The severity and yield effects of the chocolate spot disease in faba bean affected by intercropping and nitrogen input.

BACKGROUND: The aim is to study the disease suppression efficiency, yield loss rate, and yield benefits of intercropped faba bean against chocolate spot under nitrogen (N) input, to clarify the effectiveness of intercropping faba beans in controlling chocolate spot and its contribution to yield increase. RESULTS: Four N input levels and disease suppression treatments were discovered when faba bean-wheat intercropped was used. Adding N enhanced the chocolate spot's area under disease progression curve (AUDPC) by 27.1-69.9%. In contrast to monoculture, intercropping reduced the AUDPC of the chocolate spot by 32.4-51.0% (P < 0.05). Interestingly, the relative control efficacy (RCE) of intercropping at the EShan site was better. With disease suppression or non-suppression, N input increased grain yield loss and its components in faba bean. The total yield advantage effect (TE) and disease-suppression effect (DSE) of faba bean intercropped at the two experimental sites were significantly increased under N input (N1 and N2 level). The proportion of recovery yield due to intercropping suppressed disease (DSE/TE ratio) in EShan (52.1%) was higher than that in Xundian (40.9%), and the DSE of intercropping played an indispensable role in the two sites. Regression analysis of AUDPC and grain yield loss amount showed that one unit increase in chocolate spot AUDPC could cause a grain yield loss of 0.38-0.86 kg ha-1 . The partial land equivalent ratio (pLER) of intercropping faba beans at the EShan site was > 0.33. CONCLUSION: In conclusion, intercropped faba bean with N treatment (45-90 kg ha-1 ) was the best choice for maximizing the intercropping disease control effect. © 2023 Society of Chemical Industry.

Functional traits of poplar leaves and fine roots responses to ozone pollution under soil nitrogen addition.

Concurrent ground-level ozone (O3) pollution and anthropogenic nitrogen (N) deposition can markedly influence dynamics and productivity in forests. Most studies evaluating the functional traits responses of rapid-turnover organs to O3 have specifically examined leaves, despite fine roots are another major source of soil carbon and nutrient input in forest ecosystems. How elevated O3 levels impact fine root biomass and biochemistry remains to be resolved. This study was to assess poplar leaf and fine root biomass and biochemistry responses to five different levels of O3 pollution, while additionally examining whether four levels of soil N supplementation were sufficient to alter the impact of O3 on these two organs. Elevated O3 resulted in a more substantial reduction in fine root biomass than leaf biomass; relative to leaves, more biochemically-resistant components were present within fine root litter, which contained high concentrations of lignin, condensed tannins, and elevated C:N and lignin: N ratios that were associated with slower rates of litter decomposition. In contrast, leaves contained more labile components, including nonstructural carbohydrates and N, as well as a higher N:P ratio. Elevated O3 significantly reduced labile components and increased biochemically-resistant components in leaves, whereas they had minimal impact on fine root biochemistry. This suggests that O3 pollution has the potential to delay leaf litter decomposition and associated nutrient cycling. N addition largely failed to affect the impact of elevated O3 levels on leaves or fine root chemistry, suggesting that soil N supplementation is not a suitable approach to combating the impact of O3 pollution on key functional traits of poplars. These results indicate that the significant differences in the responses of leaves and fine roots to O3 pollution will result in marked changes in the relative belowground roles of these two litter sources within forest ecosystems, and such changes will independently of nitrogen load.

Canopy and understory nitrogen addition have different effects on fine root dynamics in a temperate forest: implications for soil carbon storage.

Elucidating the effects of atmospheric nitrogen (N) deposition on fine root dynamics and the potential underlying mechanisms is required to understand the changes in belowground and aboveground carbon storage. However, research on these effects in forests has mostly involved direct understory addition of N and has ignored canopy interception and processing of N. Here, we conducted a field experiment comparing the effects of canopy addition of N (CAN) with those of understory addition of N (UAN) at three N-addition rates (0, 25 and 50 kg N ha-1 yr-1 ) on fine root dynamics in a temperate deciduous forest. Fine root production and biomass were significantly higher with CAN than with UAN. At the same N-addition rate, increases in fine root production with CAN were at least two-fold greater than with UAN. At the high N-addition rate and relative to the control, fine root biomass was significantly increased by CAN (by 23.5%) but was significantly decreased by UAN (by 12.2%). Our results indicate that traditional UAN may underestimate the responses of fine root dynamics to atmospheric N deposition in forest ecosystems. Canopy N processes should be considered for more realistic assessments of the effects of atmospheric N deposition in forests.

Stoichiometry in aboveground and fine roots of Seriphidium korovinii in desert grassland in response to artificial nitrogen addition.

Nitrogen (N) input by atmospheric deposition and human activity enhances the availability of N in various ecosystems, which may further affect N and phosphorus (P) cycling and use by plants. However, the internal use of N, P, and N:P stoichiometry by plants in response to N supply, particularly for grass species in a desert steppe ecosystem, remains unclear. In this work, a field experiment was conducted at an infertile area in a desert steppe to investigate the effects of N fertilizer addition rates on the stoichiometry of N and P in a dominant grass species, Seriphidium korovinii. Results showed that for both aboveground and fine roots of S. korovinii, N inputs exponentially increased the N concentration and N:P ratios while P concentrations decreased. Meanwhile, the relationships between N and P concentrations for both aboveground and fine roots were significantly negative. Furthermore, while the N concentrations in the plants were relatively low, P concentrations were higher than the global means, resulting in a relatively low N:P ratio. These results suggest that the stoichiometric characteristics of N were different from that of P for this desert plant species. Results also show that the intraspecific variations in the main element traits (N, P, and N:P ratios) were consistent at the whole-plant level. Our results also suggest that N should be part of any short-term fertilization plan that is part of a management strategy designed to restore degraded desert grassland. These findings highlight that nutrient addition by atmospheric N deposition and human activity can have significant effects on the internal use of N and P by plants. Therefore, establishing a nutrient-conservation strategy for desert grasslands is important.

Legume cover with optimal nitrogen management and nitrification inhibitor enhanced net ecosystem economic benefits of peach orchard.

Peach (Prunus persica L.), as a traditional kind of fruits in China, was extremely dependent on large application of nitrogen (N) fertilizer to maintain high fruit yield and commercial income, resulting in raising environmental damage risk. Therefore, a three-year field trail was conducted to clarify the environmental N loss under conventional management, investigate the positive effects of optimal N management, legume cover and 3,4-dimethylpyrazole phosphate (DMPP) on N input/output and the net ecosystem economic benefits (NEEB). There are four treatments in this study: conventional fertilizer management with 521.1 kg N ha-1 yr-1 input (CU); optimal N management including 406.4 kg N ha-1 yr-1 input and deep fertilization (OP); DMPP was added to OP at rate of 1 % (w/w) (OPD); legume (white clover) was covered to OPD (OPDG). Results showed 102.9 kg N ha-1 was removed by annual fruit and residues (including pruned branches, pruned and fallen leaves), while 70.2 kg N ha-1 was lost to the environment by ammonia (NH3), nitrous oxide (N2O) and N runoff loss under the conventional fertilizer management. While, the optimal N management mitigated NH3 volatilization about 49.3 %, further added DMPP abated N2O emission by 61.4 %, besides covered white clover lowered N runoff loss by 64.5 %. The NEEB results revealed that optimal N management combined with added DMPP and covered white clover could minimize the production cost, reduce environmental damage cost by 35.9 %, increase fruit yield by 10.3 % and achieved the maximum NEEB with improvement of 27.1 %, in comparison of the conventional fertilizer management. Generally, conventional peach cultivation constituted overwhelming N loss to raise potential environmental risk. While, extending mode of optimized N management combined with DMPP and legume cover could not only realize high fruit revenue, but also abate environmental N losses, thereby should be considered as effective strategy for sustainable fruit cropping systems.

Spatio-temporal dynamics of nitrogen use efficiencies in the Chinese food system, 1990-2017.

Understanding the influence factors of nitrogen (N) use efficiencies (NUEs) in different stages of the food system at the provincial scale is critical to achieving cleaner food production while ensuring food security. Nevertheless, they are not well understood. Here we comprehensively analyzed NUE and its influence factors at different stages of the provincial food system. The results showed that per unit agricultural land N input increased by 5-92% in 27 provinces, during 1990-2010, resulting in a low NUE for the crop system when N input per unit agricultural land exceeded about 400 kg N ha-1. This situation has brought some positive changes, as N input decreased by 3-271 kg N ha-1 in 77% of the provinces in 2017, relative to that of 2010, but 10 provinces were still over 450 kg N ha-1 in 2017. Animal food production is expected to continue to expand because 35% and 68% of provinces' urban and rural households, respectively, were still below the recommended minimum animal food N consumption recommendation in 2017, posing great challenges for reducing environmental N pollution. An exciting result is that the NUE of the animal system can be improved by increasing the share of animal food contributed by poultry, eggs, milk and fish, to align with the diets recommended by the Chinese Nutrition Society. NUEs of the provincial food systems excluding Inner Mongolia, Xinjiang, Qinghai and Tibet, would increase by 13% if the net imported food N increased by 1 kg capita-1. Nevertheless, virtual NUE-including N input for imported food in the calculation of NUE-should be considered for accurate comparison of the NUEs of the provincial food systems, especially in highly urbanized areas, while N input for non-food animals should be excluded for accurate evaluation of the NUE in pastoral areas, considering their special production systems and feeding structures.