兰州大学机构库 >生命科学学院
氮素添加和种间互作对旱作农田生产力和碳排放的影响及机制
Alternative TitleEffects of nitrogen addition and interspecific interactions on dry farmland productivity and carbon emission and their mechanisms
周怡宁
Subtype硕士
Thesis Advisor熊友才
2021-05-31
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name理学硕士
Degree Discipline生态学
Keyword间作系统 氮素梯度 作物生产力 土壤呼吸 碳排效率
Abstract农业活动是温室气体的主要来源之一,合理的土地利用方式和有效的农艺措施有利于增加农业土壤肥力,封存更多的有机碳,达到高产且减少温室气体排放的目的。前期研究表明,禾禾间作及禾豆间作对旱作农田生产力和碳排放有显著影响,但不同氮素添加条件下如何响应,以及种群互作过程及机理报道较少,尤其是从经典生态学中的竞争理论和正相互作用理论揭示机理方面缺乏系统探索。 本研究以玉米、小麦和大豆为研究材料,于2019-2020年在兰州大学榆中校区农业生态试验站开展大田试验,设置了玉米-小麦间作(MW)、玉米-大豆间作(MS)、小麦-大豆间作(WS)、玉米单作(SM)、大豆单作(SS)和小麦单作(SW)六种种植模式,按照常规氮素施加标准设置N1(138 kg·ha-1)、N2(207 kg·ha-1)和N3(276 kg·ha-1)三个施氮水平,共18个处理。试验所得主要结果如下: 1.种间互作条件提高了旱地生产力和水分利用效率。玉米-小麦间作和大豆-小麦间作系统中,小麦为优势种,间作条件下小麦产量和水分利用效率增加,而玉米和大豆产量及水分利用效率降低。玉米-大豆间作系统中,大豆和玉米的产量及水分利用效率均显著增加,且间作显著性提高了玉米的干物质累积量、地上地下生物量、叶面积以及根长密度等根形态学参数。玉米-小麦间作、玉米-大豆间作和小麦-大豆间作下的土地当量比分别在0.96~1.02、1.02~1.13和0.99~1.13范围内。这表明,间作有益于提高作物水分资源利用率,且相比于禾禾间作,禾豆间作具有更高的产量优势及水分资源利用效率。 2.氮素添加显著提高了种间互作背景下旱地生产力和水分利用,且其使得各个作物的产量、玉米的干物质积累量及根长密度等根形态学参数增加。相比于N1,N2、N3下MS中玉米的产量和水分利用效率(WUEY)分别提高了15.28%和16.78%、17.97%和14.97%,大豆产量和WUEY分别提高了12.26%和8.45%、18.96%和11.68%;MW中玉米的产量和WUEY分别提高了7.97%和8.62%、9.15%和10.55%,小麦产量和WUEY分别提高了8.88%和13.86%、14.87%和18.36%;WS中小麦产量和WUEY分别提高了4.88%和11.01%、14.64%和16.06%,大豆产量和WUEY分别提高了10.10%和9.91%、20.02%和24.80%。且随着氮素添加,各间作处理的LER也随之增加。结果表明,氮素添加有益于提高间作条件下作物的生产力及水分利用,即提高作物的种间互作优势。 3.禾禾间作下,小麦根际土壤有机碳(SOC)显著提高;而禾豆间作下,玉米和小麦根际SOC均显著提高。玉米和小麦与大豆间作显著高于单作模式下玉米和小麦根际土壤有机碳含量,MS下玉米根际SOC提高了3.78%,WS下小麦根际SOC提高了9.54%;而间作降低了大豆根际土壤有机碳的含量;玉米-小麦间作显著提高了小麦根际土壤有机碳含量2.81%,而降低了玉米根际含量2.89%。且在同一氮素梯度下,与玉米/大豆间作会提高其微生物生物量碳含量。这说明,与玉米/大豆间作有助于土壤养分的提高。这是因为间作模式下存在着对于土壤养分的互补、竞争和转移,且不同物种对于资源的获取能力不同。 4.氮素添加提高了种间互作背景下作物根际SOC含量。相比于N1,N2、N3下MS中玉米的根际SOC提高了3.40%、14.16%,大豆根际SOC提高了4.19%、11.33%;MW中玉米根际SOC提高了6.78%、17.81%,小麦根际SOC提高了5.04%、9.85%;WS中小麦根际SOC提高了4.18%、7.04%,大豆根际SOC提高了3.31%、11.10%;单作玉米根际SOC分别提高了5.31%、14.15%;单作大豆根际SOC分别提高了2.74%、11.52%;单作小麦根际SOC分别提高了5.40%、10.33%。这表明,氮素添加有益于提高土壤有机质含量,即在种间互作条件下,氮素添加与土壤有机碳呈正相关关系。 5.禾豆间作下,豆科作物根际N含量减少,而禾本科作物根际N含量增加;禾禾间作下,作物根际N含量的变化因存在作物种间竞争而各不相同。对于全氮和无机氮而言,与大豆间作显著提高了玉米/小麦根际土壤全氮(TN)和无机氮含量,MS下玉米根际TN含量提高了8.48%,WS下小麦根际TN含量提高了14.82%;而间作条件下大豆根际全氮、NO3-含量和NH4+含量显著低于大豆单作,MS下大豆根际TN含量相比于大豆单作降低了9.44%,WS下降低了18.04%。玉米-小麦间作显著提高了小麦根际土壤TN含量8.71%,而降低了玉米根际TN含量7.75%。结果表明,间作有益于提高小麦根际TN和无机氮含量,而显著降低了大豆根际N含量。 6.氮素添加与种间互作背景下根际TN及无机氮含量呈正相关关系。相比于N1,N2和N3下MS中玉米的根际TN分别提高了8.55%、9.98%,大豆根际TN分别提高了11.50%、21.28%;MW中玉米根际TN分别提高了10.23%、19.01%,小麦根际TN分别提高了15.07%、23.52%;WS中小麦根际TN分别提高了6.77%、16.66%,大豆根际TN分别提高了8.21%、19.06%;单作玉米根际TN分别提高了8.04%、16.75%;单作大豆根际TN分别提高了6.78%、13.56%;单作小麦根际TN分别提高了6.69%、23.29%。结果表明,随着施氮量的增加,作物根际全氮和无机氮含量也随之增加。这说明施氮水平过高不利于植物对氮肥的吸收利用,而在土壤中转变为较多的无机氮,易造成氮肥损失。 7.种间互作条件下,整个系统的土壤碳排放总量显著降低;种间互作也显著提高了作物的碳排放效率。2019-2020年生育期内土壤呼吸速率值呈现季节性变化,其变化趋势为先上升后下降的单峰趋势。在夏季土壤呼吸速率值达到峰值,不同氮素水平和间作模式之间存在显著差异;在冬季土壤呼吸速率值最低,且各处理间无显著性差异。这是因为土壤呼吸速率受各种生态因子影响,其中土壤呼吸速率和土壤温度高度相关。受生物量大小的影响,单作模式下土壤呼吸速率值排序为:玉米单作>小麦单作>大豆单作。对于玉米而言,与大豆间作提高了其土壤呼吸速率,而与小麦间作相反;对大豆而言,小麦-大豆间作下大豆区土壤呼吸速率值低于大豆单作;对于小麦而言,间作下的小麦区土壤呼吸速率值均高于单作小麦。玉米-小麦间作和玉米-大豆间作的碳排放总量分别比玉米单作低17.50%、18.33%;小麦-大豆间作系统的碳排放总量比单作小麦降低了0.98%。相比于单作,间作均显著提高了作物的碳排放效率。且玉米-小麦间作碳排当量比在0.96~1.02之间,玉米-大豆间作在1.01~1.08之间,小麦-大豆间作在1.04~1.09之间。这说明玉米-小麦/大豆间作可有效降低作物生长发育过程中的碳排放量,且具有生产更多籽粒产量的潜力。在同一氮素梯度下,间作显著降低了整个系统的碳排放总量。 8.氮素添加提高了种间互作背景下土壤碳排放速率和碳排放总量。整体而言,相比于N1,N2、N3条件下玉米区碳排放总量提高了18.68%、23.72%;大豆区碳排放总量提高了10.42%、22.56%;小麦区碳排放总量提高了9.41%、22.09%。随着氮素添加,大豆-小麦间作系统的碳排当量比减少;而相比于N1,N2、N3下玉米-小麦间作的碳排当量比分别提高了7.29%、3.20%;玉米-大豆的碳排当量比在各氮素梯度下的差异不显著。这说明,就玉米-小麦间作系统而言,N2梯度下的碳排当量比最高,增产减排效果最好。随着氮素添加,土壤碳排放速率和碳排放总量也逐渐增加,而在适量氮素添加条件下,种间互作的增产减排效果最好。 这些结果表明,玉米/小麦与大豆间作同时结合减量施氮是一种降低碳排放、提高碳排放效率的一种有效的减排增产模式。这说明,间作模式和合理施氮相结合,既可以保证作物产量的同时,又降低了土壤碳排放,有利于农业可持续发展。其中N2梯度下,玉米-大豆间作和小麦-大豆间作模式效果最好,即正常施氮条件下,在农田系统中引入豆科作物间作的模式是一种稳产减排的可行办法。
Other AbstractAgricultural activity is the major source of greenhouse gases. Rational land use and effective agronomic measures are beneficial to increase agricultural soil fertility, store more organic carbon, and obtain high yield and reduce greenhouse gas emissions. Earlier studies have shown that cereal-cereal intercropping and cereal-legume intercropping have a significant impact on rainfed farmland productivity and carbon emissions, but there are few reports on how to respond under different nitrogen addition conditions, as well as the process and mechanism of species interactions. In particular, there is a lack of systematic exploration on the mechanism of competition theory and positive interaction theory in classical ecology. Maize, wheat and soybean were used as experimental materials in this study, and the field experiment was carried out at the Agricultural Ecological Experimental Station on Yuzhong Campus of Lanzhou University from 2019 to 2020. There were two main treatment groups: 1) different intercropping treatments: maize-wheat intercropping (MW), maize-soybean intercropping (MS), wheat-soybean intercropping (WS), sole maize (SM), sole soybean (SS) and sole wheat (SW);2) different nitrogen levels: N1 (138 kg·ha-1), N2 (207 kg·ha-1) and N3 (276 kg·ha-1). The main results of the study are as follows: 1. Interspecific interaction conditions improved dry farmland productivity and water use efficiency. In the maize-wheat intercropping system and soybean-wheat intercropping system, wheat was the dominant species. Under intercropping conditions, wheat yield and water use efficiency (WUEY) increased, while maize and soybean yield and water use efficiency (WUEY) decreased. In the maize-soybean intercropping system, the yield and water use efficiency (WUEY) of both soybean and maize significantly increased, and the intercropping significantly improved the root morphological parameters such as dry matter accumulation, shoot and root biomass, leaf area ratio (LAI), root length density and other root morphological parameters of maize. The land equivalent ratios (LER) of maize-wheat intercropping, maize-soybean intercropping and wheat-soybean intercropping were in the range of 0.96~1.02, 1.02~1.13 and 0.99~1.13, respectively. These results indicated that cereal-legume intercropping was beneficial to improving water resource utilization of crops, and had higher yield advantages and water resource utilization efficiency than that of cereal-cereal intercropping. 2. Nitrogen addition significantly increased dry farmland productivity and water use under the background of interspecific interaction. The addition of nitrogen increased the yield of each crop, the dry matter accumulation, root length density and other morphological parameters of maize. Compared with N1, under N2 and N3 treatment the yield and WUEY of maize were increased by 15.28% and 16.78%, 17.97% and 14.97%, and soybean yield and WUEY were increased by 12.26% and 8.45%, 18.96% and 11.68% in MS, respectively;in MW, the yield and WUEY of maize were increased by 7.97% and 8.62%, 9.15% and 10.55%, and wheat yield and WUEY were increased by 8.88% and 13.86%, 14.87% and 18.36% respectively;in WS, wheat yield and WUEY were increased by4.88% and 11.01%, 14.64% and 16.06%, and soybean yield and WUEY were increased by 10.10% and 9.91%, 20.02% and 24.80%, respectively. And with the addition of nitrogen, the LER of each intercropping system also increased. The results showed that nitrogen addition was beneficial to improving crop productivity and water use efficiency under intercropping conditions, that is, to improving the interspecific intercropping advantages of crops. 3. The rhizosphere SOC of wheat increased significantly under cereal-cereal intercropping;meanwhile, the rhizosphere SOC of maize and wheat increased significantly under cereal-legume intercropping. Compared with monoculture, intercropping with soybean increased the soil organic carbon content in the rhizosphere of maize and wheat. The SOC of maize rhizosphere under MS was increased by 3.78%, and that of wheat rhizosphere under WS was increased by 9.54%. Intercropping decreased the SOC content in soybean rhizosphere soil. Maize-wheat intercropping significantly increased the soil organic carbon content of wheat rhizosphere by 2.81%, while decreased the soil organic carbon content of maize rhizosphere by 2.89%. This is because there were complementation, competition, and transfer of soil nutrients in the intercropping system, and different species had different ability to acquire resources. And under the same nitrogen gradient, intercropping with maize or soybean could increase its microbial biomass carbon content. This shows that intercropping with maize or soybean contributes to improving soil nutrients. 4. Nitrogen addition increased the SOC content in the rhizosphere of crops under the background of interspecific interaction. Compared with N1, under N2 and N3 treatment, the rhizosphere SOC of maize was increased by 3.40% and 14.16%, and that of soybean was increased by 4.19% and 11.33% in MS;in MW, maize and wheat rhizosphere SOC were increased by 6.78% and 17.81%, and 5.04% and 9.85% respectively;the rhizosphere SOC of wheat and soybean were increased by 4.18% and 7.04%, and 3.31% and 11.10% respectively in WS;for sole maize, rhizosphere SOC was increased by 5.31% and 14.15%, respectively;for sole soybean, rhizosphere SOC was increased by 2.74% and 11.52%, respectively;for sole wheat, rhizosphere SOC was increased by 5.40% and 10.33%, respectively. These results indicated that nitrogen addition was beneficial to the improvement of soil organic matter content, that is, under the condition of interspecific interaction, nitrogen addition was positively correlated with soil organic carbon. 5. Under the condition of cereal-legume intercropping, the content of N in the rhizosphere of legume decreased, while that of cereal increased;under cereal-cereal intercropping, the variation of N content in the rhizosphere of crops was different due to inter-specific competition. In terms of total nitrogen and inorganic nitrogen, intercropping with soybean significantly increased the total nitrogen and inorganic nitrogen contents of maize and wheat rhizosphere soil. The TN content of maize rhizosphere and wheat rhizosphere under MS were increased by 8.48% and 14.82%, respectively. However, the contents of total nitrogen, NO3- and NH4+ in the rhizosphere of soybean under intercropping conditions were significantly lower than those under sole soybean, and the TN content in the rhizosphere of soybean under MS and WS were decreased by 9.44% and 18.04% compared with soybean monocropping. Maize-wheat intercropping significantly increased the TN content of wheat rhizosphere soil by 8.71%, while decreased the TN content of maize rhizosphere by 7.75%. The results showed that intercropping was beneficial to increasing the contents of TN and inorganic nitrogen in the rhizosphere of wheat, but significantly decreased the content of N in the rhizosphere of soybean. 6. Nitrogen addition was positively correlated with the contents of TN and inorganic N in the rhizosphere under the background of interspecific interaction. Compared with N1, under N2 and N3 treatment, the rhizosphere TN of maize was increased by 8.55% and 9.98%, respectively, and that of soybean by 11.50% and 21.28%, respectively in MS;the rhizosphere TN of maize and wheat in MW were increased by 10.23% and 19.01%, and 15.07% and 23.52%, respectively;in WS, the rhizosphere TN of wheat and soybean were increased by 6.77% and 16.66%, and 8.21% and 19.06%, respectively;for sole maize, rhizosphere TN was increased by 8.04% and 16.75%, respectively;for sole soybean, rhizosphere TN was increased by 6.78% and 13.56%, respectively;for sole wheat, rhizosphere TN was increased by 6.69% and 23.29%, respectively. The results showed that the contents of total nitrogen and inorganic nitrogen in the rhizosphere were increased with the increase of nitrogen application rate. This indicates that too high level of nitrogen application is not conducive to the absorption and utilization of nitrogen fertilizer by plants, and it is easy to cause the loss of nitrogen fertilizer due to the conversion of more inorganic nitrogen in soil. 7. Under the condition of interspecific interaction, the total soil carbon emission of the whole system decreased significantly;interspecific interaction also significantly improved the carbon emission efficiency of crops. The soil respiration rate showed a seasonal change during the growth period from 2019 to 2020, with an unimodal trend of increasing first and then decreasing. The soil respiration rate reached the peak value in summer, and there were significant differences among different nitrogen levels and intercropping patterns;in winter, the soil respiration rate was the lowest, and there was no significant difference among different treatments. This is because soil respiration rate is affected by a variety of ecological factors, among which soil respiration rate and soil temperature are highly correlated. Affected by the size of biomass, the order of soil respiration rate values under monocropping system was as follows: SM >SW >SS. For maize, intercropping with soybean increased its soil respiration rate, which was contrary to intercropping with wheat. For soybean, the soil respiration rate under wheat-soybean intercropping system was lower than that of soybean monoculture. And for wheat, the soil respiration rate under intercropping system was higher than that of sole wheat. Compared to maize monoculture, the decreases of total carbon emissions of maize-wheat intercropping and maize-soybean intercropping were 17.50% and 18.33%, respectively. Compared to wheat monoculture, the decrease of total carbon emission of wheat-soybean intercropping was 0.98%. And intercropping significantly improved the carbon emission efficiency of crops compared with monoculture. The carbon emission equivalent ratio of maize-wheat intercropping ranged from 0.96~1.02, maize-soybean intercropping ranged from 1.01~1.08, and wheat-soybean intercropping ranged from 1.04~1.09. These results indicated that maize-wheat intercropping and maize-soybean intercropping system can effectively reduce the carbon emission during crop growth and development, and had the potential to produce more grain yield. Under the same nitrogen gradient, intercropping significantly reduced the total carbon emission of the whole system. 8. Nitrogen addition increased the soil carbon emission rate and total soil carbon emission under the background of interspecific interaction. The results of this experiment showed that with the increase of nitrogen application, the soil respiration rate showed an increasing trend, and the total carbon emission also increased. On the whole, compared with N1, under N2 and N3 treatments, the total carbon emissions in maize area were increased by 18.68% and 23.72%;the total carbon emissions in soybean region were increased by 10.42% and 22.56%;and the total carbon emissions in wheat area were increased by 9.41% and 22.09%. With the addition of nitrogen, the carbon emission equivalent ratio of soybean-wheat intercropping system was decreased;compared with N1, the carbon emissions equivalent ratio of maize-wheat intercropping under N2 and N3 treatments were increased by 7.29% and 3.20%, respectively;the carbon emission equivalent ratio of maize-soybean intercropping system was not significantly different under different nitrogen gradients. In conclusion, for the maize-wheat intercropping system, the carbon emission equivalent ratio was the highest under N2 gradient, and the effect of increasing production and reducing emissions was the best. With the addition of nitrogen, soil carbon emission rate and total carbon emission increased gradually, and interspecific interaction had the best effect on yield increase and emission reduction under the condition of moderate nitrogen addition. These results suggest that maize-soybean intercropping system and wheat-soybean intercropping system combined with reduction of nitrogen fertilization is an effective mode of reducing carbon emission and increasing carbon emission efficiency. This shows that the combination of intercropping mode and rational nitrogen application can not only ensure crop yield, but also reduce soil carbon emission, which is conducive to sustainable agricultural development. Among them, under the N2 gradient, the maize-soybean intercropping and wheat-soybean intercropping modes had the best effect, that is, under the normal nitrogen application cndition, introducing the legume intercropping mode into the field planting system is a feasible way to stabilize crop yield and reduce emission.
Pages93
URL查看原文
Language中文
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/460256
Collection生命科学学院
Affiliation生命科学学院
First Author AffilicationSchool of Life Sciences
Recommended Citation
GB/T 7714
周怡宁. 氮素添加和种间互作对旱作农田生产力和碳排放的影响及机制[D]. 兰州. 兰州大学,2021.
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