Changes Of Soil Organic Carbon Pool And Its Effect On Micronutrients Availabilities In Soils Under Chinese Hickory Forests

In the light of tree growth impairment and decreasing productivity of Chinese hickory?Carya cathayensis?forests at present,a field soil survey was conducted again in 2016 in comparison with the last survey in 2008.The main results were as follows: 1)Soil organic carbon?SOC?content was significantly improved?p<0.05?in 2016,with mean of 32.15g·kg^-1 and maximum value of 54.90 g·kg^-1.The SOC content in 65% of the surveyed forestswas increased,but declined in the other.2)Soil properties in different forests varied greatly.In general,the forest soils were rich with SOC and availablenitrogen?N?.By contrast,soil acidification was popular and low soil available phosphorus?P?was also common.Moreover,low soil available potassium?K?was found in some of the forests.3)The availabilities of soil trace elements varied greatly with locations and among individual trace element as well,but they were improved comparied to that in 2008.More than 50% of the forests soil available iron were lower than 20 mg·kg^-1 in 2008,but only 40% in 2016.Most of the forests were rich in soil available manganese?Mn?,soil available copper?Cu?and soilavailable zinc?Zn?.An incubation experiment was carried outto study the effects of different organic materials?namely Feideli,a commercial organic fertilizer;potassium humate;biogas residue;and bamboo-char?on SOC pool and soil fertility especially the availabilities of soil micronutrients.Results showed that different types of organic materials and application rates had different effect on soil improvement.SOC content increased greater at higher application dosage,and bamboo-char had the greatest effect.Application of 10 g·kg^-1 dosage of Feideli or potassium humate hadmore effect on increasing soil pH and soil available nutrients of N,P and K.Some organic materials improved,while others decreased,theavailabilities of soil trace elements.Application of 10 g·kg^-1 dosage of Feideli or potassium humate evidently increased soil available Fe,Mn and Cu,and 10 g·kg^-1 dosage of biogas residue was better than other organic materials to improve soil available Zn.Results from present study indicate that organic material application could increase SOC content and improve soil fertility.There needs to control of nitrogen fertilizer application urgently,and to increase application ofpotassium and organic fertilizers and micronutrient fertilizers to promote healthy growth of Chinese hickory trees.