Abstract
Agricultural productivity is often constrained by nutrient availability; as such, copious amounts of synthetic fertilizers are applied to maintain productivity. However, the intensive use of synthetic fertilizers has reduced the capacity of the soil to carry out crucial roles such as nutrient cycling because of shifts in the microbial community composition and structure. In addition, much of the applied synthetic fertilizers become lost to the environment through run-off, which contributes to soil degradation. With the increasing demand on agricultural systems to provide food and fibre and the adverse impacts of agricultural production on the soil resource, amendments that support soil productivity are required to supply plant nutrients. One way of sustainably improving nutrient acquisition and retention is by improving soil fertility; this can be achieved through integrative farming strategies that increase organic matter levels and stimulate the microbial community. In this greenhouse study, an integrative approach that relied on plant-soil-microbe interactions was used to evaluate the usage of an agromineral as a slow-release fertilizer. This assessment was done by comparing the effects of an agromineral, the Spanish River Carbonatite (SRC), and a synthetic fertilizer (Nitrogen-Phosphorus-Potassium (NPK), 20-20-20) on soil pH, microbial abundance and respiration, as well as on the legume-Rhizobium symbiosis. I hypothesized that the SRC, rich in calcium and other essential plant nutrients, would raise soil pH, stimulate microbial abundance and respiration, and enhance the legume-Rhizobium symbiosis in comparison to the synthetic fertilizer. In addition, the microbial abundance and respiration would differ depending on the plants grown. A mix of leguminous and non-leguminous cover crops was grown for 56 days in soils treated with three soil amendments: SRC, ammonium nitrate, and NPK synthetic fertilizer. The cover crops were grown in the following pairs: 1) alfalfa and chicory and 2) red clover and oilseed radish. At harvest, soil treated with SRC had higher pH values (pH raised by 1.2 units) and exhibited a higher abundance of heterotrophic and symbiotic nitrogen-fixing bacteria than those soils lacking the SRC amendment. This effect of SRC was observed in the rhizosphere of both cover crop combinations. However, the effect of soil amendments on the phosphate-solubilizing bacteria varied between cover crop combinations. The relative abundance of phosphate-solubilizing bacteria was enhanced by the SRC amendment in the rhizosphere of red clover and oilseed radish plants; in contrast, in the rhizosphere of intercropped alfalfa and chicory, the NPK fertilizer was the amendment that stimulated the abundance of the phosphate-solubilizer bacteria. Additionally, microbial respiration was reduced in soils treated with SRC compared to that of ammonia nitrate- and NPK fertilizer-treated soils. The results indicate that soil amendments were the drivers of soil pH and abundance of symbiotic nitrogen-fixing and heterotrophic microorganisms, as well as the drivers of microbial respiration, while the plant combination had more pronounced effects on the abundance of phosphate-solubilizing bacteria. Furthermore, the SRC amendment appeared to have enhanced the legume-Rhizobium symbiosis compared to amendments lacking SRC. These preliminary findings suggest that SRC as a slow-release fertilizer may be useful as part of an integrative strategy to improve soil fertility by stimulating microbial activity.
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Claims 9
Claim · model-written summary
SRC raised soil pH by 1.2 units.
Verbatim
e0“soil treated with SRC had higher pH values (pH raised by 1.2 units) and exhibited a higher abundance of heterotrophic and symbiotic nitrogen-fixing bacteria than those soils lacking the SRC amendment.”
t0“A mix of leguminous and non-leguminous cover crops was grown for 56 days”
Claim · model-written summary
SRC increased heterotrophic bacterial abundance.
- Taxon
- cover cropst0
- Treatment
- SRCe0
- Interactor
- heterotrophice0
- Outcome
- abundance of heterotrophice0
- Direction
- highere0
- Comparator
- soils lacking the SRC amendmente0
Not reportedInteractor role
Verbatim
e0“soil treated with SRC had higher pH values (pH raised by 1.2 units) and exhibited a higher abundance of heterotrophic and symbiotic nitrogen-fixing bacteria than those soils lacking the SRC amendment.”
t0“A mix of leguminous and non-leguminous cover crops was grown for 56 days”
Claim · model-written summary
SRC increased symbiotic nitrogen-fixing bacterial abundance.
- Taxon
- cover cropst0
- Treatment
- SRCe0
- Interactor
- symbiotic nitrogen-fixing bacteriae0
- Outcome
- symbiotic nitrogen-fixing bacteriae0
- Direction
- highere0
- Comparator
- soils lacking the SRC amendmente0
Not reportedInteractor role
Verbatim
e0“soil treated with SRC had higher pH values (pH raised by 1.2 units) and exhibited a higher abundance of heterotrophic and symbiotic nitrogen-fixing bacteria than those soils lacking the SRC amendment.”
t0“A mix of leguminous and non-leguminous cover crops was grown for 56 days”
Claim · model-written summary
SRC enhanced phosphate-solubilizing bacteria in red clover and oilseed radish rhizosphere.
- Taxon
- red clover and oilseed radish plantse0
- Treatment
- SRC amendmente0
- Interactor
- phosphate-solubilizing bacteriae0
- Outcome
- relative abundance of phosphate-solubilizing bacteriae0
- Direction
- enhancede0
Not reportedInteractor roleComparator
Verbatim
e0“The relative abundance of phosphate-solubilizing bacteria was enhanced by the SRC amendment in the rhizosphere of red clover and oilseed radish plants”
Claim · model-written summary
NPK stimulated phosphate-solubilizing bacteria in alfalfa and chicory rhizosphere.
- Taxon
- alfalfa and chicory
Medicago sativa
Cichorium intybuse0 - Treatment
- NPK fertilizere0
- Interactor
- phosphate-solubilizer bacteriae0
- Outcome
- abundance of the phosphate-solubilizer bacteriae0
- Direction
- stimulatede0
Not reportedInteractor roleComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in the rhizosphere of intercropped alfalfa and chicory, the NPK fertilizer was the amendment that stimulated the abundance of the phosphate-solubilizer bacteria.”
Claim · model-written summary
SRC reduced soil microbial respiration compared with ammonium nitrate and NPK.
Verbatim
e0“microbial respiration was reduced in soils treated with SRC compared to that of ammonia nitrate- and NPK fertilizer-treated soils.”
t0“A mix of leguminous and non-leguminous cover crops was grown for 56 days”
Claim · model-written summary
Plant combination influenced phosphate-solubilizing bacterial abundance more than other measured microbial outcomes.
- Taxon
- cover cropst0
- Interactor
- phosphate-solubilizing bacteriae0
- Outcome
- abundance of phosphate-solubilizing bacteriae0
- Setting
- plant combinatione0
Not reportedDirection
Verbatim
e0“the plant combination had more pronounced effects on the abundance of phosphate-solubilizing bacteria.”
t0“A mix of leguminous and non-leguminous cover crops was grown for 56 days”
Claim · model-written summary
SRC appeared to enhance legume-Rhizobium symbiosis over amendments without SRC.
- Taxon
- legumee0
- Treatment
- SRC amendmente0
- Outcome
- legume-Rhizobium symbiosise0
- Direction
- enhancede0
- Comparator
- amendments lacking SRCe0
RhizobiumNot reportedInteractor role
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the SRC amendment appeared to have enhanced the legume-Rhizobium symbiosis compared to amendments lacking SRC.”
Claim · model-written summary
Preliminary findings suggest SRC may be useful as a slow-release soil fertility amendment.
Verbatim
e0“These preliminary findings suggest that SRC as a slow-release fertilizer may be useful as part of an integrative strategy to improve soil fertility by stimulating microbial activity.”
t0“A mix of leguminous and non-leguminous cover crops was grown for 56 days”
The same questions in other papers
fertilization · pest · Medicago sativa (alfalfa)Positive and negative results
6 papers in the same direction as this paper · 2 in the opposite direction
- no effect
- no effect
- positive
5 papers more in this group
See all 9 papers →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.