• Authors:
    • El-Tohamy, W.
    • Taalab, A.
    • Badr, M.
  • Source: Australian Journal of Basic and Applied Sciences
  • Volume: 5
  • Issue: 7
  • Year: 2011
  • Summary: Drip irrigation offers excellent method of water and nutrient supply for vegetable crops in precise amounts at a rate, which matches the plant requirements. In addition to allowing precise control of irrigation water applications, drip irrigation system offers the ability to use high frequency fertigation with water soluble N materials throughout the growing season. Little information about optimum fertigation interval for drip-irrigated crops in general and for potato in particular, is available. The present study was conducted to determine the effects of two N rates (200 and 300 kg N ha -1) and four fertigation frequencies (1, 2, 7, and 14 days) on potato yield, N uptake and soil N status in a sandy soil under drip irrigation system. Total potato yield and yield components were responsive to increase N rate and to decrease fertigation frequency. The highest tuber yields (47.16, 46.32 and 44.75 t ha -1) occurred at 300 kg N ha -1 with the frequencies of 1, 2 and 7 days, respectively while yield with the longest interval were significantly lower (37.89 t ha -1). Leaves N concentration at all sampling dates was higher in the plants received high N rate, but fertigation frequency did not significantly affect leaves N concentration except at the longest duration. Similarly, N rate and fertigation frequency resulted in significant differences in total N uptake, N recovery and apparent N use efficiency (NUE). Total N uptake was appreciable higher with increasing N rate and with more frequent than with less frequent fertigation. The averaged N recovery across fertigation frequencies was 68% and 62% and NUE was 151 and 142 kg yield -1 kg N -1 with applied 200 and 300 kg N ha -1, respectively. Analysis of soil samples at the end of last fertigation indicated considerable influence of fertigation frequency on NO 3--N distribution in the root zone of potato. The NO 3--N in lower soil profiles,(40-60 cm) depth with high N rate was marginally affected in daily, alternate and weekly fertigation while NO 3--N in the corresponding soil depth was appreciable higher in biweekly fertigation. Thus, frequent fertigation was needed to obtain maximum yield of potato in sandy soil with less nitrate leaching from root zone.
  • Authors:
    • Intrigliolo, D.
    • Castel, J.
    • Ballester, C.
    • Castel, J.
  • Source: Agricultural Water Management
  • Volume: 98
  • Issue: 6
  • Year: 2011
  • Summary: The effects of mid-summer regulated deficit irrigation (RDI) treatments were investigated on Clementina de Nules citrus trees over three seasons. Water restrictions applied from July, once the June physiological fruit drop had finished, until mid September were compared with a Control treatment irrigated during all the season to match full crop evapotranspiration (ET c). Two degrees of water restrictions were imposed based on previous results also obtained in Clementina de Nules trees ([Ginestar and Castel, 1996] and [Gonzalez-Altozano and Castel, 1999]). During the RDI period, deficit irrigation was applied based on given reductions over the ET c, but also taking into account threshold values of midday stem water potential (psi s) of -1.3 to -1.5 MPa for RDI-1 and of -1.5 to -1.7 MPa for RDI-2. Results showed that water savings achieved in the RDI-2 treatment impaired yield by reducing fruit size. On the contrary, the RDI-1 strategy allowed for 20% water savings, with a reduction in tree growth but without any significant reduction in yield, fruit size nor in the economic return when irrigation was resumed to normal dose about three months before harvest. Water use efficiency (WUE) in the RDI trees was similar or even higher than in Control trees. RDI improved fruit quality increasing total soluble solids (TSS) and titratable acidity (TA). In conclusion, we suggest that the RDI-1 strategy here evaluated can be applied in commercial orchards not only in case of water scarcity, but also as a tool to control vegetative growth improving fruit composition and reducing costs associated with the crop management.
  • Authors:
    • Intrigliolo, D.
    • Yeves, A.
    • Sanz, F.
    • Castel, J.
    • Ballester, C.
    • Castel, J.
  • Source: Acta Horticulturae
  • Issue: 922
  • Year: 2011
  • Summary: In citrus trees, regulated deficit irrigation (RDI) can be a useful irrigation strategy to reduce water supply without affecting yield. Previous studies conducted in this sense have determined irrigation water savings achieved by RDI but less is known about the actual transpiration values of the RDI trees. This information is crucial to properly carry out a water balance of an RDI orchard. In an experiment performed during 2009 on mature 'Clementina de Nules' citrus, we determined sap flow (SF) of well irrigated and RDI trees by means of the compensation heat pulse method. SF was measured in two trees per treatment instrumented with one unit of two different gauge types per tree, determining heat velocity at four different xylem depths. SF values obtained at 30-min intervals during the entire experimental period were compared with whole canopy gas exchange measurements carried out during two representative days with custom designed Mylar plastic chambers. Plant water status was determined by midday stem water potential measurements (Psi stem). Results showed that absolute SF values clearly underestimated tree water use. After calibrating SF against canopy gas exchange determinations, corrected SF values appeared more reasonable but it also increased tree-to-tree variability (CV from 0.08 to 0.17). The transpiration ratio (SF RDI/SF control) had a somewhat decreasing trend during the water restriction period according to Psi stem, but recovering before the irrigation was resumed to normal dose. Overall, the results highlight some of the problems and uncertainties when using a limited number of sap flow sensors for detecting plant water stress and for accurately measuring transpiration.
  • Authors:
    • Sanjani, S.
    • Bannayan, M.
  • Source: Agricultural and Forest Meteorology
  • Volume: 151
  • Issue: 12
  • Year: 2011
  • Summary: Climate variability and weather extremes are principal sources of fluctuations of annual productivity of many crops in arid and semi-arid environments. Temperature and precipitation are the major weather variables that determine the variability of crop yields. In this study, the relationship between weather descriptors and major irrigated crops yield were assessed for Khorasan province in northeast of Iran. Long term daily weather (1984-2007) and crop yield (wheat, barley, sugarbeet, cotton, potato, chickpea, alfalfa) data were analyzed with simple correlation analysis and also the iterative chi-square analysis identified relationships of low and high wheat yield years to maximum and minimum air temperatures within each region. Our results indicated that association between various crop yield and descriptors varied in different study location. As in Bojnourd located in the north of Khorasan yields of the crops studied did not correlate with temperature indicators, whereas in Birjand the relationship between temperature descriptors and crop yields were strong. Correlation between growing season precipitation and wheat, barley, chickpea and sugarbeet yields was positive while cotton yield decreased with increasing precipitation during the growing season. The results of chi-square analysis for wheat yield demonstrated that the critical time in which extreme temperature led to yield loss differed among regions. In Bojnourd, in late April to early May, and excess days (high or low yield years have more days meeting a cardinal value than normal years) with maximum temperature higher than 30 degrees C, wheat yield decreased while in Birjand, cooler maximum temperature (
  • Authors:
    • Santos Junior, V.
    • Silva, H.
    • Aquino, L.
    • Batista, C.
    • Pacheco, D.
  • Source: Bioscience Journal
  • Volume: 27
  • Issue: 2
  • Year: 2011
  • Summary: This paper objective was to evaluate P levels in irrigated crops or rainfed in productivity and P uptake by cotton plant. The experiment was conducted at the Instituto Federal do Norte de Minas (IFNMG), Campus Januaria. The treatments consisted of three P rates (0, 50 and 120 kg ha -1 of P 2O 5) and three cropping systems (Sprinkler, Dripping and Rainfed). It was adopted the randomized block design in factorial design with three replications. At 80 days after emergence (DAE), leaves, stems, and reproductive structures were collected. Each organ was dried, crushed, and P content determined. P content of each organ was calculated. The macro and micronutrients levels in the fifth fully expanded leaf from the apex to the base (leaf index) were determined. The P and S contents were higher in irrigated plants by dripping. The P and Mg highest values were obtained with 120 kg ha -1 de P 2O 5. The irrigated plants had higher P content in shoots compared to those under rainfed. Regardless of the method, irrigation and the highest P rates increased the quantity of reproductive structures, the quantity of the bolls per plant, and seed cotton productivity.
  • Authors:
    • Benchabane, M.
  • Source: IOBC/WPRS Bulletin
  • Volume: 62
  • Year: 2011
  • Summary: After studies (2006-2009) of the states of fading of citrus fruits in the Mitidja (Algeria), we noted a troubling epidemic evolution in some orchards where the death rates reached proportions of 5 to 10%. The symptomatologic diagnosis indicates the presence of a strong likeness between the different biotic reasons possible without the presence of symptoms typical and/or of revealing signs of the known diseases (bacteria and virus). The diagnosis of laboratory confirmed their absence. The isolations achieved from the roots and soil put often in evidence the presence of Fusarium flora dominated by Fusarium solani and Fusarium oxysporum species. The implication of these species is joined to the pedological features and to the technical practices, notably the irrigation.
  • Authors:
    • Olitrault, P.
    • Msatef, Y.
    • Handaji, N.
    • Benazzouze, A.
    • Omari, F.
    • Beniken, L.
    • Benyahia, H.
  • Source: African Journal of Agricultural Research
  • Volume: 6
  • Issue: 4
  • Year: 2011
  • Summary: Alkalinity of Moroccan soils is the major abiotic constraint on citrus production area. The best choice of citrus rootstocks adequate and resistant is a better solution to avoid this problem. The aim of this study is to develop a fast test of citrus rootstocks screening towards alkalinity. The alkaline stress was applied on ten citrus rootstocks two month old, using irrigation with a Hoagland and Arnon solution added with 1 g CaCO 3/L and adjusted at various pH levels 6, 7 and 9. Observations concerned symptoms incidence and severity of iron chlorosis after two months of rearing. Results permitted to classify Poncirus trifoliata and Flying dragon as the most sensitive to alkalinity stresses, whereas, Citrus volkameriana and Citrus macrophylla were resistant. These conclusions are equivalent with those obtained with old citrus rootstocks in field trials.
  • Authors:
    • Singh, J.
    • Bhatnagar, P.
    • Kaul, M.
  • Source: Acta Horticulturae
  • Issue: 922
  • Year: 2011
  • Summary: Studies of variation in plant environmental factors of Kinnow mandarin for at Agriculture Research Station, SriGanganagar district of Rajasthan state in India during 2002-04 with respect to three differential irrigation treatments revealed that overall maximum carboxylation efficiency (A) was estimated at 70% Etc treatment from April to June with a linear trend. It showed depression in September and October followed by a steady rise in November and December months. Stomatal conductance revealed oscillating trend with maximum in 70% Etc treatment for April and May months followed by steep rise in 40% Etc treatment for June-July. It remained static in August and September, but a trend reversal occurred in October-November with maximum stomatal conductance in 100% Etc treatment. The cumulative overall high stomatal resistance in 40% treatment might have attributed to low photosynthetic rates followed by 100% treatment and the better assimilation rates were observed under 70% treatment and were correlated with low rates of stomatal resistance. The daily course of transpiration in all the three irrigation treatments was not closely linked to solar irradiation but rather to leaf temperature. Temperatures of 25-30degreesC are optimal for photosynthesis but temperatures above 30degreesC definitely reduce photosynthetic activity. The annual trend for three consecutive years' data revealed occurrence of cyclic oscillations in photosynthesis, stomatal conductance, stomatal resistance, transpiration rate and photosynthetic active radiation under field conditions. Citrus belong to C3 plants, with photosynthetic rates lower than C4 plants. Assimilation rates ranging from 1.28 to 7.93 mmol m -2 s -1 observed under differential irrigation treatments seem realistic under optimal irrigated conditions of Western Rajasthan.
  • Authors:
    • Olesen, J.
    • Bindi, M.
  • Source: Regional Environmental Change
  • Volume: 11
  • Issue: Supplement 1
  • Year: 2011
  • Summary: Human activities are projected to lead to substantial increases in temperature that will impact northern Europe during winter and southern Europe during summer. Moreover, it is expected that these changes will cause increasing water shortages along the Mediterranean and in the south-west Balkans and in the south of European Russia. The consequences on the European agricultural ecosystems are likely to vary widely depending on the cropping system being investigated (i.e. cereals vs. forage crops vs. perennial horticulture), the region and the likely climate changes. In northern Europe, increases in yield and expansion of climatically suitable areas are expected to dominate, whereas disadvantages from increases in water shortage and extreme weather events (heat, drought, storms) will dominate in southern Europe. These effects may reinforce the current trends of intensification of agriculture in northern and western Europe and extensification and abandonment in the Mediterranean and south-eastern parts of Europe. Among the adaptation options (i.e. autonomous or planned adaptation strategies) that may be explored to minimize the negative impacts of climate changes and to take advantage of positive impacts, changes in crop species, cultivar, sowing date, fertilization, irrigation, drainage, land allocation and farming system seem to be the most appropriate. In adopting these options, however, it is necessary to consider the multifunctional role of agriculture and to strike a variable balance between economic, environmental and economic functions in different European regions.
  • Authors:
    • Mhamdi, M.
    • Boughalleb, F.
    • Hajlaoui, H.
  • Source: Agricultural Journal
  • Volume: 6
  • Issue: 3
  • Year: 2011
  • Summary: Experiments were conducted with lemon ( Citrus limon v. Eureka) and orange trees ( Citrus sinensis cv. Maltese) to determine the optimum NPK fertilizer rates for young citrus trees in greenhouse and field conditions. Greenhouse nursery trees received 0-0-0, 0-25-50, 25-25-50, 50-25-50 or 100-25-50 mg L -1 of N-P 2O 5-K 2O via drip irrigation. The results showed that increased N rates improved leaf number, shoot length, total leaf area and stem diameter. The optimum tree growth was occurred with 50 and 100 mg N L -1. Results also showed that the percentages of N in the leaves were increased in proportion to the amount of N added while the percentage of P and K were decreased. However, the concentrations of Ca, Mg, Fe, Mn and Zn were unaffected by N rates but the leaf Cu concentration increased significantly. Leaf Mg concentration was increased by the presence of K in the nutrition solution. Form this study, we recommended the use of 100 N-25 P 2O 5-50 K 2O mg L -1 for the good growth of nursery citrus plants in the absence of any possibility of deficiency or excessive accumulation of mineral elements. In the second experiment, two fertilizers mix 180-90-180 and 360-90-180 of N-P 2O 5-K 2O kg ha -1 were applied to young citrus tree in field condition. Increased the level of N had no effect on leaf number and stem diameter in Eureka lemon however shoot length and total leaf area were slightly increased and these increment in growth was higher in Maltese orange.