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The objectives of this study were to investigate the nitrogen (N) and phosphorus (P) balance fertilization strategy in paddy fields, and to evaluate the effects on N uptake and utilization in rice. In 2017-2018, the experiment was conducted using Deyou4727 hybrid rice with four different P fertilizer levels (0, 30, 60, and 90 kg/ha), marked as P0, P1, P2, P3 in turn, and four different N levels (0, 90, 150, and 270 kg/ha), similarly marked as N0, N1, N2, N3 in turn. The results showed that in the N-insufficient (N0, N1) environments, the P1 treatment increased N uptake and promoted transfer to the grain. However, high-P (P3) application increased the dry matter accumulation than other P levels, but limited the production and translocation of dry matter to some extent. In N-sufficient (N2, N3) environments, P2 level increased crop yield and N use efficiency by 11.35% and 37.01%. Unlike P2, none-P (P0) and high-P levels decreased rice dry matter translocation and transport capacity, which further affected N uptake and utilization in N-sufficient environments. Overall, the combination of the N application rate of 90 kg/ha and P application rate of 30 kg/ha, N application rate of 150, 270 kg/ha, and P application rate of 60 kg/ha had a high yield; strong nutrient accumulation and transfer ability. It was more inclined to balance N and P, which was beneficial to plant N absorption and utilization.

Anthropogenic activities have raised cadmium (Cd) concentrations in agricultural soil, emerging as a primary catalyst for the decline in crop yield. Intercropping of two or several plants is one technique among many Cd phytoremediation techniques that has gained enormous attention recently. However, the impact of cultivation modes on Cd movement in rice plants when intercropped with heavy metal (HM) hyperaccumulator plants remains unclear. Thus, this study was designed to explore the effects of cultivation modes and the intercropping of rice with Solanum nigrum L. on rice growth and Cd uptake in Cd-contaminated soil. The experimental design encompassed five treatments: dry cultivation of monocultured rice, monocultured Solanum nigrum L., and intercropped rice–Solanum nigrum L.; flood cultivation of monocultured rice; and intercropped rice–Solanum nigrum L. in a high-bed and low-ditch planting system. The results revealed a significant increase in rice growth when intercropped with Solanum nigrum L., with a notable increase of 18.32 g∙plant−1 observed in rice biomass in dry cultivation under the intercropping system. In contrast, a more modest increase of 3.67 g∙plant−1 was observed in the high-bed and low-ditch intercropped rice–Solanum nigrum L. mode. The soil total Cd was higher in dry cultivation of monocultured rice and Solanum nigrum L. compared to intercropped rice/Solanum nigrum L.-cultivated soil, with lower values recorded for intercropped rice/Solanum nigrum L. under the high-bed and low-ditch planting system. In contrast, no significant effect was noted on soil exchangeable Cd content based on the planting pattern and cultivation mode. Intercropping with Solanum nigrum L. demonstrated a significant reduction of Cd content in various rice tissues, particularly in roots at the maturity stage, while Cd content was reduced across all rice tissues under the high-bed and low-ditch planting system. The Cd content in the stem, leaves, and bran of monocropped rice was higher compared to intercropped rice. This study suggests that the rice–Solanum nigrum L. intercropping system effectively reduces rice Cd uptake, particularly under the high-bed and low-ditch planting system. [ABSTRACT FROM AUTHOR]