绿肥根茬还田和化肥用量对土壤团聚性及碳氮分布的影响

Soil aggregation and distributions of carbon and nitrogen as affected by chemical fertilizer applying rate and returning root stubble of green manure

通过3年定位试验探讨绿肥根茬还田和化肥用量对土壤团聚性及碳氮分布特征的影响。试验依据绿肥根茬还田和化肥用量共设置5个处理:100%化肥即常规施肥(100%CF);绿肥根茬还田(GM);100%化肥+绿肥根茬还田(100%CF+GM);90%化肥+绿肥根茬还田(90%CF+GM);80%化肥+绿肥根茬还田(80%CF+GM)。土壤团聚体采用湿筛法分离,有机碳和全氮含量用碳氮仪测定。结果表明:(1)0.25~2 mm团聚体在土壤中占绝对优势,但在处理间无显著差异(P>0.05)。与100%CF相比,绿肥根茬还田4个处理GM、100%CF+GM、90%CF+GM和80%CF+GM使0.05~0.25和<0.05 mm团聚体向>2 mm大团聚体转变,并显著提高团聚体稳定性,但4个处理间无显著差异;(2)有机碳和全氮含量随团聚体粒径增大而提高。>0.25 mm大团聚体对土壤有机碳和全氮贡献率最高(有机碳和全氮贡献率分别为60.1%~82.9%和66.6%~83.0%),绿肥根茬还田使这一趋势增强,即随着微团聚体向大团聚体转变,有机碳和全氮也被大团聚体固持;(3)相关分析表明,团聚体稳定性与>2 mm大团聚体质量百分比及其有机碳贡献率均极显著相关,团聚体质量百分比与该粒级团聚体有机碳贡献率极显著正相关。综上,绿肥根茬还田有利于土壤结构稳定和碳氮积累,短期内还能减施化肥,是豫南地区冬闲田综合利用和发展畜牧业的推荐途径。

In this study,a three-year experiment was conducted to investigate effects of returning root stubble of green manure and applying chemical fertilizer on soil aggregation and distribution of carbon and nitrogen.Five treatments were set up according to green manure rotation and chemical fertilizer applying rate:100%chemical fertilizer alone(100%CF);only returning root stubble of green manure(GM);100%chemical fertilizer plus green manure root stubble(100%CF+GM);90%chemical fertilizer plus green manure root stubble(90%CF+GM);80%chemical fertilizer plus green manure root stubble(80%CF+GM).Soil aggregates were separated by wet sieving,and the organic carbon and total nitrogen contents was determined by CN element.The results showed that:(1)0.25~2 mm aggregates were dominant in the soil although no significant differences were seen among treatments(P>0.05).Compared with 100%CF,0.05~0.25 and<0.05 mm aggregates were changed into>2 mm aggregates in the four treatments with green manure root stubble and aggregate stability was also increased,but there were no significant differences among the four treatments;(2)Organic carbon and total nitrogen content increased with the increase of aggregate size.The>0.25 mm aggregates contributed most to soil organic carbon and total nitrogen(the proportion of organic carbon and total nitrogen was 60.1%~82.9%and 66.6%~83.0%respectively),which tread was enhanced by returning green manure root stubble.This indicated that,with the formation of macroaggregates from microaggregates,organic carbon and total nitrogen were simultaneously sequestrated within macroaggregates under the four treatments with returning green manure root stubble;(3)Correlation analysis showed that aggregate stability was extremly significantly related to>2 mm aggregate proportion and its organic carbon proportion,and the proportion of each aggregate fraction was extremly significantly positively related to its organic carbon proportion.To sum up,returning green manure root stubble was beneficial to soil structure stability and carbon and nitrogen accumulation and could reduce application rate of chemical fertilizer in a short period of time,which was the recommended way to utilize winter fallow field,improve soil fertility,and develop animal husbandry in the south of Henan province.