洞庭湖区不同土地利用方式耕作土壤氮素含量与循环

Nitrogen cycle and content in plowable soil layer under different land-use types in Dongting Lake region.

通过对洞庭湖典型地区的密集采样分析和农户调查,研究了4种利用方式耕作土壤全N、微生物生物量氮(MB-N)含量、两者关系和N素循环特征。结果表明:耕作土壤全N、MB-N含量平均值为3.00±0.48g/kg和101.4±49.2mg/kg。双季稻、一季稻、水田旱作和旱地全N平均含量依次为3.12±0.40g/kg、3.03±0.39g/kg、2.79±0.43g/kg2、.10±0.46g/kg。4种利用方式的MB-N含量分别为124.0±56.6mg/kg、96.4±39.2mg/kg、108.0±48.6mg/kg、75.2±30.5mg/kg。除水田旱作外,MB-N与全N之间存在极显著的正相关关系(P<0.01)。土壤N素盈余量依次为双季稻(105.0kg/hm2.a)>一季稻(75.1kg/hm2.a)>水田旱作油菜(64.5kg/hm2.a)>旱地苎麻(51.9kg/hm2.a)。

By high density sampling and farming household investigation, total N content, microbial biomass N（MB-N） content, total N and MB-N relationship, and N cycle characteristics and ,N balance of plowable soil layer under different land-use types were studied in Dongting Lake region. Results show 3.00 ＋ 0.48g/kg total N content and 101.4 ＋ 49.2mg/kg MB-N content in farmlands respectively. Total N contents for double cropping paddy fields, single cropping paddy fields, dry farming paddy fields and dry lands are 3.12 ＋ 0.40g/kg, 3.03 ＋ 0.39g/kg, 2.79 ＋ 0.43g/kg and 2.10 ＋0.46g/kg;and MB-N contents are 124.0 ＋ 56.6mg/kg,96.4 ＋ 39.2mg/kg, 108.0 ＋ 48.6mg/kg and 75.2 ＋ 30.5mg/kg respectively. Except for dry farming in paddy soils, MB-N and total N are significantly passively correlative （P〈 0.01 ）for all other land-use types. The order of N surplus for the different land-use types is： double cropping paddy field（ 105.0kg/hm^2· a） 〉 single cropping phddy field （ 75.1 kg/hm^2· a） 〉 dry farming paddy soil （64.5kg/hm^2· a） 〉 dry land（51.9kg/hm^2· a）.