Honeysuckle (Lonicera japonica Thunb.) is a popular landscape plant. This study was to explore leaf photosynthetic characterization with emphasis on the coordination between photosystem II (PSII) and photosystem I (PSI) in tetraploid and its autodiploid honeysuckle (TH and DH) upon salt stress (300 mM NaCl). Leaf photosynthetic rate and carboxylation efficiency in DH and TH were significantly decreased under salt stress, and the decrease was greater in DH. PSII photoinhibition was induced in DH under salt stress, as the maximum quantum yield of PSII (Fv/Fm) was significantly decreased. PSII photoinhibition declined electron flow to PSI, but did not prevent PSI photoinhibition, as the maximal photochemical capacity of PSI (△MR/MR0) was significantly decreased by salt stress. According to the significant decrease in PSI oxidation amplitude in the first 1 s red illumination, PSI photoinhibition was more severe than PSII photoinhibition. As a result, PSII and PSI coordination was destroyed. Comparatively, salt-induced photoinhibition did not occur in TH, as no significant change was observed in Fv/Fm and △MR/MR0. Consequently, PSII and PSI coordination was not significantly affected by salt stress. In conclusion, TH maintained normal coordination between PSII and PSI by preventing photoinhibition and exhibited higher leaf photosynthetic activity than DH under salt stress. Compared with DH, lower leaf ionic toxicity due to greater root Na+ extrusion and restriction of Na+ transport to leaf might be responsible for maintaining higher leaf photosynthetic activity in TH under salt stress.

Purpose: The Yellow River delta boasts rich land resources but lacks fresh water and exhibits poor natural conditions. To rationally develop and utilize the land resources therein, it is necessary to evaluate the soil quality. Methods: Adopting specific screening conditions, principal component analysis (PCA) was used to construct a minimum data set (MDS) from 10 soil indicators. Then, a complete soil quality evaluation index system of the Yellow River delta was developed. The soil quality comprehensive index (SQI) method was used to assess the soil quality in the Kenli District, and the soil quality grades and spatial distribution were analyzed. Results: (1) The average SQI of the Kenli District is 0.523, and the best soil quality is concentrated near the Yellow River, especially in Huanghekou town. (2) The normalized difference vegetation index was positively correlate with SQI, whereas Dr (nearest distance between the sampling site and Yellow River) and Ds (nearest distance between the sampling site and Bohai Sea) were negatively correlated with SQI. Elev (sampling site elevation) was not correlated with SQI. (3) The SQI of agricultural planting is greater than that of the natural land type and significantly greater than that of nudation. The main factors limiting farmland soil quality are SK (water-soluble potassium) and pH, whereas the factor limiting the natural land type are the soil nutrient indicators. Conclusions: To improve soil quality and develop and utilize land resources, the towns should adopt systematic land development/utilization methods based on local conditions. These results have important guiding significance and practical value for the more objective and accurate evaluation of soil quality in coastal areas and the development and utilization of land resources.

The summer maize-winter barley (or wheat) rotation system is a conventional farming method in coastal areas of east China. However, researchers have paid little attention to the increasing soil degradation after successive crop rotation in coastal saline agriculture. In the current study, a two-year field experiment was conducted to investigate the changes in soil physio-chemical properties and crop grain yields under the maize-barley rotation system. Wheat straw derived biochar (BC) was applied to topsoil (0~20 cm) at four different rates (0, 7.5, 15 and 30 Mg ha⁻¹) before summer maize cultivation, and no biochar was added in the cultivation of the winter barley. Bulk density (BD), water holding capacity (WHC), water stable aggregate (WSA), soil electrical conductivity (EC), pH (1:5 water w/v) and soil organic carbon (SOC), at the harvesting time of maize and barley, were analyzed. The application of biochar increased WHC and macro-aggregate (>2 mm) content after barley harvest. Soil EC was mainly affected by the rain during maize cultivation and increased only slightly under BC treatments. However, no difference in EC was found among all treatments after barley harvest. The application of BC at 30 Mg ha⁻¹ increased the maize yield by 66% but produced no difference in the barley yield. We concluded that biochar could be an effective option to mitigate soil degradation and improve crop productivity in coastal saline agriculture.

A field experiment was conducted to investigate the effects of biochar (BC), fulvic acid (FA) and Bacillus subtilis (BS) on soil properties and crop growth in the coastal salt-affected soil. Four levels of BC (0, 7.5, 15, 30 t ha⁻¹), two levels of FA (0, 1.5 t ha⁻¹) and BS suspension (0, 108 CFU mL⁻¹) were designed during the maize cultivation. The results showed that 30 t ha⁻¹ BC treatment was the most beneficial for improving the soil qualities. The grain yields in treatments containing FA and BS were lower than that in the BC treatments, and they were lower than that in the CK treatment. The treatment of 15 t ha⁻¹ BC + BS obtained the highest grain yield, which was 1.75 times more than CK. An antagonism effect of the combination of FA and BS induced a grain yield decrease, and a higher content application of BC alleviated the negative effects.

Salt-affected soils is an important soil resource. Understanding fertilizer and salinity interaction are of great economic importance for improving crop yield and fertilizer use efficiency. A pot experiment was carried out to study the application of nitrogen (N) for ameliorating salt stress in wheat grown in the coastal saline soil of the Yellow River delta. Several controlling levels of salinity and nitrogen (0.7, 1.7, 2.7 g/kg, and 135, 270, and 405 kg/ha) were designed in a pot experiment in a stable water content state to investigate the N and salt interaction on soil properties and winter wheat growth characteristics. The results showed that the dry weight of winter wheat was promoted by salinity in the early growth stage (20 days), then it was gradually inhibited by nitrogen fertilizer. When winter wheat was grown by 54 days, the N and salinity had significant effects on the biomass of winter wheat. The nitrogen content of wheat shoot and root was mainly affected by N addition usage, and the largest value was obtained in 270 kg/ha N dosage treatments. The higher the salt content existed in the soil, the lower the growth rate shown in wheat cultivation. Under saline conditions, the N fertilizer application amount should be controlled to no more than 270 kg/ha, so that it could greatly promote wheat growth. Reasonable fertilizer usage could significantly contribute to crop yield and food quality of the saline agriculture in the Yellow River delta.