Soil salinity and alkalinity present a serious threat to global agriculture. However, most of the studies have focused on neutral salt stress, and the information on the metabolic responses of plants to alkaline salt stress is limited. This investigation aimed at determining the influence of neutral salt and alkaline salt stresses on the content of metal elements and metabolites in maize plant tissues, by using mixtures of various proportions of NaCl, NaHCO3, Na2SO4, and Na2CO3. We found that alkaline salt stress suppressed more pronouncedly the photosynthesis and growth of maize plants than salinity stress. Under alkaline salt stress conditions, metal ions formed massive precipitates, which ultimately reduced plant nutrient availability. On the other hand, high neutral salt stress induced metabolic changes in the direction of gluconeogenesis leading to the enhanced formation of sugars as a reaction contributing to the mitigation of osmotic stress. Thus, the active synthesis of sugars in shoots was essential to the development of salt tolerance. However, the alkaline salt stress conditions characterized by elevated pH values suppressed substantially the levels of photosynthesis, N metabolism, glycolysis, and the production of sugars and amino acids. These results indicate the presence of different defensive mechanisms responsible for the plant responses to neutral salt and alkaline salt stresses. In addition, the increased concentration of organic acids and enhanced metabolic energy might be potential major factors that can contribute to the maintenance intracellular ion balance in maize plants and counteract the negative effects of high pH under alkaline salt stress.

The extensive application of plastic-film mulching (PFM) has brought a series of environmental pollution due to the lack of awareness of plastic-film rational use and absence of plastic residues recycling in China. In addition, the use of degradable film instead of common polyethylene plastic film (PE film) can effectively alleviate this situation. The substitution of PE film with biodegradable film in the agricultural production of processed tomato in Xinjiang region was investigated in this study. Using bare soil as the control, we compared the effects of PE film and biodegradable film mulching on crop growth, yield, and economic benefits in processed tomato. The results indicated that: (1) Biodegradable film with a thickness of about 8 μm can meet the mechanical operation requirements, and the effect of biodegradable film mulching was completely consistent with that of PE film; (2) Four kinds of biodegradable film can meet the requirements of processed tomato growth and development, although slightly different from PE film in increasing temperature and water retention; (3) Plastic-film planting can ensure a net profit of 1.14–1.64 ten thousand CNY per hectare under the current production conditions and mode of Xinjiang region, and biodegradable film planting was observed to be essentially equal to those of PE film; (4) Nearly 50%–70% of the biodegradable film was ruptured and degraded during processed tomato harvesting, which avoided the occurrence of the winch of the plastic-film winding harvester and improves the efficiency and commodity rate of the processed tomato harvest operation. As the biodegradable film mulching causes no residual pollution, it is accepted to be an alternative to plastic-film mulching for agricultural applications and supports the sustainable development of agroecosystems in Xinjiang region.