Effects Of A Residue After Evaporation From Industrial Vitamin C Production On Nitrogen Utilization And Quality Of Non-heading Chinese Cabbage

Nitrogen plays an essential role in the growth and development of plants and is an important component of proteins,nucleic acids,phospholipids and certain growth hormones in plants.Increasing nitrogen fertilization can increase crops’chlorophyll content,promote the synthesis of proteins and other nitrogen-containing substances,and improve plant yield,among other things.In order to meet the nitrogen demand of plants,nitrogen fertilizer is usually applied,but due to factors such as irrational application of nitrogen fertilizer and leaching,the utilization rate of nitrogen fertilizer in China has been at a low level,which also harms the environment,climate change and human health.The 2-keto-L-gulonic acid(2KGA)content of RAE,a waste fermentation residue discharged from the VC industrial process,is about 25%-30%.Previous studies found that RAE had significant growth-promoting effects on plants,but the effects on plant uptake and assimilation of inorganic nitrogen were lacking.Non-heading Chinese cabbage(Brassica campestris ssp.chinensis)is highly adaptable to the soil,uses leaves as products,and has a short and rapid growth period,with fertilizer requirements dominated by nitrogen fertilizer.Therefore,in order to investigate the potential of RAE to improve plant nitrogen utilization,in this paper,we used non-heading Chinese cabbage as experimental material and provided RAE along with nitrogen fertilization for indoor pot trials to investigate the effects of RAE on plant physiology and biochemistry,soil physicochemical and key functional genes(plant and microbial).The experiment was divided into four treatment groups:(1)no nitrogen fertilizer in the substrate and tap watering group(CK);(2)nitrogen fertilizer in the substrate and tap watering group(CN);(3)nitrogen fertilizer in the substrate and RAE diluted 100 times in the watering group(1N);(4)nitrogen fertilizer in the substrate and RAE diluted 200 times in the watering group(2N).By analyzing plant growth,soil fast-acting nutrients and functional genes related to plants and soil microorganisms,the effects of RAE with nitrogen fertilizer on soil nitrogen and plant growth were clarified,and the pathways of their effects were elaborated.The main conclusions obtained were as follows:(1)RAE with nitrogen fertilizer significantly promoted plant growth.Compared with the CN group,the plant height,maximum leaf length,maximum leaf width,dry weight and fresh weight increased by 16.97%,34.43%,25.86%,77.68%and 80.76%,respectively,in the 1N treatment group;2N also significantly increased the maximum leaf length,dry weight and fresh weight by 20.77%,57.88%and 61.97%.(2)RAE with N fertilizer significantly increased plant leaves’N accumulation and N use efficiency.Compared to the CN group,RAE with nitrogen fertilizer application significantly increased 1N by 71.59%and 2N by 60.71%in terms of N accumulation in plant leaves.In terms of the nitrogen fertilizer utilization effect of the plants,RAE with nitrogen fertilizer significantly increased AE_N,PFP_N,PE_N and RE_N by 229.80%,77.68%,61.13%and 105.23%for 1N,and 171.23%,57.88%,46.08%and 86.10%for2N,respectively.(3)RAE with N fertilizer significantly promoted plant-soluble protein and chlorophyll synthesis.Compared to the CN group,1N and 2N significantly increased soluble protein by 71.35%and 65.37%,respectively,and 2N significantly increased chlorophyll content by 16.71%.There was no significant change in any of the nitrate contents.(4)RAE with nitrogen fertilizer had significant promotion effects on leaf nitrogen metabolism-related genes nitrite reductase(NIR),plastid-type glutamine synthetase(Chloroplast-GS)and NADH-based electron donor glutamate synthase(NADH-GOGAT).All three had a facilitative effect on nitrite reduction,glutamine and glutamate synthesis,indicating that RAE can promote nitrogen assimilation to the plant.(5)RAE with nitrogen fertilizer significantly affected soil NO3~--N enhancement.Compared with the CN group,1N and 2N were increased by 55.55%and 74.67%,respectively.RAE with nitrogen fertilizer significantly increased the abundance of ammonia-oxidizing archaea ammonia monooxygenase(AOA-amo A)and ammonia-oxidizing bacteria ammonia monooxygenase(AOB-amo A),indicating that RAE with nitrogen fertilizer can effectively promote the nitrification process of soil.In conclusion,RAE can significantly improve nitrogen fertilizer utilization,enhance the assimilation process of inorganic nitrogen by crops,and improve crop quality while increasing crop yield.This study provides a scientific basis for the resource utilization of RAE,which can reduce the application of nitrogen fertilizer,ensure the sustainable development of the environment,and bring an organic synergist with potential applications for improving the utilization of nitrogen fertilizer.