氮硅添加对青藏高原高寒草甸土壤氮矿化的影响

Effects of nitrogen and silicon addition on soil nitrogen mineralization in alpine meadows of Qinghai-Xizang Plateau

为了解全球气候变化背景下氮沉降对土壤氮矿化的影响及硅添加对土壤氮矿化的促进作用,该试验设置不同浓度的氮肥单独添加(0、20、40、60 g·m^(–2),分别为对照CK、N20、N40、N60)以及与硅肥配施(硅酸4 g·m^(–2), Si4),测定不同处理下0–20、20–40、40–60cm土层土壤硝态氮含量、铵态氮含量、净硝化速率、净氨化速率以及净矿化速率。结果显示:(1)单独添加氮肥,各土层土壤硝态氮和铵态氮含量均随处理浓度的增加而增加, 0–20 cm土层N20、N40、N60处理下土壤硝态氮和铵态氮分别较CK增加63.48%、126.04%、247.03%和80.66%、152.52%、244.56%;随着土层深度增加,土壤硝态氮、铵态氮含量均有下降,20–40、40–60cm土层较0–20cm土层硝态氮含量分别平均减少53.90%、76.05%,铵态氮含量分别平均减少48.62%、68.23%。(2)土壤净硝化速率、净氨化速率及净矿化速率随着氮肥浓度增加均呈上升趋势。相同氮肥添加浓度下,土壤净硝化速率、净氨化速率和净矿化速率随着土层深度增加逐渐下降(除CK外)。(3)与单独添加氮肥比较,氮硅肥配施,土壤氮含量有显著提高,在0–20 cm土层硝态氮和铵态氮较CK分别增加98.78%、192.62%、330.16%和99.96%、195.82%、306.32%,20–40、40–60 cm土层也有类似趋势。同时,氮硅配施促进了土壤氮矿化行为,在0–20 cm土层, N60Si4处理下的土壤净硝化速率、净氨化速率较单独施氮时分别增加35.88%、27.41%。以上结果表明,与单独氮肥添加相比,氮硅配施不但能提高土壤氮含量,而且能促进土壤氮的矿化作用,对大气氮沉降有一定的缓解作用。

Aims To understand the effects of nitrogen and silicon addition on soil nitrogen mineralization in the context of global climate change.Methods Nitrogen fertilizer with different concentration were added separately(0,20,40,60 g·m–2,namely CK,N20,N40,N60,respectively)and combined with silicon fertilizer(4 g·m–2 silicic acid,namely Si4).Soil nitrate and ammonium nitrogen contents,net nitrification rate,net ammonification rate as well as net mineralization rate in 0–20,20–40 and 40–60 cm depth profiles were measured.Important findings(1)When nitrogen fertilizer was applied alone,soil nitrate and ammonium nitrogen contents under N20,N40,N60 treatments in 0–20 cm soil layer increased by 63.48%,126.04%,247.03%and 80.66%,152.52%,244.56%respectively,compared with CK.With the increase of soil depth,soil nitrate and ammonium nitrogen both decreased,the nitrate nitrogen content in 20–40 and 40–60 cm soil layers decreased by an average of 53.90%,76.05%respectively and the ammonium nitrogen content decreased by an average of 48.62%,68.23%respectively,compared with 0–20 cm soil layer.(2)With the increase of N application,soil net nitrification rate,net ammoniation rate and net mineralization rate all showed an increasing trend.Under the same nitrogen fertilizer concentration,with the increase of soil depth,net nitrification rate,net ammonification rate and net mineralization rate gradually decreased(except for CK).(3)Compared with nitrogen addition alone,soil nitrogen content was significantly improved when nitrogen and silicon fertilizers were both applied,in the 0–20 cm soil layer,the increase ratio of nitrate nitrogen and ammonium nitrogen were 98.78%,192.62%,330.16%and 99.96%,195.82%,306.32%respectively,compared with CK.This trend was also found in the 20–40 and 40–60 cm soil layers.The results also showed that combined application of nitrogen and silicon had a significant effect on soil nitrogen mineralization.For example,net nitrification rate and net ammonification rate under N60Si4 treatment increased by 35.88%and 27.41%respectively in the 0–20 cm soil layer,compared with nitrogen application alone.The above results showed that compared with the nitrogen addition alone,the application of both nitrogen and silicon can not only increase the nitrogen content in different soil layers,but also promote the mineralization of soil nitrogen and therefore having a certain mitigation effect on atmospheric nitrogen deposition.