等氮量条件下不同秸秆与化学氮肥配施对黑土团聚体稳定性及其碳、氮分布的影响

刘金华; 王银海; 赵兴敏; 王鸿斌

doi:10.19336/j.cnki.trtb.2020112701

等氮量条件下不同秸秆与化学氮肥配施对黑土团聚体稳定性及其碳、氮分布的影响

Effect of Straw Combined with Chemical Fertilizer on Aggregates Stability and Distributions of Carbon and Nitrogen under Equal Nitrogen Application Rate in Black Soil

摘要

摘要:
目的为正确评价秸秆替代部分化学氮肥对黑土水稳性团聚体组成及其碳、氮分布的影响，达到肥料减施增效的目的，
方法采用田间小区试验的方法，在总施氮量240 kg hm⁻²下，设置不施秸秆与化肥，单施化肥和25%、50%、75%、100%秸秆还田配施减量化学氮肥6个处理，经过5轮施肥处理，种植5年春玉米后，采集表层土壤，测定各水稳性团聚体组成及其碳、氮含量，分析团聚体的稳定性及各粒级团聚体的碳、氮储量。
结果结果表明：与单施化肥相比，秸秆与减量化肥配施能促进水稳性大团聚体的形成，提高各粒级团聚体的碳、氮含量及土壤总有机碳储量，但对土壤总氮含量无显著影响。与25%低秸秆还田量相比，75%及以上秸秆还田量可以增加大团聚体(> 2 mm，LM)含量1.28% ~ 2.36%、粗颗粒有机质（> 0.25 mm，cPOM）含量 3.63% ~ 4.76%，降低自由态微团聚体(0.053 ~ 0.25 mm，m)含量2.29% ~ 3.08%、闭蓄态粉黏粒(< 0.053 mm，Msc)含量3.95% ~ 5.40%，提高MWD 6.57% ~ 9.28%。秸秆还田量与各粒级团聚体的碳、氮含量均呈显著正相关（s + c除外），但受各粒级水稳性团聚体组成的影响，最终只有大团聚体(> 2 mm，LM)、闭蓄态微团聚体(0.053 ~ 0.25 mm，mM)、粗颗粒有机质(> 0.25 mm，cPOM)的碳、氮储量，大团聚体(0.25 ~ 2 mm，SM)的碳储量与秸秆还田量呈显著正相关，而闭蓄态粉黏粒(< 0.053 mm，Msc)的碳、氮储量与秸秆还田量呈显著负相关。另外，75%及以下还田量不会显著提高SM、cPOM和mM粒级的C∶N。
结论东北黑土春玉米种植区可以实现75%的秸秆还田（10800 kg hm⁻²）与186 kg hm⁻²的化学氮肥配施，与等量单施化肥相比（240 kg N hm⁻²），减少氮肥用量22.5%。并且与等氮下的单施化肥和25%秸秆还田配施减量化肥相比，能显著提高土壤团聚体稳定性及单位重量表层原状土中大团聚体的有机碳、全氮储量。

Abstract: In order to accurately evaluate the effect of straw partial substituting chemical nitrogen fertilizer on the formation of soil water-stable aggregates and the distributions of carbon (C) and nitrogen (N) in black soil, achieving the goal of reducing fertilizer application and increasing fertilizer efficiency, a field trial was adopted at the total N applying amount of 240 kg hm⁻² with 6 treatments of no straw and chemical N fertilizer, chemical N fertilizer alone, and 25%, 50%, 75% and 100% of straw return combined with correspondingly reduced chemical N fertilizer. The surface soil was collected to measure the composition of soil water-stable aggregates and their associated C and N concentrations, analyze the stability of aggregates and their storages of C and N after 5 applications of straw and fertilizer during 5 years of planting spring corn. The results showed that the treatments of straw return combined with chemical N fertilizer promoted the formation of macro aggregates, increased the contents of C and N in different aggregates fractions and total soil organic C storage relative to the treatment of chemical N fertilizer alone. But it had no significant effect on soil total N storage. Compared with 25% of straw return treatment, the treatments with more than 75% of straw return increased the aggregates contents of LM (> 2 mm) by 1.28% ~ 2.36% and that of cPOM (> 0.25 mm) by 3.63% ~ 4.76%, while decreased that of m (0.053 ~ 0.25 mm) and Msc (< 0.053 mm) by 2.29% ~ 3.08% and by 3.95% ~ 5.40%, respectively. Moreover, they also increased MWD by 6.57% ~ 9.28%. Although there was a significantly positive relationship between straw return amount and the contents of C and N in each aggregate fraction (except s + c), only the C and N storages of LM, mM, cPOM and the C storage of SM were significantly positive with straw return amount when considering the effect of aggregate composition. Whereas, the C and N storages in Msc were negatively correlated with straw return amount. Additionally, the C and N ratios in SM, cPOM and mM were not significantly improved when the straw return amount was less than 75%. In general, at total N applying rate of 240 kg hm⁻², the combined application of 75% straw (10800 kg hm⁻²)and 186 kg hm⁻² chemical N fertilizer significantly improved the stability of soil aggregates and the storage of organic C and total N, compared with chemical N fertilizer alone or 25% straw combined with reduced amount of chemical N fertilizer, and reduced the applying amount of N fertilizer by 22.5% relative to the treatment of N fertilizer alone.

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