间作对马铃薯种植土壤硝化作用和硝态氮供应的影响

土壤硝态氮供应对满足作物氮素需求至关重要,但间作如何影响土壤硝态氮供应及其作用机制尚不清楚。本研究基于4个氮水平(N₀, 0 kg·hm^-2; N₁, 62.5 kg·hm^-2; N₂, 125 kg·hm^-2; N₃, 187.5 kg·hm^-2)的马铃薯单作、马铃薯与玉米间作小区试验,分析土壤硝态氮含量与强度、硝化势和氨氧化功能基因丰度的差异,探讨间作影响土壤硝态氮供应和氮调控的机理。结果表明: 土壤硝态氮含量和强度随施氮量增加而升高,但同一施氮水平下间作均低于单作。施氮提高了土壤硝化势,且单作的响应高于间作。土壤中氨氧化细菌(AOB)的amoA基因丰度大于氨氧化古菌(AOA),二者在间作时均随施氮量增加呈现先增加后降低的趋势;相同施氮量下,间作的AOA和AOB基因丰度(除N₂外)均低于单作。相关分析、回归分析和主成分分析显示,马铃薯间作后,土壤AOB、AOA的amoA基因丰度下降,硝化势减弱,导致土壤硝态氮含量和强度降低。因此,间作导致土壤硝态氮供应降低与土壤氮转化的微生物过程有关,间作条件下的马铃薯种植应注意保障土壤氮素供应。

Effects of intercropping on soil nitrification and nitrogen supply in potato field.

Nitrate supply in soils is essential to meet nitrogen (N) demand of crops. However, how intercropping would affect soil nitrate supply and the underlying mechanisms remain unclear. Based on a field experiment of mono- and inter-cropped potato amended with four N application rates (N₀, 0 kg·hm^-2; N₁, 62.5 kg·hm^-2; N₂, 125 kg·hm^-2; N₃, 187.5 kg·hm^-2), we analyzed the differences in soil nitrate content and intensity, nitrification potential, and ammonia oxidation gene abundance. We further explored the mechanisms underlying the effects of intercropping on nitrate supply and N regulation. The results showed that both content and intensity of soil nitrate increased with N application rate. Under the same N level, nitrate content in intercropping soil was lower than that in monocropping soil. Nitrogen application increased soil nitrification potential, with stronger effects in monocropping than that of intercropping. The amoA gene abundance of AOB in soil was greater than that of AOA. The abundance of amoA gene for both AOA and AOB were increased firstly and then decreased with increasing N application rate when potato intercropped with maize. Under the same N application rate, AOA gene and AOB gene in all treatments (except N₂) in intercropping were lower than those in the monocropping. The amoA gene abundance of soil AOB and AOA decreased and nitrification potential was weakened when potato intercropped with maize, resulting in a decrease of soil nitrate content and intensity. Therefore, intercropping led to a reduction of soil nitrate supply, which was related to the microbial process of soil N transformation. Much attention should be paid to soil N supply under the condition of potato and maize intercropping.