The utilization of crop straw resources has been highly emphasized by governments and academia in recent decades. The growing importance of straw decomposition in the wheat-maize rotation system and the remarkable diversity of accumulated information on this topic inspired us to quantitatively explore variations in the outcomes of individual studies. We conducted a data analysis of 46 experimental studies reporting the effects of agronomic measures on the straw decomposition rates of wheat (14 studies) and maize (38 studies). Statistical results showed that maize straw crushed and buried in soil with turn-over or rotary tillage can significantly increase straw decomposition rates. Further, with the increase in nitrogen input and straw burial depth in the soil, the maize straw decomposition rate increased significantly, while the amount of straw return showed the opposite trend. Among all agronomic measures in this research, burial depth has demonstrated a significant positive effect on the wheat straw decomposition rate. The random forest analysis identified decomposition time as the most important predictor of straw decomposition rates for wheat and maize. In addition, some agronomic measures and straw decomposition time jointly affect the decomposition rate of straw. In general, agronomic measures are effective factors in controlling straw decomposition in a wheat-maize rotation system.

To examine the safety of producing edible rapeseed in heavy-metal-contaminated farmland, field experiments were performed with 25 varieties of edible rapeseed on farmland lightly polluted with Cd in the central southern part of Hunan Province. Growing characteristics and Cd contents in rapeseed tissues were measured, and Cd uptake, translocation and removal potential were calculated. The results showed that the growth of 25 rapeseed varieties was not inhibited without withering or inconsistent changes in the shoot. The shoot and root Cd contents of rapeseed varieties ranged from 0.05 to 0.26 mg·kg⁻¹ and 0.04 to 0.26 mg·kg⁻¹, respectively. The bioaccumulation factor (BCF) showed that the shoot had a greater capacity for Cd transport than roots. The total Cd removed by rapeseed varieties ranged from 1.606 to 16.159 μg·plant⁻¹. There were significant differences in plant height, BCF of soil available Cd in the shoot, translocation factor (TCF) of Cd from root to shoot and Cd intake by rapeseed among the edible rapeseed varieties. Cluster analysis of Cd accumulation in the 25 rapeseed varieties indicated that Lvjin 1, Guanyou Qingjing and Guanyou brassica not only reduced soil pollution but also allowed for the production of safe leafy rapeseed, although Cd contents in the shoot of 25 rapeseed varieties did not exceed the national safety standards of China.

In this study, the accumulation characteristics of As, Hg, Cd, Cr, and Pb in 63 soil samples from 28 organic farms in Beijing, China, were analyzed to investigate the risk of heavy metal pollution in organic agriculture, and the key related factors were evaluated. The results revealed that the As, Hg, Cd, Cr, and Pb concentrations in the soil samples were below the risk screening values and substantially lower than those in the soil under conventional agriculture. However, the coefficients of variation for Hg and Cd were 112.45% and 38.34%, respectively, indicating a notable anthropogenic impact. Notably, 35.92% of the sampling sites had medium to high potential ecological risk values for Cd, and the Cd concentration increased considerably as the number of planting years increased. Different crop types impacted the soil heavy metal concentrations. The concentrations of Cd and As in the soil of Brassica crops were 0.265 and 12.915 mg/kg, respectively, which were substantially higher than those in the soil of other crop types. The Random Forest model indicated that soil nutrients had the most significant impact on soil heavy metal accumulation, particularly phosphorus. In conclusion, compared with conventional agriculture, organic agricultural soils have lower heavy metal concentrations and exhibit lower ecological risks, with no significant heavy metal pollution detected. However, there is a risk of Cd accumulation, and preventive measures should be implemented, especially for soils under prolonged cultivation and with potential sources of heavy Cd inputs.

To identify the general pattern of impact of the application of the mixed controlled-release urea (CRU) with urea (C-U) on grain yield, plant characteristics, NUE and soil nitrogen contents in wheat–maize production, a 5-year field trial with three release longevity and four ratios of CRU in C-U and common urea alone (U) was carried out in the North China Plain. Results with meta-analysis revealed that C-U had significant effects on grain yield and plant characteristics, NUE and soil NO₃⁻-N contents in wheat–maize production positively with the release longevity of CRU and the ratio of CRU-N in C-U. The application of C-U with 60 d or 90 d CRU for wheat and maize had the best overall effects, while C-U treatment with 30 d CRU had a significant inhibitory effect. For maize, C-U with 30% CRU-N had the largest increase rate on yield, 1000-grain weight, plant height, dry weight and NUE by 5.13%, 1.61%, 3.70%, 11.33%, and 8.63%, respectively, while C-U with 40% CRU-N had the largest reduction soil NO₃⁻-N. For wheat, the application of C-U with 40% CRU-N had a significant effect on yield, sterile spikelet number, and NUE by 4.45%, −9.76%, and −8.04%, respectively. To conclude, the use of the C-U with appropriate release longevity and the ratio of CRU has great potential to proliferate wheat–maize yields and reduce fertilizer loss especially for maize that not only provides an effective generic methodology for agriculture to improve measures but also ensures profitability.