典型红壤丘陵区土壤氮素含量及其分布的演变规律

通过对湖南省桃源县典型区域高密度采样分析和历史资料调研,探明了红壤丘陵区不同土地利用类型13年来(19902～2003)土壤氮素含量及其分布的变化:1)典型区域2003年的稻田氮素含量为1.94±0.02.g/kg,比1990年提高4.9%,主要分布区间由1990年的1.25～2.00.g/kg(分布频率为59.1%,下同)上升到2003年的1.50～2.25g/kg(77.1%),曲线图上呈近似正态分布向右偏态分布的演变趋势;2)旱土2003年的氮素含量为1.57±0.14.g/kg,比1990年提高18.0%,1990和2003年主要分布区间都为0.75～1.50.g/kg(58.2%～58.8%),但2003年分布在1.50～2.00.g/kg区间的频率为33.6%,比1990年的高出12.7个百分点,曲线图上由呈现左偏态分布向正态分布的演变趋势;3)以坡地橘园为主的林果地,2003年的氮素含量为1.15±0.02.g/kg,比1990年提高9.5%,两者的主要分布区间虽然均在0.75～1.50.g/kg之间,但2003年在此区间的分布频率为88.0%,比1990年的高出10.2个百分点,其演变趋势与稻田的基本一致;4)整个采样调研区域农业用地的土壤氮素含量,2003年的为1.58±0.03g/kg,比1990年提高3.3%。这表明在当前的施肥方式与经营管理条件下,红壤丘陵区农业用地的土壤氮素含量稳定并有增加的趋势。

Evolution pattern of soil total N content and its distribution in typical hilly red soil regions

Taking Taoyuan city as research target area,the evolution pattern of soil N content and its distribution during the last 13 years(1979—2003) under different land uses in hilly red soil regions was investigated.The results showed as follows: 1) The content of total N of paddy soil in typical area in 2003 was 1.94±0.02 g/kg.This represented a 4.9% increase compared to that in 1990.The main distribution range increased from 1.25—2.00 g/kg(distribution frequency was 59.1%,The same below) in 1990 to 1.50—2.25 g/kg(77.1%)in 2003,showing a tendency from the quasi normal distribution to right excursion distribution on the diagram of curves.2) The content of total N of dry land soil in 2003 was 1.57±0.14 g/kg,which represented a 18.0% increase compared to that in 1990.Main distribution range was 0.75—1.50 g/kg(58.2%—58.8%)both in 1990 and 2003;however,the distribution frequency ranged in 1.50—2.00 g/kg in 2003 was 33.6%,which was 0.9% higher(increased by 60.8%) than that in 1990.The distribution curve shifted from left excursion distribution to normal distribution.3) The content of total N in orchard soil(orange in slope land) was 1.15±0.02 g/kg in 2003,which represented a 9.5% increase compared to that in 1990. Main distribution range in 1990 and 2003 was similarly being 0.75—1.50 g/kg,but the distribution frequency in this range area in 2003 was 88.0%,higher than that in 1990 being 77.8%,the evolution trend of the content of N in orchard soil was similar with that in paddy soil.4)The average total N content of farmland in investigated area was 1.58±0.03 g/kg in 2003,compared to that in 1990,increased by 3.3%.This indicated that the current fertilization and management increased the content of total N in farmland soils steadily in hilly red soil regions.