Although fertilization of controlled-release fertilizer (CRF) and crop rotation have been shown the contribution to improving yield, nutrient use efficiency, and soil fertility, their interactions on the quality of relcalimed land remains unclear. Hence, a field experiment was conducted in a reclaimed land along Yangze River to investigate their interactions. Results indicated that application of bulk blending urea (BBU) of conventional urea and controlled-release urea (CRU) with appropriate dosage and frequency increased the rice yield and nitrogen agronomic efficiency (NAE). Crop rotation also improved the rice yield and NAE through enhancing the retention capability of fertility. Crop rotation combined with fertilization significantly increased the soil pH, organic carbon (SOC), total N (TN), and permanganate oxidizes carbon (POXC). The rice-green manure (RG) rotation improved soil pH and TN most, and the rice-rape (RR) rotation improved SOC most. Fertilization of conventional urea and BBU both significantly increased the labile SOC functional groups and reduced the the stabled SOC functional groups under RG rotation. Under RR rotation, however, only fertilization of conventional urea increased the labile SOC functional groups and reduced the the stabled SOC functional groups. The rice-wheat (RW) rotation showed no significant effects on the changes in soil organic functional groups. The changes in soil properties had significant effects on improving rice yield or NAE under RG and RR rotations instead of RW rotation. The findings suggested that BBU combined with crop rotations could make good use of reclaimed land through improved nutrient use efficiency and soil fertility.

The direct characterization of the spatial distribution of elements and compound binding of salt-organic associations in soil is imperative for understanding the mechanisms of organic matter decomposition and nutrient release in soil degradation and development processes. Modern spectroscopic techniques provide a feasible method for analysis at the microscale. In this study, mid-infrared attenuated total reflectance spectroscopy (FTIR–ATR) was used to obtain molecular functional group information, laser-induced breakdown spectroscopy (LIBS) was apply to obtain micro-level distribution features of elements in soil, and two-dimensional correlation spectroscopy (2DCOS) analysis was conducted to illustrate the binding combination features of mineral-organic associations in salinized from the Hetao Irrigation District in China. The results showed that the distributions of Mg, Ca, Na, and K were heterogeneous at the micro-level; the spatial distributions of Mg and Ca showed a significant correlation (r = 0.90***), while K displayed a negative correlation with the SOM contents. In soil with lower SOM contents, the elements were distributed at the top of the ablation area and enhanced with the increasing SOM content, which reflected the trends of the SOM layer thickness outside the mineral–organic associations at the micro-level. Furthermore, 2DCOS analysis suggested that the hydrogen bonds in silicate groups were stronger than those of organic functional groups, such as C=O/C=C, when combined with salt-related compounds, and Mg, Ca, Na, and K did not originate from clay mineral compounds in salinized soil, but partially originated from deposited organic associations.