• Authors:
    • Trentin, G.
    • Maldaner, I. C.
    • Radons, S. Z.
    • Heldwein, A. B.
    • Grimm, E. L.
    • Bosco, L. C.
  • Source: Revista Brasileira de Engenharia Agrícola e Ambiental
  • Volume: 15
  • Issue: 2
  • Year: 2011
  • Summary: The objective of this study was to determine the effect of different levels of irrigation and chemical control on yield and occurrence of Late Blight in potato cv. Asterix, at Santa Maria - RS. Two experiments were conducted at the Crop Science Department, Federal University of Santa Maria. One experiment was carried out during spring-summer, 2005/2006 and the second, during fall 2006. The experimental design was a complete randomized, with four replications. The Blitecast model was used to indicate the timing of spraying, by accumulating severity values (VS). Sprinkler irrigation was used corresponding to 1.0, 0.75, 0.50 ETm and no irrigation. Results showed that in dry and high temperature periods, yield was affected by irrigation, mainly when crop water demand was supplied with 100% ETm. During wet periods, yield was affected by the efficient control of Late Blight. The Blitecast model with a severity value of 18 (Bli18) was the most efficient for controlling the disease. Irrigations applied at least every three days did not affect Late Blight incidence and development.
  • Authors:
    • Hebbar, K. B.
    • Mayee, C. D.
  • Source: Current Science
  • Volume: 100
  • Issue: 11
  • Year: 2011
  • Summary: There are several reasons why plants wilt. Some of them are over-watering, lack of water, too much sun, not enough sun, too many/much fertilizers, diseases caused by infection, etc. Wilt due to lack of water or other environmental factors generally occurs gradually and hence, the cause of those can be studied and accordingly it can be controlled by devising appropriate management strategies. Moreover, plants recover with appropriate control measures and continue to yield. In this review, we discuss a typical wilt which is sudden and occurs within a few hours. Hence, understanding the cause and devising a control measure are difficult. Its sporadic distribution and untimely occurrence further complicate the effort to find the cause of this wilt. Unlike the wilt mentioned above which occurs due to lack of water, sudden wilt occurs when the soil is suddenly saturated by a downpour of rain and the sun later shines bright and hot. Paradoxically, the physiological responses, i.e. wilt symptoms to those induced by either drought or flooding are similar. However, the causal mechanism is different. Here, we demonstrate that the imbalance in uptake and loss of water under flooding is the cause of sudden/parawilt of cotton. We also discuss how plants with rapid growth rate and climate factors like bright sunshine and high temperature accentuate the problem of parawilt in cotton.
  • Authors:
    • Huang, B. Z.
    • Wu, Y. L.
    • Wei, Y. R.
    • Li, C. Y.
    • Yi, G. J.
  • Source: Acta Horticulturae
  • Issue: 897
  • Year: 2011
  • Summary: China is one of the centres of origin of banana. The crop has been cultivated there for more than 2000 years, and in the last two decades, it has become one of the most important fruit crops in the country. With a production of 8,042,702 tonnes on an area of 311,106 ha in 2008, banana comes in fourth place, only after apple, citrus and pear. As the demand for banana in the country is very high, banana produced domestically can only meet 90% of the demand, the other 10% is met by imported banana. Banana is mainly cultivated in Guangdong, Guangxi, Hainan, Fujian, Yunnan Province and Taiwan. Guangdong's cultivated area and production quantity rank first in China. The banana industry in China has been evolving fast over the past two decades. Indeed, banana production is a crucial industry in each main producing area; it plays an important role in the local economy and rural development. Many high-yielding and good-quality production techniques have been widely adopted by growers, such as micropropagated plantlets, water-saving irrigation, fertilisation, bunch management techniques, etc. Since 2003, the industrialisation of banana production has been promoted effectively through the implementation of the "Banana Industrial Upgrading Plan" developed by the Agricultural Ministry. However, Chinese banana production is still facing many challenges such as pests and diseases, adverse weather conditions and level of industrialisation. More than 3,000 ha of banana plantations have been attacked by Fusarium wilt in Guangdong. Production declined by more than 30% due to cold temperature in 1991-1992, 1999-2000 and 2002-2003, and the damage in 2007-2008 was devastating. In order to promote a healthy and persistent development of the banana industry, the National Industry System of Banana was initiated by the National Agricultural Ministry in 2008. Scientists were organised to tackle key issues, including breeding, cultivation technology, postharvest and processing, marketing and trade.
  • Authors:
    • Shukla, S.
    • Harris, W. G.
    • Obreza,T. A.
    • Sartain, J. B.
    • Schumann, A. W.
    • Mann, K. K.
  • Source: Journal of Plant Nutrition and Soil Science
  • Volume: 174
  • Issue: 6
  • Year: 2011
  • Summary: Variability in soil properties is a complication for fertilization, irrigation, and amendment application. However, only limited progress has been made in managing soil variability for uniform productivity and increased water-use efficiency. This study was designed to ameliorate the poor-productivity areas of the variable sandy soils in Florida citrus groves by using frequent small irrigations and applying organic and inorganic soil amendments. Two greenhouse experiments were set up with sorghum and radish as bioassay crops in a randomized complete block design (RCBD). The factors studied were two soil-productivity classes (very poor and very good), two water contents (50% and 100% of field capacity), two amendments (phosphatic clay and Fe humate), and two amendment rates (10 and 25 g kg -1 for sorghum and 50 and 100 g kg -1 for radish). Amendments applied at 50 and 100 g kg -1 increased the water-holding capacity (WHC) of poor soil by 2- to 6-fold, respectively. The lower rates (10 and 25 g kg -1) of amendments were not effective in enhancing sorghum growth. The higher rates (50 and 100 g kg -1) doubled the radish growth as compared to the control. The results indicate that rates greater than 50 g kg -1 of both amendments were effective in improving water retention and increasing productivity. Irrigation treatment of 100% of field capacity (FC) increased the sorghum and radish growth by about 2-fold as compared with the 50%-water content treatment. The results suggest that the root-zone water content should be maintained near FC by frequent small irrigations to enhance water availability in excessively drained sandy soils. In addition, application of soil amendments in the root zone can enhance the water retention of these soils. Furthermore, managing variable sandy soils with WHC-based irrigation can increase water uptake and crop production in the poor areas of the grove.
  • Authors:
    • Angelocci, L. R.
    • Marin, F. R.
  • Source: Agricultural Water Management
  • Volume: 98
  • Issue: 6
  • Year: 2011
  • Summary: Crop evapotranspiration (ETc) was measured as evaporative heat flux from an irrigated acid lime orchard ( Citrus latifolia Tanaka) using the aerodynamic method. Crop transpiration (T) was determined by a stem heat balance method. The irrigation requirements were determined by comparing the orchard evapotranspiration (ETc) and T with the reference evapotranspiration (ETo) derived from the Penman-Monteith equation, and the irrigation requirements were expressed as ETc/ETo (Kc) and T/ETo (Kcb) ratios. The influence of inter-row vegetation on the ETc was analyzed because the measurements were taken during the summer and winter, which are periods with different regional soil water content. In this study, the average Kc values obtained were 0.65 and 0.24 for the summer and winter, respectively. The strong coupling of citrus trees to the atmosphere and the sensitivity of citrus plants to large vapor pressure deficits and air/leaf temperatures caused variations in the Kcb in relation to the ETo ranges. During the summer, the Kcb value ranged from 0.34 when the ETo exceeded 5 mm d -1 to 0.46 when the ETo was less than 3 mm d -1.
  • Authors:
    • Syvertsen, J. P.
    • Dunlop, J. M.
    • Melgar, J. C.
  • Source: HortScience
  • Volume: 46
  • Issue: 3
  • Year: 2011
  • Summary: Oleocellosis or oil spotting on the peel of citrus fruit is a common post-harvest injury caused by improper handling. Mechanical injury allows phytotoxic oil to leak out of oil glands and cause injury to surrounding flavedo cells, resulting in oleocellosis. Mechanical harvesting (MH) of 'Valencia' sweet orange is conducted in late spring, when the next season's fruitlets are in their early stages of development. There is a concern that mechanical injury from harvesting machines can cause oleocellosis and fruit drop of young, green 'Valencia' sweet orange fruitlets, especially late in the harvest season when fruitlets are relatively large. We evaluated the effects of winter drought stress and subsequent late-season MH with a canopy shaker on oleocellosis of 'Valencia' sweet orange fruitlets. In April, mature fruit size, juice content, total soluble solids, and acidity were unaffected by previous winter drought stress treatments. Mechanical harvesting removed ~90% to 95% of mature fruit and 20% to 50% of fruitlets depending on previous drought stress treatments and harvesting date. Beginning 1 week after the late harvest (13 June), attached fruitlets were tagged and visually evaluated approximately every other month to determine oleocellosis injury until the late-season harvest 12 months later. Only 12% of the fruitlets had oleocellosis on more than 30% of their surface area. Up to 75% of the fruitlets from the previously drought-stressed trees had less than 10% of their surface area injured after MH and 11% of these fruitlets dropped before harvest. Nonetheless, there was no significant increase in fruit drop with increased surface area injured nor was juice quality affected at harvest. Overall, fruit surface oleocellosis decreased and healed as fruit expanded, but surface blemishes did not completely disappear. Thus, fruitlet oleocellosis in late-season mechanically harvested trees was cosmetic and did not increase fruit drop nor alter internal fruit quality.
  • Authors:
    • Murari, L.
  • Source: Regional Environmental Change
  • Volume: 11
  • Issue: Supplement 1
  • Year: 2011
  • Summary: One of the targets of the United Nations 'Millennium Development Goals' adopted in 2000 is to cut in half the number of people who are suffering from hunger between 1990 and 2015. However, crop yield growth has slowed down in much of the world because of declining investments in agricultural research, irrigation, and rural infrastructure and increasing water scarcity. New challenges to food security are posed by accelerated climatic change. Considerable uncertainties remain as to when, where and how climate change will affect agricultural production. Even less is known about how climate change might influence other aspects that determine food security, such as accessibility of food for various societal groups and the stability of food supply. This paper presents the likely impacts of thermal and hydrological stresses as a consequence of projected climate change in the future potential agriculture productivity in South Asia based on the crop simulation studies with a view to identify critical climate thresholds for sustained food productivity in the region. The study suggests that, on an aggregate level, there might not be a significant impact of global warming on food production of South Asia in the short term (
  • Authors:
    • Bhandary, N. P.
    • Koike, Y.
    • Nishimura, F.
    • Tsuno, H.
  • Source: Journal of Water and Environment Technology
  • Volume: 9
  • Issue: 2
  • Year: 2011
  • Summary: Matsuyama region, located in Shikoku Island, Japan faces the Seto Inland Sea on the west, where the annual rainfall is relatively less than in the other areas in Japan. In such favorable condition, the cultivation of citrus fruits is popular, and there are a large number of small reservoirs for irrigation purposes. The citrus groves are distributed in hilly areas surrounding the paddy fields and residential areas so there are higher chances for the nearby water environment to get affected by leachate from the groves. This paper investigates the water quality characteristics of the leachate from the groves, and studies the changes of the leachate quality near the collecting reservoirs. It was found that the grove soils are highly acidic and the leachate contains metals and nutrients in high concentration. On the other hand, the water quality of the leachate changed after it flowed into the reservoirs, and the concentrations became lower. It is understood that chemical and biological reactions help remove the contaminants in the reservoir, and from the standpoint of self-purification, reservoirs play an important role. This paper also discusses the kinetics of the self-purification and the quantitative estimation based on the experimental results.
  • Authors:
    • Eckard, R. J.
    • Browne, N. A.
    • Behrendt, R.
    • Kingwell, R. S.
  • Source: Animal Feed Science and Technology
  • Volume: 166-167
  • Year: 2011
  • Authors:
    • Chan, Y. C.
    • Sinha, R. K.
    • Wang, W. J.
  • Source: Waste Management & Research
  • Volume: 29
  • Issue: 5
  • Year: 2011