Bioindicators and nutrient availability through whole soil profile under orange groves after long-term different organic fertilizations

Risultato della ricerca: Article

Abstract

We investigated long-term (18 years) effects of three organic (cow manure (CM), poultry manure (PM), compost from agro-industry orange wastes (OW)) and one inorganic fertilization (IF) on various soil biological indicators (microbial biomass C, soil respiration, total phospholipid fatty acids (PLFAs), total bacteria, Gram-positive and Gram-negative bacteria and fungi) and nutrient contents (total and extractable organic C, total and mineral N, available P and K) along the profile of a Typic Haplustept under orange Mediterranean orchards. All fertilizers were added on the same N content basis (190 kg N ha−1 per year). Variables related to carbon cycling gradually worsened with depth, regardless of treatment, but at any soil depth they improved according to IF < PM < OW < CM. Similarly, mineral nutrient availability decreased with increasing soil depth, according to CM > OW > PM > IF. Organic manures favoured Gram-negative bacteria, especially between 35 and 55 cm depth, whereas Gram-positive bacteria flourished better under inorganic fertilization up to 55 cm.Organic fertilizers increased microbial biomass C, compared with IF, with CM being the most efficient, i.e. inducing the greatest C use efficiency, in turn coupled with a greater amount of fungi compared to bacteria. This is crucial from the environmental viewpoint, since fungi better contribute to soil C storage. PLFAs signatures of microbial communities reflected the differences in resources availability determined by soil depth and fertilizer type; indeed, fungi and Gram-negative bacteria responded more promptly to nutrient contents than other microbial groups. Oligotrophic conditions in deeper soil horizons increased the metabolic quotient, an indicator of stress conditions.
Lingua originaleEnglish
Numero di pagine11
RivistaSN APPLIED SCIENCES
Volume1
Stato di pubblicazionePublished - 2019

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