Abstract
A mildly acidic (pHCa 4.79, 0–10 cm depth) red-brown earth soil (Chromosol) at Condobolin in central-western New South Wales was cultivated and limed (once only) at six rates (range 0–4 t/ha) and sown with field peas (Pisum sativumL.) with and without inoculation (once only) with Rhizobium leguminosarum bv. viciae – the rhizobium for peas. The soil already contained a very small population of pea rhizobia (<4 per g soil). The experiment embraced two parallel rotations, each over 4 years: (1) year 1, inoculated peas; year 2, wheat; year 3, wheat; year 4, uninoculated peas; and (2) year 1, inoculated peas; year 2, wheat; year 3, inoculated chickpeas; year 4, uninoculated peas. The objectives of the work were to establish whether liming had any immediate and residual benefits for rhizobia and plants and, if so, to determine if the two events were linked. Liming had an immediate effect on soil pH (0–10 cm depth). Increases in pH were greater per unit of lime at lower rates of application than at higher rates. Although lime effects existed for the duration of the experiment (four seasons of cropping), there was a small decline in soil pH over time (mean decline in unlimed plots 0.16 pHCa units, mean decline in limed plots 0.47 pHCa units). In the first year (pea crop), there was a very large and highly significant response to inoculation on populations of rhizobia in soil and rhizosphere. The number of rhizobia that occurred naturally in uninoculated plots increased rapidly in high-lime plots until, by the third year, they were substantial and, by the fourth year, equal to those in the inoculated treatment. By the end of the experiment, the mean population of rhizobia in the 4 t/ha lime treatment was 7250 per g soil, compared with <4 rhizobia per g in the nil lime treatment. It was noteworthy that, in those years in the rotations when peas were not grown, populations of R. leguminosarum bv. viciae were sustained by their ability to colonise the rhizospheres of wheat and chickpea. In the first pea crop, eight parameters of plant production responded overwhelmingly to inoculation, while there was an underlying response to liming in two of those parameters. The positive effect of inoculation on peas in the first year carried over to the wheat crop of the second year, which was interpreted as a consequence of increased soil N in the inoculated plots. By the third and fourth years, soil populations of pea rhizobia in the plus inoculation and minus inoculation treatments were approximately equal, and inoculation was no longer a determinant of crop production. On the other hand, application of lime, which had only an underlying effect on pea production in the first year, significantly enhanced several parameters of the symbiosis and growth of the chickpea and pea crops, including legume nodulation and percentage nitrogen in the seed. R. leguminosarum bv. viciae, legumes and cereals each responded differently to increasing rates of lime application. Populations of rhizobia in soil and plant rhizospheres increased with each additional rate of liming. Legume productivity responded to additional lime up to 2 t/ha. There was no significant evidence that liming per se had any effect at any time on wheat production. The practical implications of these results are discussed.
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Claims 14
Claim · model-written summary
Liming immediately raised soil pH, with greater response per unit at lower rates.
- Taxon
- field peas (Pisum sativumL.)
Lathyrus oleraceust0 - Treatment
- Liminge0
- Outcome
- soil pHe0
- Direction
- Increasese0
- Comparator
- lower rates of application than at higher ratese0
- Setting
- 0–10 cm depthe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Liming had an immediate effect on soil pH (0–10 cm depth). Increases in pH were greater per unit of lime at lower rates of application than at higher rates”
t0“field peas (Pisum sativumL.)”
Claim · model-written summary
Soil pH declined over four seasons, more in limed than unlimed plots.
- Taxon
- field peas (Pisum sativumL.)Lathyrus oleraceust0
- Outcome
- soil pHe0
- Direction
- declinee0
- Value
- 0.47 pHCa unitse0
- Qualifier
- 0.16 pHCa unitse0
- Comparator
- unlimed plotse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“there was a small decline in soil pH over time (mean decline in unlimed plots 0.16 pHCa units, mean decline in limed plots 0.47 pHCa units)”
t0“field peas (Pisum sativumL.)”
Claim · model-written summary
Pea inoculation greatly increased soil and rhizosphere rhizobia in year one.
- Taxon
- peaLathyrus oleraceuse0
- Treatment
- inoculatione0
- Interactor
- rhizobiae0symbiont
- Outcome
- populations of rhizobia in soil and rhizospheree0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In the first year (pea crop), there was a very large and highly significant response to inoculation on populations of rhizobia in soil and rhizosphere”
Claim · model-written summary
Natural rhizobia in uninoculated high-lime plots rose to match inoculated plots by year four.
- Taxon
- field peas (Pisum sativumL.)Lathyrus oleraceust0
- Treatment
- high-lime plotse0
- Interactor
- rhizobiae0symbiont
- Outcome
- number of rhizobiae0
- Direction
- increasede0
- Comparator
- inoculated treatmente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The number of rhizobia that occurred naturally in uninoculated plots increased rapidly in high-lime plots until, by the third year, they were substantial and, by the fourth year, equal to those in the inoculated treatment”
t0“field peas (Pisum sativumL.)”
Claim · model-written summary
At experiment end, 4 t/ha lime had 7250 rhizobia per g soil versus fewer than four without lime.
- Taxon
- field peas (Pisum sativumL.)Lathyrus oleraceust0
- Treatment
- 4 t/ha lime treatmente0
- Interactor
- rhizobiae0symbiont
- Outcome
- population of rhizobiae0
- Direction
- higherinferrede0
- Value
- 7250 per g soile0
- Qualifier
- <4 rhizobia per ge0
- Comparator
- nil lime treatmente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“mean population of rhizobia in the 4 t/ha lime treatment was 7250 per g soil, compared with <4 rhizobia per g in the nil lime treatment”
t0“field peas (Pisum sativumL.)”
Claim · model-written summary
Pea rhizobia persisted by colonizing wheat and chickpea rhizospheres in years without peas.
- Taxon
- wheat
Triticum aestivume0 - Interactor
- R. leguminosarum bv. viciae
Rhizobium leguminosarume0symbiont - Outcome
- colonise the rhizospheres of wheat and chickpeae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“R. leguminosarum bv. viciae were sustained by their ability to colonise the rhizospheres of wheat and chickpea”
Claim · model-written summary
Inoculation strongly improved eight production parameters in first-year peas.
- Taxon
- peaLathyrus oleraceuse0
- Treatment
- inoculatione0
- Outcome
- eight parameters of plant productione0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In the first pea crop, eight parameters of plant production responded overwhelmingly to inoculation”
Claim · model-written summary
Lime produced an underlying response in two first-year pea production parameters.
- Taxon
- field peas (Pisum sativumL.)Lathyrus oleraceust0
- Treatment
- liminge0
- Outcome
- two of those parameterse0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“there was an underlying response to liming in two of those parameters”
t0“field peas (Pisum sativumL.)”
Claim · model-written summary
First-year pea inoculation positively carried over to second-year wheat.
- Taxon
- wheatTriticum aestivume0
- Treatment
- inoculatione0
- Outcome
- wheat crope0
- Direction
- positivee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The positive effect of inoculation on peas in the first year carried over to the wheat crop of the second year”
Claim · model-written summary
By years three and four inoculation no longer determined crop production.
- Taxon
- field peas (Pisum sativumL.)Lathyrus oleraceust0
- Treatment
- inoculatione0
- Outcome
- crop productione0
- Direction
- no longere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“inoculation was no longer a determinant of crop production”
t0“field peas (Pisum sativumL.)”
Claim · model-written summary
Lime significantly enhanced chickpea and pea symbiosis and growth, including nodulation and seed nitrogen.
- Taxon
- chickpea and pea
Cicer arietinumLathyrus oleraceuse0 - Treatment
- application of limee0
- Outcome
- legume nodulation and percentage nitrogen in the seede0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“application of lime, which had only an underlying effect on pea production in the first year, significantly enhanced several parameters of the symbiosis and growth of the chickpea and pea crops, including legume nodulation and percentage nitrogen in the seed”
Claim · model-written summary
Rhizobia populations rose with every additional lime rate.
- Taxon
- field peas (Pisum sativumL.)Lathyrus oleraceust0
- Treatment
- liminge0
- Interactor
- rhizobiae0symbiont
- Outcome
- Populations of rhizobia in soil and plant rhizospherese0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Populations of rhizobia in soil and plant rhizospheres increased with each additional rate of liming”
t0“field peas (Pisum sativumL.)”
Claim · model-written summary
Legume productivity rose with lime additions up to 2 t/ha.
Not reportedComparatorDirection
Verbatim
e0“Legume productivity responded to additional lime up to 2 t/ha”
Claim · model-written summary
Lime had no significant effect on wheat production.
- Taxon
- wheatTriticum aestivume0
- Treatment
- liminge0
- Outcome
- wheat productione0
- Direction
- no significant evidencee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“There was no significant evidence that liming per se had any effect at any time on wheat production”
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Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.