Irrigation Optimization via Crop Water Use in Saline Coastal Areas-A Field Data Analysis in China's Yellow River Delta.

Freshwater resources are becoming increasingly scarce in coastal areas, limiting crop productivity in coastal farmlands. Although the characteristic of crop water use is an important factor for water conservation in coastal farmlands, it has not been studied extensively. This study aimed to depict the water use process of soil-plant systems under saline stress in coastal ecosystems and optimize water management. An intensive observation experiment was performed within China's Yellow River Delta to identify the water use processes and crop coefficients (KC) and also quantify the impacts of salt stress on crop water use. The results show that shallow groundwater did not contribute to soil water in the whole rotation; KC values for wheat-maize, wheat-sorghum, and wheat-soybean rotation systems were 45.0, 58.4, and 57% less, respectively, than the FAO values. The water use efficiency of the maize (8.70) and sorghum (9.00) in coastal farmlands was higher than that of the soybean (4.37). By identifying the critical periods of water and salt stress, this paper provides suggestions for water-saving and salinity control in coastal farmlands. Our findings can inform the sustainable development of coastal farmlands and provide new insights to cope with aspects of the global food crisis.

Field performance of sweet sorghum in salt-affected soils in China: A quantitative synthesis.

Sweet sorghum is a high-yield crop with strong resistance, which has the potential to support the development of the forage farming industry in China where vast salt-affected lands are potentially arable. Nutrient management is imperative for sweet sorghum growing on salt-affected lands. Although nitrogen (N) synthetic fertilizers have long been recognized as a key factor for increasing crop yields, their effects on sweet sorghum cultivation are under debate. Consequently, this study integrated the current available observations of yield (n = 255) and partial factor productivity of nitrogen (NPFP, n = 242) of sweet sorghum in salt-affected lands, which included both inland (n = 189) and coastal (n = 66) areas. We quantitatively analyzed the effects of climatic, soil properties and management measures on biomass yield and NPFP of sweet sorghum, comparing the differences between inland and coastal salt-affected lands. We found that average biomass yield and NPFP of sweet sorghum in coastal areas were 19,082.48 ± 8262.75 kg/ha and 107.29 ± 51.44 kg/kg respectively, both significantly lower than that in inland areas (p < 0.05). The N application rate did not have significant promoting effect on the biomass yield of sweet sorghum in inland salt-affected areas (p > 0.05), whereas in coastal salt-affected areas, N application significantly increased the biomass yield of sweet sorghum. Increasing soil organic matter content could promote NPFP in inland areas. The recommended N application rate for inland salt-affected and coastal salt-affected areas were 100 kg/ha and 150 kg/ha respectively. The results indicate that it is crucial to apply nutrient management measures based on the local climatic and soil conditions, since the causes of salinity differ in coastal and inland salt-affected lands. More systematic field studies are required in the future to optimize the management of water and nutrients for sweet sorghum planting in salt-affected lands.