• Authors:
    • Mahmood, K.
    • Awan, A. R.
    • Singh, R. K.
    • Stille, L.
    • Akanda, R.
    • Smeets, E. M. W.
    • Wicke, B.
    • Faaij, A. P. C.
  • Source: Journal of Environmental Management
  • Volume: 127
  • Issue: September
  • Year: 2013
  • Summary: This study explores the greenhouse gas balance and the economic performance (i.e. net present value (NPV) and production costs) of agroforestry and forestry systems on salt-affected soils (biosaline (agro) forestry) based on three case studies in South Asia. The economic impact of trading carbon credits generated by biosaline (agro)forestry is also assessed as a potential additional source of income. The greenhouse gas balance shows carbon sequestration over the plantation lifetime of 24 Mg CO2-eq. ha(-1) in a rice-Eucalyptus camaldulensis agroforestry system on moderately saline soils in coastal Bangladesh (case study 1), 6 Mg CO2-eq. ha(-1) in the rice-wheat- Eucalyptus tereticornis agroforestry system on sodic/saline-sodic soils in Haryana state, India (case study 2), and 96 Mg CO2-eq. ha(-1) in the compact tree (Acacia nilotica) plantation on saline-sodic soils in Punjab province of Pakistan. The NPV at a discount rate of 10% is 1.1 k(sic) ha(-1) for case study 1, 4.8 k(sic) ha(-1) for case study 2, and 2.8 k(sic) ha(-1) for case study 3. Carbon sequestration translates into economic values that increase the NPV by 1-12% in case study 1, 0.1 -1% in case study 2, and 2-24% in case study 3 depending on the carbon credit price (1-15 (sic) Mg-1 CO2-eq.). The analysis of the three cases indicates that the economic performance strongly depends on the type and severity of salt-affectedness (which affect the type and setup of the agroforestry system, the tree species and the biomass yield), markets for wood products, possibility of trading carbon credits, and discount rate. (C) 2013 Elsevier Ltd. All rights reserved.
  • Authors:
    • Lamso, N. D.
    • Guéro, Y.
    • Tittonell, P.
    • Lahmar, R.
    • Bationo, B. A.
  • Source: Field Crops Research
  • Volume: 132
  • Year: 2012
  • Summary: Low inherent fertility of tropical soils and degradation, nutrient deficiency and water stress are the key factors that hamper rainfed agriculture in semi-arid West Africa. Conservation Agriculture (CA) is currently promoted in the region as a technology to reduce soil degradation, mitigate the effect of droughts and increase crop productivity while reducing production costs. CA relies on the simultaneous use of three practices: (1) minimum or zero-tillage; (2) maintenance of a permanent soil cover and; (3) diversified profitable crop rotation. The most prominent aspect of CA for degraded lands in the semi-arid tropics would be the organic soil cover that impacts on the soil water balance, biological activity, soil organic matter build-up and fertility replenishment. Yet, the organic resources are the most limiting factor in Sahelian agroecosystems due to low biomass productivity and the multiple uses of crop residues, chiefly to feed the livestock. Hence, CA as such may hardly succeed in the current Sahelian context unless alternative sources of biomass are identified. Alternatively, we propose: (1) to gradually rehabilitate the biomass production function of the soil through increased nutrient input and traditional water harvesting measures that have been promoted as "soil and water conservation" technologies in the Sahel, e.g. zai, in order to restore soil hydrological properties as prerequisite to boosting biomass production; (2) to encourage during this restorative phase the regeneration of native evergreen multipurpose woody shrubs (NEWS) traditionally and deliberately associated to crops and managed the year around and; (3) to shift to classical, less labour intensive CA practices once appropriate levels of soil fertility and water capture are enough to allow increased agroecosystem primary productivity (i.e., an active 'aggradation' phase followed by one of conservation). The CA systems we propose for the Sahelian context are based on intercropping cereal crops and NEWS building on traditional technologies practiced by local farmers. Traditionally, NEWS are allowed to grow in croplands during the dry season; they reduce wind erosion, trap organic residues and capture the Harmattan dust, influence the soil hydraulics and favour soil biological activity under their canopies. They are coppiced at the end of the dry season, leaves and twigs remain as mulch while branches are collected for domestic fuel and other uses. Shoots re-sprouting during the rainy season are suppressed as weeds. Such CA systems have limited competition with livestock due to the poor palatability of the shrub green biomass, which may increase their acceptance by smallholders. Such aggradation-conservation strategy is not free of challenges, as it may imply initial soil disturbance that entail important labour investments, substantially change the structure and management of the cropping system (annual crop-perennial plant), and lead to emerging tradeoffs in the use of resources at different scales. This paper offers a state of the art around NEWS and their integration in relay intercropping CA systems, discusses the above mentioned challenges and the main research needs to address them.
  • Authors:
    • Aragues, R.
    • Isidoro, D.
    • Barros, R.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 155
  • Year: 2012
  • Summary: Nitrogen (N) pollution induced by irrigated agriculture is a significant environmental problem. The main N inputs and outputs were measured or estimated in the semi-arid La Violada irrigation district (Spain). Data on two periods (1995-1998 and 2006-2008) were compared and related to observed changes during the decade in cropping patterns and N fertilization and irrigation management. N fertilization exceeded crop N uptake due to over-fertilization of corn (426 kg N/ha in 1995-1998 and 332 kg N/ha in 2006-2008) and alfalfa (62 kg N/ha). Between the two periods, N fertilization decreased by 56%, primarily due to a change from corn to alfalfa and barley. Accordingly, N losses in the irrigation return flows (IRF) diminished from 31% of the applied fertilizer in 1995-1998 to 20% in 2006-2008. NO 3- concentrations and NO 3-N loads in the IRF decreased from 40 mg/L and 106 kg N/ha in 1995-1998 to 21 mg/L and 22 kg N/ha in 2006-2008, due to lower N fertilization, lower corn area and improved irrigation efficiency. N contamination in the IRF will be minimized by increasing the irrigation efficiency and decreasing the corn area and its N fertilization rates, particularly when supplemental organic N is applied at pre-sowing.
  • Authors:
    • dos Santos, C.
    • Sofiatti, V.
    • Bezerra, J.
    • da Silva, B.
    • Bezerra, B.
  • Source: Agricultural Water Management
  • Volume: 107
  • Year: 2012
  • Summary: During the twentieth century, the cotton crop was the main agricultural product in the semiarid regions of Brazil, with over 3.2 million hectares planted. However, due to structural problems, this activity became uncompetitive and economically unfeasible, being virtually wiped out in the eighties. The revival of cotton growing in semiarid lands of Brazil is important to the regional economy. However, the adoptions of new technologies mainly related to the water use efficiency are needed. Thus, accurate ETc estimates are required for efficient irrigation management. The K-c method is a practical and reliable technique for estimating ETc, and has been vastly applied by the farmers in the semiarid lands of Brazil. However, the use of K-c values listed in FAO-56 can contribute to ETc estimates that are substantially different from actual ETc. Hence the importance of determining K-c values experimentally. A field study on sprinkler-irrigated cotton was carried out during the dry seasons of 2008 and 2009 years in the Apodi Plateau, Brazilian semiarid lands. This study aims to determine ETc and the K-c curve values using the Bowen Ratio Energy Balance (BREB) technique. The locally developed K-c curves are compared with generalized FAO K-c values adjusted for local climate and management. The ETc values were 716 mm and 754 mm in 2008 and 2009, respectively. These values were higher than those observed in other areas of Brazilian semiarid. These differences are attributed to weather heterogeneity in the region. The average of K-c values were 0.75, 1.09 and 0.80 for initial, middle and end, of growing season, respectively. These values were lower than the Kc-FAO-Adjusted to local conditions. For this reason, ETc values obtained from Kc-FAO-Adjusted were overestimated by 12% in both the years. The irrigation scheduling based on the Kc-FAO-Adjusted increases production cost and yield loss. (C) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Gitz, D.
    • Booker, J.
    • Bednarz, C.
    • Lascano, R.
    • Bufon, V.
  • Source: Irrigation Science
  • Volume: 30
  • Issue: 4
  • Year: 2012
  • Summary: Crop irrigation with subsurface drip (SDI) is increasing in the semiarid Texas High Plains (THP). Information on drip-tubing positioning, irrigation strategies, and wetted soil area is needed to increase rainwater effectiveness when well capacities are inadequate to meet full irrigation requirements. Time and resources necessary to test SDI strategies for different conditions through field experimentation is too large. However, a mechanistic model such as Hydrus-2D can quantify the effect of different installation geometries and irrigation strategies. Our objective was to experimentally validate the Hydrus-2D in an Amarillo soil in THP so that the model can be used to evaluate different irrigation frequency and timing strategies for SDI cotton. Results showed that Hydrus-2D simulated volumetric soil water content within +/- 3% of measured values, and simulation bias represented the smaller portion of the simulation error, indicating that the model can be used to evaluate irrigation strategies.
  • Authors:
    • Oliveira, P.
    • Coelho Filho, M.
    • Coelho, E.
  • Source: Acta Horticulturae
  • Issue: 928
  • Year: 2012
  • Summary: Meeting the increased water requirement in agriculture due to the increases of irrigated areas in order to provide food for growing populations, relies on the application of water with increased efficiency. This work evaluated the partial root drying technique for lemon 'Tahiti' trees under semi-arid climate conditions in the north of Minas Gerais. The experiment was carried out in randomized block design with nine treatments and four replicates. Treatments were based on percentages of reduction of calculated irrigation water depth, i.e., 25% corresponding to the reduction of irrigation on one quarter of the area occupied by the plant and 50% corresponding to the reduction of irrigation on half of the plant area during three phonological phases (I, II and III) of lemon 'Tahiti'. The results showed that irrigation scheduling using the partial root drying method may be performed with any of the treatments evaluated. The larger yields and water use efficiencies were obtained for treatments T7 and T8 which were a reduction of 25% of total irrigation every 7 or 15 days during flowering followed by a reduction of 50% of total irrigation every 7 or 15 days in phases II and III.
  • Authors:
    • Sutton, B.
    • Neilsen, J.
    • Mahan, J.
    • Burke, J.
    • Conaty, W.
  • Source: Crop Science
  • Volume: 52
  • Issue: 4
  • Year: 2012
  • Summary: A plant-based thermal optimum approach to irrigation scheduling provides potential benefits in that water applications are scheduled on the basis of plant response to water status. Such irrigation systems require a defined thermal optimum for the crop and while such optimum values have been identified for cotton (Gossypium hirsutum L.) cultivars in the United States, there is no information of this type for cultivars common in Australian production. This paper outlines a threefold approach to determining the optimum temperature (T-opt) of the commercial Australian cotton cultivar Sicot 70BRF in an Australian production system. It combines the use of a laboratory-based fluorescence assay, field-based net C assimilation rate (A) and stomatal conductance to water vapor (g(s)), and canopy temperature (T-c)-yield relations. The fluorescence assay showed a T-opt between 28 and 30 degrees C while leaf gas exchange rates peaked at a leaf temperature (T l) of 29 degrees C. The T-c-yield relations peaked at 26 degrees C, with yield reductions observed when T-c > 28 degrees C. We conclude the T-opt of the Australian upland cotton cultivar Sicot 70BRF to be 28 +/- 2 degrees C. This T-opt will provide valuable information for use in thermal optimum irrigation scheduling systems.
  • Authors:
    • Chehbouni, A.
    • Lepag, M.
    • Jarlan, L.
    • Ezzahar, J.
    • Erraji, T.
    • Khabba, S.
    • Er-Raki, S.
    • Hanich, L.
  • Source: Acta Horticulturae
  • Issue: 951
  • Year: 2012
  • Summary: Sap flow measurements based on heat balance method gives a direct measurement of the mass flow rate of sap in the stem. However, extrapolation of these measurements from the stem to the field scale is an important challenge. In this study, 15 branches of citrus trees with different diameters were equipped with Dynamax sap flow gauge. These individual branch measurements have been after extrapolated to the canopy transpiration by using two up-scaling methods. The first one uses the relationship between sap flow and branches diameter and the second one uses the distribution of the branch diameter in the orchards. The results showed a good agreement between the two methods estimates (R 2=0.95). A comparison between scaled-up transpiration from sap flow and measured evapotranspiration (ET ed) by eddy covariance showed an average daily difference of about 0.87 mm/day which represents 25% of ET ed. This substantial amount of water was lost through soil evaporation and part of it could be saved by improving the drip irrigation management.
  • Authors:
    • Arriaga-Sevilla, J.
    • Durán-Zuazo, V. H.
    • García-Tejero, I.
    • Muriel-Fernández, J. L.
  • Source: Agronomy for Sustainable Development
  • Volume: 32
  • Issue: 3
  • Year: 2012
  • Summary: Water shortage is becoming a severe problem in arid and semi-arid regions worldwide, reducing the availability of agricultural land and water resources. Deficit irrigation strategies can improve water-use efficiency and the sustainability of agro-ecosystems, although it is important to model the effects on yield loss due to irrigation water restrictions. This work estimates the water production function in citrus trees, determining the relationship between plant water stress and yield depression, as well as establishing a mathematical model for each phenological stage considered (flowering, fruit growth and ripening), and for the entire productive process. For three consecutive years (2006-2008), four regulated deficit irrigation treatments plus a control (100% crop water evapotranspiration (ET C)) were implemented in 13-year-old citrus trees ( Citrus sinensis L. Osb. cv. Navelina). Different water production functions were determined for each phenological stage, establishing the relationship between the irrigation water stress and crop yield. Our results show that the fruit growth and flowering stages were the most sensitive periods in relation to irrigation water deficit and yield loss. Water stress close to 50% of ET C during the flowering stage would impose a yield loss of up to 20%, whereas this same water stress level during the fruit growth or ripening stages would result in yield losses of nearly 10% and 6%, respectively. The adjustment with cross terms ( r2=0.87) estimated the yield loss with good accuracy, being very similar to data measured in each study season. Consequently, the combined effect of deficit irrigation in different stages would be an additive-multiplicative model, considering that the effect of water stress in previous periods determined the crop yield response. Our model indicated that the crop water production function under deficit irrigation programmes would have a quasi-linear relation for water deficits below to 40% ET C. The previous model functions did not enable us to establish an accurate relationship when the water stress was applied in different phenological stages. Thus, this new interpretation is valuable to improve our knowledge and predict the impact of regulated deficit irrigation and have potential application in precision water stress and sustainable irrigation scheduling for citrus.
  • Authors:
    • Arriaga, J.
    • Muriel-Fernández, J. L.
    • Durán-Zuazo, V. H.
    • García-Tejero, I. F.
  • Source: Scientia Horticulturae
  • Volume: 133
  • Year: 2012
  • Summary: This study examines the suitability of trunk dendrometers for assessing fruit growth under deficit irrigation (DI) for two consecutive years in a mature citrus orchard. Two DI programmes were applied during the maximum evapotranspirative demand period: sustained-deficit irrigation, applied at 50% ET C on average, and low-frequency deficit irrigation, applied according to plant-water status, establishing different irrigation-restriction cycles. Additionally, a control treatment at 100% ET C was monitored for the entire irrigation season. Trunk daily growth (TDG) and fruit daily growth (FDG) were estimated together with stem-water potential at midday (Psi stem) and the maximum daily shrinkage of the trunk (MDS). Significant relationships were determined for Psi stem vs. TDG ( R2=0.60), and vs. FDG ( R2=0.78). In addition, significant relationships were established between TDG vs. FDG ( R2=0.60), and between the daily increment of MDS (DeltaMDS) and FDG ( R2=0.50), revealing the strong connection between trunk and fruit variations caused by water stress. According to these findings, the DI effects on fruit growth can be monitored by means of TDF or temporal evolution of Psi stem, promising automation possibilities for appropriately regulating irrigation under DI programmes, and predicting its effects on fruit size by continuous field measurement.