Evaluating the Impact of Crop Layout Changes on N and P Nutrient Balance: A Case Study in the West Liaohe River Basin, China

Regional crop layout has changed significantly due to climate, policy, and other factors, which has impacted farmland nutrient balance. Here, we evaluated the impact of crop layout changes on N and P nutrient balance in the West Liaohe River Basin from 2000–2015. The study area has long been in a N and P surplus state. The unit N surplus exhibited a downward trend and the unit P surplus showed an increasing trend. Significant correlations existed between planting areas and nutrient surplus. The N and P surplus layout was mainly concentrated in the West Liaohe River lower reaches basin. The planting area of wheat must be reduced and the areas of maize and soybean must be controlled to adjust the N and P balance and reduce the environmental pollution risk. Chemical fertilizer and seed inputs are the main sources of N input. Furthermore, combining farming and pastoral farming is conducive to improving N and P use efficiency. Manure can be absorbed by farmland, the ratio of organic and chemical fertilizers can be reasonably set, and chemical fertilizer application can be reduced.

Changes in Crop Layout, Effects on Farmland Nutrient Balance: A Case Study in The West Liaohe River Basin, China

Estimating regional soils Nitrogen and phosphorus balance in cropland is essential to improve management practices, reduce environmental risks and develop sustainable agriculture. In this study,spatial and temporal variations in crop layout, the impact on soil N and P nutrient balance were assessed from 2000 to 2015 in the West Liaohe River Basin between 2000 and 2015. The result shows that the area of cropland is on the rise, and the spatial distribution of arable land is consistent with the distribution of the main tributaries of the West Liaohe River basin. The change in planting layout for maize and soybeans has a significant impact on the nutrient balance of farmland, which plays a critical role in modifying surplus nutrients. Nutrient surpluses on farmland were mostly concentrated in areas where maize planting layout changed between 2000 and 2015. The N nutrient surplus rate decreased by 39.3%, N utilization efficiency, increased by 70.7%; P nutrient surplus rate decreased by 3.8%, and P utilization efficiency increased by 49.3%. The average utilization efficiencies of N and P nutrients were 27.8% and 9.1%, respectively, and the utilization efficiency was low. Chemical manure is the main source of nutrients. The risk of phosphorus pollution was higher than the risk of nitrogen pollution in the West Liaohe River Basin. The lower Liaohe River Basin (below the Sujiapu) was the region with the most violent changes in nitrogen and phosphorus nutrient balance. It is recommended that reduce the amount of chemical fertilizer application, especially, reduce the amount of P application, improve the ef-ficiency of nutrient use, and focus on strengthening pollution control in key areas such as the West Liaohe River lower reaches basin (below Sujiabao), reducing the risk of agricultural nonpoint source pollution.

Occurrence and Distribution Characteristics of Antibiotic Resistance Genes in Sediments Between Urban and Rural of the Liaohe River Basin, China

Antibiotic Resistance Genes (ARGs) are considered to be emerging pollutants related to human activities. The rapid development of global urbanization has expanded human activities, thereby exacerbating the global human health risks caused by antibiotic resistance genes. The effects of urban and rural environments are multifarious, which makes the source and distribution of ARGs in the environment diversification. Understanding the distribution and spread of ARGs is essential for studying the environmental behavior of ARGs. In this study, the occurrence 296 genes were detected by the high-throughput qPCR technology, and FC value was used to analyze the diversity of ARGs and Mobile Genetic Elements (MGEs) in sediments between urban and rural areas of the Liaohe River Basin, China. The co-occurrence of MGEs and ARGs was analyzed using network to decipher core genes. A total of 187 ARGs and 10 MGEs were detected in all sediment samples. The average number of genes detected in urban sites is 89 higher than that in rural sites. The high abundance and various types of ARGs and MGEs detected in urban river sediments indicates that the occurrence of urban ARGs is more complex. MGEs were detected high levels and were significantly correlated with the abundance and diversity of ARGs in river sediments providing evidence that MGEs were related to the occurrence and distribution of ARGs and tnpA(tnpA-07, tnpA-01 and tnpA-03) gene were at the key position of co-occurrence of various types of ARGs.