This study was conducted to determine the effect of biochar application on nitrogen (N) leaching, ammonia (NH3) volatilization, and fertilizer N use efficiency (NUE) in two soils with different properties (loamy and sandy). Ryegrass (Lolium perenne L.) incubation experiments (with 15N-enriched urea applied) and an N loss simulation study were conducted at biochar application rates of 2% and 4%. The results showed that 15N utilization increasedby 8.83-9.06% following the addition of biochar to sandy soil during the first season compared with the control. However, this significant effect was not observed in the loamy soil, in which significantly more urea-N was retained in the soil following biochar application. Furthermore, based on the results of the N leaching and NH3 volatilization experiments, 29.19% and 28.65% NO3-N leaching reductions were induced by 2% and 4% biochar amendments in loamy soil, decreasing the total inorganic N that was leached (NH4+-N plus NO3-N) by 26.46% and 26.82%, respectively. However, although the amount of leached NH4+-N decreased in biochar-amended sandy soil, the cumulative NH3 volatilizations were 14.18-20.05% higher than in the control, and 22.55% more NO3--N was leached from biochar-amended sandy soil, resulting in a negative effect on N retention. According to this study, biochar can be effectively used to improve the NUE in sandy soil and reduce N loss from loamy soil.

Understanding how nitrogen concentrations respond to biochar amendment in different types of soils is important for agricultural management. Here, we analyzed the effects of amendment with rice hull biochar on sandy soil, red soil, and alkaline soil (coastal solonchak) over 13 months, focusing on factors such as ammonium (NH4+-N) and nitrate (NO3−-N) cumulative leachate losses, pH, cumulative volumes of leachates, NH4+-N and NO3−-N abundance of soils, soil dehydrogenase, and nitrogen-related soil enzyme activities. Our results indicated that biochar amendment increased the pH of red soil but decreased the pH of both sandy and coastal solonchak soils; promoted the retention of NH4+-N in red and sandy soils, but not in coastal solonchak; and reduced the loss of NO3−-N during the early stages of leaching but accelerated losses during subsequent leaching stages. Soil nitrogen supply capacity (NH4+-N + NO3−-N) greatly increased over the short term, with significant differences between treatments. Further, biochar enhanced concentrations of NH4+-N and NO3−-N in soils, and the addition of biochar stimulated the enzymatic and microbial activities in soil, which may increase the abundance of NH4+-N and NO3−-N. Finally, we found that the response of NH4+-N and NO3−-N to biochar addition varied among the different soil types.

ABSTRACT Biochar as a soil amendment has been shown to improve soil quality and crop growth. However, biochar’s effect on urea-N use efficiency in long term is not well elucidated. Here we studied urea-N (15N isotope) allocation in plants and soil in the presence of maize (Zea mays L.) stover biochar (equivalent to 46 t ha-1) during a 4-yr pot trial. Results showed that biochar only increased maize biomass (about 9%) with high amount of urea addition, which indicates the increased maize dry weight by biochar application could be attributed to synergistic effects between biochar and urea. Soil total N contents and fertilizer N retention were increased by 20% and 10.47% to 94.52%, respectively, indicating that biochar was more capable for fertilizer N retention than promote plant adsorption. Moreover, inorganic N content in biochar treatment was greatly increased, which implies the increased N mineralization. In total, we concluded that biochar application was a potential urea enhancer during plant production.

A produção de arroz japonica no norte da China desempenha um papel importante na segurança alimentar para o mundo. Transferência de genes mediada por Agrobacterium está se tornando uma abordagem poderosa para gerar germoplasma e desenvolver variedades. No entanto, a eficiência transgênica das variedades de arroz japonica no norte da China tem sido completamente desconhecida, o que obstrui o desenvolvimento da criação de transgênicos e a exploração das funções dos genes. Neste estudo, as eficiências da transgenia de seis variedades de arroz japonica desenvolvidas no Norte da China são avaliadas. As taxas de indução de calo primário e secundário das variedades são semelhantes. Contudo, a eficiência transgênica e a capacidade de regeneração das variedades são bem distintas. Foi estabelecida uma plataforma para a transformação das variedades de arroz e proposta uma variedade adequada, SN9816, para transferência de genes. SN9816 pode ser aplicada como um germoplasma-elite para melhoramento transgênico e pesquisa básica de biologia molecular no norte da China ou em uma área na mesma latitude.

The production of japonica rice in northern China plays an important role in food security for the world. Agrobacterium-mediated gene transfer is becoming a powerful approach to generate germplasm and develop varieties. However, the transgenic efficiency of the japonica rice varieties in northern China has been completely unknown, which obstructs the development of transgenic breeding and the exploration of gene functions. In this study, the transgenic efficiencies of six japonica rice varieties developed in northern China are evaluated. The rates of primary and secondary callus induction of the varieties are similar. However, transgenic efficiency and the regeneration ability of the varieties are greatly different. The results have established a platform for transformation of the rice varieties and proposed a suitable variety, SN9816, for gene transfer. SN9816 can be applied as an elite germplasm for transgenic breeding and basic research of molecular biology in northern China or an area in the same latitude.