• Authors:
    • Duc, T. T.
    • De Rouw, A.
    • Valentin, C.
    • Jouquet, P.
    • Orange, D.
    • Tureaux, T. H. des
    • Huon, S.
    • Hai, A. P. H.
  • Source: Geoderma
  • Volume: 177
  • Year: 2012
  • Summary: In Vietnam soil erosion is a major environmental problem with respect to soil fertility, water quality and downstream property damages and involves 40% of total land surface. Due to a continuous and persistent decrease of soil quality under annual crops, farmers gradually convert their fields to grazing lands and their crops to fodder cultures or tree plantations. Experimental 1-m(2) field plots with three replicates each were monitored for two years (2006-2007) to evaluate the impact of three different fodder treatments (Paspalum atratum, Panicum maximum and Stylosanthes guianensis) on runoff and soil detachment in a cultivated catchment of North Vietnam. These experiments were designed to monitor at local scale the protective effect of vegetation cover against splash and rain-impacted erosion. The lowest runoffs (ca. 3.0-4.4%), sediment yields (ca. 14-19 g m(-2) yr(-1)) and soil organic carbon losses (ca. 0.7 g C m(-2) a(-1)) were obtained for P. maximum that provided the best soil protection with respect to the two other treatments. These values were low as compared to cultivated crops (cassava and rainfed rice). Soil surface characteristics (mainly biological activity and crusting) did apparently not play a key role, most likely because each plant cover provided, with its own efficiency, protection against rainfall erosivity and rapid plant regrowth wiped out traces of flow detachment. The extent of soil detachment and sediment export, mainly controlled by cut and carry operations of fodder management, was reduced by increasing slope length from 1 to 5 m. The choice of dense fodders such as P. maximum appears to be, in terms of improved livelihood and environment sustainability, an interesting issue for uplands farmers. (C) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Gamba, F.
    • Cruz, G.
    • Scattolini, A.
    • Prieto, V.
  • Source: Agrociencia (Montevideo)
  • Volume: 16
  • Issue: 1
  • Year: 2012
  • Summary: Citrus canker, caused by Xanthomonas citri pv citri, affects all Citrus production regions worldwide with tropical or subtropical climate. This work studies the relationship between rain, temperature, susceptibility of lemon leaves, and the appearance of symptoms of canker The evolution of citrus canker symptoms during five months of vegetative growth in a lemon Lisbon type orchard with disease background were analyzed. The data used were generated in the assessment of three growth flushes in plots with six (Treatment I) and ten (Treatment II) copper oxide sprays respectively. Daily rainfall and temperature were registered every 20 minutes. The parameters of the logistic curve of disease progress were calculated. Shoot age at disease outbreak and maximum disease value were determined. Rain was assumed to initiate an infection event from which a model of hour-degree accumulation was applied to predict the date for new symptoms appearance. Under the conditions of local infection, only the rains over 10 mm produced symptoms at the predicted date according to the model used. It was demonstrated that tissue susceptibility became a secondary factor once the environmental conditions became favourable to dissemination and symptoms expression. The method used demonstrated to be an useful tool to predict the risk of new symptoms appearance and to plan monitoring of the disease.
  • Authors:
    • Wang, N. Y.
    • Mondal, S. N.
    • Sutton, B.
    • Jeyaprakash, A.
    • Palm, M. E.
    • Peres, N. A.
    • Dewdney, M. M.
    • Schubert, T. S.
    • Rascoe, J.
    • Picton, D. D.
  • Source: Plant Disease
  • Volume: 96
  • Issue: 8
  • Year: 2012
  • Summary: In March 2010, citrus black spot symptoms were observed on sweet orange trees in a grove near Immokalee, Florida, USA. Symptoms observed on fruit included hard spot, cracked spot and early virulent spot. Hard spot lesions were up to 5 mm, depressed with a chocolate margin and a necrotic, tan centre, often with black pycnidia (140-200 m) present. Cracked spot lesions were large (15 mm), dark brown, with diffuse margins and raised cracks. In some cases, hard spots formed in the centre of lesions. Early virulent spot lesions were small (up to 7 mm long), bright red, irregular, indented and often with many pycnidia. In addition, small (2-3 mm), elliptical, reddish brown leaf lesions with depressed tan centres were observed on some trees with symptomatic fruit. Chlorotic halos appeared as they aged. Most leaves had single lesions, occasionally up to 4 per leaf. The causal organism was identified as Guignardia citricarpa based on cultural, morphological and genetic (ITS) analyses. This is thought to be the first report of black spot in North America.
  • Authors:
    • Dabar, S.
    • Soni, S. N.
  • Source: Journal of Soils and Crops
  • Volume: 22
  • Issue: 1
  • Year: 2012
  • Summary: After the green revolution and the development stage of cotton production in India the acceptance of improved cotton production technology/practices was getting the prime attention for increasing their production and productivity. Cotton research schemes and several extension education programmes were introduced to offer the education and training to farmers in respect of adopting the viable and proven improved cotton production technology/practices for their practical utilization in order to increase the income. In this context study was conducted in Dhar district. Madhya Pradesh to know the technological adoption level of cotton growers and to find out the association between socio personal and economic attributes of cotton growers with level of adoption. The study was conducted in the year of 2008-09. The study revealed that in respect of overall technology adoption, maximum cotton growers 50.22% adopted high level of technology followed by 34.11% respondents who adopted medium level and 15.67% respondents adopted low level of improved cotton production technology on their farms. The high level of adoption were reported in various extent i.e. in case of irrigation management (60.00%) followed by insect control measure (58.00%), rhizobium culture (58.00%), seed treatment (55.00%), recommended dose of fertilizer (52.00%), method of sowing (47.00%), weed management (46.00%), pest control measure (41.00%) and improved variety of seed (35.00%) respectively. The Study also revealed postive nature of phenomena the relationship between socio personal and economic characteristics of cotton growers and adoption level of improved cotton production technology. The zero order correlation coefficient of characteristic of cotton growers depicted in respect of age was 0.470**, for caste 0.283**, for level of income 0.392**, for level of employment 0.468**, for social participation 0.289** and for size of family 0.431. These characteristics were found to positively significant with adoption level of cotton production technology at 0.01 level of probability respectively. On the other hand, the characteristics like size of land holding had the correlation coefficient value of 0.200*, for material possession 0.248*, for economic motivation 0.201*, for attitude towards improved practices 0.215* and for extension participation 0.247* and these values were found positively significant with adoption level of cotton production technology at 0.05 level of probability respectively.
  • Authors:
    • Ribeiro, L.
    • Mendes, M. P.
    • Silva, E.
    • Cerejeira, M. J.
  • Source: Environmental Science & Pollution Research
  • Volume: 19
  • Issue: 7
  • Year: 2012
  • Summary: Purpose: To assess groundwater exposure to pesticides, in agricultural areas of 'Ribatejo' region (Portugal), and the influence of some key factors in that exposure, field, laboratory and modelling studies were carried out. Methods: The study was performed in maize, potato, sugar beet, tomato and vegetables agricultural areas, located in a shallow aquifer, with pesticides use and, in most cases, with irrigation practices. Pesticides used in the studied agricultural areas and having leaching potential were selected, being considered also other pesticides included in priority lists, defined in Europe. Evaluation of groundwater exposure to pesticides was carried out by successively: (1) groundwater sampling in seven campaigns over the period 2004-2006; (2) pesticide analysis [including isolation and concentration from the groundwater samples and further determination by gas chromatography-mass spectrometry (GC-MS) of 14 herbicides, four insecticides and two metabolites]; and (3) analysis and discussion of the results by applying joint correspondence analysis (JCA). Results: From the 20 pesticides and metabolites selected for the study, 11 were found in groundwater. Pesticides and metabolites most frequently detected were atrazine, alachlor, metolachlor, desethylatrazine, ethofumesate, alpha-endosulfan, metribuzine, lindane and beta-endosulfan. The results showed that groundwater exposure to pesticides is influenced by local factors - either environmental or agricultural, as precipitation, soil, geology, crops and irrigation practices. Spring and autumn were more associated with the detection of pesticides being more likely to observe mixtures of these compounds in a groundwater sample in these transition seasons. Conclusions: This work evidences the importance of models, which evaluate pesticides environmental behaviour, namely their water contamination potential (as Mackay multicompartimental fugacity model) and, specially, groundwater contamination potential (as GUS and Bacci and Gaggi leaching indices), in pesticide selection. Moreover, it reveals the importance to adapt proper statistical methods according to level of left-censored data. Using JCA was still possible to establish relations between pesticides and their temporal trend in a case study where there were more than 80% of data censored. This study will contribute to the Tagus river basin management plan with information on the patterns of pesticide occurrence in the alluvial aquifer system.
  • Authors:
    • Soomro, B. A.
    • Markhand, G. S.
    • Soomro, M. H.
  • Source: Pakistan Journal of Botany
  • Volume: 44
  • Issue: 1
  • Year: 2012
  • Summary: The drought is one of the biggest abiotic stresses for crop production in arid and semi-arid agriculture. Thus it is a challenge for plant scientists to screen and develop the drought tolerant cotton lines. In this study, 31 cotton genotypes/cultivars were evaluated under two irrigation regimes i.e., seven irrigations (Control) and two irrigations (Stress), using split plot design with four replications. The crop growth, yield and some physiological parameters were studied. There were high inter-varietal differences for all the parameters under control as well as drought stress. Although all the varieties for all parameters were significantly affected by drought but however, CRIS-9, MARVI, CRIS-134, CRIS-126, CRIS-337, CRIS-355 and CRIS-377 maintained highest performance for all the parameters studied under high drought conditions.
  • Authors:
    • Foratto, L. C.
    • Salomão, L. C.
    • Quaggio, J. A.
    • Boas, R. L. V.
    • Souza, T. R. de
  • Source: Pesquisa Agropecuária Brasileira
  • Volume: 47
  • Issue: 6
  • Year: 2012
  • Summary: The objective of this work was to evaluate nutrient dynamics in soil solution after fertigated application of nitrogen, phosphorus, and potassium to orange trees. The experiment was carried out from September 2007 to October 2009, in 'Valencia' and 'Hamlin' orange orchards grafted onto citrumelo 'Swingle' rootstock. Five doses of N, P 2O 5 and K 2O (0, 25, 50, 100 and 200% of the recommended dose) were evaluated. Soil solution was extracted from 30 and 60 cm soil depths using extractors with porous cups. Eleven evaluations were done during the experimental period, with extractions beginning 12 hours after fertigation. Increasing nutrient doses decreased pH (pH-3.5, at the highest dose), and increased electrical conductivity (CE-1.5 dS m -1, at the highest dose) and the amounts of NH 4, NO 3, P, K, Mn, and Zn in the soil solution, in both sampled depths. In the months with heavier rainfall, there was nutrient potential losses by leaching, since higher concentrations of NO 3, K, and B were observed at the 60 cm soil depth. Soil solution analysis, obtained by extractors with porous ceramic cups, can be considered an auxiliary tool for monitoring and assessing nutrient availability to plants.
  • Authors:
    • Albrigo, L. G.
    • Syvertsen, J. P.
    • Melgar, J. C.
  • Source: Acta Horticulturae
  • Issue: 928
  • Year: 2012
  • Summary: The loss of leaves, branches and flowers along with bark scuffing and root exposure that can occur during mechanical harvesting (MH) has not reduced long term yields of healthy trees. Nonetheless, such visible injuries have limited the widespread adoption of mechanical harvesting in Florida's citrus industry. There was little measurable physiological stress from MH in healthy, well-managed trees as leaf water relations, CO 2 assimilation and final yield were not affected. The abscission compound CMNP, can effectively reduce fruit detachment force and result in fewer visible injuries. Late season MH of 'Valencia' sweet orange remains a major problem when young fruitlets for next crop become large enough to be harvested prematurely. We determined if winter drought stress from January to March could delay flowering and fruitlet development so they would be too small to be susceptible mechanical harvesting. Drought stress during winter delayed flowering 2-3 weeks, reduced flowering and vegetative growth but did not reduce new fruit set relative to irrigated trees. Fruit growth after the delayed bloom caught up with the irrigated treatments so final yield and fruit quality were not affected. During mechanical harvesting, previously drought stressed trees had a higher fruit removal efficiency and less loss of the smaller young fruit than continuously irrigated trees for up to three months. Thus, winter time drought stress can be an effective practice to delay flowering and to avoid young fruit loss during late season mechanical harvesting of 'Valencia' oranges. Fruitlet oleocellosis in late season mechanical harvested trees did not increase fruitlet drop nor alter internal fruit quality.
  • Authors:
    • Stamatiadis, S.
    • Samaras, V.
    • Tsadilas, C.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 43
  • Issue: 1-2
  • Year: 2012
  • Summary: A 2-year field experiment was conducted in central Greece (Platykampos, Larissa) to investigate productivity parameters of cotton under conditions of water stress. A Latin square split-plot design with three replications was used to evaluate the effect of three irrigation levels (250, 350, and 450 mm) and three fertilization rates (60, 110, and 160 kg N ha(-1)), where irrigation level was the whole-plot factor and the fertilizer was the split-plot factor. The results showed that irrigation level had no significant effect on soil chemical properties, but these only changed with fertilizer application. Concentration of soil nitrates increased in proportion to the amount of applied fertilizer in early July. The associated rise in electrical conductivity (EC) was not sufficiently high as to adversely affect salt-tolerant cotton. The soil acidity produced during formation of nitrate was evident by a soil pH decrease of 0.2 units in the high fertilizer application. A great decline of nitrate N and EC and a rise of pH in all treatments in early August indicated rapid N uptake by the crop during the late stage of vegetative growth. In contrast, cotton yield was not affected by the rate of fertilizer application but by the level of irrigation. This is the reason that correlations between soil properties and yield were insignificant in early July and August. It appears that there was sufficient N available to the crop from sources other than fertilizer N (soil-derived N and irrigation N). Preplant soil nitrates were greater than residual nitrates in the second growing season and indicated depletion of soil mineral N pools of the order of 36 kg N ha(-1) in the 0- to 25-cm depth. Significant negative correlations between soil properties and cotton yield appeared only at the end of the season and indicated that depletion of soil mineral N increased with increasing crop N requirement or irrigation level.
  • Authors:
    • Tolentino, J. B.
    • Coelho, R. D.
    • Vellame, L. M.
  • Source: Revista Brasileira de Fruticultura
  • Volume: 34
  • Issue: 1
  • Year: 2012
  • Summary: The total citrus area irrigated in Brazil has increased over the decades. The main cause of this increasing is due to the use of rootstocks tolerant to Citrus Sudden Death however they are less tolerant to drought than Rangpur lime. This research aims to study the influence of rootstock and soil type on transpiration of young plants of Valencia orange. The experiment was conducted in a greenhouse at the Department of Biosystems Engineering, ESALQ/USR Orange seedlings were planted in boxes of 500 L. It was determined simultaneously sweating of 20 plants through thermal dissipation probes (sap flow). It was monitored solar radiation, relative humidity and air temperature sensors were installed to 2 m tall at the center of the greenhouse. The reference evapotranspiration (ETo PM) was calculated by the standard method suggested by FAO. According to these results it is concluded that plant transpiration of Valencia oranges are influenced not only by the type of rootstock but also by leaf area growth and phenological stage, and its relationship with ETo pM is not linear in the whole range of evaporative demand of the atmosphere.