The effects of one-time basal application of different mixtures of slow-release urea (SRU) and conventional urea (CU) on yield and nitrogen use efficiency (NUE) of rice and wheat were investigated to determine the appropriate ratios of SRU to CU for one-time basal fertilization in a rice–wheat rotation farmland under full residue incorporation. A field plot experiment was used in this study. Six treatments were established as follows: CK (no nitrogen fertilizer applied), T0 (100% CU, 50% applied as basal fertilizer and 50% applied as jointing fertilizer), T3 (one-time basal application of SRU and CU mixture with 30% SRU), T5 (one-time basal application of SRU and CU mixture with 50% SRU), T7 (one-time basal application of SRU and CU mixture with 70% SRU), and T10 (one-time basal application of 100% SRU). The results showed that the combined application of SRU and CU increased the yields of rice and wheat. Treatment T7 resulted in the highest rice yield, and T3 resulted in the highest wheat yield, which were 25.6% and 29.4% higher, than those of treatment T0, respectively. Compared with treatment T0 (application of CU alone), the combined application of SRU and CU resulted in 27.4–96.5% and 22.8–57.1% higher NUE in rice and wheat, respectively.

The most important measures for salt-affected mudflat soil reclamation are to reduce salinity and to increase soil organic carbon (OC) content and thus soil fertility. Salinity reduction is often accomplished through costly freshwater irrigation by special engineering measures. Whether fertility enhancement only through one-off application of a great amount of OC can improve soil properties and promote plant growth in salt-affected mudflat soil remains unclear. Therefore, the objective of our indoor pot experiment was to study the effects of OC amendment at 0, 0.5%, 1.0%, 1.5%, and 2.5%, calculated from carbon content, by one-off application of sewage sludge on soil properties, rice yield, and root growth in salt-affected mudflat soil under waterlogged conditions. The results showed that the application of sewage sludge promoted soil fertility by reducing soil pH and increasing content of OC, nitrogen and phosphorus in salt-affected mudflat soil, while soil electric conductivity (EC) increased with increasing sewage sludge (SS) application rates under waterlogged conditions. In this study, the rice growth was not inhibited by the highest EC of 4.43 dS m−1 even at high doses of SS application. The SS application increased yield of rice, promoted root growth, enhanced root activity and root flux activity, and increased the soluble sugar and amino acid content in the bleeding sap of rice plants at the tillering, jointing, and maturity stages. In conclusion, fertility enhancement through organic carbon amendment can “offset” the adverse effects of increased salinity and promote plant growth in salt-affected mudflat soil under waterlogged conditions.

China is facing a shortage of arable land resources, and the mudflat salt-affected soil along the east coast of China is an important reserve arable land resource. In this study, we conducted a randomized field trial to investigate the effects of vermicompost application rate (0, 25, 50, 125, and 250 t ha−1) on barley growth and heavy metal accumulation in mudflat salt-affected soil. We found that vermicompost application decreased bulk density, electrical conductivity (EC), and pH of mudflat salt-affected soil while increasing its organic carbon, nitrogen, and phosphorus contents. With the increase in vermicompost application rate, the yield of grain and total biomass of barley plants increased. The yield of grain in the vermicompost application treatments of 25, 50, 125, and 250 t ha−1 increased by 66.0%, 226.0%, 340.0%, and 512.0%, respectively, relative to the control. In addition, the concentrations of heavy metals (Cd, Cr, Cu, and Zn) in mudflat salt-affected soil and barley plant increased as the vermicompost application rate increased.

Computer technology has been used to study the different combination of catalyst and temperature on the ethanol conversion (one-way conversion rate of 100% per unit time ethanol (alcohol intake - ethanol residue)/ethanol intake) and C4 olefin selectivity (the proportion of all products of C4 olefin), it is necessary to decompose the catalyst composition into several indicators. The effects of several indexes on ethanol conversion and C4 olefins selectivity were analyzed by computer technology. Canonical correlation analysis was used to study them, and the coefficient before each component represented the degree of importance. The results showed that the higher the catalyst combination temperature, the higher the weight of hydroxyapatite, the higher the ethanol conversion and C4 olefins selectivity, and vice versa. When the C4 olefin yield (its value is the selectivity of C4 olefin to ethanol conversion) is as high as possible, the multiple linear stepwise regression function of catalyst parameters and temperature on C4 olefin yield is obtained. MATLAB software was used to calculate the function formula. The absolute value of coefficients determines the importance of each index to C4 olefin yield. Combined with chemical reaction, when the mass ratio is 200:200 and the temperature is 400℃, the yield of C4 olefins can be maximized, and the yield of C4 olefins is 44.728%. Through the establishment of decision tree regression model by computer technology, it can be intuitively concluded that when the temperature is lower than 350℃, the best experimental condition is the C4 olefins yield of 17.264%.