对间隙淋洗长期通气培养条件下黄土高原土壤供氮能力的评价

Evaluation of soft N-supplying capacity on the Loess Plateau under long-term alternate leaching aerobic incubation conditions

采用间隙淋洗长期通气培养法,通过对黄土高原物理化学性质差异较大的10种农田土样起始矿质氮、起始提取态总氮、起始可溶性有机氮,以及培养期间淋洗矿质氮、淋洗总氮、可溶性有机氮含量及其与作物吸氮量关系的研究,分析并评价黄土高原主要农田土壤氮素矿化能力以及包括和不包括培养淋洗可溶性有机氮对土壤供氮能力的影响。结果表明,供试土样起始可溶性有机氮平均为N 23.9 mg/kg,是起始提取态总氮的28.8%,土壤全氮的2.4%。在通气培养淋洗总氮中,可溶性有机氮所占比例不高,经过217 d通气培养,淋洗出的可溶性有机氮平均为N 28.8mg/kg,占淋洗总氮量的19.8%。相关分析表明,淋洗可溶性有机氮量与第l季作物吸氮量相关不显著,但与连续2季作物总吸氮量显著相关。淋洗矿质氮、淋洗总氮与两季作物总吸氮量的相关系数明显高于与第一季作物吸氮量的相关系数;与第一季作物吸氮量达显著相关水平,与连续两季作物吸氮量达极显著相关水平。总体上看,可溶性有机氮和土壤全氮、土壤微生物氮不能作为反映短期可矿化氮的指标;间隙淋洗通气培养淋洗液中淋洗矿质氮、淋洗总氮是评价可矿化氮的较好指标,不仅适宜于第一季作物,而且也适用于对连续两季作物土壤供氮能力的评价。

The long-term alternate leaching aerobic incubation is the most important method for evaluating soil N supplying capacity. Initial mineral N（Nmin）, extractable total soluble N and soluble organic nitrogen（SON）, mineral N（MNL = NO3ˉ-N ＋ NH4^＋ -N）, total soluble N （ TNL = SON ＋ MNL） and cumulative SON leached during aerobic incubation, and their correlations with crop N-uptake of 10 types of farmland soils with different physical and chemical properties on the Loess Plateau were investigated. Soil N mineralizable capability and effect of mineralized N with or without SON on soil N-supplying capacity was studied. The results showed that mean content of initial SON（N 23.9 mg/kg） across 10 soils was 28.8% of initial total soluble nitrogen and 2.4% of total soil N. After 217d＇s aerobic leaching incubation, the mean cumulative SON content was N 28.8 mg/kg, 19.8% of cumulative TNL. Correlation analysis results showed that cumulative SON had significant correlation with N-uptake of two successive season crops while no significant correlation with the first season crop. With or without SON, TNL and MNL were significantly correlated with crop N-uptake, and the correlation with N-uptake of two successive season crops was stronger than that with N-uptake of the first season crop. Furthermore, a significant correlation （P 〈 0.01 ） was observed between TNL, MNL and N-uptake of two successive sea- son crops. In summary, MNL and TNL could be used as indices for potential mineralizable N, which are not only suitable for the first season crop but also suitable in evaluating soil N-supplying capacity for two successive season crops; while SON, total soil N and soil microbe N were not good indices for soil potential mineralizable N in short-term.