Analysis On Soil Fertility And Changing Tendency Of The Typical Arable Brown Soil

There are some phenomena about most arable soil in Shenyang,such as excessively using chemical fertilizer,unreasonable coordination application of organic manure and chemical fertilizer,singleness cultivation and so on.All of phenomena influence the soil fertility to some extent.This paper made a study of the soil fertility status,the soil fertility evolutionary trends of soil fertility on typical arable brown soil of Dongling and the east of Sujiatun sections in Shenyang,with the methods of sampling in the open air and indoor analysis.The evaluation has been made on the soil integrate fertility used the methods of weight coefficient and the method of vague analysis,and then realize the obstacle factors, fertility-building measures.The results as following:1 The following is the nutrients status of arable brown soil.The content of organic matter is 20.10±4.03g kg^-1 and 53.28%of the soil samples are in the relatively low level. The content of total nitrogen(1.19±0.35g kg^-1) and available nitrogen(113.05±26.77 mg kg^-1) are mostly in medium and relatively high level.The content of available phosphorus is 23.57±14.94mg.kg^-1 and 52.68%of the soil samples are in the rich or relatively high level. The content of available potassium is 76.10±26.81mg·kg^-1 and 85.22%of soil samples are lack level.The average number of the CEC is 17.22±2.66cmol kg^-1,which is in the middle level.The variation of soil nutrients is not high except the available phosphorus.The spatial distribution of different nutrient item is not consistent,but the nutrients content of the north section are relatively rich.The content of available calcium and the magnesium are higher than the limit values.The variation range of trace elements in arable brown soil is large,but the content is rich.Only 7.14%of available zinc is relatively deficiency.2 Comparing with the data of the second soil general survey,the content of some nutrients and organic matter ascend a little.The content of organic matter increases from 17.7g kg^-1 to 20.01g kg^-1.The content of total nitrogen increase from 1.01g kg^-1 to 1.19g kg^-1.The content of available nitrogen increases from 89.20mg kg^-1 to 113.05mg kg^-1(increasing 26.74%).The content of available phosphorus has a obvious uptrend (increasing 187.32%),increasing from 8.20mg kg^-1to23.57mg kg^-1.The content of available potassium decreases from 108 mg kg^-1 to 76.10 mg kg^-1.3.The pH value of arable brown soil has a downtrend.The pH value is between 5.1 and 7.5 in 1982 and average value is 6.48.The pH value is between4.5 and 7.6 in 2008 and average value is 5.60.The pH value of 54.36%arable brown soil doesn't reach 5.5.The acidification is serious.Compared with the data of the second soil general survey,the pH value decrease 0.88.4.Analysis on the reason of soil acidification,the BS of arable brown soil has a downtrend.The BS changes from 53.51%to 92.94%,and the average BS is 69.91%.The average BS percentage of the soil samples is only 61.91%,pH of which is under 5.5.The relation between BS and pH are in notable positive correlation,r=0.7502^**.There were more Ca²⁺ and Mg²⁺ in composition of base ions.The amount of K⁺ and Na⁺ are less in composition of base ions.The study also shows that Ca²⁺ saturation is 43.63%.The relation between Ca²⁺ saturation and pH is in positive correlation too,r=0.7718^**.Environment factor,unreasonable fertilization and cultivation,soil texture are also important factors to soil acidification.5.The texture of most of the soil tested is silt loam.The average value of bulk density is 1.15 g cm^-3,the total porosity is 55.65%and the capillary porosity is 43.48%.These physical standards of soil are suitable for plants growing and the variation intensity is low. The average value of the air porosity is 12.81%.The air porosity of 33.34%soil samples is lower than 10%.The air porosity of soil is relatively low.The average aggregates content of wind drying soil is 80.44%that particle diameter is more than 0.25mm.The average water-stable aggregates content is only 22.29%and the average value of aggregates stability is 0.29.The quality and quantity of water-stable property of aggregates is bad.6.It affected plants growing as the depth of arable layer became lower and the depth of plow sole became deeper.The depth of arable layer range is between 7.5 and 25cm.The average value is 15.45cm.There are 49.09%soil samples which the depth of arable layer is less 15cm.Comparing with the data of the second soil general survey,the depth of arable layer decrease 2.36cm and the depth of plow sole increase 2.97cm.7.Soil integrate fertility of arable brown soil is evaluated by the method of using correlation coefficient to decide weight coefficient and the method of vague analysis, through selecting ten indexes which contributed a lot to soil fertility.The integrate fertility level of arable brown soil is moderate or more.There are no soil samples which fertility level is high(soil fertility integrate index is more than 0.8).There are 50.00%soil samples which fertility level is moderate or more(soil fertility integrate index is between 0.6 and 0.8.).There are 10.64%soil samples which index did not reach 0.5.The major factors that limiting soil fertility are imbalance of soil nutrient,relatively low potassium content,low organic matter content,relatively bad soil structure,not many stable aggregates,shallower arable layer,deeper plow sole,decreasing pH and apparent trend of soil acidification.