Study On Distribution Of Available Phosphorus In Soil On Slope During Seasonal Freezing And Thawing

Due to the influence of seasonal freezing-thawing,the soil available p content in northeast China is very unstable.In this study,the effects of slope direction,slope position and soil depth on the content of available p and the spatial and temporal distribution of relevant indicators in seasonal freezing-thawing period were investigated by field sampling.The results provide a theoretical basis for the sustainable use of soil nutrients and the effective evaluation of regional nutrients in slope areas in seasonal freezing-thawing areas.The main conclusions are as follows:?1?Seasonal freezing-thawing is the main factor affecting the content of available p in slope.The overall performance was the increase of the effective phosphorus content,which increased slowly in the early freezing-thawing period until the peak in the middle and late February,and then decreased slowly.pH?organic matter and water content in the freezing-thawing period were consistent with the change trend of available phosphorus,and the correlation reached a significant level.The correlation coefficient of organic matter was the highest,and the conductivity showed no regularity.?2?Slope direction has certain influence on soil available phosphorus,and the overall performance is that the overcast slope is larger than the positive slope.At the end of freezing-thawing period,the content of available p in yin-yang slope was significantly higher than that in the non-freezing-thawing period,which was 28.92mg/kg and 39.99mg/kg respectively.In late February 2016,the maximum value of available phosphorus was reached.At this time,the content of available phosphorus in the yin-yang slope increased by 175.20 mg/kg and106.25mg/kg respectively,compared with that in the case of unfreezing and thawing.The slope direction has significant influence on soil organic matter,and the freezing and thawing effect has significant influence on conductivity and water content.During the whole freezing-thawing process,the correlation between p and pH and organic matter of yin-yang slope reached a significant level.?3?Slope position has a significant effect on soil available p,which is one of the main factors for the change of soil available p content in slope during seasonal freezing-thawing period.The overall performance was that the effective phosphorus content increased with the slope.At the end of freezing-thawing period,the effective phosphorus content of S0,S30,S60and S90 increased by 8.56mg/kg,57.92mg/kg,42.02mg/kg and 45.27mg/kg,respectively,compared with that of unfrozen thawing.The influence of slope position on organic matter is very significant,the effect of freeze-thaw action on pH and conductivity of different slope positions is very significant,and the influence on water content is significant.The correlation between p and pH and organic matter at different slope positions was significant.?4?In the process of seasonal freezing-thawing,there was a significant difference in the content of available phosphorus in each layer of soil.The overall expression was that the content of available phosphorus decreased with the increase of soil layers,i.e.,h_15-20 The layers of soil effective phosphorus content are peak in late February,h_15-20,h_10-15,h_5-10 and h_0-5,respectively,than when it's freezing and thawing of 47.01 mg/kg,77.00 mg/kg,170.08 mg/kg and 129.92mg/kg,the surface layer,the addition of 0 to 10 cm of soil effective phosphorus is significantly higher than 10-20 cm deep soil.During the whole freezing-thawing period,the correlation between soil available phosphorus and pH and organic matter reached a significant level in each layer,and the correlation between soil available phosphorus and water content in the surface 0-5cm reached a significant level.