Non-solarized Soil Research Articles

Effects of Soil Solarization and Grafting on Tomato Yield and Southern Root-knot Nematode Population Densities

High tunnel production has increased in the past 10 years in Kentucky with more than 1500 high tunnels constructed across the state. Tomato is the most popular and most valuable high tunnel crop per square foot. This has contributed to a lack of rotation and increased pressure from root-knot nematodes (RKN; Meloidogyne spp.). Infection by RKN leads to root galling and reduces the host plant’s ability to take up water and nutrients. Sustainable strategies are needed to manage increasing RKN populations for long-term health of high tunnel soils. Soil solarization is a nonchemical management strategy that has shown promise in other regions and in open field systems. Because tunnels are primarily used to produce high-value crops and are often used for season extension, solarizing during the off-season would be the most beneficial for growers because solarizing would require taking the tunnel out of production. The primary objective of this study was to determine whether springtime soil solarization in Kentucky high tunnels followed by use of resistant tomato cultivars is a viable and effective management strategy for RKN populations. Soil solarization was performed in two commercial high tunnels naturally infested with southern RKN (Meloidogyne incognita) for 2, 4, and 6 weeks and compared with a nonsolarized control. Soil temperatures reached during solarization were assessed at 7.6-, 15.2-, and 22.8-cm soil depth. After solarization, tomato was transplanted, including ‘Cherokee Carbon’ grafted onto RKN-resistant rootstocks ‘Fortamino’ and ‘Estamino’, RKN-resistant nongrafted ‘Caimon’, and susceptible ‘Cherokee Carbon’ as the control. The highest soil temperature achieved was 50 °C during 6 weeks of solarization at 7.6-cm soil depth compared with 38 °C reached in nonsolarized soil. Soil population densities of RKN increased each month after solarization and were generally lower after solarization with resistant tomato cultivars. The interaction of soil solarization and tomato cultivars was significant with respect to RKN densities in soil and roots. The mean RKN soil and root population densities in the nonsolarized, nonresistant treatment combination was significantly greater compared with all other treatments (P < 0.0001). Population densities of RKN were significantly higher in the nonsolarized control compared with solarized treatments (P = 0.0002). Nongrafted ‘Cherokee Carbon’ had significantly more RKN in surrounding soil compared with all other tomato treatments. Tomato yield was unaffected by soil solarization, but there were significant differences based on tomato cultivars alone; nongrafted ‘Cherokee Carbon’ yielded less than the resistant ‘Caimon’. Together, solarization and resistant cultivars reduced RKN population densities in soil and roots, which can provide growers with a nonchemical approach for long-term RKN management and high tunnel resiliency.

Effectiveness of integrated solarization technology in managing soil-borne pathogens and weeds in citrus seedlings under greenhouse conditions

Solarization Technology utilizes solar radiation to kill soil-borne pests, diseases, and weeds in an environmentally and eco-friendly way. In this study, we assessed the efficacy of integrating solarisation with sticky traps on two potting mixtures (sawdust and soil) for three Citrus species (Citrus sinensis, C. reticulata, and C. limon). Eight treatments were tested viz., non-solarized sawdust, non-solarized soil, solarized soil, solarized soil with sticky traps, non-solarized soil with sticky traps, non-solarized sawdust with sticky traps, solarized sawdust, and solarized sawdust with sticky traps, each replicated thrice and were arranged in a randomized complete block design (RCBD). Thirty sterilized seeds of each Citrus species were sown per treatment and monitored for one year in 2019. Analysis of variance (ANOVA) revealed a significant difference in weed control between the treatments at p ≤ 0.05. Tukey’s post hoc test showed weed growth differences between treatments with sawdust and ones with soil as media. More weeds grew in non-solarized soil (32%), compared to non-solarized soil with sticky traps (30%), solarized soil with sticky traps (21%), solarized soil (17%), and treatments with sawdust media did not allow weed growth (0%). A Kruskal Wallis test revealed a significant effect of treatments on the survival percentage of Citrus seedlings (X2 = 36.008, df = 7, p< 0.001), mean of chewed leaves (X2 = 20.850, df = 7, p = 0.004) and percentage levels of low chlorophyll (X2 = 21.073, df = 7, p =0.004) at the p ≤ 0.05 level. Highest number of Citrus seedlings with folded leaves were observed in non-solarized sawdust with sticky traps (mean rank = 119.50), followed by non-solarized soil with sticky traps (112.22), and solarized sawdust (107.69), while the lowest in non-solarized sawdust (90.96), solarized soil (90.91), non-solarized soil (88.25), solarized sawdust with sticky traps (85.44) and lastly solarized soil with sticky traps (82.54). Citrus seedlings with sawdust media were observed to be nitrogen deficient (Mean ranks 118.43 - 141.63). Solarized soil with sticky traps had the least number of Citrus seedlings with leaf miner symptoms (Mean rank = 12.50). Therefore, solarized soil with sticky traps was the most suitable treatment for the control of soil-borne pathogens. Treatments with sawdust media effectively stopped weed growth while those with solarized soil media reduced their growth. Integration of sticky traps was very pivotal in the management of whiteflies and other honey dew secreting insects. We recommend a similar study under field conditions.

Experimental investigation on the effect of soil solarization incorporating black, silver, and transparent polythene, and straw as mulch, on the microbial population and weed growth

Soil solarization is a non-chemical method for eliminating crop-threatening weeds and selectively decontaminating soil. The effect of various soil solarization with black, silver, transparent polythene sheet and straw as mulching on the microbial count and weed growth was studied experimentally. The farm investigation comprised six soil solarization treatments: mulching with black, silver, and transparent polyethylene sheets of 25 μm (μ), organic mulch (soybean Straw), weed-free, and control. All six treatments were repeated in four sets in a Randomized Block Design (RBD) plot size of 5.4 m × 4.8 m. Black, silver, and transparent polythene mulches significantly reduced fungal count compared to non-solarized soil. Straw mulch significantly increased soil fungal count. Solarized treatments had much lower bacterial populations than straw mulch, weed-free, and control treatments. Black, silver, straw mulch, and transparent polythene had 18746, 22763, 23999, and 3048 weeds ha−1 at 45 days after transplanting (DAT). The analysis of dry weed weight demonstrated a significantly low weed dry weight of 0.44 t/ha for black polythene (T1) based soil solarization, representing an 86.66% reduction in dry weed biomass. Soil solarization had the lowest weed index (WI), with black polythene mulch (T1) reducing weed competition. Among various soil solarization treatments, black polythene (T1) showed the highest weed control efficiency of 85.84%, indicating its suitability for use in weed control. The results suggest that soil solarization is effective for soil disinfestation and weed control with polyethene mulch and summer heat in central India.

Yield Response and Antioxidant Activity of Greenhouse Organic Pumpkin (Cucurbita moschata Duch.) as Affected by Soil Solarization and Biofumigation

In intensive cropping systems, soil fumigation, i.e., the use of gas chemical pesticides applied to the soil covered with impermeable plastic film, represents an effective method to control most of the soilborne pests. However, its general non-selectivity to the useful soil microflora and microfauna together with their significant environmental problems has limited their use. Numerous studies have concerned the application of less impactful but, at the same time, equally effective disinfection methods. These are techniques with a low environmental impact that are particularly suitable for horticultural systems. Among these, both soil solarization and biofumigation are popular techniques, even in organic vegetable cropping systems. This paper reports the results of a study to evaluate the effects of soil solarization on the yield response and the antioxidant levels of organic pumpkin (Cucurbita moscata Duch.). Solarization was carried out alone and with the addition of some organic matrices, such as compost, manure and green manure species. The evaluation of the antioxidant activity was carried out with DPPH (1,1-diphenyl-2-picrylhydrazyl radical) assay: DPPH has a specific absorption band, which disappears in presence of an antiradical compound, showing its antioxidant capacity. Our results revealed that the pumpkins grown in solarized soil had IC50, i.e., the concentration of sample which reduced the initial DPPH of 50%, values ranging between 0.6 to 18.0 mg mL−1, lower than the values of IC50 of pumpkins grown in non-solarized soil, which ranged from 36.0 to 43.6 mg mL−1. The obtained results highlighted the validity and utility of solarization for the organic vegetable crops. Furthermore, this technique has also shown its effectiveness in the long term since yield increases concerned several crops in succession. Finally, our results highlighted that heat treatment solarization can influence the level of several compounds in the pumpkin, and, therefore, also of the polysaccharides.

Effect of soil solarization on tomato (Solanum lycopersicum L.) growth and impact on native microbial diversity of farm soil in Nigeria

BackgroundTomato plant leaves can be wilted by the presence of various species of soil-residing bacteria, especially Ralstonia solanacearum. Soil solarization has proven to be an environment-friendly method for disease management in various crops. Therefore, this study aimed to evaluate solarization as an effective and non-chemical way to control R. solanacearum population in farm soil cultivated with tomato plants. The tomato variety UC 82 was raised on a nursery bedding for 3 weeks, after which four solarization-based treatments were applied to the field plots where tomato plants were cultivated subsequently. Agronomic, pathological, and soil temperature data were recorded from the soil samples, while isolation, Gram staining, morphological, biochemical, and physicochemical analyses were carried out on the same soil samples.ResultsThe bacterial species identified from the pre-experiment soil included Enterobacter cloacae, Serratia marcescens, and Proteus mirabilis, while for the post-experiment were Citrobacter freundii, Klebsiella pneumoniae, P. mirabilis, Salmonella sp., and Citrobacter diversus. Occurrences of bacteria and fungi populations in solarized soils were R. solanacearum, Aspergillus niger, Aspergillus flavus, Penicillium, Rhizopus spp., Actinomycetes, and yeast.ConclusionsThe results obtained showed that solarization reduced the native soil microbial populations since the solarized soils had a lower occurrence of bacteria and fungi than the non-solarized soils. Thus, the present study suggests that solarization is effective in reducing the pathogenic bacteria population on farm soils.

The effects of soil solarization and application of a Trichoderma biocontrol agent on soil fungal and prokaryotic communities

AbstractSoil solarization and biological control are two management strategies that have been used globally to manage soil‐borne plant pathogens. However, the broader effects of these strategies on soil microbial communities have not been well described. Soil prokaryotic and fungal communities were investigated by environmental DNA amplicon sequencing as part of field trials conducted in San Rafael, CA, and in Corvallis, OR. We examined microbial community changes following soil solarization, amendment with the biocontrol agent Trichoderma asperellum (TA), or solarization followed by application of the biocontrol agent. Soil solarization caused significant changes to prokaryotic and fungal communities by reducing species richness and diversity. Soil water potential was determined to be a significant factor affecting the prokaryotic community. Application of TA to solarized or nonsolarized soil did not significantly alter the microbial communities. However, solarization resulted in diminished microbial densities that appeared to enhance subsequent establishment of the biocontrol agent. This study revealed how specific environmental variables of heat intensity and soil moisture contribute to changes in the abundance of individual taxa and taxonomic groups.

WEED CONTROL BY SOLARIZATION AND MULCHING IN COWPEA DEVELOPMENT

Weeds are a serious threat to agriculture because they compete with crops, thereby interfering in production. As such, this study aimed to assess weed control using soil solarization and mulching on the growth and yield of cowpea. A completely randomized design was used, with eight treatments and four repetitions. The treatments consisted of a combination of two management practices, namely soil solarization (with and without) and three mulches (castor bean, rattlepod and spontaneous vegetation), as well as no mulching. Non-solarized soil and without mulch increased the number and dry weight of weeds, while the main stem length of the cowpea plants decreased. Mulching increased the pod length and number of seeds per pod regardless of solarization, as well as shoot dry weight and moisture content. By contrast, root dry weight increased in the absence of mulching, particularly in non-solarized soil. Soil solarization reduces weed infestation in cowpea crops, especially when associated with mulching.

Weed infestation and growth of cowpea in soil managed with solarization and mulching

The growth and production of agricultural crops are greatly hampered by weed interference. The objective of this study was to evaluate weed infestation and growth and dry mass of cowpea cultivated in soil with solarization and mulching. The research was carried in the Agricultural Sciences Center of the Federal University of Alagoas, Rio Largo, AL. A completely randomized experimental design was used, with eight treatments and four replications. The treatments consisted of the combination of soil with and without solarization together with different mulching, such as T1: Os tratamentos consistiram da combinação de solo com e sem solarização junto a diferentes coberturas mortas, como sendo T1: solarized soil with mulching of castor bean, T2: solarized soil with mulching of rattlepod, T3: solarized soil with mulching of spontaneous vegetation, T4: solarized soil without mulching, T5: non-solarised soil with mulching of castor bean, T6: non-solarised soil with mulching of rattlepod, T7: non-solarised soil with mulching of spontaneous vegetation and T8: non-solarised soil and without mulching. The number of weeds was higher in treatments without mulching, independent of solarization, T4 and T8. Already, the growth of the plants and the number of bean leaves were higher in the solarized soil with mulching of castor bean, T1, and lower in the non-solarized soil and without mulching, T8, in contrary to the dry mass of the root. Solarization with solar collector when associated with mulching inhibits the infestation of weeds in cowpea, while its growth is benefited by solarization + mulching, by mulching without solarization, as well as the solarization without mulching.

Rhizobium improves nutritive suitability and tolerance of Phaseolus vulgaris to Colletotrichum lindemuthianum by boosting organic nitrogen content

Symbiotic nitrogen fixing Rhizobium species have been reported to trigger induced resistance reactions that are inhibitive to aboveground antagonists. We tested the hypothesis that root infection by nitrogen-fixing Rhizobium triggers enzyme-mediated induced resistance reactions, which lead to the production of defensive compounds that suppress aboveground colonization by foliar pests. An experiment was conducted using common bean Phaseolus vulgaris, comprising of factorial treatments of Rhizobium inoculation (with or without), C. lindemuthianum (with or without) and soil type (solarized and non-solarized). Anthracnose disease incidence was higher in plants under dual inoculation with C. lindemuthianum and Rhizobium than in plants inoculated with C. lindemuthianum alone (p < 0.05). Concentrations of N-based compounds in the form of total protein and the enzymes, peroxidase, ascorbate peroxidase and lipid peroxidase were higher in rhizobial plants, while that of catalase enzyme and the C-based compounds namely flavonoids, tannins and phenols were lower. Plant size and growth duration were not different between the treatments (p > 0.05). Soil pH, organic carbon and the concentration of nutrients (N, P, Na, Ca, Mg, Zn, Cu) in solarized soil were higher than in non-solarized soil, while Fe and K were lower. There was no evidence to support induced resistance since anthracnose disease was high in Rhizobium inoculated plants. High disease incidence without reduction in plant growth can be interpreted as host plant tolerance. In conclusion, Rhizobium infection of common bean enhances the production of N-based nutritive compounds, while limiting the production of C-based organic compounds associated with plant resistance, thereby promoting host plant suitability to C. lindemuthianum, and possibly enhancing host plant tolerance to the pathogen.

Rhizosphere stochiometry, fruit yield, quality attributes and growth response to PGPR transplant amendments in strawberry (Fragaria × ananassa Duch.) growing on solarized soils

Plant Growth Promoting Rhizosphere microorganisms transplant amedements were tested for improving growth, yield, quality traits, runner production and rhizosphere stochiometry of strawberry cv. Chandler. The plants were grown on solarized and non-solarized organic matter rich soil. Exogenous root inoculation of six PGPR inoculants viz., Pseudomonas florescence, Bacillus subtilis, Azotobacter chroococcum, K-mobilizing bacteria and AM fungi were carried out in different combinations in a randomized completely block design with three replicates. The solarization was done with transparent plastic sheet. Application of 250 g PGPRs consourtium along with soil solarization significantly improved vegetative growth traits, rhizosphere microbial count, fruit number, cumulative yield, fruit quality traits as compared to non-solarized (natural) conditions. Root soil ratio of resident microbes at 15 cm depth was also worked out in the rhizosphere zone and non-rhizosphere zone. The data suggested an increased rhizosphere acid- and alkaline phosphate and dehydrogenase enzyme activity can be used as a good indicator of phosphorus nutrition in solarized organic soils compared to non-solarized (natural) soils. The results suggested that PGPR inoculations could alleviate the deleterious effects of soil borne microbial population on the phenological and pomological attributes of strawberry plants under organic growing solarized soils. Root inoculation with PGPR probiotics significantly affected leaf nutrient concentration in terms of DOP and ΣDOP indexes which showed an increase in N, P, K and Mg concentration in the leaves in solarized plots compared to natural plots. Principal component analysis induced the differences at various PGPR probiotics applied has identified maximum of the total variance based on the Eigen value (>1) and explained 65.38% (PC1), 79.68% (PC2), 88.05% (PC3) and 92.67% (PC4) of the cumulative variance. PC4 accounted for highest total cumulative variances among fruit phenological, morphometric and generative potential strawberry traits. The study indicated PGPR probiotics coupled with soil solarization as a promising technology to maintain healthy rhizosphere, and as an alternative to chemicalised farming of strawberry to enhance quality production in calcareous soils of Shiwalik foothills of north-west Himalayas.

Efficacy of soil solarization on black root rot disease and speculation on its leverage on nematodes and weeds of strawberry in Egypt

BackgroundStrawberry (Fragaria ananassa Duch.) is an economically important crop in Egypt. Yet complex black root rot disease of strawberry caused by Fusarium solani, Rhizoctonia solani, and Pythium sp. can cause considerable yield losses. Therefore, this study aimed at evaluating different aspects of soil solarization against this disease. Such an evaluation would better be viewed in the context of other beneficial effects of soil solarization on nematodes and weeds.Materials/methodsGrowth agar disks, growth suspension, and resting stages of strawberry black root rot fungi were evaluated at different temperatures and exposure times using digital hot water bath. Cloth bags artificially infested with single fungal species were buried into the soil before soil solarization at soil depths of 1–10, 11–20, and 21–30 cm at three spots of each plot for each of the abovementioned fungi for 3, 6, or 9 weeks. The disease incidence and severity in solarized and un-solarized soil was compared with the application of the fungicide Actamyl. Effects of soil solarization on nematodes and weeds were also consulted.ResultsThe lethal temperature to F. solani, Pythium sp., and R. solani was 58, 58, and 56 °C, respectively when exposure time was 1 min. Chlamydospores were killed at 62 °C while sclerotia were killed at 58 °C in hot water for 1 min. Maximum soil temperature in solarized soil was raised by 15, 14, and 12 °C at depths of 1–10, 11–20, and 21–30 cm as compared with non-solarized soil. Solarization for 3, 6, and 9 weeks significantly reduced the disease incidence and severity and increased the strawberry yield. Complete reduction in total count of all tested fungi was obtained after 9 weeks at all tested depths. A review of collective soil pest and pathogen control via solarization documented its beneficial application.ConclusionThe study may exploit hot months in Egypt for soil solarization against the serious root rot disease either singly or in an integrated pest management program.

Soil Solarization and Calcium Cyanamide Affect Plant Vigor, Yield, Nutritional Traits, and Nutraceutical Compounds of Strawberry Grown in a Protected Cultivation System

Soil solarization is a hydrothermal procedure of disinfesting soil of soilborne diseases and pests. Solarization can be combined with many other chemical or non-chemical alternatives to afford integrated pest and diseases management or improve plant yield. Calcium cyanamide (CaCN2) is a fertilizer used in agriculture sector and is also effective in suppressing soilborne pathogens. The present study assessed the influences of different pre-plant CaCN2 dosages on strawberry grown on solarized or non-solarized soil. Soil solarization and 500 kg ha−1 CaCN2 significantly increased early marketable yield by 105.3%, total marketable yield by 53.0% and firmness by 3.0%, respectively compared with the control (no solarization × 0 kg ha−1 of CaCN2). Exposing solarized plots to CaCN2 at 1000 kg ha−1 significantly increased fruit ascorbic acid content by 77.5% and phenolic content by 13.3% compared with fruits from control plants. Overall, plants grown on solarized soil performed better than those cultivated on no-solarized plots. Plants grown on soil treated with a dosage of 500 or 1000 kg ha−1 CaCN2 increased plant height, number of shoots plant−1, number of leaves plant−1, root collar diameter, plant visual quality, anthocyanins, and antioxidant capacity compared to control plants. Fruits from plants grown on soil exposed to CaCN2 with a dosage of 500 and 1000 kg ha−1 showed a lower N fruit content (5.4 and 19.5%, respectively) than control plants (non-treated control).

Solarization-based pesticide degradation results in decreased activity and biomass of the soil microbial community

Pesticides are chemical compounds, mostly synthetic, which are used widely in agricultural fields to prevent and to control pests and soil-borne diseases. The synthetic nature of these compounds makes some of them non-biodegradable and they may accumulate in harmful concentrations in soils. Solarization seems to be a non-chemical strategy that could enhance pesticide degradation in soils. Here, we evaluate the combined impact of pesticides and solarization on the microbial community of a Mediterranean soil. For this purpose, enzyme activities, basal respiration, and the biomass and composition of the microbial community (through analysis of phospholipid fatty acids, PLFAs) were evaluated in solarized and non-solarized soils, in a 90-day greenhouse experiment with a combination of different pesticides. The degradation of the pesticides in the solarized soils was 30% greater than in non-solarized samples. However, solarization also affected the soil microbial community. The soil respiration was lowest in solarized samples without pesticides, while the enzyme activities were greater in non-solarized samples (with and without pesticides). Both the bacterial and fungal PLFA contents declined in solarized samples. The G+/G− ratio was highest in the solarized samples without pesticides and in the non-solarized samples with pesticides. Considering such impacts on the soil microbial community and the relationship of soil microbes with soil ecosystem services, the utilization of solarization must be carefully considered when adopting strategies for pesticide degradation in Mediterranean soils.

Soil management and mulching for weed control in cowpea

ABSTRACT More efficient weed control managements can be achieved through different strategies, given that the population of these plants changes according to the system used. This study aimed at assessing solarization methods associated with different mulches for weed control in the cowpea crop. The methods used were soil solarization, with plastic sheeting and with solar collector, associated with the following mulches: castor bean, rattlepod and spontaneous vegetation. Weed phytosociology was calculated by frequency, density and abundance. The most infesting families were Asteraceae, Poaceae and Amaranthaceae. The species with the highest frequency, density and abundance in the treatments without mulching was Cyperus rotundus, while Bidens spp. occurred only in non-solarized soil and without mulching. The largest number of weeds was found in the treatments without mulching in non-solarized soil or soil solarized with plastic sheeting, the latter being less efficient than the solar collector. Mulching inhibits the weed infestation in cowpea crops, irrespective of soil solarization. However, rattlepod as mulch is more efficient in the solarization with plastic sheeting than with a solar collector.

Long and short term effects of solarization on soil microbiome and agricultural production

Soil solarization, a method of chemical-free pest treatment, is a practical and cost-effective way to treat organic farming soil. This method uses polyethylene sheets to capture solar irradiation that heats the soil. Together with heat generated during composting of fresh organic matter, this method can effectively treat many soil-borne pathogens. In this study we examined the effects of solarization with the addition of compost at three maturation levels, on soil microbial community structure and function along with plant performance. Similar hydrolytic activity among the treatments (as measured by FDA hydrolysis) was measured in the first year of solarization. High level of activity was obtained in soil amended with immature compost at the beginning of the second year, suggesting residual (carry-over) effects of previous-year treatments. Amplicon sequencing of 16S rRNA encoding genes was used to study soil bacterial community structure. Diversity and richness of bacterial communities were found to be negatively affected by solarization in all treatments. Interestingly, bacterial communities of solarized soils clustered together, regardless of compost amended and type, separated from the cluster of communities from non-solarized soils of all amendments. Specifically, long and short terms negative effects of solarization on the relative abundance of Alphaproteobacteria, Acidobacteria and Actinobacteria were noticed. In contrast, solarization positively affected Bacilli and Gammaproteobacteria abundance in both long and short term. Furthermore, solarization had long and short term positive effects on productivity of eggplant and wheat plants. This study is the first to describe in high details the combined effects of solarization and amendment of composts of different maturation levels.

The Effects of Soil Solarization and Compost on Soil Suppressiveness against Fusarium Oxysporum f. sp. Melonis

ABSTRACTSoil suppressiveness against Fusarium was tested using solarized and non-solarized soils combined with composts of three maturation levels, and a non-amended control. The soils were sampled on three dates: after previous year solarization but before current year solarization (0 weeks), at the end of the solarization period of the current year (4 weeks), and 4 weeks later (recovery time). Melon seedlings were inoculated with Fusarium spores and disease severity was assessed. The study showed a reduction of soil suppressiveness capacity against Fusarium oxysporum f. sp. melonis after 1 year of solarization (0 weeks). Fusarium disease severity in artificially inoculated melon plants, expressed by area under the disease progress curve, was higher in solarized soil than in non-solarized soil. Compost addition lowered the disease severity, both in the solarized and in the non-solarized soils. However, suppression was not obtained at the end of the solarization period, whereas compost beneficial effect was found at this time.

Impact of soil solarization on the ciliate community structure of a greenhouse soil

Soil solarization is an ecologically friendly method of controlling various plant pathogens and pests, but also affects non-pathogenic members of the soil biota. Here, we studied the impact of soil solarization on the community structure of soil ciliates using a culture-independent molecular approach, namely denaturing gradient gel electrophoresis (DGGE) of targeted 18S rRNA gene fragments. Greenhouse soil with added organic fertilizers was solarized for 33 days at an average temperature of 47–48°C. Solarization caused a drastic change in the ciliate community. The variation between replicates was large, which suggested that the distribution of ciliates was spatially heterogeneous in the soil, probably due to their decreased numbers. In contrast, non-solarized soil had a stable and homogeneous ciliate community during the experimental period. In solarized soil, most of the original ciliate community recovered 76 days after solarization. Sequence analysis of DGGE fragments indicated that both r-selected and K-selected species of ciliates were affected by solarization but recovered with time after solarization. Our results demonstrated both the vulnerability and resilience of the ciliate community to soil solarization and also the utility of using molecular-based analysis of ciliate communities as bioindicators of soil stress caused by solarization.

Long term effect of soil solarization on soil properties and cauliflower vigor

The effect of soil solarization on physical, chemical and biological properties of soil was studied, along with the response of cauliflower seedlings following solarization. Nursery beds were covered with transparent polyethylene sheet and soil temperature and moisture were recorded. Soil samples were collected five times for analysis. Three cauliflower nurseries were raised at 30-day intervals; germination was recorded 10 days after sowing and seedling length 30 days after sowing. The maximum temperature in solarized soil ranged from 40.2–47.2°C, with an increase of 5.2° to 9.9°C over non-solarized soil. There was a conservation of 5.48% moisture in solarized soil as compared with non-solarized. Solarization significantly increased electrical conductivity, organic carbon, nitrogen and potassium over pre-solarized soil. The mean pH, EC, Ca, Mg, N, P, K and C recorded in solarized soil was higher than in non-solarized. Soil solarization reduced the population of fungi from 25.68 x 104 to 4.8 x 104, bacteria from 20.28 x 106 to 5.66 x 106, actinomycetes from 31.60 x 105 to 4.40 x 105, and reduction in population was recorded even after 90 days, when compared with non-solarized soil. Solarization effectively reduced (>97%) population of plant parasitic and free living nematodes. Cauliflower seedlings in solarized soil had a better vigor index than non-solarized soil. Present findings reveal that soil solarization could be exploited for nutrient management and soilborne pests control, with a better vigor index of vegetable nursery.

Soil Solarization and Biological Control for Managing Mesocriconema xenoplax and Short Life in a Newly Established Peach Orchard.

The effects of soil solarization, with and without a Pseudomonas spp. cocktail or wheat rotation as alternatives to chemical control of Mesocriconema xenoplax, were investigated from 2004 to 2011. Preplant solarization and soil fumigation (67% methyl bromide + 33% chloropicrin mixture; henceforth, referred to as MBr) was initiated in 2004 in an orchard infested with M. xenoplax and a history of peach tree short life (PTSL). Plots consisted of nine treatments: (i) nonsolarized soil-alone, (ii) nonsolarized soil with bacteria cocktail (nonsolar-bacteria), (iii) nonsolarized soil with wheat (nonsolar-wheat), (iv) nonsolarized soil with bacteria cocktail and wheat (nonsolar-bacteria-wheat), (v) solarized soil-alone, (vi) solarized soil with bacteria cocktail solar-bacteria), (vii) solarized soil with wheat (solar-wheat), (viii) solarized soil with bacteria cocktail and wheat (solar-bacteria-wheat), and (ix) preplant MBr fumigation. Peach trees were planted into all plots in 2005. Nematode populations were suppressed 20 months longer after orchard establishment in solar-alone and solar-wheat plots than solar-bacteria and solar-bacteria-wheat plots. Pseudomonas spp. cocktails did not have a pronounced effect in suppressing M. xenoplax in this study. Fumigation effect on M. xenoplax population density dissipated 24 months after application. Solar-wheat-treated soil was as effective as preplant MBr fumigation in increasing tree survival from PTSL for at least 6 years after orchard establishment.

Soil solarization enhances growth and yield in dry beans

Dry beans are one of the most important crops in Mexico. However, in the last decade this crop averaged yields as low as 0.7 tons per hectare. Therefore, the purpose of this study was to test if soil solarization is a suitable pre-planting soil treatment to improve growth, nutrition and yield of beans in northeast Mexico. Five different periods of soil solarization were evaluated during the spring of 2008: 0, 30, 40, 50 and 60 days of soil solarization. Soil temperatures were recorded during soil solarization to estimate total heat units. After soil solarization bean seeds were sown in plastic-mulched rows and leaf area, potassium, calcium and magnesium concentration and yield were measured. Leaf area and concentrations of potassium, calcium and magnesium were increased by all treatments of soil solarization when compared with the non-solarized soil. Sixty days of soil solarization produced yields of 3.7 tons per hectare while no solarization produced yields of 2.1 tons per hectare. Soil heat units were positively correlated with yield, suggesting that the increase in yield is due to an increase in heat accumulation during soil solarization in addition to an increase of leaf area and to an enhancement of plant nutrition.