The productive performance of intercropping

Intercropping with faba bean under appropriate row configuration increases root yield and active ingredient content of Codonopsis pilosula

Continuous cultivation of the medicinal herb Codonopsis pilosula (C. pilosula) declines root yield and active ingredient content. Scientific and reasonable intercropping patterns can improve yield and active ingredient accumulation. However, how intercropping systems affect root yield and active ingredient content of C.pilosula is still poorly understood. We conducted a field experiment with four treatments, including monoculture C. pilosula (MC), one row of C. pilosula intercropping with one row of faba bean (IC1), two rows of C. pilosula intercropping with one row of faba bean (IC2), and four rows of C. pilosula intercropping with one row of faba bean (IC3), to explore the response of leaf traits, root yield, and active ingredient content of C. pilosula to cropping patterns. The results showed that intercropping significantly increased the root yield of C. pilosula by 7.0-18.7%, lobetyolin yield by 8.6-25.2%, atractylenolide III yield by 34.2-54.0%, and syringin yield by 31.1-53.4% compared to monoculture, and the largest yield advantage occurred in IC2. The results also showed that intercropping significantly improves leaf size, net photosynthetic rate, and C metabolism enzyme activity of C. pilosula. Correlation analysis and partial least squares path model showed that improved root and active ingredient yield in intercropping can be attributed to enhanced leaf photosynthesis and C metabolism, indicating that appropriate row configuration in C. pilosula/faba bean intercropping system could increase the yield of C. pilosula by enhancing light use efficiency. These findings suggest that two rows of C. pilosula intercropping with one row of faba bean is a promising approach to establishing a high-yield and sustainable C. pilosula agroecosystem.

Dominant species predict plant richness and biomass in global grasslands

The bidirectional relationship between plant species richness and community biomass is often variable and poorly resolved in natural grassland ecosystems, impeding progress in predicting impacts of environmental changes. Most biological communities have long-tailed species abundance distributions (for example, biomass, cover, number of individuals), a general property that may provide predictive power for species richness and community biomass. Here we show mathematical relationships between community characteristics and the abundance of dominant species arising from long-tailed distributions and test these predictions using observational and experimental data from 76 grassland sites across 6 continents. We find that community biomass provides little predictive ability for community richness, consistent with previous findings. By contrast, the relative abundance of dominant species quantitatively predicts species richness, whereas their absolute abundance quantitatively predicts community biomass under both ambient and altered environmental conditions, as expected mathematically. These results are robust to the type of abundance measure used. Three types of simulated data further show the generality of these results. Our integrative framework, arising from a few dominant species and mathematical properties of species abundance distributions, fills a persistent gap in our ability to predict community richness and biomass under ambient and anthropogenically altered conditions.

Belowground Interaction in Tea/Soybean Intercropping Enhances Tea Quality by Improving Soil Nutrient Dynamics

Although tea (Camellia sinensis)/soybean (Glycine max) intercropping is widely applied in tea gardens, the underlying mechanisms driving tea quality promotion remain largely unclear. This study explores the effects of intercropping on tea quality, soil nutrient availability, and soybean growth and analyzes their mutual relationship. Field experiments revealed that intercropping increased tea leaf water extracts, polyphenols, and amino acids by 4.36-8.99%, 14.76-15.23%, and 14.73-16.36%, respectively, across two growth stages. Furthermore, intercropping boosted organic matter, available nitrogen (N), phosphorus (P), and potassium (K) in the tea rhizosphere. Enzyme activities, including acid phosphatase, alkaline phosphatase, urease, and β-glucosidase, were also elevated in tea/soybean intercropping. In soybean, shoot and root biomass, weight and number of nodules, and N, P, and K content increased over cultivation time. Correlation analysis showed that tea water extracts and polyphenols were positively linked to soil available P and alkaline phosphatase activities. Soybean root and nodule growth were correlated with soil N and P activation and tea water extracts, indicating that soybean-mediated underground interactions drive mineral nutrient mobilization in rhizosphere, further improving tea quality. This study provides mechanistic insights into tea/soybean intercropping, offering practical implications for sustainable tea cultivation practices.

Development and Breeding of Herbicide-Resistant Sorghum for Effective Cereal-Legume Intercropping

Weeds bring a serious challenge to crop production, and herbicides is the most effective and economic way to manage it in field. Sorghum is a critical crop for staple food, fodder, and biofuel. However, the lack of herbicide-resistant sorghum germplasm severely impedes its production. Here, we conducted a large-scale screening and identified 13 sorghum mutant lines resistant to imidazolinone (IMI) herbicides. Two unique mutation sites in SbALS (acetolactate synthase), thus namely Sbals-1 (A93T) and Sbals-2 (S624N) are discovered, both enhance sorghum tolerance to imazamox. Notably, under high concentrations of imazamox, sbals-1 presented a superior growth phenotype and elevated SbALS activity than sbals-2, a difference that can be attributed to the predicted protein structures. Breeding with Sbals, both grain- and grass-type sorghum, shows great weed control and field performance. The herbicide imazamox resistance is further evaluated in a soybean population for sorghum-soybean strip intercropping, identifying 123 highly resistant soybean varieties. Field intercropping tests indicated health growth of both soybean and sorghum lines post-imazamox treatment, which enhance field clearance of weed. This study, therefore, provides valuable insights not only for herbicide-resistant sorghum breeding but also for the successful implementation of efficient and sustainable cereal-legume intercropping systems.

Intercropping of non-leguminous crops improves soil biochemistry and crop productivity: a meta-analysis

Plant species-rich systems tend to be more productive than depauperate ones. In agroecosystems, increasing crop plant diversity by including legumes often increases soil nitrogen (N) and improves soil fertility; however, such generality in outcomes of non-leguminous crop mixture is unknown. Here, through a meta-analysis of 174 individual cases, we explored the current global research trend of intercropping of exclusively non-leguminous crops (ICnl) and quantified its effect on agroecosystem productivity key metrics, for example crop plant health, soil chemistry, and microbial community under diverse experimental conditions. ICnl increased plant biomass and disease suppression and provided a notable yield advantage over monocultures. In addition to phosphorus and potassium, ICnl also increased plant-available soil N, which, along with increased soil microbial abundance, was positively associated with increased soil organic matter. These positive effects were more pronounced in experiments with long duration (> 1 yr), field soil conditions, and soil pH > 7. ICnl improves several crop productivity metrics, which could augment sustainable crop production, particularly when practiced for a long duration and in alkaline soils.

Effect of Compound Planting Mode on Nutrient Distribution in Cotton

Composite planting has become one of the primary agricultural practices promoted in recent years, especially in the northwest inland cotton regions of China, where various economic trees and crops are intercropped with cotton. However, research on the microclimatic differences affecting cotton growth and the nutrient allocation strategies for cotton's key economic organs (i.e., seed, batt, and shell) in strip composite cropping systems remains limited. In this study, we examined the nutrient allocation strategies of cotton under multiple composite cropping patterns and proposed the most suitable cultivation patterns for this region in the northwest inland region of China, utilizing an allometry partitioning index and ecological stoichiometry, based on a long-term positional experiment. The results revealed that the nutrient distribution of cotton was of equal speed with the combined planting with trees, while there was an allometric distribution index of N and P between the combined planting with maize. The effect of the compound planting mode on the nutrient-use efficiency of cotton was mainly reflected in the organ differentiation stage of its reproductive growth stage. Specifically, cotton showed lower nutrient-use efficiency in reproductive organs when intercropped with low shrubs and herbaceous crops, likely due to the insufficient protective capacity of these plants for cotton. Interestingly, strip intercropping with tall trees improved cotton's nutrient-utilization efficiency. However, it also resulted in reduced nitrogen and phosphorus content in cotton batt. Moreover, soil indicators such as available nitrogen and electrical conductivity positively influenced the nutrient uptake of cotton shells and roots, while soil phosphorus promoted the nutrient absorption of cotton seed but inhibited the nitrogen and phosphorus of cotton shell and the nitrogen of cotton batt. These findings suggest that nutrient partitioning in cotton is influenced by a variety of soil factors. According to these results, the combined planting pattern of cotton and apple trees should be considered in practice to improve cotton yield and economic benefits in the northwest inland region of China.

The Promotion of Alternative Crop Production Paradigms Should Be Founded on Proven Science-Based Approaches

Recent discourse on the need to adopt alternative approaches to sustainable crop production has strongly criticized modern, usually referred to as "industrial", agriculture as the main cause of environmental problems and a loss of biodiversity, which is concerning given that modern agriculture currently feeds over 90% of the global population. Ongoing criticisms of modern agriculture have escalated into calls to replace it, largely based on the belief that alternative approaches will lead to sustainable crop production, although food production potential is rarely mentioned. This paper critically analyzes two such alternatives, agroecology and the Vision for Adapted Crops and Soils (VACS), a sub-set of agroecological approaches with a focus on the Global South. In the case of agroecology, this paper considers the role of diversity in cropping systems and the input reduction paradigm, as well as labor productivity. Modern agriculture already provides a wide range of science-based, proven crop and field diversification options without the need to rely on in-field crop species diversity. Furthermore, a reduction in or the elimination of chemical fertilizers with a preference for compost and manure is not a viable strategy where soils are severely degraded. In the case of the VACS, the planned emphasis on "opportunistic", locally adapted, traditional/indigenous crops is challenged by the importance of introduced crops to food production, especially in Africa. We conclude by recommending a pragmatic approach to using all of the available agricultural practices wisely to produce enough food in an environmentally responsible manner. Global leadership is needed to bring the divergent views of scientists and environmentalists together to improve food production and nutrition, livelihoods, and the agricultural environment.

Effects of Increasing CO2 Concentration on Crop Growth and Soil Ammonia-Oxidizing Microorganisms in a Fababean (Vicia faba L.) and Wheat (Triticum aestivum Yunmai) Intercropping System

Elevated carbon dioxide (eCO2) levels can enhance crop yields but may simultaneously reduce quality, impacting both macronutrient and micronutrient concentrations, and potentially decreasing protein content in cereal grains. This study examined the effects of elevated CO2 (eCO2) and nitrogen (N) fertilization on crop growth, yield, and soil nitrogen cycling through a glass greenhouse experiment using Eutric Regosol soil. The experimental design incorporated two CO2 gradients: ambient CO2 (aCO2) at approximately 410 ppm during the day and 460 ppm at night, and eCO2 at approximately 550 ppm during the day and 610 ppm at night. Additionally, two nitrogen fertilization treatments were applied: no fertilizer (N0) and 100 mg N kg-1 dry weight (DW) soil (N100). Crops were cultivated under two cropping systems: the monoculturing of fababean (Vicia faba L.) or wheat (Triticum aestivum Yunmai) and the intercropping of both species. The results demonstrated that eCO2 significantly enhanced the growth and yield of both fababean and wheat, particularly when nitrogen fertilization was applied. Nitrogen fertilizer application did not always enhance crop yield, considering the complexity of nitrogen management under elevated CO2 conditions. Furthermore, the intercropping of fababean and wheat presented multiple advantages, including improved crop yields, enhanced soil health, and increased ecosystem services. These findings suggest that intercropping can serve as a sustainable strategy to boost productivity and ecosystem resilience in the face of climate change. The changes in nitrogen application and CO2 concentration affect the gene copy number of ammonia-oxidizing bacteria and archaea, which may affect the nitrogen cycling process in soil. There are complex interactions between crop biomass, nitrogen accumulation, transpiration rate, photosynthetic rate and stomatal conductance with soil properties (e.g., pH, organic matter, nitrogen content) and microbial community structure. The interaction between CO2 concentration, nitrogen application level and crop intercropping pattern had significant effects on crop growth, soil properties and microbial communities. Future research should prioritize investigating the long-term effects of intercropping on soil productivity and the development of management strategies that optimize the benefits of this cropping system.

Intercropping with Robinia pseudoacacia reduces soft rot incidence in konjac by modulating the root bacterial community

BACKGROUND

Soft rot (Pectobacterium aroidearum and Dickeya) is a devastating soil-borne bacterial disease that threatens konjac production. Intercropping with false acacia has been shown to significantly reduce soft rot incidence in konjac by shifting the microbial community. However, how intercropping shapes the root bacterial community and affects soft rot incidence remains unclear. To address this, we investigated three konjac intercropping systems (false acacia, paulownia, and maize) to explore the relationships among intercropping, soft rot incidence, root bacterial community, soil enzyme activity, and soil properties.

RESULTS

Konjac intercropped with false acacia exhibited the lowest soft rot incidence and the lowest abundance of pathogenic taxa. Soft rot incidence was negatively correlated with total soil nitrogen and potassium but positively correlated with total and available soil phosphorus. The bacterial community structure and function in konjac roots differed among intercropping types, mainly driven by available soil phosphorus. Beneficial microorganisms such as Bradyrhizobium and Variovorax were enriched under a false acacia intercropping system and were negatively correlated with soil-available phosphorus. Additionally, the stable bacterial community in healthy konjac roots under false acacia may make konjac less susceptible to pathogen invasion.

CONCLUSION

The study showed that intercropping reduced the soft rot incidence by regulating the structure and stability of the konjac root bacterial community, and soil-available phosphorus was the main factor affecting the difference in the konjac root bacterial community, which provided a basis for the management of soil fertilization in konjac cultivation. © 2024 Society of Chemical Industry.

Photosystem rearrangements, photosynthetic efficiency, and plant growth in far red-enriched light

Arabidopsis plants were grown in white light (400-700 nm) or in white light supplemented with far-red (FR) light peaking at 730 nm. FR-enriched light induced the typical shade avoidance syndrome characterized by enhanced length of seedling hypocotyl and leaf petiole. FR supplementation also caused a noticeable decrease in the carotenoid and chlorophyll content that was attributable to a block of pigment accumulation during plant development. The carotenoid decrease resulted from a downregulation of their biosynthesis pathway rather than carotenoid degradation. The losses of photosynthetic pigments are part of structural and functional rearrangements of the photosynthetic apparatus. The plastoquinone pool was chronically more oxidized in plants acclimated to white + FR light compared to white light-grown plants. Growth in FR-enriched light was associated with a higher photochemical efficiency of PSII compared to growth in white light and with a substantial increase in root and shoot biomass production. Light distribution between the photosystems was modified in favor of PSII by an increase in the PSII/PSI ratio and an inhibition of state transitions. Neither LHCII abundance nor nonphotochemical energy dissipation in the PSII chlorophyll antennae were modified significantly by the addition of FR light. A PSI supercomplex, not previously observed in Arabidopsis, was specifically found in plants grown in FR-enriched light. This large PSI complex contains a supplementary Lhca1-4 dimer, leading to a total of 6 LHCI antennae instead of 4 in the canonical PSI. Through those photosystem rearrangements and the synergistic interaction with white light, FR light is photosynthetically active and can boost photosynthesis and plant growth.

The alteration of interspecific interaction responded to various relative sowing time in wheat/maize intercropping

Introduction

An interspecific interaction is an important reason for the yield advantage of interspecific cropping compared with sole cropping, and the relative sowing time of species is an important factor affecting interspecific competitiveness. Our purpose was to explore the effects of different relative sowing times on the interspecific competition-recovery phenomenon in wheat and maize intercropping systems.

Methods

Three planting methods (wheat/maize intercropping, wheat and maize sole cropping) and different relative sowing times of wheat were used to carry out field experiments over two years. Sequential harvest of subplots was performed between 3 and 6 times, and the biomass data were fitted to logistic growth model.

Results

Delaying the sowing time of wheat reduced the wheat yield, biomass and nutrient acquisition and increased those of maize, but wheat still had an intercropping advantage during the co-growth period. At the same time, the nutrient acquisition of maize was still inhibited, but its recovery growth advanced. Changing the relative sowing time of wheat significantly changed the maximum instantaneous growth rates of wheat and maize. Delaying the relative sowing time of wheat significantly reduced its maximum instantaneous growth rate, while enhancing that of maize, leading to a balanced mutual benefit.

Conclusions

Delaying the sowing time of wheat to the same sowing time as maize will change wheat/maize intercropping from asymmetrical interspecific facilitation to symmetrical interspecific facilitation. However, in this case, intercropped wheat still had an interspecific competitive advantage in the co-growth stage, and intercropped maize still underwent a competition-recovery process.

The productivity-stability trade-off in global food systems

Historically, humans have managed food systems to maximize productivity. This pursuit has drastically modified terrestrial and aquatic ecosystems globally by reducing species diversity and body size while creating very productive, yet homogenized, environments. Such changes alter the structure and function of ecosystems in ways that ultimately erode their stability. This productivity-stability trade-off has largely been ignored in discussions around global food security. Here, we synthesize empirical and theoretical literature to demonstrate the existence of the productivity-stability trade-off and argue the need for its explicit incorporation in the sustainable management of food systems. We first explore the history of human management of food systems, its impacts on average body size within and across species and food web stability. We then demonstrate how reductions in body size are symptomatic of a broader biotic homogenization and rewiring of food webs. We show how this biotic homogenization decompartmentalizes interactions among energy channels and increases energy flux within the food web in ways that threaten their stability. We end by synthesizing large-scale ecological studies to demonstrate the prevalence of the productivity-stability trade-off. We conclude that management strategies promoting landscape heterogeneity and maintenance of key food web structures are critical to sustainable food production.

Enhancing production efficiency through optimizing plant density in maize-soybean strip intercropping

Introduction

Due to limited arable land resources, intercropping has emerged as an efficient and sustainable production method for increasing total grain yield per unit land area. Maize-soybean strip intercropping (MSSI) technology is being widely promoted and applied across China. However, the combination of optimal density for achieving higher production efficiency of both soybean and maize remains unclear. The objective of this study was to evaluate the differences in yield, economic benefits, land, and nitrogen (N) efficiency in MSSI systems under different densities.

Methods

Five maize/soybean density combinations (67,500/97,500 plants ha-1, D1; 67,500/120,000 plants ha-1, D2; 67,500/142,500 plants ha-1, D3; 60,000/142,500 plants ha-1, D4; 52,500/142,500 plants ha-1, D5) were set under the same N input in the field experiment.

Results and discussion

The results demonstrated that optimizing the density in the intercropping system could enhance production efficiency. Increasing the density of soybean and maize significantly increased the total grain yield (D3 > D2 > D1 > D4 > D5). The D3 treatment, exhibiting the best comprehensive performance, also promoted increases in leaf area index, dry matter accumulation, and N absorption and utilization. Path analysis indicated that density had the most substantial impact on maize yield, while grain number had the greatest influence on soybean yield, with contribution rates of 49.7% and 61.0%, respectively. These results provide valuable insights into optimal field density for summer planting in MSSI, facilitating its wider adoption.

Optimization of N Fertilizer and Synergistic Intercropping to Enhance the Productivity Advantage of Faba Bean and Effective Control of Chocolate Spot Epidemics

Intercropping of wheat/faba bean is a common practice within the legume-cereal family. However, the benefits of nitrogen (N) fertilizer-optimized synergistic intercropping in improving faba bean productivity while controlling the prevalence of chocolate spot disease have not been established. This study conducted continuous field experiments spanning two planting seasons to investigate two key findings: (i) Optimizing N fertilizer application can enhance the productivity of intercropped faba bean. (ii) The percentage severity index (PSI) during the period of maximum prevalence rate (Rmax) of faba bean chocolate spot disease poses a substantial challenge to faba bean yield. The results indicated that the land equivalent ratio and transgressive overyielding index for each intercropping treatment increased with higher N fertilizer application, exceeding a value of 1, and the land saving proportion also exceeded 0. Intercropping primarily enhances productivity, as measured by the harvest index (HI), by amplifying the complementary effect rather than the selection effect, thus improving the net benefit of intercropping. The HI of single and intercropped faba bean increased with the N1 and N2 treatments in both planting seasons. However, the HI of single and intercropped faba bean at the N3 level decreased significantly, ranging from 17.85 to 29.62%. Furthermore, a notable negative correlation was established between the PSI during critical epidemic (initial epidemic, maximum epidemic rate, and late epidemic) periods and observed and expected faba bean yields. As the PSI increased, faba bean yields decreased, and the PSI of intercropping at different periods was lower than that observed in the single cropping. Additionally, intercropping with the optimized N fertilizer treatment (N2 treatment) exhibited an enhanced relative control effect on chocolate spot disease in faba bean, ranging from 35.21 to 52.36%. This finding confirmed the productivity advantage of intercropping faba bean. In conclusion, this study suggested that optimizing N fertilizer application can enhance the productivity of intercropped faba bean. Wheat/faba bean intercropping effectively controlled the PSI during the period of Rmax, which would otherwise threaten faba bean yield. Consequently, this practice ensured sustained advantages of wheat/faba bean intercropping.

A "love match" score to compare root exudate attraction and feeding of the plant growth-promoting rhizobacteria Bacillus subtilis, Pseudomonas fluorescens, and Azospirillum brasilense

Introduction

The rhizosphere is the zone of soil surrounding plant roots that is directly influenced by root exudates released by the plant, which select soil microorganisms. The resulting rhizosphere microbiota plays a key role in plant health and development by enhancing its nutrition or immune response and protecting it from biotic or abiotic stresses. In particular, plant growth-promoting rhizobacteria (PGPR) are beneficial members of this microbiota that represent a great hope for agroecology, since they could be used as bioinoculants for sustainable crop production. Therefore, it is necessary to decipher the molecular dialog between roots and PGPR in order to promote the establishment of bioinoculants in the rhizosphere, which is required for their beneficial functions.

Methods

Here, the ability of root exudates from rapeseed (Brassica napus), pea (Pisum sativum), and ryegrass (Lolium perenne) to attract and feed three PGPR (Bacillus subtilis, Pseudomonas fluorescens, and Azospirillum brasilense) was measured and compared, as these responses are directly involved in the establishment of the rhizosphere microbiota.

Results

Our results showed that root exudates differentially attracted and fed the three PGPR. For all beneficial bacteria, rapeseed exudates were the most attractive and induced the fastest growth, while pea exudates allowed the highest biomass production. The performance of ryegrass exudates was generally lower, and variable responses were observed between bacteria. In addition, P. fluorescens and A. brasilense appeared to respond more efficiently to root exudates than B. subtilis. Finally, we proposed to evaluate the compatibility of each plant-PGPR couple by assigning them a "love match" score, which reflects the ability of root exudates to enhance bacterial rhizocompetence.

Discussion

Taken together, our results provide new insights into the specific selection of PGPR by the plant through their root exudates and may help to select the most effective exudates to promote bioinoculant establishment in the rhizosphere.

Responses of diazotrophic network structure and community diversity to alfalfa-maize intercropping are soil property-dependent

Introduction

Intercropping and soil properties both affect soil diazotrophic communities. However, the specific effects that alfalfa-maize intercropping has on diazotrophic networks and community diversity under different soil properties remain unclear.

Methods

In this study, we investigated the soil diazotrophic communities of two crop systems, alfalfa monoculture (AA) and alfalfa-maize intercropping (A/M), in two sites with similar climates but different soil properties (poor vs. average).

Results and discussion

The diazotrophic network complexity and community diversity were higher at the site with poor soil than at the site with average soil (p < 0.05). Community structure also varied significantly between the sites with poor and average soil (p < 0.05). This divergence was mainly due to the differences in soil nitrogen, phosphorus, and organic carbon contents between the two sites. At the site with poor soil, the A/M system had lower diazotrophic diversity, lower network complexity and greater competition between diazotrophs than the AA system (p < 0.05) because intercropping intensified the soil phosphorus limitation under poor soil conditions. However, in the average soil, it was the A/M system that had an altered diazotrophic structure, with an increased abundance of 11 bacterial genera and a decreased abundance of three bacterial genera (p < 0.05).

Conclusion

Our results indicated that the effects of alfalfa-maize intercropping on diazotrophic communities were soil property-dependent.

Plant diversity drives positive microbial associations in the rhizosphere enhancing carbon use efficiency in agricultural soils

Expanding and intensifying agriculture has led to a loss of soil carbon. As agroecosystems cover over 40% of Earth's land surface, they must be part of the solution put in action to mitigate climate change. Development of efficient management practices to maximize soil carbon retention is currently limited, in part, by a poor understanding of how plants, which input carbon to soil, and microbes, which determine its fate there, interact. Here we implement a diversity gradient by intercropping undersown species with barley in a large field trial, ranging from one to eight undersown species. We find that increasing plant diversity strengthens positive associations within the rhizosphere soil microbial community in relation to negative associations. These associations, in turn, enhance community carbon use efficiency. Jointly, our results highlight how increasing plant diversity in agriculture can be used as a management strategy to enhance carbon retention potential in agricultural soils.

Seasonal soil health dynamics in soy-wheat relay intercropping

There is growing interest in intercropping as a practice to increase productivity per unit area and ecosystem functioning in agricultural systems. Relay intercropping with soy and winter wheat may benefit soil health due to increased diversity and longer undisturbed soil cover, yet this remains largely unstudied. Using a field experiment in Eastern Germany, we studied the temporal dynamics of chemical, biological, and physical indicators of soil health in the topsoil over a year of cultivation to detect early effects of soy-wheat relay intercropping compared to sole cropping. Indicators included microbial abundance, permanganate-oxidizable carbon, carbon fractions, pH, and water infiltration. Relay intercropping showed no unique soil health benefits compared to sole cropping, likely affected by drought that stressed intercropped soy. Relay intercropping did, however, maintain several properties of both sole crops including an increased MAOM C:N ratio and higher soil water infiltration. The MAOM C:N ratio increased by 4.2 and 6.2% in intercropping and sole soy and decreased by 5% in sole wheat. Average near-saturated soil water infiltration rates were 12.6, 14.9, and 6.0 cm hr-1 for intercropping, sole wheat, and sole soy, respectively. Cropping system did not consistently affect other indicators but we found temporal patterns of these indicators, showing their sensitivity to external changes.

Aerobiology of the Family Lamiaceae: Novel Perspectives with Special Reference to Volatiles Emission

Lamiaceae is a botanical family rich in aromatic species that are in high demand such as basil, lavender, mint, oregano, sage, and thyme. It has great economical, ecological, ethnobotanical, and floristic importance. The aim of this work is to provide an updated view on the aerobiology of species from the family Lamiaceae, with an emphasis on novelties and emerging applications. From the aerobiology point of view, the greatest interest in this botanical family is related to the volatile organic compounds emitted by the plants and, to a much lesser extent, their pollen. Research has shown that the major volatile organic compounds emitted by the plants from this botanical family are monoterpenes and sesquiterpenes. The most important monoterpenes reported across studies include α-pinene, β-pinene, 1,8-cineole, menthol, limonene, and γ-terpinene. Most reports tend to cover species from the subfamily Nepetoideae. Volatile oils are produced by glandular trichomes found on aerial organs. Based on general morphology, two main types are found in the family Lamiaceae, namely peltate and capitate trichomes. As a result of pollinator-mediated transfer of pollen, Lamiaceae species present a reduced number of stamens and quantity of pollen. This might explain the low probability of pollen presence in the air from these species. A preliminary synopsis of the experimental evidence presented in this work suggests that the interplay of the organic particles and molecules released by these plants and their environment could be leveraged for beneficial outcomes in agriculture and landscaping. Emerging reports propose their use for intercropping to ensure the success of fructification, increased yield of entomophilous crops, as well as in sensory gardens due to the therapeutic effect of volatiles.

Associational Effects of Desmodium Intercropping on Maize Resistance and Secondary Metabolism

Intercropping is drawing increasing attention as a strategy to increase crop yields and manage pest pressure, however the mechanisms of associational resistance in diversified cropping systems remain controversial. We conducted a controlled experiment to assess the impact of co-planting with silverleaf Desmodium (Desmodium uncinatum) on maize secondary metabolism and resistance to herbivory by the spotted stemborer (Chilo partellus). Maize plants were grown either in the same pot with a Desmodium plant or adjacent to it in a separate pot. Our findings indicate that co-planting with Desmodium influences maize secondary metabolism and herbivore resistance through both above and below-ground mechanisms. Maize growing in the same pot with a Desmodium neighbor was less attractive for oviposition by spotted stemborer adults. However, maize exposed only to above-ground Desmodium cues generally showed increased susceptibility to spotted stemborer herbivory (through both increased oviposition and larval consumption). VOC emissions and tissue secondary metabolite titers were also altered in maize plants exposed to Desmodium cues, with stronger effects being observed when maize and Desmodium shared the same pot. Specifically, benzoxazinoids were strongly suppressed in maize roots by direct contact with a Desmodium neighbor while headspace emissions of short-chain aldehydes and alkylbenzenes were increased. These results imply that direct root contact or soil-borne cues play an important role in mediating associational effects on plant resistance in this system.

Biodiversity increases resistance of grasslands against plant invasions under multiple environmental changes

Biodiversity often helps communities resist invasion. However, it is unclear whether this diversity-invasion relationship holds true under environmental changes. Here, we conduct a meta-analysis of 1010 observations from 25 grassland studies in which plant species richness is manipulated together with one or more environmental change factors to test invasibility (measured by biomass or cover of invaders). We find that biodiversity increases resistance to invaders across various environmental conditions. However, the positive biodiversity effect on invasion resistance is strengthened under experimental warming, whereas it is weakened under experimentally imposed drought. When multiple factors are imposed simultaneously, the positive biodiversity effect is strengthened. Overall, we show that biodiversity helps grassland communities resist plant invasions under multiple environmental changes. Therefore, investment in the protection and restoration of native biodiversity is not only important for prevention of invasions under current conditions but also under continued global environmental change.

Improvement of cool-season food legumes for adaptation to intercropping systems: breeding faba bean for intercropping with durum wheat as a case study

Although the transition toward a more sustainable agricultural system is sparking the interest of scientists and farmers around the globe, breeding programs are still focusing on optimizing cultivars intended for the monoculture system, and most cultivars available on the market are not suitable for intercropping. The incorporation of versatile cool-season food legumes (CSFLs) in the intercropping system is a promising way toward more diversified and sustainable cropping systems. However, as the selection of good-performing cultivars under sole cropping does not always lead to a good performance in intercropping, the development of an alternative breeding scheme for intercropping is now a necessity. The case study of faba bean-wheat intercropping was used to select for traits associated with better performance of faba bean, resulting in identifying the combined grain yield, 100-seed weight, number of pods per plant, and canopy height as key traits for faba bean-wheat intercropping suitability. Incorporating these traits in the breeding programs would be the cornerstone of the prospective transition.

Harnessing monocrop breeding strategies for intercrops

Intercropping is considered advantageous for many reasons, including increased yield stability, nutritional value and the provision of various regulating ecosystem services. However, intercropping also introduces diverse competition effects between the mixing partners, which can negatively impact their agronomic performance. Therefore, selecting complementary intercropping partners is the key to realizing a well-mixed crop production. Several specialized intercrop breeding concepts have been proposed to support the development of complementary varieties, but their practical implementation still needs to be improved. To lower this adoption threshold, we explore the potential of introducing minor adaptations to commonly used monocrop breeding strategies as an initial stepping stone towards implementing dedicated intercrop breeding schemes. While we acknowledge that recurrent selection for reciprocal mixing abilities is likely a more effective breeding paradigm to obtain genetic progress for intercrops, a well-considered adaptation of monoculture breeding strategies is far less intrusive concerning the design of the breeding programme and allows for balancing genetic gain for both monocrop and intercrop performance. The main idea is to develop compatible variety combinations by improving the monocrop performance in the two breeding pools in parallel and testing for intercrop performance in the later stages of selection. We show that the optimal stage for switching from monocrop to intercrop testing should be adapted to the specificity of the crop and the heritability of the traits involved. However, the genetic correlation between the monocrop and intercrop trait performance is the primary driver of the intercrop breeding scheme optimization process.

Coadaptation of coexisting plants enhances productivity in an agricultural system

Growing crops in more diverse crop systems (i.e., intercropping) is one way to produce food more sustainably. Even though intercropping, compared to average monocultures, is generally more productive, the full yield potential of intercropping might not yet have been achieved as modern crop cultivars are bred to be grown in monoculture. Breeding plants for more familiarity in mixtures, i.e., plants that are adapted to more diverse communities (i.e., adaptation) or even to coexist with each other (i.e., coadaptation) might have the potential to sustainably enhance productivity. In this study, the productivity benefits of familiarity through evolutionary adaptation and coevolutionary coadaptation were disentangled in a crop system through an extensive common garden experiment. Furthermore, evolutionary and coevolutionary effects on species-level and community-level productivity were linked to corresponding changes in functional traits. We found evidence for higher productivity and trait convergence with increasing familiarity with the plant communities. Furthermore, our results provide evidence for the coevolution of plants in mixtures leading to higher productivity of coadapted species. However, with the functional traits measured in our study, we could not fully explain the productivity benefits found upon coevolution. Our study investigated coevolution among randomly interacting plants and was able to demonstrate that coadaptation through coevolution of coexisting species in mixtures occurs and promotes ecosystem functioning (i.e., higher productivity). This result is particularly relevant for the diversification of agricultural and forest ecosystems, demonstrating the added value of artificially selecting plants for the communities they are familiar with.

Grain yield and interspecific competition in an oat-common vetch intercropping system at varying sowing density

Introduction

Oat (Avena nuda L.) and common vetch (Vicia sativa L.) intercropping in the northern regions of China has resulted in substantial production capabilities. However, there is currently a dearth of comprehensive research on whether this intercropping system can enhance productivity through increased sowing densities and underlying interspecies interaction mechanisms.

Methods

A two-year field experiment was conducted in 2022 and 2023 to investigate the yield, biological efficiency, economic efficiency, and competition indicators of oats and common vetch in a high-density intercropping system. Two cropping patterns (monocropping and intercropping) and five sowing densities (D1: 4.5×106 plants ha-1; D2:5.4×106 plants ha-1; D3:6.3×106 plants ha-1; D4: 7.2×106 plants ha-1; and D5: 8.1×106 plants ha-1) were arranged in a randomized block design.

Results

At the same sowing density, the intercropped oats exhibited greater grain yield than the monocultures. Increasing the oat sowing density significantly enhanced oat yield, with the D3 level in intercropping showing the highest yield increase, ranging from 30.98% to 31.85%, compared with the monoculture. The common vetch intercropping grain yield was maximized in the D2 treatment. The land equivalent ratio was maximized at the D2 level in both years and was significantly higher than D1, with the land equivalent coefficient, system productivity index, and percentage yield difference suggesting that increasing oat sowing densities improved the productivity of the intercropping system, with the best performance observed at the D2 level. For both years, the proportionate actual yield loss of oat was the highest at the D3 level; significantly surpassing D1, proportionate actual yield loss of common vetch and actual yield loss were the highest at level D2, both significantly surpassing D1. These indicates that appropriate densification contributes to the realization of the advantages of intercropping. With an increased oat sowing density, the economic benefits of the intercropping system were maximized at the D2 and D3 levels. Regarding intercropping competition, oat was the dominant crop under different sowing densities (Aggressivity for oat (AO)>0, relative crowding coefficient for oat (KO)>1, competition ratio for oat (CRO)>1), whereas common vetch was the inferior crop. Compared with the D1 level, the D2 level harmonized the aggressivity, competitive ratio, and relative crowding coefficients of oat and common vetch, significantly increasing crowding coefficient for common vetch (KV) and competition ratio for common vetch by 19.76% to 21.94% and 4.80% to 7.51%, respectively, while reducing KO and CRO.

Discussion

This result suggests that in the intercropping of common vetch and oat in alpine regions, rational densification can harmonize interspecific competition and thus improve the biological efficiency and economic benefits of intercropping systems.

Upland rice varietal mixtures in Madagascar: evaluating the effects of varietal interaction on crop performance

Introduction

Rice plays a critical role in human livelihoods and food security. However, its cultivation requires inputs that are not accessible to all farming communities and can have negative effects on ecosystems. simultaneously, ecological research demonstrates that biodiversity management within fields contributes to ecosystem functioning.

Methods

This study aims to evaluate the mixture effect of four functionally distinct rice varieties in terms of characteristics and agronomic performance and their spatial arrangement on the upland rice performance in the highlands of Madagascar. The study was conducted during the 2021-2022 rainfall season at two close sites in Madagascar. Both site differ from each other's in soil properties and soil fertility management. The experimental design at each site included three modalities: i) plot composition, i.e., pure stand or binary mixture; ii) the balance between the varieties within a mixture; iii) and for the balanced mixture (50% of each variety), the spatial arrangement, i.e., row or checkerboard patterns. Data were collected on yields (grain and biomass), and resistance to Striga asiatica infestation, Pyricularia oryzea and bacterial leaf blight (BLB) caused by Xanthomonas oryzae-pv from each plot.

Results and discussion

Varietal mixtures produced significantly higher grain and biomass yields, and significantly lower incidence of Pyricularia oryzea compared to pure stands. No significant differences were observed for BLB and striga infestation. These effects were influenced by site fertility, the less fertilized site showed stronger mixture effects with greater gains in grain yield (60%) and biomass yield (42%). The most unbalanced repartition (75% and 25% of each variety) showed the greatest mixture effect for grain yield at both sites, with a strong impact of the varietal identity within the plot. The mixture was most effective when EARLY_MUTANT_IAC_165 constituted 75% of the density associated with other varieties at 25% density. The assessment of the net effect ratio of disease, an index evaluating the mixture effect in disease reduction, indicated improved disease resistance in mixtures, regardless of site conditions. Our study in limited environments suggests that varietal mixtures can enhance rice productivity, especially in low-input situations. Further research is needed to understand the ecological mechanisms behind the positive mixture effect.

Diverse cropping systems lead to higher larval mortality of the cabbage root fly (Delia radicum)

Root herbivores pose a major threat to agricultural crops. They are difficult to control and their damage often goes unnoticed until the larvae reach their most devastating late instar stages. Crop diversification can reduce pest pressure, generally without compromising yield. We studied how different diversified cropping systems affected the oviposition and abundance of the specialist cabbage root fly Delia radicum, the most important root herbivore in Brassica crops. The cropping systems included a monoculture, pixel cropping, and four variations of strip cropping with varying intra- and interspecific crop diversity, fertilization and spatial configuration. Furthermore, we assessed whether there was a link between D. radicum and other macroinvertebrates associated with the same plants. Cabbage root fly oviposition was higher in strip cropping designs compared to the monoculture and was highest in the most diversified strip cropping design. Despite the large number of eggs, there were no consistent differences in the number of larvae and pupae between the cropping systems, indicative of high mortality of D. radicum eggs and early instars especially in the strip cropping designs. D. radicum larval and pupal abundance positively correlated with soil-dwelling predators and detritivores and negatively correlated with other belowground herbivores. We found no correlations between the presence of aboveground insect herbivores and the number of D. radicum on the roots. Our findings indicate that root herbivore presence is determined by a complex interplay of many factors, spatial configuration of host plants, and other organisms residing near the roots.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10340-023-01629-1.

The productive performance of intercropping

Crop diversification has been put forward as a way to reduce the environmental impact of agriculture without penalizing its productivity. In this context, intercropping, the planned combination of two or more crop species in one field, is a promising practice. On an average, intercropping saves land compared with the component sole crops, but it remains unclear whether intercropping produces a higher yield than the most productive single crop per unit area, i.e., whether intercropping achieves transgressive overyielding. Here, we quantified the performance of intercropping for the production of grain, calories, and protein in a global meta-analysis of several production indices. The results show that intercrops outperform sole crops when the objective is to achieve a diversity of crop products on a given land area. However, when intercropping is evaluated for its ability to produce raw products without concern for diversity, intercrops on average generate a small loss in grain or calorie yield compared with the most productive sole crop (-4%) but achieve similar or higher protein yield, especially with maize/legume combinations grown at moderate N supply. Overall, although intercropping does not achieve transgressive overyielding on average, our results show that intercropping performs well in producing a diverse set of crop products and performs almost similar to the most productive component sole crop to produce raw products, while improving crop resilience, enhancing ecosystem services, and improving nutrient use efficiency. Our study, therefore, confirms the great interest of intercropping for the development of a more sustainable agricultural production, supporting diversified diets.