Dynamics of Nutrients in Organic Substrates and Enzyme Activities in Tomato Rhizosphere in Greenhouses
To clarify the response patterns of root enzyme activities to environmental factors such as nutrients in soil/substrates,we carried out pot experiments with greenhouse soil,pinecone residue,and peat in Yunnan.Four treatments,including soil without crop cultivation(CK),cultivation of tomatoes in greenhouse soil(T1),cultivation of tomatoes in pinecone residue(T2),and cultivation of tomatoes in peat(T3),were designed to investigate the dynamics of nutrients in substrates and enzyme activities in tomato rhizosphere.The results showed that nitrate nitrogen and ammonium nitrogen exhibited different trends at different stages,following a trend of T2>T3>T1>CK at the 16th week.The content of available phosphorus showed consistent trends across treatments,being the highest in T2,42.26%higher than that in CK at the 16th week.The content of available potassium exhibited a unimodal pattern,following the trend of T2>T1>CK,and decreased slowly and did not fluctuate in T3 treatment.The content of organic matter was significantly higher in T3 than in other treatments.Additionally,the catalase activity slowly declined,with no significant differences among treatments.The level of fluorescein diacetate(FDA)hydrolase was the highest in T2,reaching 83.412 μmol/(d·g)at the fourth week and 76.757 μmol/(d·g)at the eighth week,which were significantly higher than those in other treatments.The dehydrogenase activity was strongest in T2 and T1,with significant differences observed after 12 weeks.The sucrase activity in T2 reached 84.584 μmol/(d·g),which increased by 60.32%-65.56%compared with those in other treatments.The urease activity showed a rising trend,being the highest in T2 throughout the experiment period.The Mantel test indicated that nitrate nitrogen,ammonium nitrogen,available potassium,and organic matter were all associated with enzyme activities in the rhizosphere.In conclusion,pinecone residue and peat were superior to conventional greenhouse soil in maintaining nutrients.Pinecone residue benefited the enhancement of enzyme activities in tomato rhizosphere,and the FDA hydrolase had the closest relationship with nutrients.
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