Macronutrient in soils and wheat from long-term agroexperiments reflects variations in residue and fertilizer inputs

Microbial consortia and biochar as sustainable biofertilisers: Analysis of their impact on wheat growth and production

The European Union is among the top wheat producers in the world, but its productivity relies on adequate soil fertilisation. Biofertilisers, either alone or in combination with biochar, can be a preferable alternative to chemical fertilisers. However, the addition of biofertilisers, specifically plant growth promoting microbes (PGPM), could modify grain composition, and/or deteriorate the soil composition. In this study, the two wheat cultivars Triticum aestivum (Bramante) and T. durum (Svevo) were cultivated in open fields for two consecutive years in the presence of a commercial PGPM mix supplied alone or in combination with biochar. An in-depth analysis was conducted by collecting physiological and agronomic data throughout the growth period. The effects of PGPM and biochar were investigated in detail; specifically, soil chemistry and rhizosphere microbial composition were characterized, along with the treatment effects on seed storage proteins. The results demonstrated that the addition of commercial microbial consortia and biochar, alone or in combination, did not modify the rhizospheric microbial community; however, it increased grain yield, especially in the cultivar Svevo (increase of 6.8 %-13.6 %), even though the factors driving the most variations were associated with both climate and cultivar. The total gluten content of the flours was not affected, whereas the main effect of the treatments was a variation in gliadins and low-molecular-weight-glutenin subunits in both cultivars when treated with PGPM and biochar. This suggested improved grain quality, especially regarding the viscoelastic properties of the dough, when the filling period occurred in a dry climate. The results indicate that the application of biofertilisers and biochar may aid the effective management of sustainable wheat cultivation, to support environmental health without altering the biodiversity of the resident microbiome.

Long-term agro-management strategies shape soil bacterial community structure in dryland wheat systems

Soil microbes play a crucial role in soil organic matter decomposition and nutrient cycling and are influenced by management practices. Therefore, quantifying the impacts of various agricultural management practices on soil microbiomes and their activity is crucial for making informed management decisions. This study aimed to assess the impact of various management systems on soil bacterial abundance and diversity, soil enzyme activities and carbon mineralization potential in wheat-based systems. To accomplish this, soil samples from 0 to 15 cm depth were collected from ongoing long-term field trials in eastern Oregon region under wheat (Triticum aestivum L.)-fallow (WF), WF with different tillage (WT), wheat-pea (Pisum sativum L.) (WP), WF under different crop residue management (CR) and natural undisturbed/unmanaged grassland pasture (GP). These trials consisted of an array of treatments like tillage intensities, nitrogen rates, organic amendments, and seasonal residue burning. This study was a part of the Soil Health Institute's North American Project to Evaluate Soil Health measurements (NAPESHM). Bacterial community structure was determined using amplicon sequencing of the V4 region of 16SrRNA genes and followed the protocols of the Earth Microbiome Project. In addition, extracellular enzyme activities, and carbon mineralization potential (1d-CO2) were measured. Among different trials, 1d-CO2 in WT, WP, and CR studies averaged 53%, 51% and 87% lower than GP systems, respectively. Enzyme activities were significantly greater in GP compared to the other managements and followed similar trend as respiration. We observed higher evenness in GP and higher richness in spring residue burning treatment of CR study. Our results indicated that species evenness is perhaps a better indicator of soil health in comparison to other indices in dryland wheat systems.

Response of Wheat Cultivars to Organic and Inorganic Nutrition: Effect on the Yield and Soil Biological Properties

The deterioration of soil biological health is the most important aspect associated with the sustainability of cereal-based food production systems. The application of organic nutrient sources is widely accepted and recommended for sustaining crop productivity and preserving soil fertility. Therefore, a study was carried out to assess the effects of different levels of farmyard manure (FYM10: 10 t ha−1, FYM20: 20 t ha−1, FYM30: 30 t ha−1), including inorganic fertilizer (NPK) on the soil and the biological properties of five high-yielding wheat cultivars (HD 2967, DPW 621-50, PBW 550, and WH 1105) over a three-year period (2014–2015 to 2016–2017). The results showed that the application of NPK produced significantly higher yields compared to different levels of FYM and the control during all the study years. The continuous addition of a higher rate of FYM at 30 t ha−1 was found to be beneficial in terms of enhancing crop yield gain, thereby bridging the yield gap to only 7.2% in the third year; the gap was 69.1% in the first year with NPK application. The microbial population and microbial biomass carbon were significantly higher in the FYM treatments compared to the NPK treatment. The activities of different soil enzymes were observed to be significantly maximum in the FYM30 treatment. Similarly, the addition of FYM significantly improved the soil respiration and microbial activity over the NPK and control treatments. Based on the principal component analysis, fluorescein diacetate, bacteria, fungi, and actinomycetes were observed as sensitive biological parameters for the assessing of soil biological health. The soil biological index (SBI) determined with the sensitive parameters was in the decreasing order of FYM30 (0.70), FYM20 (0.61), FYM10 (0.55), NPK (0.18), and control (0.15). Considering both the SBI and the sustainability yield index together, the performance of WH 1105 was found to be better compared to the rest of the wheat cultivars. Our results conclude that the application of FYM in the long run increases the crop yield (24.3 to 38.9%) and improves the soil biological process, leading to the improved biological index of the soil.