秸秆和生物质炭添加对陇中黄土高原旱作农田土壤氮素矿化的影响

通过采集2014年设置于甘肃省定西市李家堡镇的不同碳源配施氮素田间定位试验土壤进行120天的室内培养试验,利用Stanford间歇淋洗培养法研究了无碳素和氮素添加(N0)、只施氮素(N100)、秸秆配施氮素(SN100)和生物质炭配施氮素(BN100) 4种施肥方式对陇中黄土高原旱作农田土壤氮素矿化的影响。结果表明:秸秆和生物质炭配施氮素提升了表层土壤氮素矿化量,分别比只施氮素显著提升16.5%和15.4%;土壤氮素矿化呈现先快速增加而后迅速下降,降速逐渐转为慢速直至稳定的趋势,硝化速率,氨化速率分别在7,15天时达到最大,45,30天时趋于稳定。秸秆和生物质炭配施氮素均可显著提升上层土壤氮素矿化速率,硝化速率和氨化速率则处于一种相对平衡的状态。土壤各有机氮组分在培养前后的变化量与土壤氮素矿化量之间的冗余分析结果表明,对土壤可矿化氮贡献最大的是氨基酸态氮,酸解未知氮次之;矿质态氮与未酸解氮呈负相关,与各酸解有机氮组分均呈正相关。此外,相比于不施氮,在施氮条件下添加秸秆和生物质炭增加了表层土壤各有机氮组分的变化量,说明添加秸秆和生物质炭可通过改变各有机氮组分占全氮的比例来增加易矿化氮的含量,从而促进有机氮组分的矿化,以提升土壤供氮潜力。

Effects of Straw and Biochar Addition on Soil Nitrogen Mineralization in Dryland Farmland of the Loess Plateau

A 120-day indoor culture experiment was conducted by collecting soils with different carbon sources combined with nitrogen fertilizer in a field experiment set in Lijiabu Town, Dingxi City, Gansu Province since 2014. The Stanford batch elution culture method was used to study the effects of four fertilization methods, including no carbon and nitrogen addition (N0), only nitrogen application (N100), straw combined with nitrogen (SN100) and biochar combined with nitrogen (BN100), on soil nitrogen mineralization. The fertilization was applied to experimental fields in the dry farmland of the Loess Plateau in central Gansu. The results showed that compared with nitrogen application only, straw and biochar combined with nitrogen fertilizer significantly increased nitrogen mineralization in surface soil by 16.5% and 15.4% respectively. Soil nitrogen mineralization showed a rapid increase and then a rapid decrease, and the decreasing rate gradually leveled off. The nitrification rate and ammonification rate reached their maximum at 7 and 15 days, and stabilized at 45 and 30 days, respectively. The nitrogen mineralization rate of the upper soil was significantly increased by straw and biochar combined with nitrogen fertilizer. The nitrification rate and ammonification rate were in a relatively balanced state. The redundancy analysis between the changes of soil organic nitrogen fractions before and after culture and the amount of soil nitrogen mineralization showed that the largest contribution to soil mineralized nitrogen was amino nitrogen, followed by acid unknown nitrogen. Mineral nitrogen was negatively correlated with unacidolyzed nitrogen and positively correlated with all fractions of acidolyzed organic nitrogen. In addition, compared with no nitrogen application, adding straw and biochar under nitrogen application increased the variation of organic nitrogen fractions in the surface soil. These results indicated that the addition of straw and biochar could increase the content of easily mineralized nitrogen by changing the proportion of organic nitrogen fractions to total nitrogen, thus subsequently promote the mineralization of organic nitrogen fractions and improve the potential of soil nitrogen supply.