• Authors:
    • Bedoussac, L.
    • Justes, E.
  • Source: Field Crops Research
  • Volume: 124
  • Issue: 1
  • Year: 2011
  • Summary: There are many indices available to evaluate the potential advantages of intercrops and species interactions but correct choice of index is crucial in making accurate interpretations. This study compared and evaluated the relevance in understanding intercrop functioning of some well-known indices (aggressivity, AG; cumulative relative efficiency index, REIc; land equivalent ratio, LER) and other potentially useful indices (change in contribution, CC; interspecific and intraspecific interaction index, IE and IA; comparative absolute growth rate, CGR). Data collected from a two-year field experiment in SW France with different fertiliser N levels comparing wheat ( Triticum turgidum L., cv. Nefer) and pea (winter pea, Pisum sativum L., cv. Lucy) grown as sole crops or intercrops in a row substitutive design were used to calculate, compare and evaluate the relevance of the selected indices for understanding intercrop functioning. It was found that AG indices (calculated with or without considering sowing density or actual plant density) did not provide the information generally claimed in the literature (i.e. whether a crop is dominant or dominated). Consequently, their use is clearly unadvisable except when analysed jointly with partial land equivalent ratios. The LER index proved to be clearly relevant, versatile and helpful in illustrating the pattern of competitive outcomes in intercropping experiments, in particular when plotting partial LER values of wheat as a function of those of pea. However, LER cannot identify intraspecific and interspecific interactions. To do so we suggest using the intraspecific and interspecific interaction indices, which can also reveal possible facilitation phenomena and allow description of species change in the contribution index (CC). Interaction dynamics between crops that determine the final balance and the outcome of all competitive interactions occurring between the two crops can be evaluated using the CGR index, which is preferable to REIc, particularly when crops differ greatly in their dry weight. Careful choice of index and interpretation of the results are thus essential in correctly understanding species interactions (globally and dynamically) and intercrop efficiency compared with sole crops. Such indices can help highlight and reveal cereal and legume traits suited to intercropping and also appropriate cropping sequences and management techniques, allowing efficient intercropping. However, the results must always be related to actual data values (yield, dry weight or N accumulated) because the indices used cannot evaluate intrinsically quantitative performance but only the relative performance of intercrops compared with that of sole crops.
  • 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-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.
  • Authors:
    • Otero, A.
    • Goni, C.
  • Source: ISHS Acta Horticulturae
  • Issue: 889
  • Year: 2011
  • Summary: Supplementary irrigation in Citrus sinensis (L.) Osbeck 'Spring' navel and Citrus unshiu Marcow trees were studied according to fruit development stages on the northwestern region of Uruguay (32S, 58W) from 2000 to 2009. The effective rainfall (Pe) variability between consecutive years is bigger than the reference evapotranspiration (ETo) variability; despite the annual water balance seems to be adequate for excellent yields. Water deficit occurs at different intensities during fruit growth stages I, II and III. Supplementary irrigation was necessary in 'Spring' navel and satsuma 'Owari' during stage I and II, although 'Spring' navel requires occasionally irrigation during stage III. The major irrigation impact was to increase the fruit weight but not the number of fruits. The increment in the marketable fruit was related to the best size distribution of the fruits, also it was verified an attenuation on the alternate bearing. An inverse and significant relationship was found between the ETo/Pe ratio and the relative yield reduction in the stage I (R 2=0.73) and in stage II (R 2=0.91); and between the ETo/Pe and the fruit weight in satsuma 'Owari', (R 2=0.56) (R 2=0.85) respectively. The yield reduction between trees without irrigation and all year irrigated represents 20% in 'Spring' navel and 40% in satsuma 'Owari'. Maximum water application of 1000-1200 m 3 ha -1 was required for irrigated trees on stage I and between 1800-2000 m 3 ha -1 for the stages I+II. In a close up view, supplementary water is required to reach maximum marketable yield and alternate bearing reduction in citrus production in temperate conditions.
  • 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:
    • Armengot, L.
    • Blanco-Moreno, J. M.
    • Jose-Maria, L.
    • Xavier Sans, F.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 145
  • Issue: 1
  • Year: 2011
  • Summary: Agricultural intensification, at local and landscape scales, has caused a decrease in plant diversity and changes in species composition in cereal fields. To better understand the role of landscape complexity and farming systems in shaping plant assemblages, it is of interest to focus on functional traits rather than on floristic composition, which may help to highlight trends in vegetation patterns. We analysed the relative abundance of various functional attributes (different life forms, growth forms, wind-pollinated species and wind-dispersed species) at three contrasted field positions (boundary, edge and centre) of 29 organic and 29 conventional cereal fields distributed in 15 agrarian localities of NE Spain. Agricultural intensification affected the biological attributes of the vegetation in dryland Mediterranean cereal fields; local factors (farming system and position) had a more prominent role in affecting plant functional composition than the surrounding landscape. Local factors were important for life form distribution, growth form and pollination type, whereas landscape complexity mainly affected the proportion of wind-dispersed species. Therefore, depending on the objective of the study, it is important to select functional attributes sensitive to the different scales of agricultural intensification, especially because landscape complexity and land-use intensity are commonly related.
  • Authors:
    • José-María, L.
    • Sans, F. X.
  • Source: Weed Research
  • Volume: 51
  • Issue: 6
  • Year: 2011
  • Summary: Weed seedbanks are a reserve of weed diversity and can contribute to the prediction of future weed problems in arable fields. Managing seedbanks should therefore help in optimising biodiversity and controlling weed infestations. This study assessed the effects of management system (organic vs. conventional) and landscape complexity on seedbank size and species richness at the edges and centres of Mediterranean dryland cereal fields and examines the relationship between specific management practices and seedbanks. Field edges and organic fields had more species-rich, denser seedbanks than field centres and conventional fields, and landscape complexity had a limited effect on arable seedbanks. Accordingly, the promotion of low-intensity farming practices regardless of landscape complexity, especially at field edges, would be an effective measure for conservation purposes in Mediterranean agroecosystems. Nevertheless, the high seed density of organic seedbanks reveals the need for more effective seedbank management. The analysis of the effects of specific management practices highlights the importance of cleaning crop seeds properly to reduce seedbank size and using complex rotations, especially as this tends to conserve species richness while reducing seed abundance.
  • Authors:
    • Bacalan, G. E.
    • Kaman, H.
    • Uz, I.
    • Sonmez, N. K.
    • Uz, B. Y.
    • Ersahin, S.
    • Kurunc, A.
    • Emekli, Y.
  • Source: Agricultural Water Management
  • Volume: 98
  • Issue: 6
  • Year: 2011
  • Summary: Identification of nitrate (NO 3) leaching hot spots is important in mitigating environmental effect of NO 3. Once identified, the hot spots can be further analyzed in detail for evaluating appropriate alternative management techniques to reduce impact of nitrate on groundwater. This study was conducted to identify NO 3 leaching hot spots in an approximately 36,000 ha area in Serik plain, which is used intensively for agriculture in the Antalya region of Southern Turkey. Geo-referenced water samples were taken from 161 wells and from the representative soils around the wells during the period from late May to early June of 2009. The data were analyzed by classical statistics and geostatistics. Both soil and groundwater NO 3-N concentrations demonstrated a considerably high variation, with a mean of 10.2 mg kg -1 and 2.1 mg L -1 NO 3-N for soil and groundwater, respectively. The NO 3-N concentrations ranged from 0.01 to 102.5 mg L -1 in well waters and from 1.89 to 106.4 mg kg -1 in soils. Nitrate leaching was spatially dependent in the study area. Six hot spots were identified in the plain, and in general, the hot spots coincided with high water table, high sand content, and irrigated wheat and cotton. The adverse effects of NO 3 can be mitigated by switching the surface and furrow irrigation methods to sprinkler irrigation, which results in a more efficient N and water use. Computer models such as NLEAP can be used to analyze alternative management practices together with soil, aquifer, and climate characteristics to determine a set of management alternatives to mitigate NO 3 effect in these hot spot areas.