Impacts of Organic and Conventional Management on the Nutritional Level of Vegetables

The nutrient concentration of fruits and vegetables in the U.S.A. has declined in the past 50–70 years. Crop management practices utilizing on-farm inputs are thought to increase crop nutritional quality, but few studies have evaluated this under long-term side-by-side trials. An experiment was conducted from 2004 to 2005 at Rodale Institute’s long-term Farming Systems Trial to investigate the nutritional quality of vegetables under organic manure (MNR) and conventional (CNV) farming systems, with or without arbuscular mycorrhizal fungi (AMF) treatment. AMF reduced the vitamin C content in carrots in both systems in 2004, but the reduction was 87% in CNV and 28% in MNR. AMF also reduced antioxidants in carrots in both CNV and MNR. This trend was likely due to the suppression of native AMF colonization by the non-native AMF inoculum used. Between 2004 and 2005, MNR increased the vitamin C in green peppers by 50% while CNV decreased the vitamin C in red peppers by 48%. Tomatoes under MNR had a 40% greater vitamin C content compared to CNV in 2005. The vegetable yield declined between 2004 and 2005, except for tomato, where the yield increased by 51% and 44% under CNV and MNR, respectively. In general, MNR tended to increase the nutrient concentration of vegetables compared with CNV, while the AMF effects were inconclusive

Comportamiento del ñame (Dioscorea spp.)

Eighteen yam (Dioscorea spp.) cultivars from five species were evaluated for yield and severity of mosaic, anthracnose, and black leafspot (Curvularia spp.). Plantings were established at Mayagüez and Isabela, Puerto Rico, in the 1985-86 and 1986-87 growing seasons. Severe mosaic was found on D. trifida (Mina), which was the lowest producing cultivar both seasons. Five cultivars of D. esculenta (Kombi, Seti, Doli, Muni, and Beti) showed moderately severe mosaic symptoms in 1985-86, and black leafspot symptoms in 1986-87. Among these cultivars, Doli produced the highest tuber yields, 21,000 kg/ha (9.4 tons/acre). Among D. alata cultivars, differences in anthracnose were related to genotype, location, and season. Leon Globe and Forastero were the most susceptible and lowest yielding cultivars. Gunung produced the highest yield, a maximum of about 40,000 kg/ha (17.9 tons/acre). It was least affected by anthracnose, with less than 15% defoliation in November. Tuber yields in D. alata cultivars were highly associated with anthracnose severity ratings (r = —0.81 * *) . Both seasons more anthracnose was found in Isabela than in Mayagüez. Anthracnose was more severe in 1986-87 than 1985-86.Se evaluaron 18 cultivares de cinco especies de ñame (Dioscorea spp.) por su rendimiento y resistencia a mosaico, candelilla y la mancha negra en el campo durante 2 años consecutivos en Mayagüez e Isabela, Puerto Rico. La cultivar Mina de la especie D. trifida mostró síntomas severos de mosaico por lo cual arrojó una baja producción. Se evaluaron cinco variedades de ñame de papa, D. esculenta; todos mostraron síntomas de mosaico y ataques por la mancha negra de la hoja causada por Curvularia spp. La cultivar Doli sobresalió por su alta producción. En D. alata hubo gran variación en la severidad de la candelilla (antracnosis) causada por Colletotrichum gloeosporioides Penz. En los dos años hubo brotes de la candelilla más severos en Isabela que en Mayagüez. Leon Globe y Forastero fueron las cultivares más susceptibles a la candelilla. Gemelos fue severamente atacado por candelilla en Isabela en 1985-86 y moderadamente en 1986-87. Esta misma variedad resistió la candelilla en Mayagüez en 1986-87. Estas variaciones en reacción sugieren la existencia de distintas razas patológicas de Colletotrichum gloeosporioides en ñames en Puerto Rico o un gran efecto del lugar en la reacción de atracnosis

Título en español.

Both Meloidogyne incognita and Pratylenchus zeae, acting separately, reduced significantly the height of the primary shoots, fresh and dry weight of shoots and leaves, and fresh weight of roots of sugarcane cultivar PR 980. The combined action of both nematode species also caused a significant reduction of the height of the primary shoots, weight of shoots and dry weight of leaves, but the reduction was less than that produced in plants inoculated with only one species alone. Also, when both species of nematodes were present simultaneously, the number of internodes was significantly reduced, as compared to the control, but there was no difference in the reduction caused by both species when they were applied together or each one alone. Pythium graminicola reduced significantly the height of primary shoots. The combination of each nematode species with the fungus produced a highly significant reduction of the height of the primary shoots. The reduction was lower than that produced by each nematode species acting separately, but higher than that induced by the fungus alone. No significant reduction was caused by the three microorganisms acting in combination. The data suggested a possible acute antagonism among the two nematode species and the fungus. It also indicated that M. incognita, P. zeae and P. graminicola are pathogenic to sugarcane.Resumen en español

Título en español

Preplant fungicide baths were tested on yam (Dioscorea rotundata Poir cv. Habanero) seed pieces (114-g sections) from sound tubers to determine their effect on emergence and yield of yams. Field plots were free of damaging populations of parasitic nematodes and had not been previously planted with yams. Yam seed pieces treated with captan or captan plus thiabendazole or captan plus benomyl increased field emergence (95, 96 and 91%, respectively) over that of nontreated controls (52%). Early emergence (5 weeks after planting) was greater for captan plus thiabendazole (24%) than for captan plus benomyl (1%), captan alone (2%), or the nontreated control (1%). Final stand counts (9 weeks after planting) were not statistically different among the fungicide treatments (91-96%). These counts were highly correlated with total tuber yield (r = 0.84**), total number of harvested tubers (r = 0.77**), and mean tuber weight (r = 0.74**). Plants from nontreated seed pieces produced a higher number of tubers per plant (1.64) compared with those from fungicide treated seed-pieces (1.16-1.20). Yield losses in nontreated seed pieces (48%) were related to losses in mean tuber weight (37%) and in total number of tubers (20%) per area when compared to the treated seed pieces. Greatest per plant and total yield and greatest tuber weight were found for the captan plus thiabendazole treatment, compared with captan alone or captan plus benomyl. Early and greater emergence of yam seed pieces appear to be important determinants of yield and tuber size in Habanero yams. In this experiment, even with good seed pieces and in a well-prepared seedbed, yam emergence and yield were diminished by one-half without fungicide treatment.Pedazos de 115 g de ñame Habanero (Dioscorea rotundata Poir) de alta calidad se trataron par una hora con fungicidas, 48 horas antes de sembrarlos para determinar el efecto sobre el brote y el rendimiento. Se escogió un predio experimental que no había estado sembrado de ñames previamente y estaba libre de nematodos parásitos del ñame. Se registró, 91 , 95 y 96% de brote en los pedazos tratados con captan + benomyl, captan, y captan + thiabendazole, respectivamente, comparado con 52% en los que no se trataron con fungicida (testigo). El brote temprano (5 semanas después de la siembra) fue mayor en los pedazos tratados con captan + thiabendazole (24%) que en los tratados con captan + benomyl (1%), con captan (2%) o el testigo (1%). A las 9 semanas, los tratamientos con fungicidas no fueron diferentes significativamente en el porcentaje de pedazos que brotaron (91-96%). Se determinaron correlaciones positivas entre el porcentaje de pedazos que brotaron y el rendimiento (r = 0.77**); el número total de tubérculos cosechados (r = 0.84**) y el peso medio de los tubérculos (r = 0.74**). El testigo produjo más tubérculos por planta (1.64) que los tratados con fungicidas (1.16-1.20). Las pérdidas en el rendimiento del testigo (48%) estuvieron asociadas con las pérdidas en el peso por tubérculo (37%) y con el total producido por área (20%). Se registró un mayor rendimiento tanto por planta como por área y por tubérculo en los que se trataron con captan + thiabendazole que con captan o captan + benomyl. Los factores que determinan la producción total y el tamaño de los tubérculos son el brote más temprano y el brote de un número mayor de pedazos. En este estudio aún cuando se seleccionaron tubérculos de alta calidad y se sembraron en condiciones óptimas, el brote y el rendimiento se redujo casi a la mitad cuando los pedazos no se trataron con un fungicida antes de sembrarlos