EFFECTS OF SOIL SOLARIZATION ON FUNGAL AND BACTERIAL POPULATIONS ASSOCIATED WITH AMARANTHIS VIRIDIS L. (AFRICAN SPINACH) IN LAGOS, NIGERIA

Soil solarization is increasingly used to control soil-borne pathogens because it is environment-friendly. However, performance varied geographically, necessitating experimental trials before its introduction. This study assessed the effects of solarization on soil-borne bacteria and fungi, growth, and proximate composition of Amaranthus viridis (African spinach) in Lagos, Nigeria. Two raised beds were solarized for six weeks with a transparent and black polyethylene sheet, and a non-solarized (control) bed was equally made. The vegetable seeds were planted and their growths were recorded for four weeks. Soil samples at 15-20cm deep and leaves were obtained for microbiological and proximate analysis, respectively. The mean temperature of transparent xxpolyethylene’s soil was 45.33 oC, black polyethylene (35 oC), and non-solarized (33.50 oC). The mean height and width of transparent polyethylene’s A. viridis were 24 and 3cm, black polyethylene (19 and 2.2 cm), and non-solarized (17 and 1.6cm). The transparent polyethylene’s soil had 3100 and 250 cfu/g bacterial and fungal colonies, black polyethylene (3200 and 1900 cfu/g), and non-solarized (37000 and 1900 cfu/g), respectively. The proximate contents of the transparent polyethylene’s A. viridis were (70 moisture, 10 ash, 4.24 protein, 1.45 fat and 9.94 % fibre), black polyethylene (73.35 moisture, 8.36 ash, 3.1% protein, 1.23 fat, and 6.77 % fibre), and non-solarized (76.09 moisture, 5.91 protein, 3.15 ash, 1.31 fat and 6.75 % fibre). Overall, statistical differences (p ≤ 0.05) existed between the solarized and non-solarized and between transparent and black polyethylene (transparent>black>non-solarized). Thus, solarization could be an effective strategy for controlling soil-borne bacteria and fungi of A. viridis in the area studied.

Evaluation of Organic Weed Management Practices on Growth, Yield and Weed Control Efficiency in Soybean-chickpea Sequence under Irrigated Condition

Background: Weeds are widely reported as a key constraint in organic agriculture. Soybean-chickpea is important cropping sequence adopted in Maharashtra State under irrigated condition. Weed management is a serious problem in both the crop and it mostly controlled through chemical weed control. Today, widespread use of herbicides has resulted in purporated environmental and health problem as well as residual problems to succeeding crops. Now a days residue free food requirement is high. In organic farming cultural and mechanical methods are necessary to break the weed cycle. So, keeping this point in view present investigation was carried out to evaluate organic weed management practices on growth, yield and weed control in soybean-chickpea sequence under irrigated condition. Methods: A field experiment was conducted during Kharif and rabi seasons of 2017-18 and 2018-19. The present investigation consisted of ten weed management practices viz. two hand weeding at 20-25 and 45-50 DAS, one hoeing 20-25 DAS + one hand weeding at 45-50 DAS, soybean + sunhemp incorporation after 35-40 DAS in kharif season and chickpea + safflower (2:1) in rabi season, stale seed bed + reduced spacing + 2 tonne of wheat straw + one hand weeding at 25 DAS, soil mulch at the time of sowing + one hand pulling at 25 DAS, incorporation of neem cake 1.5 tonne/ ha 15 days before sowing + one hand weeding at 25 DAS, soil solarization with 25 μ polythene mulch during summer + one hand weeding at 25 DAS, mulching with straw, weed free and weedy check. Result: The higher values of growth attributes was recorded by weed free treatment which was on par with two hand weeding at 20-25 and 45-50 DAS and soil solarization with 25 μ polythene mulch during summer + one hand weeding at 25 DAS and significantly superior over rest of the treatments during both the year study. Application of stale seed bed with reduced spacing and 2 tonne of wheat straw along with one hand weeding 25 DAS recorded higher soybean equivalent yield followed by soybean + sunhemp incorporation (35-45DAS) in kharif and chickpea + safflower (2:1) in rabi season during both the year. The lower weed density, dry weight and highest weed control efficiency at 40 days after sowing for both monocot and dicot weeds was recorded by weed free treatment followed by soil solarization with 25 μ polythene mulch during summer + one hand weeding at 25 DAS in soybean and chickpea during both the year.

Use of non-chemical methods for the management of southern blight disease of carrot incited by Sclerotium rolfsii

This experiment was conducted to assess the effect of Trichoderma harzianum, soil solarization, and biofumigant on southern blight dis-ease of carrot incited by Sclerotium rolfsii isolate CS 5. A series of in-vitro and in-vivo trials laid out to select a virulent isolate of S. rolfsii against the carrot variety New Kuroda and evaluated the mustard, cabbage, cauliflower, and broccoli leaf extracts for choosing an effec-tive biofumigant against test pathogen. Mustard was the most effec-tive in inhibiting the radial growth, and sclerotia formation (80.37 and 83.37%) of S. rolfsii (isolate CS 5) at 40% level of concentration followed by cabbage leaf extract (62.22 and 68.69%). On the contrary, a total of 10 isolates of T. harzianum were screened against the test pathogen on Potato Dextrose Agar (PDA) medium for choosing a dominant isolate of T. harzianum. The isolate Th-6 was found as the most active in inhibiting the radial growth (84.44%) of S. rolfsii fol-lowed by Th-1 (75.56%). In the application of T. harzianum, biofumi-gation, and soil solarization, the treatment appeared to be the most superior in reducing pre- and post-emergence mortality of carrot during secondary field trials. The lowest southern blight disease inci-dence (10.77%), and disease severity (12.78%) were found at the same treatment. Subsequently, the yield of carrot was increased 155.18% which might be due to the reduction of carrot disease as well as the addition of organic materials in the soil.

Soil Solarization to Eradicate Soilborne Phytophthora spp. in Container Nurseries with Surface Gravel1

To describe the effect of soil solarization in the presence of a gravel layer on the soil surface of container nurseries, we investigated belowground temperatures and soil water potential during solarization with different thicknesses of a surface gravel layer (2.5 cm, 7.5 cm, or no gravel) (1 in, 3 in, or no gravel) in relation to survival of soilborne Phytophthora spp. inoculum. In field trials conducted for 4 weeks with Phytophthora ramorum Werres and Phytophthora pini Leonian in San Rafael, California and with P. pini in Corvallis, Oregon, infested rhododendron leaf inoculum was placed on the surface, and at 5 cm (2 in) and 15 cm (6 in) below the surface. In solarized plots with thicker layers of gravel, inoculum buried in the soil layer was killed in shorter treatment periods by higher elevated temperatures. Inoculum at the surface and within the gravel layer was also killed, but showed greater tolerance to heat under the lower water potential conditions as compared to the soil layer. P. pini has a significantly longer survival in heat than P. ramorum, allowing it to serve as a conservative surrogate for P. ramorum in testing solarization outside the quarantine facility. This study demonstrates how presence of a gravel layer influences soil solarization effectiveness in reducing Phytophthora inoculum survival. Index words: Phytophthora ramorum, Phytophthora pini, soil disinfestation, disease management, soil temperature, soil water potential, ornamentals. Species used in this study: Phytophthora ramorum Werres, de Cock & Man in't Veld, Phytophthora pini Leonian.