The incorporation of chicory (Cichorium intybus) into phased crop-pasture farming systems requires an understanding of the dynamics of nitrogen (N) mineralisation of residues and the potential supply ...of N to subsequent crops. A 3-year field experiment was conducted to compare relative N mineralisation rates from the pure chicory pasture, compared to the chicory-subterranean clover (Trifolium subterraneum) or lucerne (Medicago sativa)-subterranean clover pastures. Existing pastures were chemically fallowed in either spring or the following autumn. Soil mineral N and soil gravimetric water content were measured at 0, 6 and 12 months after pasture removal. Six months after pasture removal, chicory-subterranean clover pasture exhibited the highest N mineralisation rate for the spring and autumn removals (0.36 and 0.37 kg mineral N ha−1 day−1, respectively), whereas lucerne-subterranean clover pasture had the lowest for the spring and autumn removals (0.04 and 0.05 kg mineral N ha−1 day−1, respectively). However, the daily N mineralisation rate for the lucerne-subterranean clover pasture increased dramatically to 0.51 and 0.98 kg mineral N ha−1 day−1 12 months after pastures were removed in spring and autumn, respectively. In contrast, the chicory pasture produced 0.15 vs 0.63 kg mineral N ha−1 day−1 for the spring and autumn removals, respectively. Including subterranean clover in mixtures with chicory significantly increased the availability of mineral N by 28% with the spring removal and 45% with the autumn removal compared to the pure chicory pasture. Due to the quicker rate of N mineralisation with chicory-based pastures, an opportunity exists to remove chicory-based pastures later than lucerne-based pastures without having a detrimental effect on N supply to the following crop while still providing additional feed for livestock.
•Nitrogen mineralisation of chicory residues occurs more rapidly than lucerne residues.•Including subterranean clover in a mixture with chicory significantly increases soil mineral nitrogen.•Chicory-based pastures can be removed later than lucerne-based pastures prior to cropping phase in a semi-arid environment.
Abstract
Purpose
Chicory (
Cichorium intybus
) scavenges more soil mineral nitrogen (N) than perennial ryegrass (
Lolium perenne
). A glasshouse study was conducted to test whether (a) the percentage ...of N derived from the atmosphere (%Ndfa) by a companion legume differs when grown with chicory or perennial ryegrass, and (b) there is an optimal ratio of non-legume:legume in a pasture mix that maximises biological N
2
fixation.
Methods
Chicory or perennial ryegrass was grown as a monoculture, or in a mixture with either lucerne (alfalfa,
Medicago sativa
) or subterranean clover (
Trifolium subterraneum
) at 25:75, 50:50 or 75:25 ratio (non-legume:legume based on plant numbers). Monocultures of lucerne and subterranean clover were included as controls.
Results
All treatments containing chicory extracted more mineral N from the soil than corresponding treatments containing perennial ryegrass. Subterranean clover %Ndfa was greater than lucerne. Combining lucerne with chicory in a 50:50 or 75:25 mixture increased the efficiency of N
2
fixation by > 20%. Growing chicory with subterranean clover in mixtures of 50:50 or 75:25 resulted in the highest %Ndfa for growth among all treatments (
P
< 0.05). However, the amounts of N
2
fixed by subterranean clover in the perennial ryegrass-subterranean clover mixture were similar to those in the chicory-subterranean clover mixture since dry matter accumulation from subterranean clover was higher when grown with perennial ryegrass.
Conclusion
The %Ndfa of legumes was greater when grown with chicory than perennial ryegrass. Chicory mixed with subterranean clover or lucerne in 50:50 ratios provided the optimum balance between legume dry matter yield and N
2
fixation.
As functional diversity influences the benefits conferred on host plants by arbuscular mycorrhizal fungi (AMF) and large scale commercial inoculation is currently impracticable, strategies are ...required to manage communities of indigenous AMF associated with different hosts within agricultural cropping systems. In a non-sterilized soil, using 454 pyrosequencing of the LSU-D2 rDNA gene, host plant AMF diversity was assessed following successions of different plant species, grown with or without prior soil disturbance. Diversity present in the roots of two species of the Fabaceae (Ornithopus compressus and Trifolium subterraneum) was compared with those of two species of Poaceae (Lolium rigidum and Triticum aestivum). When spores and colonised root fragments formed were the main propagules source (disturbed soil), the communities of AMF present in the two legumes were clearly different from those of the two members of the Poaceae but were similar for plants within each family, consistent with there being preferential symbioses existing within an AMF population for host classes. Significantly, wheat grown in undisturbed soil immediately after the legume O. compressus acquired a mycorrhizal fungal community closely related to that of the previous host plant, and different to that found when the soil was disturbed or not cropped prior to the growth of the wheat. Parallel effects were seen in the succession from L. rigidum to T. subterraneum, indicating that these effects are not unique to the legume-wheat sequence. These results also suggest that, under no-till cropping, selected cover crops or crops in rotation could help build mycorrhizal communities that function throughout a sequence of several main crops.
•Plants from Fabaceae and Poaceae differentially select AMF from a diverse population.•The dominant propagule determines the AMF present in the host plant.•In a plant succession, ERM from the first controls the AMF community in the second.•Intact ERM provides a tool for managing AMF biodiversity within cropping systems.
Annual forage legumes across southern Australia continue to be devastated by soilborne diseases. Nine fungicide seed treatments (thiram, metalaxyl, iprodione, phosphonic acid, propamocarb, ...fluquinconazole, difenoconazole + metalaxyl, ipconazole + metalaxyl, sedaxane + difenoconazole + metalaxyl) and four foliar fungicide treatments (phosphonic acid, metalaxyl, propamocarb, iprodione) were tested on four subterranean clover cultivars against individual oomycete soilborne pathogens
,
, and
and the fungal pathogen
. Best treatments were then further tested across southern Australia in 2 years of field experiments. Under controlled conditions, seed treatment with thiram was best against damping-off caused by
across the four cultivars (Woogenellup, Riverina, Seaton Park, Meteora), while metalaxyl was the most effective for maximizing root and shoot weights. Against
, metalaxyl, iprodione, difenoconazole + metalaxyl, ipconazole + metalaxyl, and sedaxane + difenoconazole + metalaxyl, all reduced damping-off; sedaxane + difenoconazole + metalaxyl, fluquinconazole, and ipconazole + metalaxyl all reduced lateral root disease across two or more cultivars; while iprodione, thiram, and sedaxane + difenoconazole + metalaxyl increased shoot dry weight. Against
, metalaxyl was the most effective in reducing tap and lateral root rot followed by ipconazole + metalaxyl or phosphonic acid for tap and lateral rot, respectively. Against
, there were no effects of fungicides. For
and
, there were strong seed fungicide × cultivar interactions (
< 0.001). Under controlled conditions for foliar fungicide spray treatments, phosphonic acid was best at preventing productivity losses from
, but was ineffective against
,
, or
. Overall, controlled environment studies highlighted strong potential for utilizing seed treatments against individual pathogens to ensure seedling emergence and early survival, with seed and foliar sprays enhancing productivity by reducing seedling damping-off and root disease from individual pathogens. However, in field experiments over 2 years across southern Australia against naturally occurring soilborne pathogen complexes involving these same pathogens, only rarely did fungicide seed treatments or foliar sprays tested show any benefit. It is evident that currently available fungicide seed and/or foliar spray treatment options do not offer effective field mitigation of damping-off and root disease on annual forage legumes that underpin livestock production across southern Australia. The main reason for this failure relates to the unpredictable and ever-changing soilborne pathogen complexes involved, highlighting a need to now refocus away from fungicide options, particularly toward developing and deploying new host tolerances, but also in deploying appropriate cultural control options.
Subterranean clover (
L., Ts) is a geocarpic, self-fertile annual forage legume with a compact diploid genome (n = x = 8, 544 Mb/1C). Its resilience and climate adaptivity have made it an ...economically important species in Mediterranean and temperate zones. Using the cultivar Daliak, we generated higher resolution sequence data, created a new genome assembly TSUd_3.0, and conducted molecular diversity analysis for copy number variant (CNV) and single-nucleotide polymorphism (SNP) among 36 cultivars. TSUd_3.0 substantively improves prior genome assemblies with new Hi-C and long-read sequence data, covering 531 Mb, containing 41,979 annotated genes and generating a 94.4% BUSCO score. Comparative genomic analysis among select members of the tribe Trifolieae indicated TSUd 3.0 corrects six assembly-error inversion/duplications and confirmed phylogenetic relationships. Its synteny with
,
,
and
genomes were assessed, with the more distantly related
and
.
showing higher levels of co-linearity with Ts than between Ts and its close relative
. Resequencing of 36 cultivars discovered 7,789,537 SNPs subsequently used for genomic diversity assessment and sequence-based clustering. Heterozygosity estimates ranged from 1% to 21% within the 36 cultivars and may be influenced by admixture. Phylogenetic analysis supported subspecific genetic structure, although it indicates four or five groups, rather than the three recognized subspecies. Furthermore, there were incidences where cultivars characterized as belonging to a particular subspecies clustered with another subspecies when using genomic data. These outcomes suggest that further investigation of Ts sub-specific classification using molecular and morpho-physiological data is needed to clarify these relationships. This upgraded reference genome, complemented with comprehensive sequence diversity analysis of 36 cultivars, provides a platform for future gene functional analysis of key traits, and genome-based breeding strategies for climate adaptation and agronomic performance. Pangenome analysis, more in-depth intra-specific phylogenomic analysis using the Ts core collection, and functional genetic and genomic studies are needed to further augment knowledge of
genomes.
Background and aims Biochar can be produced from a wide range of organic sources with varying nutrient and metal concentrations. Before making irreversible applications of biochar to soil, a ...preliminary ecotoxicological assessment is desirable. Methods First, we determined the effect of biochar type and rate on early growth of wheat in a soil-less Petri dish bioassay. Second, we investigated the effect of the same biochars on seed germination and early growth of wheat in ten soils with varying texture using a glasshouse bioassay. Finally, we investigated whether these biochars had similar effects on three plant species when grown in one soil. Results Biochar type and application rate influenced wheat seed germination and seedling growth in a similar manner in both the soil-less Petri dish and soil-based bioassay. Germination and early root growth of mung bean and subterranean clover differed from that of wheat in response to the five biochars. Conclusions We recommend use of the soil-less Petri dish bioassay as a rapid and simple preliminary test to identify potential toxicity of biochars on seed germination and early plant growth prior to biochar application to soil.
PDF
