No-tillage and liming increase the root mycorrhizal colonization, plant biomass and N content of a mixed oat and vetch crop

Abstract

The combination of no-tillage (NT) and liming has been proposed as feasible means to restore degraded acid soils. However, the synergistic effect of both practices on nutrient acquisition by crops has not been addressed. Similarly, the simultaneous impact on arbuscular mycorrhizal fungi (AMF) is under-investigated despite its essential role in plant growth and nutrient uptake, especially under stress conditions. We evaluated the plant growth, nutrient acquisition and mycorrhizal root colonization at three stages during a growing season along with soil properties of a rainfed oat (Avena sativa L.) and vetch (Vicia sativa L.) mixture under Mediterranean condition. The experiment was located in south-west Spain where tillage type (no tillage: NT and traditional tillage: TT) and lime application were evaluated in a full factorial design. Liming raised soil pH, increased soil calcium and magnesium availability and stimulated the microbial activity while NT enhanced soil carbon content. Both practices improved oat biomass production (40 times at biomass harvest) and root colonization of both crops (80 % and 60 % higher respect to TT without liming in oat and vetch, respectively). Liming enhanced vetch biomass production (20 times at harvest) and foliar N content, while NT increased foliar N content of oat. Plant phosphorous (P) contents were unaffected by the treatments. The high N:P of both crops indicates P limitation despite of the high soil P content. The P limitation together with the increased N supply could lead to strengthening of mutualism between plants and AMF, where P acquisition through AMF is stimulated in order to take advantage of the “luxury” N supply provided by NT and liming. Thus, both practices together increase nutrient use efficiency by stimulating crop-microbe interactions.