Sugar Beet Yield and Processing Quality in Relation to Nitrogen Content and Microbiological Diversity of Deep Soil Layer

Abstract

The aim of this study was to estimate the effects of different soil factors on sugar beet yield and processing quality. The parameters investigated included: (i) nitrogen (N) availability; (ii) overall microbial diversity and (iii) abundance of bacterial genes involved in key functions of the N cycle. These traits have been evaluated throughout the entire soil layer (0-2.5 m) explored by the sugar beet root system. Soil samples were taken from two nearby sites (A and B) in the Eastern Po Valley, Italy. At each site, three soil profiles were sampled every 0.5 m and the main soil physical and chemical characteristics were evaluated. ARISA (Amplified Ribosomal Intergenic Spacer Analysis) and Real Time PCR analyses were performed on genomic DNA extracted from soil samples for the estimation of microbial diversity and the quantitative presence of genes for ammonium monooxygenase (amoA-Archaea) and nitrite reductase (nirK). To assess the root length density, observations were made by means of minirhizotrons. At site B profile, organic matter as high as 13 % and min-N around 28 mg kg -1 were found between 2 and 2.5 m depth. Sugar beets harvested at this site showed less sugar content and processing quality than at site A (soil similar to B but without deep N accumulation). Soil collected below 0.5 m displayed a more species-rich composition of microbial communities than in the upper layer. The presence of amoA (nitrification) and nirK (denitrification) genes was found in all layers explored (down to a depth of 2.5 m). These findings highlight the contribution of the deep layers to key processes of the soil N cycle and its availability for deep-rooted crops. The usefulness of sampling soil to the depth reached by the roots to assess N fertilizer requirements is discussed.

Over‐dispersed count data in crop and agronomy research

“…The yield of sugar and fodder beet depends, among others, on assimilation surface including the number of leaves (Norton, ; Stevanato et al, ). The number of leaves in this data set comes from the two‐factor experiment (seeding data and nitrogen fertilization) carried out in the Experimental Station of the Faculty of Agriculture and Biology, Warsaw University of Life Science, Poland.…”

Understanding the sugar beet holobiont for sustainable agriculture

“…Microbial rhizosphere communities shift during the maturation of the host plant. Sugar beet fibrous roots can reach up to 3 m depth (Stevanato et al, 2010), with the highest root length density at a depth of around 1 m (Stevanato et al, 2010(Stevanato et al, , 2016. With the increasing length of the taproot, a vertical gradient of microbial diversity, increasing with depth, establishes alongside the fine roots under field conditions (Stevanato et al, 2016).…”

“…Although root biomass is positively correlated with N fertilization, sugar concentration in roots negatively correlates with N fertilization, resulting in an optimum curve regarding sucrose yield dependent on N application rate (Milford, 2006 ; Hergert, 2010 ). Consequently, fertilization regimes usually aim to let sugar beets become N-deficient several weeks before harvest to increase processing efficacy (Stevanato et al, 2016 ). Fertilization affects bacterial soil and rhizosphere microbiome community composition, including lowering the abundance of bacterial and archaeal nitrogen fixation-associated gene transcripts.…”

“…An indication for reduced nitrogen fixation with a concurrent increase of nitrification and aerobic ammonia oxidation in sugar beet rhizospheres was also found in a long-term crop rotation field (Du et al, 2022a ). Archaeal nitrification in the rhizosphere further positively correlates with increasing soil depth (Stevanato et al, 2016 ).…”

“…Sugar beet fibrous roots can reach up to 3 m depth (Stevanato et al, 2010 ), with the highest root length density at a depth of around 1 m (Stevanato et al, 2010 , 2016 ). With the increasing length of the taproot, a vertical gradient of microbial diversity, increasing with depth, establishes alongside the fine roots under field conditions (Stevanato et al, 2016 ). Proteobacteria are enriched compared to bulk soil in pre-harvest taproot rhizospheres, Acidobacteria, Actinobacteria, Bacteroidetes , and Gemmatimonadetes were mentioned as codominant bacterial phyla (Houlden et al, 2008 ; Kusstatscher et al, 2019a ; Cardinale et al, 2020 ; Huang et al, 2020 ; Du et al, 2022a ).…”