• Authors:
    • El-Wakeel, F.
    • Eid, M.
  • Source: Journal of American Science
  • Volume: 7
  • Issue: 5
  • Year: 2011
  • Summary: This study was carried out through two successive seasons (2008 and 2009) in a private orange orchard in Qalubia governorate Egypt in a three years old Navel orange trees budded on sour orange rootstock on clay loam soil (Typic Torriorthents). Planting distance was 2.55* meters apart and flood irrigation was used by river Nile water. Two nitrogen rates were used 150 and 300 g N/tree/y in three forms 100% mineral nitrogen (M.N.) as ammonium nitrate, 100% organic nitrogen (O.N.) as compost and mixed (50% M.N.+50% O.N.) each of these treatments with or without K humate addition (6 kg/feddan). All fertilization treatments were divided into equal five doses added every two months from February to October during the two seasons. The obtained results showed that the highest stem thickness increment percentage was recorded by mixed nitrogen form (50% M.N.+50% O.N.). Mixed nitrogen form with K-humate recorded the highest significant value of plant height increment percentage in the first season, but in the second season, using nitrogen form at 150 g N/tree/y without K-humate recorded the highest significant value. Leaf N content had higher significant values with M.N. treatments. Leaf P content showed insignificant differences among treatments. Mixed N source at 300 g N/tree/y without K-humate recorded a higher significant value of leaf K content, in the second season compared with other treatments. Leaf Ca content showed a higher significant value by organic and mixed N form treatments in the first season. Leaf Mg, Fe, Mn and Zn contents increased significantly with M.N. treatments in the first season. While in the second season leaf Fe content had a higher significant value with O.N. treatments. Leaf Mn content illustrated the lowest significant mean level by using N form at 150 g N/tree/y treatment. While, leaf Zn content recorded a higher significant value with mixed nitrogen source at 150 g N/tree/y with K-humate addition compared with all other treatments. From this results we recommended that the mixed sources of N fertilizer (50% M.N.+50% O.N.) at 150 g N/tree/y is the best N fertilizer, and the application of K-humate or humic acid at commercial rate is not recognized for the young Navel orange trees in clay loam (Typic Torriorthents) soil.
  • Authors:
    • Carneiro, P. T.
    • Melo, A. S. de
    • Soares Filho, W. dos S.
    • Gheyi, H. R.
    • Brito, M. E. B.
    • Fernandes, P. D.
  • Source: Acta Scientiarum Agronomy
  • Volume: 33
  • Issue: 2
  • Year: 2011
  • Summary: Water and soil salinity affects the growth, development and production of fructiferous species, such as citrus. The use of tolerant rootstocks can guarantee the agribusiness of citrus under such conditions. Thus, the sensibility to salinity during the phase of rootstock formation of varieties and selected hybrids was studied. The experiment was carried out in a greenhouse, with five levels of irrigation water salinity [control, tap water with electrical conductivity (EC w) of 0.41 dS m -1, and water with EC w of 1.0, 2.0, 3.0 and 4.0 dS m -1] and seven genotypes, in a randomized block design and five replications each consisting of four plants, during 150 day period. Growth and physiologic variables were evaluated. Significant effects of genotypes and salinity in the variables were observed. The most expressive reduction was found for total dry matter with unit increase of EC w. A linear reduction was observed in hybrids LVK * LVA-009 and TSK * TRENG-256. Among the evaluated genotypes 'Volkamer' lemon was the least sensitive to saline stress.
  • Authors:
    • Primo-Millo, E.
    • Legaz, F.
    • Forner-Giner, M. A.
    • Forner, J.
  • Source: Journal of Plant Nutrition
  • Volume: 34
  • Issue: 10
  • Year: 2011
  • Summary: This study assesses the nutritional behavior of the new citrus rootstocks Forner-Alcaide no. 5 (FA-5) and Forner-Alcaide no. 13 (FA-13) under saline conditions compared to that of their parents, Cleopatra mandarin (CM) and Poncirus trifoliata (PT). Eighteen month-old plants grafted with Valencia orange scions were used in the experiment. The plants were grown in a greenhouse and irrigated over an eight-week period with nutrient solutions to which different amounts of sodium chloride (NaCl) had been added, namely 0, 20, 40 and 60 mM. Relative growth and the uptake of major mineral elements [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg)] were then determined. It was noted that the reduction in relative growth caused by salt treatment was greater in plants grafted on PT than those on FA-13, FA-5 and CM. Increasing the salt level in the growth medium reduced the absorption of the above mineral elements in all scion-rootstock combinations. However, this decrease was generally more marked in plants grafted on PT than in those on CM and FA-5. Plants on FA-13 showed an intermediate behavior. Positive correlations were found between growth and mineral element uptake by salt treated plants. Nutrient uptake was also plotted against chloride (Cl) and sodium (Na) concentrations in leaves and roots at increasing salt levels. This showed that N absorption was closely correlated (inversely) with Cl content in leaves, whereas K, Ca and Mg uptakes were correlated (inversely) with Na concentration in roots. This suggests that the accumulation of saline ions impacts growth and nutrient uptake by citrus plants.
  • Authors:
    • Primo-Millo, E.
    • Rodriguez-Gamir, J.
    • Forner-Giner, M. Á.
    • Iglesias, D. J.
  • Source: Journal of Plant Growth Regulation
  • Volume: 30
  • Issue: 3
  • Year: 2011
  • Summary: In this work we investigated the function of abscisic acid (ABA) as a long-distance chemical signal communicating water shortage from the root to the shoot in citrus plants. Experiments indicated that stomatal conductance, transpiration rates, and leaf water potential decline progressively with drought. ABA content in roots, leaves, and xylem sap was also increased by the drought stress treatment three- to sevenfold. The addition of norflurazon, an inhibitor of ABA biosynthesis, significantly decreased the intensity of the responses and reduced ABA content in roots and xylem fluid, but not in leaves. Polyethylene glycol (PEG)-induced osmotic stress caused similar effects and, in general, was counteracted only by norflurazon at the lowest concentration (10%). Partial defoliation was able to diminish only leaf ABA content (22.5%) at the highest PEG concentration (30%), probably through a reduction of the active sites of biosynthesis. At least under moderate drought (3-6 days without irrigation), mechanisms other than leaf ABA concentration were required to explain stomatal closure in response to limited soil water supply. Measurements of xylem sap pH revealed a progressive alkalinization through the drought condition (6.4 vs. 7.1), that was not counteracted with the addition of norflurazon. Moreover, in vitro treatment of detached leaves with buffers iso-osmotically adjusted at pH 7.1 significantly decreased stomatal conductance (more than 30%) as much as 70% when supplemented with ABA. Taken together, our results suggest that increased pH generated in drought-stressed roots is transmitted by the xylem sap to the leaves, triggering reductions in shoot water loss. The parallel rise in ABA concentration may act synergistically with pH alkalinization in xylem sap, with an initial response generated from the roots and further promotion by the stressed leaves.
  • Authors:
    • Nakamura, M.
    • Fujita, A.
    • Kameoka, T.
  • Source: Agricultural Information Research
  • Volume: 20
  • Issue: 3
  • Year: 2011
  • Summary: Satsuma mandarin cultivated in Nanki, Mie Prefecture, Japan, is a delicious and highly profitable crop. However, the lack of new agricultural workers makes it difficult to preserve specialized agricultural skills and transfer them to new generations of workers. To support farmers, we introduced a small, stationary agricultural robot, "Field Server", which measures environmental and growing conditions in real time in orchards that used a mulch and drip irrigation system able to produce high-quality fruit despite variable weather. We developed an important cultivation diagnosis tool to support farmers based on the hardness of fruit, and monitored soil and tree water stress by means of time-domain reflectometry, (TDR), evapotranspiration, and soil moisture stress, as well as meteorological conditions. Using these parameters, we developed a water stress index for satsuma mandarin. To provide practical diagnostic techniques to support orange cultivation based on the measured data, we developed a network of sensors for measuring soil moisture content and tree water stress. We also investigated the relationship between fruit quality and the soil and tree water status to test their effectiveness as a diagnostic index. We also compared a convenient soil moisture sensor (Watermark) based on TDR and showed farmers how to install the sensor in the orchards. It was possible to continuously measure the soil moisture content except where multiple water supplies complicated the measurement process. We also found that tree water stress could be accurately estimated using TDR to measure the soil and tree moisture contents.
  • Authors:
    • Virendra, K.
    • Gorantiwar, S. D.
    • Gadge, S. B.
    • Mahesh, K.
  • Source: Journal of Agrometeorology
  • Volume: 13
  • Issue: 1
  • Year: 2011
  • Summary: A study was carried out to estimate crop evapotranspiration (ETc) for different crops growing under surface (SI) and microirrigation (MI) methods in the command area of Mula Irrigation Project in Maharashtra, India. A spreadsheet-based computer model was developed to estimate the ETc values and compute the water requirement. The climatological data obtained from the meteorological observatory located at All India Co-ordinated Research Project on Water Management, Rahuri (Maharashtra), from 1975 to 2005 was used. The crop water requirement under MI methods was less than that under SI methods. The saving in water for MI method was maximum under pomegranate and lime (88%) and minimum for summer groundnut (38%) when compared to the SI method. Similar saving in water was also observed for other crops under MI methods. The percentage saving in MI methods was 75, 62, 64, 73, 68, 61, 43, 51, 65, 48, 53, 70, 63, 65, 63, 40, 52 and 63% for pawpaw, banana, sugarcane, grapes, kharif soyabean, rabi tomato, kharif groundnut, rabi onion, cotton, gram, potato, kharif brinjal [aubergine], cabbage, summer brinjal, summer cucumber, summer onion, summer okra and summer chilli, respectively, when compared to the water requirement under SI method. Thus, there is a saving of at least 50% of water if drip irrigation method is used instead of SI method. This indicates that in the case of water scarcity there is possibility of bringing additional area under irrigation by using the saved amount of water.
  • Authors:
    • Muriel-Fernández, J. L.
    • Jiménez-Bocanegra, J. A.
    • Durán-Zuazo, V. H.
    • Romero, R.
    • García-Tejero, I.
  • Source: Acta Horticulturae
  • Issue: 922
  • Year: 2011
  • Summary: Three different deficit-irrigation strategies were studied: sustained deficit irrigation (SDI), regulated deficit irrigation (RDI), and low-frequency deficit irrigation (LFDI) in different commercial citrus orchards located in the Guadalquivir river basin SW Spain. Each irrigation treatment was based on different water-stress ratio (WSR), which is the ratio of water supplied to deficit-irrigation treatment with respect to the control treatment (100% ET C). Midday stem-water potential (Psi Stem) was measured during the irrigation periods and was used to characterize plant-water status. Also, integrated stem-water potential (Psi Int) was calculated for all treatments and used as a timing water-stress indicator for the crop. Yield and fruit quality were evaluated at harvest in each treatment taking into account the temporal and spatial variability, associated mainly with local weather conditions, and agronomic orchard management. Relationships among water applied, Psi Int and yield response were performed to quantify the effects of deficit irrigation on yield and fruit-quality parameters. Analysis of data showed that, in all cases, the irrigation-water restriction significantly affected yield and some fruit-quality parameters (total soluble solids, titratable acidity, and maturity index). The results confirmed that the water productivity (WP) was positively related to water amount and irrigation strategy applied. Consequently, when WSR of 0.70 was applied (moderate deficit irrigation) RDI strategy showed better results than the SDI. However, with WSR of 0.60 (severe water reduction), LFDI strategy provided the best crop response. Under Mediterranean climate and water scarcity conditions, the application of DI strategies allowed water savings up to 1000 m 3 ha -1 yr -1. In DI treatments, the total water applied was better correlated with WP than with yield, indicating that this parameter should be used when trying to improve irrigation management.
  • Authors:
    • Muriel-Fernandez, J. L.
    • Duran-Zuazo, V. H.
    • Garcia-Tejero, I.
  • Source: Comunicata Scientiae
  • Volume: 2
  • Issue: 2
  • Year: 2011
  • Summary: Long-term impact of different sustained-deficit irrigation (SDI) treatments on a 13-year-old orange orchard ( Citrus sinensis L. Osbeck, cv. Salustiana) was studied from 2004 to 2008. The experiment consisted of a control irrigation treatment which was applied at 100% of the crop evapotranspiration (ETc) values for the whole season, and three SDIs imposed as a function of different water-stress index (WSI) values, defined as the ratio of the actual volume of water supply to the ETc rate. The values defined by the WSI were 0.75, 0.65, and 0.50. The plant-water status was measured through the midday stem-water potential (Psi Stem). Yearly, yield and fruit quality were evaluated at harvest in each treatment, and a global analysis was carried out using the whole dataset. Overall, no significant differences were found in fruit yield between SDIs and control treatments, although significant differences appeared in some of the fruit-quality parameters (total soluble solids and titrable acidity) which also showed significant relationships with integrated stem-water potential (Psi Int) and irrigation water applied. These findings lead us to conclude that SDIs have important and statistically significant effects on fruit quality. Thus, the application of sustained-deficit irrigation (SDI with WSI of 50) provides promising possibilities for optimising citrus irrigation and boosting the water productivity for citrus orchards in a semiarid Mediterranean climate.
  • Authors:
    • Muriel-Fernández, J. L.
    • Durán-Zuazo, V. H.
    • García-Tejero, I.
    • Martínez-García, G.
    • Jiménez-Bocanegra, J. A.
  • Source: Agronomy for Sustainable Development
  • Volume: 31
  • Issue: 4
  • Year: 2011
  • Summary: Citrus is a crop of major economic importance in Spain, cultivated during the dry season when irrigation is essential to guarantee yields of high quality. As water resources are progressively more insufficient, more effective water management in agriculture is crucial. Deficit irrigation in many agricultural crops has frequently proved to be an efficient tool for improving water-use efficiency. We hypothesise that, despite the effectiveness of deficit irrigation, the most suitable strategy in citrus orchards remains to be defined for Mediterranean environment. In this study, for the period from 2006 to 2008, a 12-year-old orange orchard, Citrus sinensis L. Osb. cv. Navelina, grafted onto Carrizo citrange, C. sinensis L. Osb. * Poncirus trifoliata L. Osb., were subjected under two deficit-irrigation strategies defined as follows: (1) low-frequency deficit irrigation applied according to the plant-water status, and (2) sustained-deficit irrigation with a water-stress ratio of 0.6, defined as the ratio of actual water-limited supply in this treatment related to the water supply of the control treatment. The control treatment was irrigated at 100% of ET C for the entire irrigation season (ET C: crop evapotranspiration). Midday stem-water potential (Psi stem) and stomatal conductance ( gS) were used to estimate the water status of the trees. The lowest Psi stem and g S values were registered in the deficit-irrigation treatments with a seasonal pattern consistent with the irrigation dynamics applied in each case. Psi stem and gS values significantly differed from those of the control trees. Although the integrated stress levels were similar in deficit-irrigation treatments, differences in yield and fruit quality were found, having a more positive response to low-frequency deficit irrigation with an increase of 25% in yield in comparison to the sustained-deficit irrigation treatment. Here, we thus demonstrate the significant differences in water productivity. Indeed, water productivity parameter not only depends on the amount of water, but also on the irrigation strategy applied, which promoted substantial water savings without significant impact on yield. The present study highlights that low-frequency deficit irrigation should be adopted as a most appropriate strategy for achieving sustainable water management and attains reasonable yields and improves quality in citrus orchards under Mediterranean semiarid climate.
  • Authors:
    • Muriel-Fernández, J. L.
    • Durán-Zuazo, V. H.
    • García-Tejero, I. F.
    • Jiménez-Bocanegra, J. A.
  • Source: Functional Plant Biology
  • Volume: 38
  • Issue: 2
  • Year: 2011
  • Summary: The continuous monitoring of crop water status is key to the sustainable management of water stress situations. Two deficit irrigation (DI) treatments were studied during the maximum evapotranspirative demand period in an orange orchard ( Citrus sinensis (L.) Osb. cv. Navelina): sustained deficit irrigation irrigated at 55% crop evapotranspiration (ET C), and low-frequency deficit irrigation treatment, in which the plants were irrigated according to stem water potential at midday (Psi stem). Additionally, a control treatment irrigated at 100% of ET C was established. The daily canopy temperature ( TC) was measured with an infrared thermometer camera together with measurements of trunk diameter fluctuations (TDF), Psi stem and stomatal conductance ( gS). The time course of all physiological parameters and their relationships were analysed, confirming that canopy air temperature differential ( TC- Ta) variations and TDF are suitable approaches for determining the water stress. In addition, the maximum daily shrinkage (MDS) and TC- Ta showed high sensitivity to water stress in comparison to Psi stem and gS. Significant relationships were found among MDS and TC- Ta with Psi stem and gS, for monitoring the crop water status by means of MDS vs Psi stem and TC- Ta vs Psi stem. Thus, the combination of these techniques would be useful for making scheduling decisions on irrigation in orchards with high variability in plant water stress.