Effects of anaerobic soil disinfestation carbon sources on soilborne diseases and weeds of okra and eggplant in Nepal
Introduction
Vegetables are a high value agricultural commodity in Nepal and an important component of nutritional security. Vegetables are cultivated on 245,037 ha with production of 3,298,816 Mg and productivity of 13.46 Mg ha−1 (Anonymous, 2015). Vegetable production is increasing in Nepal, particularly during the off-season, due to higher market prices and increasing per capita consumption. Therefore, vegetable production significantly contributes to the economic stability of farming households. Due to continuous monoculture of vegetables and intensified off-season production, increased pressure from diseases and pests has caused large losses in productivity, mainly caused by soilborne diseases, plant parasitic nematodes, and weeds. Managing these production problems is challenging in Nepal as there are few options available to predominantly smallholder farmers who cannot afford high cost tactics such as chemical fumigation and steam sterilization. Soil solarization is another tactic but is only effective at high temperatures and requires a long treatment time (4–6 weeks) (Chellemi et al., 1997), therefore it is not feasible in temperate regions of Nepal or during the winter season.
Okra and eggplant are hosts of root-knot nematode (Meloidogyne spp.), which causes reduced productivity in these vegetable species in Nepal (Baidya et al., 2017) as well as other parts of the world. Meloidogyne incognita is dominant species in Nepal (Bhardwaj and Hogger, 1984). Wilting disease of eggplant is caused by several fungal pathogen species, however Fusarium oxysporum (presumed F. oxysporum f. melongenae) is a major challenge in Nepalese farming systems. Both of these pathogens can survive several years in soil if proper management is not employed.
The practice known as anaerobic soil disinfestation (ASD), biosolarization, biological soil disinfestation, or reductive soil disinfestation (RSD) is a promising method currently being evaluated and deployed in developed countries (Shennan et al., 2017; Shrestha et al., 2016; Ueki et al., 2018). Broad-spectrum effects on diseases, pests, and weeds have been demonstrated, and there are no known environmental or health hazards. The process can be applied anywhere using locally available resources (Butler et al., 2012). ASD treatment involves the incorporation of decomposable carbon sources in soil, irrigation to saturation and covering with plastic to control the exchange of gases (Blok et al., 2000; Butler et al., 2014; Momma et al., 2013). The decomposition of ASD carbon sources induces the transformation of soil microbial communities that create conditions antagonistic to most phytopathogens (Messiha et al., 2007; Strauss et al., 2017), including the formation of organic acids and volatile compounds, and significant changes in soil pH and metal ion concentrations (Momma et al., 2013). Studies conducted in Asia (Momma et al., 2013; Huang et al., 2015c), Europe (Overbeek et al., 2014) and America (Rosskopf et al., 2017; Shennan et al., 2017; Strauss et al., 2017) have shown that ASD is an effective alternative to chemical soil fumigation for soilborne pest management. Anaerobic soil disinfestation was shown to be effective for management of soilborne pests in eggplant production in Florida, United States, (Butler et al., 2012), but has not been examined previously as a tool for managing soilborne diseases in okra.
Although ASD is gaining popularity in developed countries (Rosskopf et al., 2017; Shrestha et al., 2016), it has not been tested widely in developing countries. The objective of this study was to assess the effectiveness of locally available carbon sources and feasibility of ASD to control soilborne diseases, root-knot nematode and weeds in vegetable cropping systems in the western plain (terai) region of Nepal.
Section snippets
Materials and methods
The study was conducted at the Regional Agricultural Research Station (RARS), Khajura, Banke, Nepal during 2016 and 2017, at an altitude of 181 m above mean sea level. The soil of the experimental plots was sandy loam, pH 7.2, 1.97% organic matter, 0.16% nitrogen, 51.4 kg ha−1 available phosphorus and 97.7 kg ha−1 available potassium (Regional Soil Testing Laboratory, Khajura, Banke, Nepal). The field had a history of more than five years of eggplant seed production, Fusarium wilt and root-knot
Data collection and analysis
Soil parameters, including soil temperature, and pH (2016 trials only), were recorded twice a day (7:00–8:00 a.m. and 4:00–5:00 p.m.) in three randomly selected places in each plot by inserting the probe of a “4 in 1” soil tester instrument (SR300B PH Meter, HXS, Guangdong, China) through a small tear in the plastic sheet. The tear was immediately sealed after probe removal with electrical tape. Measurements were initiated on the second day of carbon source incorporation and performed on 3-day
Soil temperature
Overall soil temperatures were higher in summer 2016 than in winter 2016–17. During the ASD treatment period in summer 2016, starting soil temperatures were lower than final temperatures, while the opposite occurred in winter 2016–2017 (data not shown). The average soil temperature over the ASD treatment period was significantly affected by ASD treatment and varied depending on the carbon source used (Table 2). For all three field trials, with the exception of plots amended with rice
Discussion
Management of soilborne diseases and weeds in vegetable crops is increasingly challenging in Nepal due to long term monoculture practices, intensive off-season farming and lack of effective management tactics. Furthermore, Nepales agriculture is dominated by small holder farmers, and high cost technologies such as chemical fumigation and steam sterilization for soilborne disease management are inaccessible to these farmers. Altogether, diseases cause more than 30% yield reduction in vegetable
Acknowledgements
This study was supported by the United States Agency for International Development under Cooperative Agreement No. AID-OAA-L-15-00001 to Virginia Tech and the Feed the Future Innovation Lab for Integrated Pest Management, state and federal funds appropriated to The Ohio State University-Ohio Agricultural Research and Development Center, and Nepal Agricultural Research Council. We thank Mr. Gopi Krishna Shrestha and other field workers and staff of RARS, Khajura for their support in conducting
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2022, Soil and Tillage ResearchCitation Excerpt :Reductive soil disinfestation (RSD), also known as biological soil disinfestation (BSD) or anaerobic soil disinfestation (ASD), is a pre-planting soil management practice, which incorporates readily decomposable organic amendments (e.g., molasses, composts, crop residues, etc.) into soils, followed by irrigating and mulching the soils with plastic films to create highly reductive soil conditions (Butler et al., 2014; Huang et al., 2017; Meng et al., 2018). It is expected that such a procedure improves soil productivity by introducing organic carbon (C) while creating a strongly reductive environment to suppress soil-borne pathogens, nematodes, and weeds (Shrestha et al., 2016; Zhou et al., 2019; Khadka et al., 2020). Furthermore, recent studies have demonstrated the positive effects of RSD application in suppressing soil diseases and increasing crop yields in cucumber (Huang et al., 2015), watermelon (Liu et al., 2018), and lisianthus (Zhou et al., 2019).
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2021, Science of the Total EnvironmentCitation Excerpt :This practice may stimulate environmental N losses e.g. in form of N2O or by N leaching during the ASD period (Li et al., 2010; Liang et al., 2015). However, so far research on ASD has focused on its efficiency in eliminating soil borne diseases and how ASD is affecting the soil microbial community (Butler et al., 2012; Liu et al., 2019; Khadka et al., 2020). Only few studies, looked into the effect of ASD on soil N2O emissions (Zhu et al., 2014; Di Gioia et al., 2017; Jiang et al., 2020), while we are not aware of any study assessing N leaching during the ASD period.