Simulations and Experiments of the Soil Temperature Distribution after 2.45-GHz Short-Time Term Microwave Treatment

Microwave treatment is a green and pollution-free soil disinfection method. The application of microwaves to disinfect soil before cultivation is highly important to increase crop yields and protect the ecological environment. The electromagnetic field is an important parameter influencing the soil temperature field in the process of microwave soil treatment, and the change in soil temperature directly affects soil disinfection. Therefore, this article carried out research on the heating pattern in North China loess due to microwave treatment. First, COMSOL software was employed to simulate the microwave soil treatment process to analyze microwave penetration into soil. Second, with the application of microwaves at the designed frequency produced with a 2.45-GHz tunable microwave generating microdevice, soil with water contents of 0%, 10%, 20%, and 30% was treated for 10~60 s (at 10-s time intervals), and experiments on the influence of the microwave output power, treatment time, and soil moisture content on the soil temperature were performed via the controlled variable method. The simulation results indicate that with increasing soil moisture content, the microwave frequency inside the soil model increases, and the electric field intensity value decreases in the model at the same depth. After microwaves traverse through the 20-cm soil model, the incident field strength is three orders of magnitude lower than the outgoing field strength. The results of the microwave soil treatment experiment reveal that: (1) Compared to microwave output power levels of 1.8 and 1.6 kW, a level of 2 kW is more suitable for microwave soil disinfection. (2) After treatment, the highest temperature occurs on the soil surface, not within the soil. (3) The location of the highest soil internal temperature after microwave treatment increasingly approaches the soil surface with increasing soil moisture content, and the microwave output power does not affect the location of the highest soil internal temperature. Combining the electromagnetic field simulation and microwave soil treatment experiment results, it was found that the higher the field strength is, the higher the temperature value, and the highest soil internal temperature after microwave treatment often occurs at the first electromagnetic wave peak.

METHODOLOGICAL INSTRUCTIONS FOR THE EFFECTIVE APPLICATION OF GLOBODERA-RESISTANT POTATO VARIETIES IN THE FIGHT AGAINST GOLDEN POTATO NEMATODE IN PERSONAL AUXILIARY FARMS

The decisive link in the system of comprehensive measures to contol the golden potato nematode is the use of globodera-resistant varieties and hybrids of potatoes. Before recommending any globodera-resistant potato variety for private household plots, it is necessary to carry out a comparative assessment of varieties in the globoderosis focus. This purpose is served by demonstration experiments that allow us to identify the positive and negative aspects of varieties and clearly show agricultural specialists and the population the advantages of nematode-resistant varieties. Effectively reduced the number of golden potato nematodes in the soil (by more than 60%) globodera-resistant varieties (Zhukovsky early, Impala, Santa, Scarb, Lady Rosetta, Picasso, Riviera, Arizona, etc.) with a powerful and branched root system when grown on a fertile, light in texture soil with the introduction of mineral and organic fertilizers, sufficient supply of soil moisture during May and June. Their cultivation led to a decrease in the incidence of globoderosis and, accordingly, an increase in potato yield. In order to increase the efficiency of soil disinfection with the help of globodera-resistant varieties and to obtain the optimal potato yield in private household plots, it is necessary to take the following measures: 1. In autumn – autumn plowing to the depth of the arable layer. In spring – cultivation to a depth of 12–14 cm with simultaneous harrowing. 2. It is recommended to cultivate potatoes in an anti-nematode crop rotation or fruit change no earlier than the third or fourth crop. The effectiveness of nematode-resistant varieties increases with the use of organic and full dose of nitrogen fertilizers. 3. To activate the activity of predatory, parasitic fungi and other antagonists of potato nematodes, it is necessary to apply organic fertilizers (manure, peat, compost) to the soil of potato plantings.

Assessment of Commercial Fungicides against Onion (Allium cepa) Basal Rot Disease Caused by Fusarium oxysporum f. sp. cepae and Fusarium acutatum

The onion basal rot disease is a worldwide threat caused by species of the genus Fusarium. Today, Israel’s control of this disease is limited to a four-year growth cycle and Metam sodium soil disinfection. Here, commercial chemical fungicides were evaluated as control treatments against two of the primary pathogens involved, F. oxysporum f. sp. cepae and F. Acutatum. Out of 10 fungicides tested on culture plates, 3, Prochloraz, Azoxystrobin + Tebuconazole, and Fludioxonil + Sedaxen, had strong inhibitory effects on mycelial growth and were selected and tested in seeds in vitro. The preparations were applied as a seed coating and tested in two commercial cultivars, Riverside (Orlando, white cv.) and Noam (red cv.). Prochloraz (0.3% w/w concentration), the most promising compound, was efficient in reducing the Noam cv. sprouts’ disease symptoms. This preparation had no harmful in situ-toxicity effect and did not influence the plants’ seed germination and early development. In Noam cv. potted 30-day-old sprouts, the Prochloraz treatment was able to reduce the harmful impact of F. oxysporum f. sp. cepae. on the seedlings’ wet biomass, but was not effective in the Riverside cv. or against the F. acutatum pathogen. This suggests that future protective strategies must include an effective protective suit tailored to each of the pathogen species involved and the onion cultivar. The methods presented in this work can be applied for rapidly scanning multiple compounds while gradually ruling out ineffective ones. Eventually, this screening will enable field testing of the highest potential fungicides that successfully pass the pot experiments.

Evaluation of Broadcast Steam Application with Mustard Seed Meal in Fruiting Strawberry

Soil disinfestation with steam has potential to partially replace fumigants such as methyl bromide, chloropicrin, and 1,3-dichloropropene because it is effective, safer to apply, and has less negative impact on the environment. Here, we compared the efficacy of steam and steam + mustard seed meal (MSM) to chloropicrin on soil disinfection, plant growth, and fruit yield in a strawberry (Fragaria ×ananassa) fruiting field. The MSM was applied at 3368 kg·ha−1 before the steam application. Steam was injected into a 3-m-wide reverse tiller that was set to till 30 to 40 cm deep. Soil temperatures at depths of 10, 20, 25, and 35 cm were monitored. Steam and steam + MSM treatments reduced the viability of purslane seeds and nutsedge tubers, microsclerotia density of Verticillium dahliae, propagule density of Pythium ultimum, cumulative weed densities, and biomass compared with the nontreated control. Moreover, the steam application was as efficacious as chloropicrin on these pests. The growth and fruit yield of strawberries grown on soils previously treated with the steam and steam + MSM treatments were similar to those in the chloropicrin treatment and were higher than those in the nontreated control. Our study indicated that steam, steam + MSM, and chloropicrin are equally effective at suppressing weeds and soilborne pathogens. These results suggest that the steam and steam + MSM treatment can be a practical alternative for soil disinfestation in conventional and organic strawberry fields.

Can Anaerobic Soil Disinfestation (ASD) be a Game Changer in Tropical Agriculture?

Anaerobic soil disinfection (ASD) has been identified as an alternative soil-borne pathogen control strategy to chemical fumigation. ASD involves the application of an easily liable carbon source followed by irrigation to field capacity and maintenance of an anaerobic condition for a certain period. A literature search undertaken on ASD found that more than 50 comprehensive research projects have been conducted since its first discovery in 2000. Most of these studies were conducted in the USA and in the Netherlands. Though the exact mechanism of ASD in pathogen control is unknown, promising results have been reported against a wide range of pathogens such as fungi, nematodes, protists, and oomycetes. However, it is interesting to note that, except for a few studies, ASD research in the developing world and in the tropical countries has lagged behind. Nevertheless, with soil quality depletion, reduction in arable lands, and exponential population growth, a drastic change to the current agricultural practices should be adapted since yield gain has reached a plateau for major staple crops. Under such circumstances, we identified the gaps and the potentials of ASD in tropical agricultural systems and proposed promising biodegradable materials.

Checklist application to evaluate good management practices in aquaculture

The objective of the study was to evaluate good management practices through a Checklist for aquaculture enterprises in the Marajó archipelago (Pará, Brazil). The research was carried out in the municipality of Curralinho, as part of the actions of the project “Transfer of technology through training and technical assistance for creators of tambaqui, Colossoma macropomum, in the archipelago of Marajó/PA” of the Federal Institute of the Pará (IFPA), Campus Breves, between September 2019 and January 2020. A total of 13 fish farms participated in the survey. The instrument for data collection was a checklist, which includes items related to the management of fish farming. After applying the checklist, it was possible to identify that the implementation of fish farming, identification of infrastructure, soil management and application of limestone, occurrence of diseases and storage of fry, presented levels of non-conformities between 75% to 79%. The items filters and anti-leak prevention, handling during the process of draining the tanks, stocking density and handling of fishing, presented levels of non-conformities between 80 - 89%. For the item soil disinfection the level of non-conformities was 94% and for the items: fertilization, protection of tanks with anti-bird nets, water quality, biometrics management, transfer management, cleaning procedures and equipment asepsis and the condition and safety of fish farming workers, presented levels of non-conformities varying between 95 - 100%. It was concluded that all sites are not suitable for good practices and therefore put the species' fish farming in the region at risk.

Effects of Chemical and Solar Soil-Disinfection Methods on Soil Bacterial Communities

The actctivated carbon + solar radiation membrane is an eco-friendly soil disinfestations method for managing soil-borne plant pathogens. However, little was known the impact of Activated carbon + solar radiation membrane on bacterial community structure in strawberry production systems under field conditions. A comprehensive evaluation of the impacts of different soil disinfection methods on the bacterial community structure is fundamental to understand the role of disinfection in maintaining soil health. The changes in the soil bacterial diversity and community composition were detected using realtime fluorescence quantitative PCR (RTFQ PCR) and next-generation sequencing techniques to better understand the effect of soil disinfection. The bacterial community composition was monitored after disinfection using dazomet (DZ), chloropicrin (CP), 100 kg/ha activated carbon + solar radiation membrane (AC1), 200 kg/ha activated carbon + solar radiation membrane (AC2), and 300 kg/ha activated carbon + solar radiation membrane (AC3) and compared with the control (CT). The results indicated that the different dosages of activated carbon (AC1, AC2, and AC3) did not affect the bacterial community structure. On the other hand, DZ and CP considerably reduced the soil biomass and abundance of bacterial species. Chemical fumigants influenced the bacterial community structure, with DZ treatment leading to the dominance of the phylum Firmicutes, accounting for approximately 54%. After fumigation with CP, Proteobacteria and Acidobacteria were the dominant phyla. Beta diversity analysis and principal coordinate analysis revealed that the bacterial communities in the soil treated with DZ and CP formed clusters. Redundancy analysis indicated that soil pH, available potassium, and available phosphorus were the key factors influencing microbial metabolic functional diversity. Thus, it was verified that the damage caused by activated carbon + solar radiation membrane—a potential alternative for chemical fumigant—to the soil bacterial community was less than that caused by chemicals DZ and CP.