Can mineral and organic fertilization help sequestrate carbon dioxide in cropland?

The soil organic matter content represents a huge reservoir of plant nutrients and an effective safeguard against pollution; beside it can sequestrate atmospheric CO₂. Since 1966 up to now in the Southeast Po valley (Italy), the soil organic C (SOC) and total N (TN) dynamics in the 0–0.40 m soil layer under a maize–wheat rainfed rotation are studied as influenced by organic and mineral N fertilizations. Every year in the same plots cattle manure, cattle slurry, and crop residues (i.e. wheat straw and maize stalk) are ploughed under to 0.40 m depth at a same dry matter rate (6.0 and 7.5 t DM ha⁻¹ year⁻¹ after wheat and maize, respectively) and are compared to an unamended control. Each plot is splitted to receive four rates of mineral fertilizer (0–100–200–300 kg N ha⁻¹). In the whole experiment, in 2000 SOC concentration was lower than in 1966 (6.77 and 7.72 g kg⁻¹, respectively), likely for the deeper tillage that diluted SOC and favoured mineralization in deeper soil layer. From 1972 to 2000 SOC stock did not change in the control and N fertilized plots, while it increased at mean rates of 0.16, 0.18, and 0.26 t ha⁻¹ year⁻¹ with the incorporation of residues, slurry and manure, corresponding to sequestration efficiencies of 3.7, 3.8 and 8.1% of added C with the various materials. TN followed the same SOC dynamic, demonstrating how it depends on the soil organic matter. Manure thus confirmed its efficacy in increasing both SOC content and soil fertility on the long-term. In developed countries, however, this material has become scarcely available; slurry management is expensive and implies high environmental risks. Moreover, in a C balance at a farm (or regional) scale, the CO₂ lost during manure and slurry stocking should be considered. For these reasons, the incorporation of cereal residues, even if only a little of their C content was found capable of soil accumulation, appears the best way to obtain a significant CO₂ sequestration in developed countries. Our long-term experiment clearly shows how difficult it is to modify SOC content. Moreover, because climate and soil type can greatly influence SOC dynamic, to increase CO₂ sequestration in cropland, it is important to optimize the fertilization within an agricultural management that includes all the agronomic practices (e.g. tillage, water management, cover crops, etc.) favouring the organic matter build up in the soil.     

Being exposed to low concentrations of pirimiphos-methyl and chlorfenapyr has detrimental effects on the mobility of Trogoderma granarium

BACKGROUND

Sublethal effects of insecticides may negatively affect several biological and behavioral traits of insects. The lethal effects of pirimiphos-methyl and chlorfenapyr have been previously showed on Trogoderma granarium, but little knowledge is available about their sublethal effects at low concentrations on both sexes. Herein, the sublethal effects of pirimiphos-methyl and chlorfenapyr on the mobility of T. granarium males and females were investigated.

RESULTS

Lethal concentration (LC) values of pirimiphos-methyl and chlorfenapyr were lower for T. granarium females than males. LC values on males were LC₁₀ = 0.000788 and 0.00139 mg active ingredient (a.i.) cm⁻², LC₃₀ = 0.00350 and 0.00535 mg a.i. cm⁻², and LC₅₀ = 0.00986 and 0.0136 mg a.i. cm⁻² for pirimiphos-methyl and chlorfenapyr respectively. LC on females were LC₁₀ = 0.000704 and 0.00110 mg a.i. cm⁻², LC₃₀ = 0.00323 and 0.00428 mg a.i. cm⁻², and LC₅₀ = 0.00925 and 0.0110 mg a.i. cm⁻² for pirimiphos-methyl and chlorfenapyr respectively. The walking duration of beetles exposed to LC₃₀ of pirimiphos-methyl was significantly lower than the individuals exposed to LC₁₀ and LC₃₀ of both insecticides and control ones. Pirimiphos-methyl LC₃₀-exposed males remained more time on their back (101.7 s) than females (46.9 s), while the latter stayed immobile longer than males (381.7 s versus 371.9 s). The highest speed was recorded for control beetles (14.17 mm s⁻¹ females vs. 12.44 mm s⁻¹ males), while the lowest speed was observed in pirimiphos-methyl LC₃₀-treated males (8.36 mm s⁻¹) and females (9.66 mm s⁻¹).

CONCLUSIONS

Overall, males and females exposed to low concentrations of pirimiphos-methyl and chlorfenapyr showed reduced motility. This knowledge can be exploited further to unlock behavioral effects of insecticides for effective pest management programs in warehouses. © 2023 Society of Chemical Industry.     

Effects of three esca-associated fungi on Vitis vinifera L.: IV. Diffusion through the xylem of metabolites produced by two tracheiphilous fungi in the woody tissue of grapevine leads to esca-like symptoms on leaves and berries

Two naphthalenone pentaketides (scytalone and isosclerone) and α-glucans (pullulan) are produced in vitro and in planta by Phaeomoniella chlamydospora (Pch) and Togninia minima (Tmi), two tracheiphilous fungi associated with the ‘esca’ disease of grapevines. The possible role of such fungal metabolites in inducing symptoms on leaves and berries was studied in a vineyard of Vitis vinifera cv. Italia located in southern Italy. During early spring, pruning off two to four branches per vine allowed samples of xylem sap to be collected. Vine bleeding, assessed as ml day⁻¹ vine⁻¹, reached its maximum at bud burst and stopped within 28 days. The total amount of sap collected from healthy vines was about a quarter of that from esca-affected vines. During the same period, the leaf water potential of diseased vines increased progressively (i.e. showed less negative values), indicating a dysfunction in water and nutrient supply to the new growth. Both fungi were isolated from the xylem sap and from the woody tissue of branches and the trunk of diseased vines. Conidia isolated from the sap showed a high germination rate (>90%). Bioactive concentrations of the two pentaketides were detected in xylem sap, leaves and berries at various stages of seasonal growth. Exopolysaccharides, including pullulan, were found in the xylem sap. Absorption of culture filtrates of Pch and Tmi, as well as weak solutions of purified preparations of scytalone, isosclerone or pullulan, on detached leaves and berries caused symptoms similar to those shown by the esca-affected vines in the field.     

Effects of three esca-associated fungi on Vitis vinifera L.: V. Changes in the chemical and biological profile of xylem sap from diseased cv. Sangiovese vines

A vineyard of Vitis vinifera cv. Sangiovese was surveyed for incidence of esca and xylem sap collection. Sap samples were collected from healthy vines and from those with dual infection by Phaeomoniella chlamydospora (Pch) and Togninia minima (Tmi) or triple infection by Pch, Tmi and Fomitiporia mediterranea (Fme), during each early spring in a 3-year period (2001–2003). In order to analyse the possible trends in the climatic data, temperature and rainfall were assessed. At sap harvesting, aliquots of sap were assayed for phytotoxicity and extracted with ethyl acetate for phytotoxin recovery. Moreover, the exopolysaccharide (EPS) content was evaluated on several sap samples during the bleeding period. Conidia of Pch and Tmi, mycelium of Fme and their secondary metabolites were found in the sap of the esca-affected vines, indicating that the pathogens and their by-products together with some defence substances were accumulated and then translocated. Bioactivity tests showed toxicity of the sap from esca-affected vines to healthy detached leaves of cv. Sangiovese. The daily amount of sap, the pH, and the volume (J_v) and solute (J_s) fluxes were analysed as a function of the infecting fungi. Pullulan, glucogalactomannan(s) and arabinogalactan(s) are the main EPS in the esca-infected vines, whereas in the sap of healthy vines no traces of pullulan were found. Scytalone and isosclerone usually produced in vitro by Pch and Tmi were also detected in the sap of vines infected by Pch and Tmi or by Pch, Tmi and Fme. The endogenous phytohormone content of healthy vines evaluated by the cutting bioassay was different from that of infected vines. Four phenolics belonging to three classes e.g., benzoic acid derivatives, stilbenes and flavonol-glycosides were separated and identified by HPLC.     

Effects of three esca-associated fungi on Vitis vinifera L.: II. Characterization of biomolecules in xylem sap and leaves of healthy and diseased vines

Secondary metabolites and host defense compounds were shown to occur in xylem sap, and leaves of Vitis vinifera cv. Italia and cv. Matilde naturally infected by the esca-associated fungi Phaeomoniella chlamydospora (Pch), Togninia minima (Tmi) and Fomitiporia mediterranea (Fme). Samples of xylem sap and leaves were collected from healthy vines and from vines showing severe symptoms of brown wood-streaking caused by Pch and Tmi, or from vines with symptoms of both brown wood-streaking and white rot caused by Fme. Xylem sap collection was carried out during the early spring of 2003 and 2004, corresponding to the phenological phases: (A) cotton bud; (B) green tip; (C) leaves out; (D) stretched out leaves; and (E) visible clusters. In the present work we have studied the accumulation of biomolecules (pentaketides and α-glucans), host defense compounds (benzaldehydes, benzoic acid and cinnamic acid derivatives, flavonols, flavanols, flavan-3-ol derivatives and stilbenes) at different stages of grapevine development. Accumulation and changes in total phenolics and recurring phenolics, and of three phytotoxic secondary metabolites (scytalone, isosclerone and pullulan) were analyzed by HPLC. On comparing results for cv. Italia and cv. Matilde, it can be seen that phenolic concentrations are strongly related to the cv.