1. Introduction
An extreme imbalance between the arable area and population exists in China which has 20 percent of the world’s population but only 7 percent of the world’s arable land (Piao et al., 2010). With the rapid socio-economic development, more and more arable lands are occupied by industry and urban construction, resulting in a sharp decrease in the arable land (Li, Liu, & Yang, 2018). So far, under the pressures of food safety and the arable land red line continued to increase, enclose tideland for cultivation are widely used to increase the arable land and ensure the adequate production of grain (L. Chen et al., 2020; Li et al., 2018; J. Zhao et al., 2020). However, the soil in reclamation land usually is seriously impoverished which mainly manifests as salination, soil nutrient deficiency, extremely low organic matter content , etc. The high fertility of the soil is the basis for maintaining a high yield of crops (Stewart, Pierzynski, Middendorf, & Prasad, 2020). Therefore, it is necessary to take a series of measures to improve soil fertility and reduce the risk of crop failure for reclamation land.
Application of chemical fertilizer is the most common way to improve the permeability of soil structure and provide abundant nutrients for crops to maintain grain production (Huang et al., 2019). However, traditional fertilizers, especially nitrogen (N) fertilizer, are extremely water-soluble and are easily transferred and transformed between the soil-water-atmosphere environment according to the soil structure and property (Fu, Duan, Zhu, Gao, & Xu, 2021). The soil in reclamation land is mainly sandy loam with lower fertility holding capacity, resulting in the inefficient of traditional fertilizers. Moreover, unreasonable application of fertilizer has the risk of the non-point source due to the losses of reactive N to the surface water, groundwater, and atmosphere (J. Chen et al., 2018; Liu et al., 2021; Yang & Lin, 2019). Coated controlled-release fertilizer (CRF) is prepared by coating the conventional fertilizer with a hydrophobic material and it has the characteristics of controlled nutrient release (Shen, Du, Zhou, & Ma, 2017). Nutrients in coated CRF are regulable to supply for crop growth according to the requirement by adjusting the amount and property of coating (Tomaszewska & Jarosiewicz, 2002). The improvements of the water efficiency, N-use efficiency, and grain yield of maize by application of controlled-release urea (CRU) combined with subsoiling had been confirmed by Hu et al. (2013) in northern China. Guo et al. (2019) also demonstrated that the CRU treatment decreased the annual NH3 volatilization, CH4 emission by 64.8%, 19.7%, and 35.2%, respectively in a paddy field. Gao et al. (2021) showed that the CRF treatment significantly improved soil aggregate characteristics and increased humic acid, fulvic acid, lignin-like molecules, and protein-like molecules content. Therefore, CRF has the potential to improve fertilizer use efficiency, soil structure, and soil fertility and relieve a series of environmental problems, such as eutrophication and groundwater pollution. However, the effects of CRF on the improvement of soil fertility and the change in soil organic and mineral components in the soil from reclamation land are few studied.
Crop rotation has been applied for millennia across China which mainly includes the maize-wheat rotation, peanut-wheat rotation, rice-rape rotation, rice-wheat rotation, and rice-green manure rotation (Zeng et al., 2016). As an environmentally friendly strategy, crop rotation can adequately control nutrients, water, weeds, pests, and diseases, as well as maintain soil structure and fertility which increases the productivity of the land (Bender, Wagg, & van der Heijden, 2016; German, Thompson, & Benton, 2017). For example, Ghosh et al. (2020) indicated that replacing wheat with chickpea in the rice-wheat rotation increased grain yield by 5-8%. A previous study also suggested that the adoption of 2- and 4-year of crop rotations in rain-fed environments could result in high yield compared with continuous cropping (Sindelar, Schmer, Jin, Wienhold, & Varvel, 2016). Malobane, Nciizah, Mudau, and Wakindiki (2020) indicated that the sweet sorghum-grazing vetch-sweet sorghum rotation increased ammonium (NH4+-N) and nitrate (NO3-N) by 3.42% to 5.98%, respectively. A 9-year corn-wheat-corn-wheat-corn-wheat-alfalfa-alfalfa-alfalfa (Lotuscorniculatus L.) rotation indicated that rotation had positive effects on soil organic carbon (SOC), total nitrogen (TN), and soil microbial biomass C, N, and activity (Giacometti et al., 2021). Recently, a meta-analysis across China had demonstrated that crop rotation increased yields by 20% compared to continuous monoculture and the improvement performed better in coarse or medium soil texture and medium level of initial SOC and at low N fertilization rate (J. Zhao et al., 2020). Even so, the impacts of the combination of crop rotation and CRF application on grain yield, soil fertility, and changes in soil organic and mineral components remain unclear, especially in barren soil.
A field trial of three types of crop rotation (rice-green manure, rice-rape, and rice-wheat) combined with different N fertilizer treatments was conducted in a reclamation land. The types of N fertilizer included conventional urea and bulk blending urea (BBU) of conventional urea and CRU. Soil organic and mineral components were characterized by Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) and mid-infrared attenuated total reflection spectroscopy (FTIR-ATR). The main objective of this study was to investigate the influences of fertilization, crop rotation, and their interaction on rice grain yield, dynamics of soil inorganic N and plant N uptake, soil properties, and soil organic and mineral components.