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Background and aims: Overyielding in intercropping compared to monoculture has been widely reported. One of the mechanisms may be the alteration of the microbial community in intercropping and especially the amelioration of the negative effects of pathogens that can accumulate in monocultures. Here we test whether inoculation with arbuscular mycorrhizal fungi (AMF) and wheat take-all disease influences overyielding and whether changes in the microbial communities generate feedbacks on plant growth. Methods: In Experiment 1, wheat and faba bean were grown in monoculture or intercropping to form three planting patterns. Plants were inoculated with or without wheat take-all disease ( Gaeumannomyces graminis), and one, six, or no AM fungi, to create 6 soil conditioned treatments. Soils from Experiment 1 were used as inocula in Experiment 2 to test the feedback on plant growth from monocultures and the legacy benefits of intercropping. Results: No significant influence of AMF on plant growth was observed in either experiment. In Experiment 1, AMF had no significant effect in suppressing take-all but take-all tended to decrease AMF colonization. Shoot biomass and competitive ability of wheat was suppressed by take-all in both experiments. Wheat and faba bean showed overyielding in both the take-all and non-take-all treatment in Experiment 1 but only overyielding in the take-all treatment in Experiment 2. Growth of wheat and faba bean were suppressed in conspecific soil, and this negative feedback was observed across all take-all and AMF treatments, and regardless of competition. Biomass of wheat and faba bean was higher in soil from intercropping than in monoculture soil, and this positive legacy benefit of intercropping did not depend on take-all, AMF or plant competition. Conclusions: We find support for alterations of the soil community causing negative plant soil feedback and positive legacy benefits of intercropping. Our results are consistent with microbial dynamics generating overyielding in intercropping by reducing the negative influence of soil pathogen build-up on conspecific host plants and simultaneously compensatively improving growth of neighbor plants. [ABSTRACT FROM AUTHOR]

Background Phosphorus (P), iron (Fe) and zinc (Zn) are essential elements for plant growth and development, but their availability in soil is often limited. Intercropping contributes to increased P, Fe and Zn uptake and thereby increases yield and improves grain nutritional quality and ultimately human health. A better understanding of how intercropping leads to increased plant P, Fe and Zn availability will help to improve P-fertilizer-use efficiency and agronomic Fe and Zn biofortification. Scope This review synthesizes the literature on how intercropping of legumes with cereals increases acquisition of P, Fe and Zn from soil and recapitulates what is known about root-to-shoot nutrient translocation, plant-internal nutrient remobilization and allocation to grains. Conclusions Direct interspecific facilitation in intercropping involves below-ground processes in which cereals increase Fe and Zn bioavailability while companion legumes benefit. This has been demonstrated and verified using isotopic nutrient tracing and molecular analysis. The same methodological approaches and field studies should be used to explore direct interspecific P facilitation. Both niche complementarity and interspecific facilitation contribute to increased P acquisition in intercropping. Niche complementarity may also contribute to increased Fe and Zn acquisition, an aspect poorly understood. Interspecific mobilization and uptake facilitation of sparingly soluble P, Fe and Zn from soil, however, are not the only determinants of the concentrations of P, Fe and Zn in grains. Grain yield and nutrient translocation from roots to shoots further influence the concentrations of these nutrients in grains. [ABSTRACT FROM AUTHOR]

Abstract: Phytoremediation of phthalic esters (PAE) polluted agricultural soils near electrical-waste dismantling areas in east China is a topic of much public concern. In this study, monocropping and intercropping of alfalfa (Medicago sativa L.), Elsholtzia splendens and Sedum plumbizincicola were compared for their potential in phytoremediation of contaminated soil. Regardless of whether alfalfa was cultivated in monoculture (A) or in combination with E. splendens (AE) or with S. plumbizincicola (AS), and also with all three (AES) in intercropping, concentrations of six PAEs in soil were significantly reduced (p < 0.01) by 87.2, 91.2, 87.2 and 89.4% compared to the control. Intercropping enhanced the decline in soil PAEs and increased soil microbial biomass and microbial functional diversity, and alfalfa shoots and roots took up more of the target pollutants than the other two plant species. DEHP was the most abundant of the target PAEs in soil, roots and shoots. The biological concentration factors (BCFs) of alfalfa in monoculture were relatively high, but the transfer factor (TF) and phytoextraction efficiency, which ranged from 1.16 to 1.69 %, were higher in intercropping systems. Thus, rhizospheric remediation by intercropping of the three-species contributed to PAE removal from the soil and may represent a promising in situ bioremediation strategy for PAE contaminated soils. [Copyright &y& Elsevier]

Nutrient and water management is crucially important in shallow-rooted vegetable production systems characterized by high input and high environmental risk. A 2-year field experiment on greenhouse cucumber double-cropping systems examined the effects of root zone nitrogen management and planting of sweet corn as a catch crop in the summer fallow period on cucumber yield and soil Nmin dynamics compared to conventional practices. Cucumber fruit yields were not significantly affected by root zone N management and catch crop planting despite a decrease in N fertilizer application of 53% compared to conventional N management. Soil Nmin content to a depth of 0.9 m decreased markedly and root zone (0–0.3 m) soil Nmin content was maintained at about 200 kg N ha−1. Root zone N management efficiently and directly reduced apparent N losses by 44% and 45% in 2005 and 2006, respectively. Sweet corn, the summer catch crop, depleted Nmin residue in the soil profile of 1.8 m at harvest of winter–spring season cucumber by 304–333 kg N ha−1, which contributed 19–22% reduction in N loss. Compared to conventional N management, N loss was reduced by 56% under root zone N management and catch crop planting. [ABSTRACT FROM AUTHOR]

Background and Aims: Studies verify that intercropping increases soil macro-aggregates but the mechanism underlying the increase is poorly understood.Methods: Three long-term field experiments were conducted starting in 2009 at three sites in an oasis in northwest China. The first was a split-plot design: Rhizobium (with or without inoculation) and three cropping systems (faba bean/maize intercropping and corresponding monocultures). The second and third experiments were both single-factorial randomized block designs with nine cropping systems (maize intercropped with faba bean, chickpea, soybean, or oilseed rape, and the corresponding monocultures). Soil aggregates were determined by the wet sieving method. Microbial biomass and community composition in 2015 and 2016 were determined by phospholipid fatty acid (PLFA) and high throughput sequencing analysis of 16S rRNA.Results: Soil macro-aggregates (> 2 mm) in intercropping systems increased by 15.5-58.6% across three sites and two years, an effect derived partly from increased relative abundance of soil Sordariales, from enhanced arbuscular mycorrhizal fungi biomass, or from reduced relative abundance of Nitrospirae, depending on soil type.Conclusions: Intercropping alters soil microbial community composition and further facilitates soil aggregation. These findings provide insights into the mechanisms underlying the maintenance of biodiversity in ecosystem functioning. [ABSTRACT FROM AUTHOR]

Background and aims: Intercropping often produces more biomass than the average of the corresponding monocultures, particularly in sustainable, low-input agriculture. Characterizing plant-plant interactions is fundamental for a better understanding of the ecological functioning of intercropping. However, there is little information on whether mycorrhizal networks exhibit different effects upon intra- and interspecific plant interactions in intercropping systems. Methods: Microcosms with one inner and three outer compartments were used. The inner compartment was separated from the outer compartments by a 30-μm nylon mesh or a solid barrier or remained open to allow full interactions between plants grown in the different compartments, creating three treatments, namely −Roots−CMNs (solid barrier), −Roots+CMNs (mesh), and +Roots+CMNs (no barrier). Either faba bean ( Vicia faba) or maize ( Zea mays) was grown as the donor plant in the inner compartment. Maize was combined with maize, wheat ( Triticum aestivum) or the weed species foxtail ( Setaria viridis) as the neighboring plant species. Faba bean was combined with faba bean, maize, or foxtail. The low-P soil was inoculated with the arbuscular mycorrhizal fungus (AMF) Funneliformis mosseae or remained uninoculated. Results: In the absence of AMF, plant growth was restricted by P deficiency and root interactions did not significantly affect plant-plant interactions. The presence of AMF enhanced plant biomass (maize by 104.5 %, faba bean by 61.6 %) and nutrient (N and P) uptake. Significant overyielding occurred in treatments where roots and hyphal networks of all plant species intermingled. The weed (foxtail) was suppressed by interspecific interactions while maize and faba bean benefitted from a mycorrhizal network and the presence of intermingling roots. Conclusions: In low-P soils, mycorrhizal networks contribute to overyielding in intercropping by enhancing the biomass and nutrient uptake of the mycorrhiza-dependent plant species. The biomass depression of weed species by AMF and/or root interactions may have ecological implications in weed control in intercropping systems. [ABSTRACT FROM AUTHOR]

In two long-term field experiments the zinc (Zn)/cadmium (Cd) hyperaccumulatorSedum plumbizincicola (S. plumbizincicola)was examined to optimize the phytoextraction of metal contaminated soil by two agronomic strategies of intercropping with maize (Zea mays) and plant densities. Soil total Zn and Cd concentrations decreased markedly after long-term phytoextraction. But shoot biomass and Cd and Zn concentrations showed no significant difference with increasing remediation time. In the intercropping experiment the phytoremediation efficiency in the treatment “S. plumbizincicolaintercropped with maize” was higher than inS. plumbizincicolamonocropping, and Cd concentrations of corn were below the maximum national limit. In the plant density experiment the phytoremediation efficiency increased with increasing plant density and 440,000 plants ha−1gave the maximum rate. These results indicated thatS. plumbizincicolaat an appropriate planting density and intercropped with maize can achieve high remediation efficiency to contaminated soil without affecting the cereal crop productivity. This cropping system combines adequate agricultural production with soil heavy metal phytoextraction. [ABSTRACT FROM AUTHOR]

Background and aims: Few studies have addressed the effects of root physiological plasticity on interspecific interactions. The present study aimed to investigate the plasticity of wheat and maize roots and their responses to nitrogen (N) application rates and neighboring species in wheat/maize intercropping. Methods: The roots of wheat and maize were sampled three times by auger after about 90 days of co-growth in the intercropping treatment with five levels of N application and sole crops at one N application rate. Results: Intercropped wheat altered its root length density (RLD) and lateral root distribution with different N application regimes, while lateral root distribution of intercropped maize was less sensitive to N application regimes. In addition, wheat had a 54.5 % (38-69 days) −375 % (0-37 days) higher N uptake rate per unit root length (NURl) when intercropped with maize compared with sole cropping but intercropped maize had either 58.3 % lower (0-37 days) or similar NURl than did sole cropped maize at the same N application rate. Conclusions: Our findings suggest that the competitive ability of the plant species for underground resources is conducive to plasticities in RLD, lateral root distribution in response to soil N, and N uptake efficiency to neighboring species. [ABSTRACT FROM AUTHOR]

Long-term application of sewage sludge resulted in soil cadmium (Cd) and zinc (Zn) contamination in a pot experiment conducted to phytoextract Cd/Zn repeatedly usingSedum plumbizincicolaandApium graceolensin monoculture or intercropping mode eight times. Shoot yields and soil physicochemical properties changed markedly with increasing number of remediation crops when the two plant species were intercropped compared with the unplanted control soil and the two monoculture treatments. Changes in soil microbial indices such as average well colour development, soil enzyme activity and soil microbial counts were also significantly affected by the growth of the remediation plants, especially intercropping withS. plumbizincicolaandA. graveolens. The higher yields and amounts of Cd taken up indicated that intercropping of the hyperaccumulator and the vegetable species may be suitable for simultaneous agricultural production and soil remediation, with larger crop yields and higher phytoremediation efficiencies than under monoculture conditions. [ABSTRACT FROM PUBLISHER]

Background: Overyielding (i.e., mixtures of crops yielding higher than expected when compared with monocultures) and increased nutrient acquisition have been found in many intercropping systems. However, there are very few published studies on long-term changes in soil chemical and biological properties in intercropping systems compared to sole cropping. Methods: A field experiment was established in 2003 in Gansu province, northwest China. The treatments comprised three intercropping systems (either continuous or rotational wheat/maize, wheat/faba bean, maize/faba bean intercropping), rotational cropping (wheat-maize, wheat-faba bean, faba bean-maize, and wheat-maize-faba bean rotations), and monocropping (sole wheat, faba bean and maize) systems. In 2011 (ninth year of the experiment) and 2012 (tenth year) the yields and some soil chemical and biological properties were examined after all crop species were harvested. Results: There was overyielding by 6.6 % and 32.4 % in wheat/maize intercropping in 2011 and 2012, respectively. Faba bean/maize intercropping was enhanced by 34.7 % and 28.6 %, respectively but not wheat/faba bean intercropping. Soil organic matter, total nitrogen, Olsen P, exchangeable K and cation exchange capacity in all intercropping systems did not differ from the monocultures except for soil pH in wheat/maize and faba bean/maize intercropping in 2011 and soil exchangeable K and cation exchange capacity (CEC) in 2012. Soil pH in wheat/maize and faba bean/maize intercropping was significantly reduced by 3.2 % and 1.9 %, respectively. Soil exchangeable K in wheat/maize, faba bean/maize and wheat/faba bean intercropping declined markedly by 15 %, 21.7 % and 12.1 %, respectively. Soil cation exchange capacity in wheat/maize, faba bean/maize and wheat/faba bean intercropping was notably lower than the corresponding monocultures by 17.5 %, 23.3 % and 18.3 %, respectively. Soil enzyme activities after 9 and 10 years of intercropping differed little from monocultures or rotations. Conclusions: The results indicate that intercropping overyielded compared with monocropping or rotational cropping and also maintained the stability of most of the soil chemical and enzyme activities relative to rotations and monocropping in the relatively fertile soil studied. [ABSTRACT FROM AUTHOR]

Yield and nutrient acquisition advantages are frequently found in intercropping systems. However, there are few published reports on soil fertility in intercropping relative to monocultures. A field experiment was therefore established in 2009 in Gansu province, northwest China. The treatments comprised maize/faba bean, maize/soybean, maize/chickpea and maize/turnip intercropping, and their correspoding monocropping. In 2011 (the 3rd year) and 2012 (the 4th year) the yields and some soil chemical properties and enzyme activities were examined after all crop species were harvested or at later growth stages. Both grain yields and nutrient acquisition were significantly greater in all four intercropping systems than corresponding monocropping over two years. Generally, soil organic matter (OM) did not differ significantly from monocropping but did increase in maize/chickpea in 2012 and maize/turnip in both years. Soil total N (TN) did not differ between intercropping and monocropping in either year with the sole exception of maize/faba bean intercropping receiving 80 kg P ha−1 in 2011. Intercropping significantly reduced soil Olsen-P only in 2012, soil exchangeable K in both years, soil cation exchangeable capacity (CEC) in 2012, and soil pH in 2012. In the majority of cases soil enzyme activities did not differ across all the cropping systems at different P application rates compared to monocrops, with the exception of soil acid phosphatase activity which was higher in maize/legume intercropping than in the corresponding monocrops at 40 kg ha−1 P in 2011. P fertilization can alleviate the decline in soil Olsen-P and in soil CEC to some extent. In summary, intercropping enhanced productivity and maintained the majority of soil fertility properties for at least three to four years, especially at suitable P application rates. The results indicate that maize-based intercropping may be an efficient cropping system for sustainable agriculture with carefully managed fertilizer inputs. [ABSTRACT FROM AUTHOR]

Abstract: Rational soil/rhizosphere-plant phosphorus (P) management strategies in intercropping systems are poorly understood. Three years of field experiments with different rates of P fertilizer (0, 40 and 80kgha−1) as main effects and maize (Zea mays L.) intercropping with oilseed rape (Brassica napus L.), turnip (Brassica campestris L.), faba bean (Vicia faba L.), chickpea (Cicer arietinum L.) and soybean (Glycine max L.) with the respective monocultures as subplot effects were carried out to study the influence of fertilizer P application on productivity, shoot P content, apparent recovery of fertilizer P and soil Olsen-P in intercrops and monocultures. Average total grain yields and shoot P contents of maize/turnip, maize/faba bean, maize/chickpea and maize/soybean intercropping increased by 30.7%, 24.8%, 24.4%, and 25.3% and by 44.6%, 30.7%, 39.1%, and 28.6%, respectively, compared with the weighted means of the corresponding monocultures, and were highest at 40kgPha−1. Moreover, the average apparent recovery of fertilizer P of the intercropping systems increased from 6.1% to 30.6% at 40kgPha−1 and from 4.8% to 14.5% at 80kgPha−1 compared with overall monoculture systems on average over three years. The results indicate that intercropping and a rational P application rate (e.g. 40kgPha−1) maintained maximum total grain production and shoot P content, P balance of inputs/outputs and soil Olsen-P at an appropriate level (21.3mgkg−1), and maximum apparent recovery of fertilizer P (30.6%) through exploitation of the biological potential for efficient acquisition of P and other resources by interspecific interactions toward a sustainable and productive agricultural system. [Copyright &y& Elsevier]

Highlights: [•] A ‘competition–recovery–overyielding’ process was found in dynamics of root length growth and distribution of intercropped maize. [•] The stronger the associated crop roots, the more depressed the intercropped maize root development and shoot biomass. [•] Root lengths in 0–1.0m at jointing and in 0–0.3m of soil profiles at grain-filling were response to P fertilization. [•] Dynamics of root length growth and distribution correlated well with corresponding shoot biomass accumulation of maize. [ABSTRACT FROM AUTHOR]

A field experiment was conducted to study the phytoremediation of phthalic acid esters (PAEs) by legume (alfalfa, Medicago sativa L.)-grass (perennial ryegrass, Lolium perenne L. and tall fescue, Festuca arundinacea) intercropping in contaminated agricultural soil at one of the largest e-waste recycling sites in China. Two compounds, DEHP and DnBP, were present in the soil and in the shoots of the test plants at much higher concentrations than the other target PAEs studied. Over 80% of ‘total’ (i.e., all six) PAEs were removed from the soil across all treatments by the end of the experiment. Alfalfa in monoculture removed over 90% of PAEs and alfalfa in the intercrop of the three plant species contained the highest shoot concentration of total PAEs of about 4.7 mg kg−1 DW (dry weight). Calculation of phytoextraction efficiency indicated that the most effective plant combinations in eliminating soil PAEs were the three-species intercrop (1.78%) and the alfalfa monocrop (1.41%). Phytoremediation with alfalfa was effective in both monoculture and intercropping. High bioconcentration factors (BCFs) indicated the occurrence of significant extraction of PAEs by plants from soil, suggesting that phytoremediation may have potential for the removal of PAEs from contaminated soils. [ABSTRACT FROM PUBLISHER]

Increasing crop nitrogen use efficiency while also simultaneously decreasing nitrogen accumulation in the soil would be key steps in controlling nitrogen pollution from agricultural systems. Long-term field experiments were started in 2003 to study the effects of intercropping on crop N use and soil mineral N accumulation in wheat ( Triticum aestivum L. cv 2014)/maize ( Zea mays L. cv Shendan16), wheat/faba bean ( Vicia faba L. cv Lincan No. 5) and maize/faba bean intercropping and monocropping systems. Monocropping was compared with two types of strip intercropping: continuous intercropping (two crops intercropped continuously on the same strips of land every year) and rotational intercropping (two crops grown adjacently and rotated to the other crop's strip every year). Maize/faba bean intercropping had greater crop N uptake than did wheat/faba bean or wheat/maize. Wheat/maize accumulated more mineral N in the top 140 cm of the soil profile during the co-growth stage from maize emergence to maturity of wheat or faba bean. Continuously intercropped maize substantially decreased soil mineral N accumulation under wheat and faba bean rows (60-100 cm soil depth) at maize harvest. Soil mineral N accumulation under wheat rows increased with rotational intercropping with faba bean. Rotational intercropping may potentially alleviate the adverse effects of wheat on N use by other crops and increase the nitrogen harvest index of wheat, maize and faba bean. Intercropping using species with different maturity dates may be more effective in increasing crop N use efficiency and decreasing soil mineral N accumulation. [ABSTRACT FROM AUTHOR]

Interspecific interactions and soil nitrogen supply levels affect intercropping productivity. We hypothesized that interspecific competition can be alleviated by increasing N application rate and yield advantage can be obtained in competitive systems. A field experiment was conducted in Wuwei, Gansu province in 2007 and 2008 to study intercropping of faba bean/maize, wheat/maize, barley/maize and the corresponding monocultures of faba bean ( Vicia faba L.), wheat ( Triticum aestivum L.), barley ( Hordeum vulgare L.) and maize ( Zea mays L.) with N application rates of 0, 75, 150, 225 and 300 kg N ha. Total land equivalent ratios (TLER) were 1.22 for faba bean/maize, 1.16 for wheat/maize, and 1.13 for barley/maize intercropping over the 2-year study period. Maize was overyielding when intercropped with faba bean, but underyielding when intercropped with wheat or barley according to partial land equivalent ratios (PLER) based on grain yields of individual crops in intercropping and sole cropping. There was an interspecific facilitation between intercropped faba bean and maize, and interspecific competition between maize and either wheat or barley. The underyielding of maize was higher when intercropped with barley than with wheat. Fertilizer N alleviated competitive interactions in intercrops with adequate fertilizer N at 225 kg ha. Yield advantage of intercropping can be acquired with adequate nitrogen supply, even in an intensive competitive system such as barley/maize intercropping. This is important when using intercropping to develop intensive farming systems with high inputs and high outputs. [ABSTRACT FROM AUTHOR]

Interspecific facilitation on N2 fixation and complementarity use of soil mineral N in cereals and legumes intercropping. [Display omitted] • Rhizobium-inoculated faba bean/maize intercropping had advantages. • The recovery of fertilizer N was increased by intercropping and rhizobium inoculation. • Intercropping lowered accumulation of N min in the soil profile at maize harvest. • Intercropping with rhizobium inoculation enhances productivity and reduces the risk of environment. Although intensive modern agriculture, featured with high inputs of chemicals, contributed to global food production, simultaneously caused a series of serious issues, such as loss of biodiversity, soil degradation, and environment risk. The objective of our study is to integrate various inherit biological potentials of cropping system to gain higher productivity with lower external inputs. Field experiments were conducted over a two-year period (2008-2009) with five fertilizer-N application rates (0, 75, 150, 225 and 300 kg N ha−1) to study the influence of fertilizer N application on the productivity and N utilization of a Rhizobium -inoculated maize (Zea mays L.)/faba bean (Vicia faba L.) intercropping system on a reclaimed desert soil (Sierozems). Average grain yields of faba bean and maize with inoculation increased by 50.0 and 19.6 %, respectively, and reached a maximum land equivalent ratio of 1.78 with zero fertilizer N application in 2009 compared with sole crops. The nodulation of intercropped faba bean was significantly higher with Rhizobium inoculation, especially with an optimum N application rate of < 150 kg N ha−1. Average %Ndfa and Ndfa increased by 42.5 and 86.6 %, respectively, based on interspecific interaction and inoculation. The average apparent N recovery of the intercropping system with inoculation increased by 146.5 % at 75 kg N ha−1 relative to the weighted mean values of sole crops. Intercropping saved fertilizer N compared to sole crops suggested by a fertilizer N equivalent ratio (NFER) > 1. Furthermore, intercropping with rhizobium inoculation saved more fertilizer N than that without rhizobium inoculation. After the faba bean harvest, intercropped maize made better use of the nitrogen taken up to grow faster than sole maize. At the maize harvest the intercropping system showed higher grain yield and N acquisition in the aboveground parts and lower Nmin accumulation in the soil profile, an effect that declined with fertilizer N application. The results therefore indicate that Rhizobium -inoculated maize/faba bean intercropping on the reclaimed desert soil with a moderate fertilizer N application rate enhancede productivity, biological N 2 fixation and apparent N recovery with lower environmental risk. [ABSTRACT FROM AUTHOR]

One-third of all the cultivated land area is used for multiple cropping and half of the total grain yield is produced with multiple cropping in China. There have been numerous studies on nutrient acquisition by crops in legume/non-legume intercropping systems, but few on nutrient uptake in cereal/cereal intercropping. This paper describes a field experiment in which integrated wheat/maize and maize/faba bean systems were compared with sole wheat and sole faba bean cropping to assess the effects of intercropping on nutrient uptake by wheat, maize, and faba bean under various application rates of nitrogen (N) and phosphorous (P) fertilizers. Results show that both N and P fertilizers and intercropping enhanced N uptake by wheat, while only P fertilizer and intercropping increased P acquisition by wheat. The advantage of N uptake by border rows of wheat intercropped with maize declined with increasing N fertilizer application rate, but that of P acquisition was not affected by P fertilizer. The amounts of both N and P taken up by maize intercropped with faba bean were much higher than those by maize intercropped with wheat throughout the period of intercropping. Both fertilization and intercropping did not influence the N and P uptake by faba bean. [ABSTRACT FROM AUTHOR]