RESUMO
Cereal/legume intercropping is likely to achieve the optimal exploitation of soil and atmospheric nitrogen (N) sources to maintain high production and quality levels with low N inputs, as an attempt to eliminate underlying environmental effects. Nevertheless, the extent of the effect of cereal/legume intercropping on nodulation and N fixation of intercropped legumes in root interaction requires extensive verification. In the present study, root interaction of alfalfa/triticale intercropping was simulated in pots with the use of root separation types (pot with no barrier (A-T), pot with nylon mesh barrier (NA-T), pot with plastic barrier (PA-T), and alfalfa alone (SA)) in pots. Moreover, the experiment was measured at a range of N levels (N21, N210) and growing stages (branching, budding and initial flowering stages) in growth chamber. As alfalfa was growing, the total nodule number (TNN), effective nodule number (ENN) and nitrogenase activity (NA) of alfalfa with A-T and other cropping systems more noticeably differed from each other at higher N levels, whereas their diversification was reduced at lower N levels. As alfalfa was growing continuously, fresh nodule weight per plant (PNW) and single fresh nodule weight (SNW) with A-T and other cropping systems were amplified more significantly. The nodulation and N fixation ability under N21 were more significant than those under N210. Dry weight of plant per pot (TDW) and nitrogen accumulation of plant per pot (TNA) with A-T were obviously higher than those with other systems in the initial flowering stage, except for TNA under N21. The parameters regarding the nodulation and N fixation ability were significantly positively correlated on the whole. However, SNW and TNA were not significantly correlated, neither were SNW and TDW. According to the mentioned results, the closer root interaction, the better the nodulation form and N fixation ability of alfalfa will be, and the higher the biomass and N accumulation of all plants in pots will be. Interspecific facilitation in alfalfa/triticale intercropping system resulted in a greater yield and N accumulation; it also ultimately enhanced nodulation and N fixation ability, which can be applied in sustainable systems to avoid N loss to the environment and enhance N use efficiency.
RESUMO
Based on field experiments in 2017-2019, we examined the characteristics, yield effect and regulatory mechanism of light energy utilization in alfalfa/gramineous forage grass intercropping. With monoculture of alfalfa, forage triticale (C3 plant), and forage maize (C4 plant) as control, we measured the yield effect, the effect of light energy utilization factor on yield formation, the characteristic difference and mechanism of light energy utilization under alfalfa/triticale and alfalfa/maize intercropping patterns. Results showed that land equivalent ratios of both intercropping patterns were all greater than 1, indicating that land utilization ratio and yield benefit of the two intercropping patterns were higher than that of monoculture, among which alfalfa/triticale intercropping pattern was the most promising one. The contribution of light energy utilization factors to yield was following an order of leaf area index (1.531) > net photosynthetic rate (0.882) > intercellular CO2 concentration (0.282) > transpiration rate (-0.229) > canopy opening (-0.291) > PAR interception rate (-0.681) > stomatal conductance (-0.751). Among them, leaf area index was not only one of the important indices to characterize photosynthetic capacity, but also an important component factor of forage crop yield aiming at harvesting nutrients. Therefore, among all factors of photosynthetic characteristics, net photosynthetic rate was the main factor affecting yield. The net photosynthetic rate of alfalfa, triticale and maize under intercropping showed the same pattern, and being different from that of monoculture. The main ways for intercropping to increase net photosynthetic rate included: triticale and maize increased net photosynthetic rate and yield by enhancing the carboxylation fixation capacity of CO2 and the utilization capacity of strong light, while alfalfa could improve its net photosynthetic rate and promote growth under low light, by increasing the content of chlorophyll b in functional leaves, changing chlorophyll composition and enhancing the collection and transmission of light energy.
Assuntos
Agricultura , Medicago sativa , Fotossíntese , Folhas de Planta , Poaceae , Zea maysRESUMO
Semi-arid region of Northwest China is characterized by barren soil, with high pH and high carbonate content. Saline-alkali land is easily formed in this area, which inhibits soil microbial activity and results in soil nutrient loss. To improve soil health in this area, effects of intercropping alfalfa and triticale on rhizosphere soil nutrients and bacterial community structure were examined though a three-consecutive-year experiment. The results showed that soil organic matter (SOM) content of alfalfa rhizosphere in intercropping was significantly higher than that in monoculture, while pH and available potassium (AK) content were lower than that in monoculture. The concentrations of SOM, available nitrogen (AN), available phosphate (AP) and AK of triticale rhizosphere in intercropping were significantly higher than those in monoculture. The bacterial sequences, OTUs, richness, and diversity of alfalfa and triticale in rhizosphere soil were all higher than those in monoculture. At phylum level, Proteobacteria and Bacteroidetes were dominant, accounting for 31.1%-33.4% and 22.4%-32.2% of the total OTUs, respectively. The relative abundance of Bacteroidete was higher in intercropping than in monoculture. Actinomycetes in the monoculture were significantly higher. Acidobacteria in the intercropping triticale was significantly higher than that in monoculture triticale. Verrucomicrobia in intercropping alfalfa was significantly more abundant than that in monoculture of alfalfa. At genus level, Algoriphagus, Flavobacterium, Gp6, and Chryseolinea in monoculture were greater than those in intercropping, and Cellvibrio showed an opposite trend. Results of correlation analysis showed that the abundance of Proteobacteria and Bacteroidetes were negatively correlated with soil pH, while that of Bacteroidetes were positively correlated with SOM, TN and AN. However, the abundance of Chloroflexi, Planctomycetes, Acidobacteria, Verrucomicrobia, and Gemmatimonadetes was negatively correlated with SOM and AN. Overall, alfalfa-triticale intercropping is an effective strategy to improve soil health in semi-arid region of Northwest China.
Assuntos
Rizosfera , Triticale , Agricultura , China , Medicago sativa , Nutrientes , Solo , Microbiologia do SoloRESUMO
To explore light energy utilization characteristics and yield effect of different legume-gramineae intercropping patterns, we set up five kinds of monocropping patterns including alfalfa, triticale, oats, maize and sorgo as reference in a field experiment. The light energy utilization chara-cteristics and productivity of four kinds of intercropping patterns including alfalfa-triticale, alfalfa-oats, alfalfa-maize and alfalfa-sorgo were examined. The contribution degree of each light energy index to yield formation was analzyed using path analysis method. The results showed that the contribution of each index of light energy to yield from large to small was as follows: leaf area index (LAI)=1.236, net photosynthetic rate (Pn)=0.519, canopy openness (DIFN)=0.302, intercellular CO2 concentration (Ci)=-0.026, stomatal conductance (gs)=-0.116, transpiration rate (Tr)=-0.188, PAR interception rate (FIPAR)=-1.708. Light use efficiency (LUE) as a comprehensive indicator of light energy utilization had the largest value (1.367). Compared with monoculture, the values of LAI, Pn, gs, Tr and FIPAR of four kinds of gramineae grasses increased under intercropping and the values of DIFN and Ci decreased, while alfalfa showed an opposite trend. Compared with monoculture, the LUE of four kinds of gramineae grasses under intercropping was significantly increased. The increase rates of triticale and oats (35.2% and 30.4%) were higher than that of maize and sorgo (28.7% and 26.3%). The decrease rates of alfalfa intercropping with triticale and oats (6.1% and 8.3%) were obviously lower than that of maize and sorgo (21.8% and 24.5%). The values of land equivalent ratio (LER) of four kinds of intercropping patterns was all greater than 1. The LER values of alfalfa-triticale and alfalfa-oat were significantly higher than those of alfalfa-maize and alfalfa-sorgo. It could be seen that LAI had the largest direct contribution to yield, followed by Pn. Among the four intercropping patterns, two patterns, alfalfa-triticale and alfalfa-oats, had greater improvement potential of light energy utilization and yield.