Abstract
The effects of biochar on soil–plant–microorganisms systems are currently being extensively investigated. Considering that arbuscular mycorrhizal fungi (AMF) play an essential role in nutrient dynamics, the present study aims at understanding vine shoot-derived biochar effects on AMF activity and the impact of their multiplication in soils on water-stress resistance of plants. Three agronomic tests were performed in greenhouse pots. The first experiment evaluated the effects of three factors: final pyrolysis temperature for biochar production (400 °C and 600 °C), application rate (0 weight-wt.- % as a control, 1.5 wt. %, and 3.0 wt. %) and texture of the growing media (sandy-loam and clay-loam origin) on AMF, microbial communities and phosphatase activity. In the second experiment, an indigenous consortium of AMF was multiplied through the solid substrate method and sorghum as a trap plant with biochar addition. This process was compared to a control treatment without biochar. Obtained inocula were tested in a third experiment with lettuce plants under different water irrigation conditions. Results from the first experiment showed a general increase in AMF activity with the addition of the biochar produced at 400 °C in the sandy-loam texture substrate. Results of the second experiment showed that the biochar addition increased AMF root colonization, the number of AMF spores and AMF infective potential. Results of the third experiment showed that biochar-derived AMF inoculum increased AMF root colonization, AMF spores, dry biomass and the SPAD index in a lettuce crop under low-water irrigation conditions.
Highlights
New crop varieties and biotechnologies are being investigated in dealing with droughtstress events in agriculture [1]
The morphological identification of the spores reveled that Glomus spp. was the main species identified in the samples of both soils (77% in S1 and 94% in S2)
A general increase in root arbuscular mycorrhizal fungi (AMF) colonization was observed from 210 to 330 days after sowing (D210 and D330); the average values of AMF root colonization decreased in the last period, which could be related to winter temperatures and the final development of the crop
Summary
New crop varieties and biotechnologies are being investigated in dealing with droughtstress events in agriculture [1]. Improving the physical and biological fertility of the soil is becoming a mandatory practice to preserve its productive capacity, even though chemical fertilization remains the focus of intensive agricultural systems. One of the most studied organic amendments to enrich soil fertility is biochar, a carbon-rich product obtained by thermal degradation of biomass under a limited supply of oxygen, at temperatures usually below 700 ◦C, which is produced to be added to the soil as a means of improving its quality and increasing carbon storage [2]. Biochar amendment significantly enhances the nutrient availability and nutrient retention of a wide range of soils [6], in addition to the positive contribution to the improvement of other physical and biological soil properties [7,8,9,10] and to metal retention [11]. The capacity of this material to provide or enhance soil fertility extremely depends on the type of feedstock and pyrolysis conditions [12]
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