Non-fumigated Plots Research Articles

Tomato Production and Soil Pest Control in Relation to Width of Fumigated and Mulched Bed and Soil Fumigation Rate1

Abstract Polyethylene mulched bed widths (28, 56, 84 and 112 cm) with methyl bromide-chloropicrin gas mixture (67-33%, 280 kg/ha) soil fumigation were evaluated in 2 tests for soil pest control and production of tomato (Lycopersicon esculentum Mill.). In 2 other tests, methyl bromide-chloropicrin rates of 0, 70, 140, 210 and 280 kg/ha applied under a 112-cm wide mulched bed were evaluated. Populations of root-knot nematodes, parasitic soil fungi, and root-gall indices decreased with increases in mulched bed width. All fumigation rates resulted in decreased populations of root-knot larvae, Fusarium spp., Pythium spp., Rhizoctonia solani and root-gall indices compared with non-fumigated plots. In greenhouse tests, tomato seedlings emerged and survived best in potted soil from mulched plots with the widest bed and those treated with the highest rate of fumigant. Marketable tomato yields increased linearly with increased bed width in 1 test whereas yields were similar among treatments in the other tests.

Effects of Soil Fumigation, Rotation, and Nitrogen on Yield, Petiole NO3-N, and Verticillium Wilt of Potatoes1

Abstract The effects of soil fumigation with Telone C-17 on yield, petiole NO3-N levels and verticillium wilt (incited by Verticillium albo-atrum Reinke & Berth and V. dahliae Kleb.) of potatoes (Solanum tuberosum L.) grown continuously and in a 2-year rotation with corn since 1972 at 8 rates of nitrogen were studied in 1978 and 1979. Soil fumigation resulted in significant yield increases where potatoes were grown continuously. Potatoes grown in rotation responded to fumigation only in 1979. Continuous culture of potatoes resulted in reduced yields in both years. Nitrate-N levels were substantially lower in petioles from fumigated plots than in non-fumigated plots. Yield responses from fumigation and rotation were the result of reduced severity of verticillium wilt infestation. Soil fumigation and rotation had equal effects on yield and verticillium wilt, particularly in 1979.

Comparison of methyl bromide and herbicide effects on endomycorrhizal formation, seedling production, and weed control in sweetgum seedbeds

Sweetgum seedlings were grown in fumigated and nonfumigated nursery plots where equal portions were treated with a preemergence application of 1.1 kg/ha of trifluralin and a postemergence application of 1.7 kg/ha of napropamide. Methyl bromide at 478 kg/ha significantly decreased average root dry weight. Endomycorrhizal formation on one, two, and three month-old seedlings was not significantly decreased by fumigation or herbicide application. Weeding times for herbicide plots were less than half that for fumigated plots. These results show that herbicides can provide better control of annual weeds and produce better sweetgum seedlings than fumigating with methyl bromide.

Contribution of Mycorrhizae to P Nutrition of Crops Growing on an Oxisol1

AbstractMost plant species, including the major crops, form symbiotic mycorrhizal associations between their roots and certain fungi which influence nutrient uptake, especially P, from infertile soils. How well‐supplied the phosphate must be before mycorrhizae cease to enhance P uptake is not known; nor have the effects of mycorrhizae on external P requirements of crops been adequately determined in the field. This study examined the influence of mycorrhizae on the P requirements of crops in a tropical field environment on a Tropeptic Eutrustox. Plant growth and P uptake by non‐mycorrhizal and mycorrhizal plants (methyl bromide‐fumigated and nonfumigated soil) were measured at 10 levels of soil P using seven plant species. Brassica chinensis, which does not form symbiotic mycorrhizal associations, consistently grew better and took up more P from the fumigated than from the non‐fumigated soil. All other species growing in nonfumigated plots formed associations with mycorrhizae. In general, plants growing on fumigated soil did not become infected with mycorrhizae. In P‐deficient situations, plant concentration of P was enhanced by the mycorrhizal associations. The levels of soil P at which fumigation ceased to make a difference in the P percentage in plants of the various species were as follows: Glycine max (L.) Merr. (0.1 µg P/ml), Vigna unguiculata L. (0.2 µg P/ml), Allium cepa L. (0.8 µg P/ml), Leucuenu leucocephala (1.6 µg P/ml), Stylosanthes hamata and Manihot esculenta (1.6 + µg P/ml). We suggest that this listing may be the order in which these species depend on mycorrhizae in P‐deficient soils. As a mean of six species growing on the two lowest soil P levels, P uptake by mycorrhizal plants was 25 times greater than by plants without mycorrhizal associations. Thus, some crops appear to be quite dependent upon a mycorrhizal association for P absorption from a soil of high sorption capacity.

P nutrition of cassava, including mycorrhizal effects on P, K, S, Zn and Ca uptake

The nutritional requirements of cassava are ill-defined. This paper deals with the P requirements of cassava and the effect of P on other nutrients both in the presence of VA mycorrhizae and in soils when VA mycorrhizae were eliminated by fumigation. Cassava was grown on field plots with ten levels of phosphorus (0.002-1.6 ppm P in solution) on two Oxisols in Hawaii. Six cultivars were compared at one location. At the other location the significance of vesicular-arbuscular (VA) mycorrhizae on the nutrition of cassava was investigated. There was a substantial increase in vegetative growth with increased P fertilization in the cultivar experiment; however, root yields were not greatly affected. Even at very low extractable soil P levels (Bray-1 P, 1 ppm) five out of the six cultivars did not respond to P fertilization. One cultivar, Ceiba, produced 42–48 t/ha of roots when P in solution was in the range 0.003-0.025 ppm. In the second experiment the role of VA mycorrhizae was studied by fumigating one half of each plot with methyl bromide which destroyed VA mycorrhizal fungi. Plants grown on the fumigated plots did not become infected with VA mycorrhizae during the first 80 days of the growing period. Cassava, cultivar Ceiba, was grown along with six other species. One of these was chinese cabbage which does not form mycorrhizal associations. Leaves from non-mycorrhizal cassava plants (fumigated plots) invariably contained less P on a percentage basis than leaves from mycorrhizal plants (non-fumigated plots). On the low P plot, leaf P decreased from 0.30 to 0.11% when VA mycorrhiza formation was precluded by fumigation. Likewise K and S concentrations in leaves decreased by 30% and Zn by 10%. There was no evidence that mycorrhizae promoted Ca uptake. These observations provide a basis for explaining why the P requirements of cassava in nutrient solution culture are very great, whereas cassava is generally unresponsive to P fertilization in the field.

The Response of Strawberry Yields to Soil Fumigation and Nitrogen Fertilization1

Abstract Strawberry (Fragana × ananassa Duch. cv. Surecrop) plots fumigated with Vorlex (a mixture of methyl isothiocyanate and dichloropropanes-dichloropropenes) averaged 1148 kg per ha more berries than nonfumigated plots. Granular urea applied to the soil before planting was as effective in increasing fruit yield as an application split before planting and in August of the first growing year. Yield increased as the amount of Ν applied increased, but was not influenced by Ν source.

Reflective Film Mulches, Millet Barriers, and Pesticides: Effects on Watermelon Mosaic Virus, Insects, Nematodes, Soil-borne Fungi, and Yield of Yellow Summer Squash1

Abstract Field studies were conducted in 1973 and 1974 to determine the effects of various reflective film mulches, vegetal barriers of millet (Pennisetum americanum (L.) K. Schum), and soil- and foliar-applied pesticides on yields and control of the watermelon virus complex (WMV), insects, nematodes, and soil-borne pathogens affecting yellow summer squash (Cucurbita pepo var melopepo L. Alefi, ‘Dixie’). All film mulches used (aluminum; white and blue plastic; brown paper) significantly reduced WMV in both fruits and plants. The millet barrier caused a significant reduction in WMV infected plants. In 1974, the systemic insecticide, carbofuran (Furadan) and/or sprays of mineral oil, significantly reduced WMV in non-mulched plots. Brown paper mulch significantly increased infestation of pickleworms, Diaphania nitidalis (Stoll) and all mulches significantly reduced infestations of serpentine leafminers, Liriomyza munda Frick. Leafminers were also controlled with carbofuran. Film mulches had no significant effect on populations of plant-parasitic nematodes and plant-pathogenic fungi. Both groups of pests were controlled with DD-MENCS (a mixture of 1,3-dichloropropene, 1,3-dichloropropane, methylisothiocyanate), but not with carbofuran or sodium azide. Film mulch increased squash yield 70 to 610% over the unmulched control. Plants in non-fumigated plots covered with aluminum and white plastic mulches produced significantly greater yields than plants in plots covered with blue plastic and brown paper mulches. Soil pesticides significantly increased yields over the non-fumigated control, and, averaged across main plots, DD-MENCS = DD-MENCS + carbofuran > carbofuran + sodium azide > sodium azide = nontreated check. The effects of film mulch were greatest in the non-fumigated check. Conversely, the effects of soil fumigation were negligible under film mulch and one could be substituted for the other.