FAO Method Research Articles

Crop coefficient for cotton under plastic mulch and drip irrigation based on eddy covariance observation in an arid area of northwestern China

Crop coefficient (Kc) is an important parameter in irrigation management. Kc values published by Food and Agriculture Organization (FAO) are subject to uncertainties and adjustment when applied to different areas under different climates and/or irrigation methods. This study investigated Kc of cotton in an experimental site under plastic mulch and drip irrigation in the Tarim River Basin in northwestern China through a 3-year crop evapotranspiration (ETc) observation by using the eddy covariance system. The average ETc during the growing seasons in 3 years is 526mm, and the locally developed Kc values during the initial, mid, and late seasons are 0.23, 0.88, and 0.44, respectively. The relationships between Kc and leaf area index (LAI), Kc and growing degree days (GDD), and Kc and growing days after sowing (GD) were further analyzed. The relationship between weekly Kc and GDD, as well as weekly Kc and GD, during the growth stage after sowing is fitted to a third-order polynomial model (R2=0.96 and 0.95, respectively). Meanwhile, the relationship between weekly Kc and LAI is suitably described using a logarithmic model (R2=0.87). As LAI was not measured every day, daily and weekly models were reestablished based on LAI measurement days. The performance of the LAI model is low on a weekly basis (R2=0.88, 0.88, 0.72 for GD, GDD, and LAI models, respectively) but accurate on a daily basis (R2=0.81, 0.81, 0.89 for GD, GDD, and LAI models, respectively). GD is a reliable indicator to estimate Kc of cotton under plastic mulch and drip irrigation and provides a basis for evapotranspiration estimation in cotton fields by using the FAO-56 method. This study provides valuable supplementary and reference information for efficient water management in cotton cropping systems in arid regions.

Water irrigation management using remote sensing techniques: a case study in Central Tunisia

The optimization of water resources management in arid region needs reliable information and knowledge on water resources and water requirements. Remote sensing and Geographic Information System techniques are used to estimate the Irrigation Water Requirements (IWR) in the Regueb-watershed for the summer season, when the peak of the water consumption is reached. The landsat 8 images were used to identify irrigated area and to estimate the IWR in dry season. Five methods were applied for the identification of irrigated area based on supervised classification and spectral indices. Two different approaches were applied to estimate IWR: K c-NDVI method based on the relationship between the Normalized Difference Vegetation Index (NDVI) and the crop coefficient (K c) and FAO approach based on the empirical equation of Penman–Monteith and the single K c given by FAO-56. The maximum likelihood classifier (MLC) performed the highest overall accuracy (85 %) and a kappa coefficient of 0.82. The IWR resulting values range from 10 to 14.5 Mm3 in summer season. To evaluate the methodology, five test areas were selected based on the diversity of crops in the whole study area. The validation of results indicates that the IWR values calculated using FAO method were in good agreement with the IWR values derived from remote sensing approach.

Studies on Use of TNAU- UV Light Trap for Management of Phosphine Resistance in Lasioderma serricorne (F.) (Coleoptera:Anobiidae) in Turmeric Warehouses

Lasioderma serricorne (F.) commonly called cigarette beetle is a cosmopolitan, polyphagous and major insect pest of stored turmeric that is known to be resistant to the phosphine fumigation. Practical studies were carried out to assess the efficacy of TNAU UV-Light Trap in mass trapping of L. serricorne during the pre and post fumigation periods and its role in phosphine resistance management in L. serricorne in turmeric warehouses. Adult beetles collected from UV light traps before and after fumigation were tested through bioassay on the basis of the response of adults to discriminating concentration of 0.07mg L -1 for 24 h exposure period using modified FAO method (FAO, 1975). The results of the present study showed that, the mean number of adults caught per trap/day before and after fumigation ranged from 52.7 to 83.5 and 9.6 to 18.2 beetles per light trap, respectively. The bioassay results showed that, the phosphine resistance level in L. serricorne collected from UV- Light traps ten days before and after fumigation ranged from 52.85 to 65.37 and 68.24 to 76.53 per cent, respectively. Further, the beetles caught in large numbers in light traps during the post fumigation period were found to be more resistant to phosphine than the pre fumigation population. Hence, UV- Light trap can be used as one of the resistance management strategy for phosphine resistance in L. serricorne in turmeric warehouses since mass trapping of L. serricorne was recorded in TNAU- UV Light trap during pre and post fumigation periods.

Validation and calibration of solar radiation equations for estimating daily reference evapotranspiration at cool semi-arid and arid locations

ABSTRACTIn this work, the applicability of 12 solar radiation (RS) estimation models and their impacts on daily reference evapotranspiration (ETo) estimates using the Penman‐Monteith FAO-56 (PMF-56) method were tested under cool arid and semi-arid conditions in Iran. The results indicated that the average increase in accuracy of the ETo estimates by the calibrated RS models, quantified by the decrease in RMSE, was 2.8% and 6.4% for semi-arid and arid climates, respectively. Mean daily deviations in the estimated ETo by the calibrated RS equations in semi-arid climates varied from −0.283 mm/d-1 for the Glover‐McCulloch model to 0.080 mm/d for the El-Sebaii model, with an average of −0.109 mm/d-1, and in arid climates, they ranged from −0.522 mm/d-1 for the Samani model to 0.668 mm/d for the El-Sebaii model, with an average of 0.125 mm/d-1.Editor D. Koutsyiannis; Associate editor Not assigned

Energy balance and evapotranspiration of melon grown with plastic mulch in the Brazilian semiarid region

Melon plants (Cucumis melo L.) are grown in the state of Rio Grande do Norte (RN), the largest producer of melons in Brazil, with plastic mulch and agrotextiles. Studies of crop evapotranspiration (ET) under these conditions are required to ensure adequate irrigation. This study aimed to determine the crop coefficients (Kc) of irrigated melon plants grown with mulch and agrotextiles in the region of Mossoro, RN, based on the Bowen Ratio Energy Balance (BREB) method. Two experiments were conducted at different times during the 2009/2010 season in a melon producing area (4°59'52 S, 37°23'09 W, and 54 m elevation) to define ET and Kc. Due to the plastic cover and reduced precipitation during the experiments, the Kc obtained by the BREB method was considered the basal Kc - KcbBREB. The results were compared with the Kcb from the FAO 56 Bulletin. There was close agreement between BREB and FAO ET measurements (12 % underestimation by the FAO method for the entire crop season), with sizeable differences only during the initial phenological stage. The mean KcbBREB values of the two field campaigns were 0.26, 0.96 and 0.63 for the initial, midseason and late stages, respectively. The high KcbBREB value in the initial growth phase may be related to the effect of the plastic mulch and agrotextiles on the energy balance at the surface. The relationship between KcbBREB and fc had high correlation, making possible an estimation of the melon Kcb based on the level of crop ground cover.

Assessment of the FAO traditional land evaluation methods, A case study: Iranian Land Classification method

AbstractLand evaluation is a critical step in land‐use planning. Although many methods have been developed since the formulation of the FAO framework for land evaluation, several of the more traditional approaches still remain in widespread use but have not been adequately evaluated. Contrary to more recent land evaluation systems, which need considerable data, these systems only require basic soil and landscape information to provide a general view of land suitability for major types of land use. As the FAO initially presented its qualitative framework for land‐use planning, based on two previous methods developed in Iran and Brazil, in this study we assessed the reliability and accuracy of a traditional land evaluation method used in Iran, called land classification for irrigation (LCI), comparing its results with several qualitative and quantitative methods and actual yield values. The results showed that, although simpler than more recently developed methods, LCI provided reliable land suitability classes and also showed good relationships both with other methods analysed and with actual yields. Comparisons between qualitative and quantitative methods produced similar results for common crops (a barley–alfalfa–wheat–fallow rotation). However, these methods performed differently for opportunist crops (such as alfalfa) that are more dependent on income and market conditions than on land characteristics. In this work, we also suggest that using the FAO method to indicate LCI subclasses could help users or managers to recognize limitations for land‐use planning.

Land Suitability Evaluation for Plantation Forest Development Based on Multi-criteria Approach

Information of land suitability is needed to prioritize suitable forest plantation for land use development. This is important to increase land productivity and eficiency on forest management decision making process. This research aimed to: (1) to evaluate land suitability based on pedo-agroclimate characteristics for plantation forest development; (2) to identify the farming-based socio-cultural and economic characteristics; (3) to determine the priority level of trees that will be cultivated through plantation forest development. This research was conducted from January to May 2015 in four districts namely: Kapontori, Lasalimu, South Lasalimu, and Siotapina (KALALASSI region). These are located in Buton Island, Southeast Sulawesi Province, Indonesia. The research method used was a spatial research method using GIS [1];[3]. The research has three main activities: data collection, evaluation, and mapping. Data collection included data on land biophysics, climate, and forest management development using survey method. Land evaluation was carried out on FAO method [14] and [15]. The major of trees were determined using LQ method [16] and the priority level of trees determine using MCDM method through the application of AHP [3];[4]. The last but not the least, spatial data development was used to map recommended forest land uses. The results showed that: (1) there were three major of trees in the research area, namely: Teak, Mahogany and Silk Tree; (2) based on land suitability classification, there are two classes found in the KALALASSI region, namely: moderately suitable (S2) which were located 3,836.05 ha for Teak and Mahagony, and Marginally Suitable (S3), which are located 3,343.45 ha for Teak, 3,467.20 ha for Mahagony, and 10,106.22 ha for Silk Tree; (3) the sequence of trees priority in KALALASSI region is Teak, Silk Tree, and Mahogany, then based on these recommendation, forest land uses and management plan were developed.

Physicochemical and Bacteriological Analysis of Well Water in Kaduna Metropolis, Kaduna State

The study was carried out to determine the physicochemical and bacteriological quality of well water from Kaduna metropolis. The physiochemical quality of the water was analyzed using FAO (1997) method and the result obtained showed that the water sample was acidic, some neutral but they all fell within the range as recommended by WHO, and NAFDAC, the water sample fell within the recommended range for Nitrite, turbidity, conductivity and chloride. The bacteriological quality of the water was also determined by most probable number technique, the total coliform count and the differential E. coli count in which several tubes with diluted buffered solution to dilute the water sample and then incubated for 24 hrs, this is called the presumptive test while for the confirmation test, positive tubes from the presumptive test were inoculated into separate growth medium for total coliform and E. coli and then incubated. The results obtained showed that total coliforms were observed ranging from 11.0 to 63.0 cfu/ml with Sabon Tasha (TS) having the highest counts and Nasarawa (NS) with the least counts, while only two sites—Sabon Tasha (ST) and Kakuri (KK)—were recorded to have feacal contaminations. E. coli was identified suggesting that the water samples from the two were having recent feacal contamination.

ANALYZING TRENDS IN REFERENCE EVAPOTRANSPIRATION IN NORTHWEST PART OF IRAN

Evapotranspiration is one of the most important components of the hydrological cycle. It is essential in all of hydro climatological studies, irrigation and drainage calculations, water balance, and crop water requirements. The aim of this study is to investigate temporal trends of reference evapotranspiration (ETo) in the Northwest part of Iran. For this purpose, the meteorological data from 20 synoptic stations over a 22-year time period (1986–2007) were used. After the calculation of ETo using the Penman-Monteith FAO-56 method, the non-parametric Mann-Kendall test was used to investigate the temporal trends on monthly, seasonal and annual scales. The Sen’s estimator method was used and to calculate the slope of the trend line. The results indicated that the ETo trend was increasing (positive) in various months, except for the Sarab station in December. On a monthly scale, the Maragheh station showed the highest positive slope in August, and the Bijar station showed the highest negative slope in May. 43.34% of the stations showed a significant trend, and 56.66% did not show a significant trend. In seasonal and annual time periods there was not a significant decreasing trend in any of the stations. The analysis of the results shows that in the spring 20%, in the summer 55%, in the fall 70%, in the winter 75%, and on an annual scale 60% of the stations under study showed an increasing trend. For modeling these changes, the spatial distribution of ETo trends (on monthly, seasonal, and annual scales) were mapped in ArcGIS. Final models determine that most stations in this study show an increasing trend on monthly, seasonal and annual scales.

A Life-Size and Near Real-Time Test of Irrigation Scheduling with a Sentinel-2 Like Time Series (SPOT4-Take5) in Morocco

This paper describes the setting and results of a real-time experiment of irrigation scheduling by a time series of optical satellite images under real conditions, which was carried out on durum wheat in the Haouz plain (Marrakech, Morocco), during the 2012/13 agricultural season. For the purpose of this experiment, the irrigation of a reference plot was driven by the farmer according to, mainly empirical, irrigation scheduling while test plot irrigations were being managed following the FAO-56 method, driven by remote sensing. Images were issued from the SPOT4 (Take5) data set, which aimed at delivering image time series at a decametric resolution with less than five-day satellite overpass similar to the time series ESA Sentinel-2 satellites will produce in the coming years. With a Root Mean Square Error (RMSE) of 0.91mm per day, the comparison between daily actual evapotranspiration measured by eddy-covariance and the simulated one is satisfactory, but even better at a five-day integration (0.59mm per day). Finally, despite a chaotic beginning of the experiment—the experimental plot had not been irrigated to get rid of a slaking crust, which prevented good emergence—our plot caught up and yielded almost the same grain crop with 14% less irrigation water. This experiment opens up interesting opportunities for operational scheduling of flooding irrigation sectors that dominate in the semi-arid Mediterranean area.

Support vector machine based modeling of evapotranspiration using hydro-climatic variables in a sub-tropical environment

Existing models and methods report crop coefficient (Kc) as a function of time but do not consider the variations due to surface conditions, wetting methods, meteorological conditions, and other biophysical factors. These limitations result in erroneous crop evapotranspiration (ETc) estimates, especially for non-standard conditions (e.g. plastic mulch). We present Support Vector Machine (SVM), a data-driven model based on statistical learning theory, for predicting generic Kc and ETc using a uniquely large dataset (10 seasons) from lysimeters for multiple crop-seasons combination under the plastic mulch conditions. The data used in this study were obtained from six years of lysimeter-based measurements (Shukla et al., 2006, 2012, 2014a, 2014b; Shukla and Knowles, 2011) for two distinctly different crop types (vine and erect) under two contrasting irrigation methods, drip and sub-irrigation. The SVM-based models predicted bell pepper (erect crop; r2=0.71) and watermelon (vine crop; r2=0.82) Kc as a function of time, water table depth, and number of rainfall events. The time since transplant represents the plant growth and, therefore, transpiration. The water table depth and rainfall events capture the effect of surface soil moisture on evaporation. The crop type-specific model is robust since it works for two different irrigation methods and growing seasons (spring and fall). The SVM model was superior to the Artificial Neural Network and Relevance Vector Machine models, two data-driven models used in hydrology. The errors in predicting ETc from the SVM model were only 2.6% and 11.2% for watermelon and bell pepper, respectively, highlighting the model accuracy. For both crops, the SVM predicted Kc values were not statistically different from the actual Kc values. In contrast, the FAO-56 values were significantly lower than the actual Kc values for both bell pepper (p=0.016) and watermelon (p=0.025). When evaluated in the context of watershed-scale budgets, the SVM model improved the accuracy in ETc estimates by 49.3mm over the FAO-56 method, and this improvement represents 70% (70.7mm) of the observed surface flow. Improved accuracy of the SVM model makes it useful in deriving local Kc using readily available hydro-climatic data for applications ranging from field-scale water management to watershed-scale modeling. The proposed model can be used to develop region-specific Kc to improve ETc estimates. Future efforts should be made to explore the development of similar models for open-field crops.

Water relations of two contrasting sugarcane genotypes

High-fibre sugarcane (energy-cane) cultivars have generated a lot of interest as candidates for bio-fuel production in marginal areas, especially when cellulosic ethanol is also considered. However, a better understanding is required of how much water would be used during cultivation and of their response to drought in terms of water relations. The aim of the study was to investigate the water relations of a high-fibre sugarcane hybrid (Saccharum spp F1 hybrid, 04G0073, referred to as G73) under well watered and drought stress conditions, and compare it with that of a traditional sugarcane cultivar (Saccharum spp, cultivar N19). This would help with a better understanding of the underlying physiology of differences in water use and drought response between high-fibre and traditional sugarcane. The trial consisted of four plots which were planted in a rainshelter facility at Mount Edgecombe, South Africa in October 2011. Two plots received adequate water for the duration of the trial (well-watered treatments), while the other two received no water after 10 February 2012 (water stress treatments), except for the unintended intrusion of water into the root zone on 3 March 2012. The experiment ended on 7 May 2012. Volumetric soil water content was measured with a neutron water meter and daily sap flow was recorded using the non-intrusive heat-balance method. Leaf water potential (ψL) was measured periodically with a pressure chamber, while stomatal conductance was measured periodically with a LiCor 6400. The study has shown that the heat balance method (constant heat source) of measuring sap flow velocity is a suitable technique for estimating transpiration rate in sugarcane. Transpiration rates of well-watered G73 were higher (11%) than that of well-watered N19, presumably due to a higher green leaf area index (GLAI) (6%). There was no evidence to suggest that parameters for calculating maximum evapotranspiration using the Penman-Monteith or FAO method need to be adjusted for high-fibre varieties. Transpiration rates of N19 were reduced sooner and at higher levels of soil water status, than that of G73, as water stress levels increased. G73 had the ability to maintain higher stomatal conductance (gs) than N19 at the same soil water status level, even though leaf water potential was similar between the genotypes. Higher transpiration rates of stressed G73 plants facilitated extended extraction of water from a drying soil profile, which could be a detrimental trait in marginal areas where long dry spells are common. Reduced rates of transpiration and water extraction from the soil profile through stomatal control could be a desirable trait for survival and optimal biomass production in marginal areas. G73 had higher biomass yield (12%) and WUE (10%) under well-watered conditions compared with N19 but water stress reduced both yield and WUE of G73 by 44% and 24%, respectively. The data obtained from the current study will be used for deriving crop parameters for sugarcane crop models with regards to energy-cane genotypes and may be useful in identifying marginal areas suitable for energy-cane cultivation.

English

We evaluated the potential of sap flow values estimated from records with the heat dissipation method for irrigation in an olive orchard (Olea europaea L, cv. Meski) near Enfidha, Tunisia. Trees were cultivated at 7 × 7 m spacing. Two drip irrigation treatments were imposed using the sap flow and the FAO methods. The two treatments were irrigated by 100% of crop evaptranspiration (ETc). T1: ETc measured by the sap flow method and T2: ETc estimated by the FAO method. Sap flow, leaf and stem water potentials, leaf photosynthetic activity, stomatal conductance and transpiration rate were recorded in representative trees from both treatments, during the full irrigation season from April to August. Results showed that the irrigation dose calculated from T2, based on FAO method compared to the T1, based on sap flow decreased by about 25%. Under T1 irrigation scheduling strategy, the daily transpiration decreased by 20% and consequently the water potentials were decreased significantly. Infect, olive trees under T1 were moderately stressed and subsequently leaf gas exchange parameters were affected by about 15%.   Key words: Sap flow, water potential, leaf photosynthetic activity, olive tree, Olea europaea irrigation scheduling.

Combination of fuzzy and AHP methods to assess land suitability for barley: case study of semi arid lands in the southwest of Iran.

Land suitability analysis, commonly known as land evaluation, is considered an interface between land resourcesurvey and land use planning and management. Land evaluation be carried out to estimate the suitability of land fora specific use such as arable farming or irrigated agriculture. There are several established techniques for generatingland suitability evaluation. This research was carried out to evaluate the capability of a combined fuzzy AHP methodfor land suitability evaluation for barley crops in the southwest of Iran, and to compare the results with the standardmethod of the FAO framework. Eight soil parameters were chosen for cropland suitability analysis and thematicmaps were developed with Kriging method for each of these parameters. Different fuzzy membership functionsobtained from the literature were employed and weights for each parameter were calculated according to AHP.Landscape and soil requirements for barley were determined based on the FAO method. Finally, land suitabilityclasses were provided for each land unit. Comparing the results with expert judgments shows that the fuzzy AHPmethod has a higher accuracy than the standard FAO method. Further development of the fuzzy AHP method wouldbe advantageous for improving the accuracy of land suitability analysis.

Climate Based Risk Assessment for Maize Producing Areas in Rainfed Agriculture in Mexico

Rainfed areas in Mexico accounts for 14 million hectares where around 23 million people live and are located in places where there is a little climatic information. The severe drought that has impacted northern Mexico in the past several years as well as other parts of the country, has forced decision takers to look for improved tools and procedures to prevent and to cope with this natural hazard. For this paper, the methodology of the Food and Agricultural Organization of the United Nations (FAO) for estimating water balance variables was modified to provide crop yield estimations under rainfed agriculture in maize producer states of Mexico. The water balance accounts for the daily variation of soil water content having main input rainfall (Pp) and main output crop evapotranspiration (Eta). The algorithm computes crop yield using two distinctive approaches: 1) one based on surplus/deficit functions for each crop considered and 2) yield estimations based on soil water balance and water function productions of the crop being analyzed. For computing water balance and crop yields, a computer model is built that incorporates the FAO method for water balance (MODEL SICTOD: Computational System for Decision Taking, acronym in Spanish) which stochastically generate precipitation based on wet/dry transition probabilities using a first order Markov chain scheme. Maps of average crop yields were obtained after interpolating model outcomes for the main maize producer states of Mexico: Jalisco, Michoacan, Guerrero, Puebla Oaxaca and Chiapas. Different planting dates were analyzed, early (90 days of length period), intermediate (120 days of length period) and late (150 days of length period). Crop yield variability correlates to the transition probability on having a wet day following a dry day. Results have shown high yield variation and probability of crop yield failure and climatic risk follows a distinctive pattern according to planting date and rainfall occurrence. The approach used is of great support for decision taking processes.

Assessment of environmental hazards in the north western coast -Egypt using RS and GIS

Soil erosion, salinity and sodicity hazards are serious problems in the northern west coast of Egypt and lead to reducing the soil quality and increasing the degradation of soil resources. Sidi Barrani and Al-Sallum regions are selected as study areas which are located from a longitude of 25°10′00″ to 26°55′00″East and from a latitude of 31°00′0″ to 31°37′30″ North. Erosion hazard was estimated using the ‘Universal Soil Loss Equation’ (USLE), which is a simple empirical model that is widely used for assessing long-term annual soil loss .The salinity and sodicity hazards were estimated based on FAO method as standard reference. The resultant map of annual soil erosion shows a maximum soil loss of 60th−1y−1with a close relation to foot slopes and wide units on the steep side-slopes (with high LS value) and the erodibility value reached to 0.1th−1y−1. Meanwhile sand beaches and sabkha units are characterized by high environmental hazards of both water erosion, salinity and sodicity, while in the overflow basin units are identified as low environmental hazards. The spatial environmental hazards assessment is conducted by using integrated GIS and RS which can serve as effective inputs in deriving strategies for sustainable land use planning and management.

Hydrological modeling of the unsaturated zone — Evaluation of uncertainties related to the FAO soil classification system

An essential input for environmental studies, especially for hydrological simulations is the soil information, which is usually provided by spatial soil databases. Despite the growing number of related analyses little is known about the uncertainty associated to databases. This study aimed to evaluate this issue. (i) the World Soil Classification System was used to classify soil horizons of the Unsaturated Soil Hydrologic Database of Hungary, (ii) the resulting soil classes were statistically analyzed, (iii) various static measures were derived and dynamic numerical simulations were carried out to assess the uncertainties of the classification method from hydrologic viewpoint. The results question the reliability of the FAO method.

Influence of different cultivars–locations on maximum daily shrinkage indicators: Limits to the reference baseline approach

The use of biosensors for irrigation scheduling is an interesting way to improve water use efficiency. Trunk diameter variations (TDV) have been studied in several species as a biosensor capable of detecting water stress. The most frequently used parameter for this purpose from TDV is maximum daily shrinkage (MDS). In the present study, MDS was studied in olive trees in two locations in Spain (Badajoz and Ciudad Real), with different cultivars in each one (‘Morisca’ in Badajoz and ‘Cornicabra’ in Ciudad Real), for three years in one location and four years in the other. In order to establish a reference baseline for both locations the relationship between vapour pressure deficit (VPD) and MDS was calculated. Four irrigation treatments were used: one control, irrigated by the FAO method, two in relation to stem water potential threshold and one based on both the trunk growth and MDS from linear variable differential transducers (LVDT). Heteroscedasticity was found in MDS data, so the transformation of the square root (SQR) of the data was necessary be done. The reference baseline with SQR of MDS vs VPD was significantly different between varieties/locations. A local calculation is thus needed to obtain an accurate reference baseline. The relationship between SQR of MDS vs stem water potential (SWP) showed a lineal fit with values higher than −1.8MPa. In order to ensure that the relationship between SWP and MDS is not due to their relation to VPD, SWP and MDS were divided by their theoretical values in function of VPD. It was observed that the response of MDS to water stress is much weaker than SWP and in this range of SWP (higher of −1.8MPa) variations of MDS are only due to VPD. The number of sensors necessary for precise measurement of MDS was, on average, more than thirty.

기상자료 분석을 통한 대관령 지역의 작물 최저 한계온도일 추정

대관령 지역의 과거 38년간 (1972-2009)의 기상자료를 수집하여 최저한계온도를 추정하였다. 최저한계온도 출현 빈도 추정은 Gumbel의 극한치 확률분포이론을 도입하여 기온자료의 확률분포함수를 도출하여 이루어졌다. 그 결과 저온 출현일 빈도는 작물의 생산안정성과 밀접한 관계가 있기 때문에 조사하였으며, 저온 출현일이 앞당겨질수록 작물을 일찍 심어 안정된 생육을 유지할 수 있어 그 만큼 수량을 높일 수 있을 것으로 판단되었다. 대관령 지역에서 한계 저온 <TEX>$5^{\circ}C$</TEX> 이상이 5일 이상 지속되는 날짜를 보면 4월 3일, 4월 10일, 4월 20일, 4월 28일, 5월 8일로 나타났으며, 한계저온이 나타나는 시기가 앞으로 당겨질수록 그 시기 (한계저온 <TEX>$5^{\circ}C$</TEX> 출현일)가 출현할 확률이 작아지고 재현되는 기간이 길어져, 작물을 재배할 기회가 줄어들어 작물 파종 및 정식이 어렵게 된다. 따라서 재현기간을 순서대로 보면 50, 25, 10, 5, 2년 이었다. 기온 <TEX>$5^{\circ}C$</TEX>에 적응하는 저온성 작물 (배추, 샐러리, 토마토, 딸기 등)은 5월 8일 이후에 파종 또는 정식하면 대관령 지역에서 안정된 수량을 얻을 수 있을 것으로 판단되었다. Daegwallyeong area to be formed along the mountainous terrain more above 800 m of sea level is known as the cold zone to occur frequently wind, rain and fog. This study to evaluate the stability of crop production and agricultural production potential in the Daegwallyeong was calculated for the low temperature frequency of occurrence and potential evapotranspiration changes with announce the release of Korea Meteorological Administration (KMA) from 1972 to 2009 up to 38 years. Evapotranspiration calculated FAO and other international standard method authorized under the PENMAN-MONTEITH Method was used, and the low temperature onset and frequency of the Gumbel probability density function was used. As a result, the variation of day evaporation for 38 years were showed to respectively width of variation from maximum <TEX>$9mm\;day^{-1}$</TEX> to minimum <TEX>$0.5mm\;day^{-1}$</TEX>. The frequency of reappearance to first emergence day that lasts more than 5 days with temperature <TEX>$5^{\circ}C$</TEX> over is 3 April a 50-year frequency, 10 April a 25-year frequency, 20 April a 10-year frequency, 28 April a 5-year frequency, 8 May a 2-year frequency. Psychrotrophic crop to growth temperature more than <TEX>$5^{\circ}C$</TEX> can be secured to stable production with planting after May 8, prior to planting for normal growth can be seen that the risk of growth.

Monitoring evapotranspiration of irrigated crops using crop coefficients derived from time series of satellite images. I. Method validation

Crop coefficients (the ratio of actual and reference evapotranspiration, ET/ETo) can be derived from vegetation indices (VIs) obtained by remote sensing. If ground meteorological stations are available to calculate ETo, then the FAO method for estimating the ET of actual crops may be applied in combination with series of satellite images if it is assumed that the crops are not water stressed. This approach was evaluated for two annual crops (cotton and garlic) and three tree crops (mandarin, olive, and peach) using measurements of evapotranspiration, made with the eddy covariance method, as ground truth. Thirty images acquired by the Landsat 5 TM and Landsat 7 ETM+ sensors were used to calculate VIs and derive crop coefficients. The assessment (based on 557 data pairs) led to an overall positive valuation of the method. The root-mean-square deviation over all estimates was 0.75mmday−1. It was concluded that the VI-ETo method is valid and robust for estimating spatially distributed evapotranspiration in large, irrigated areas. Weaknesses of the method were identified and new research to overcome these deficiencies is proposed.