may be a promising approach for reclamation and utilization of saline soils in arid northwestern China. China’s National Mediumand Long-Term Program for Food Security (2008−2020) shows that China’s food security faces serious challenges, including rigid growth of commissary consumer demand, reduction of the arable land, and shortage of agricultural water resources. According to the Ministry of Land Resources of China, China is approaching the arable land “red line” (120 million hectare) because of urbanization, salinizaition and desertification. Saline soils, which are precious candidate arable land resources, occupy a significant strategic position in agriculture. Recently, rational reclamation and suitable utilization of saline soils in arid areas has become a major issue in China and has attracted increasing awareness from both government administrators and scientists. In China, about 25 million hectare saline soils in arid area remain uncultivable because of high salinity and water scarcity. Various approaches to reclaim saline soils including engineering, mechanical, chemical and biological are widely applied in northwestern China. However, such approaches have not yielded desirable results due to high costs or water limitations. Revegetation of saline soils with salt hyperaccumulating halophytes is a proactive phytoremediation method. Many halophytes such as Suaeda maritima and Sesuvium portulacastrum are reported to accumulate high contents of salt in their above ground tissues, and saline soils can be remediated by harvesting the plants regularly. To plant halophytes with limited water resources, this is a question of primary importance for arid saline soil recovery. Drip-irrigation is an effective irrigation technique to improve water use efficiency and is widely applied in traditional crops all over the world, especially in arid regions. This technology has the potential to plant halophytic crops and to obtain high-yield biomass with less irrigation water. Many halophytes have succulent leaves or small leaves, so we expect that water consumption for halophyte cultivation may be less than or similar to local crops grown under drip-irrigation. We hope that by using this system, a crucial step will be taken to break the bottleneck of biological reclamation of saline soils in arid areas. Not only can saline agriculture reclaim saline soils efficiently, it can also directly provide food, fodder, renewable energy and raw materials for industry. Scientists have found thousands of halophytes with great potential for development. Halophytes grown under saline conditions show levels of biomass and seed production comparable to conventional crops. For instance, Salicornia bigelovii, an oil-seed halophyte, could produce ca. 18 tons ha−1 of biomass and 2 tons ha−1 of seeds. Some halophytes have high nutritional value as forage or fodder crops. The restricting factor is their high salt content, but this limitation can be moderated by leaf protein extraction. Although the direct consumption of halophytic crops by humans and animals is limited, their seeds are being considered as new sources of grains or vegetable oils. Recent research carried out in Pakistan showed that some halophytes have potential as bioethanol crops.