FAO Method Research Articles

Impact of using two different sources of water quality for simulation of salt and moisture content in unsaturated zone

Monitoring water quality and moisture content throughout the root zone become essential for proper management and for reduction of undesirable and diverse effects caused by using different water quality. In the field level, poor management of using different quality water can cause a huge reduction on the vegetation production. Two field plots were selected in Al-Khalis region in Diyala governorate as a case study. Four scenarios were applied for the data collected for a complete season from a local meteorological station and by using HYDRUS-3D V2.05 software package to simulate water and salt transport through a 1m depth of unsaturated zone. Irrigation scheduling was estimated using FAO method. The net water depth required for a season was 65 mm for 7 days irrigation interval and 21 irrigation events. For depths (20, 40, 60, 80, and100 cm) the salt concentration were simulated for the four scenarios and for the whole season. For the limit of controlling soil salinity at low level in initial and develop stage of plantation, it has been found that the Fourth scenario has to be chosen.

Nonparametric trend analysis of reference evapotranspiration for Khyber Pakhtunkhwa, Pakistan

Reference evapotranspiration (ETo) is a key element of the hydrological cycle that integrates atmosphere demand and surface environment conditions. In this study, we aimed to determine the trend of ETo using nonparametric methods – Mann-Kendall and Sen's slope estimator, whereas ETo is estimated using globally accepted Food and Agriculture Organization (FAO) Penman-Montieth FAO-56 (PM) method. We used ten years data (2000–2009) of 11 weather stations located in Khyber Pakhtunkhwa Province, Pakistan. We identified a decreasing trend in ETo rate has been recorded mostly in winter, pre-monsoon and spring with an upward trend during autumn and red-summer. Further, the statistical analysis shows a significant decreasing trend in ETo during winter. In summary, we provide a systematic approach that may be used in agro meteorological modelling and irrigation development.

Incorporating field wind data to improve crop evapotranspiration parameterization in heterogeneous regions

Accurate parameterization of reference evapotranspiration (ET0) is necessary for optimizing irrigation scheduling and avoiding costs associated with over-irrigation (water expense, loss of water productivity, energy costs, and pollution) or with under-irrigation (crop stress and suboptimal yields or quality). ET0 is often estimated using the FAO-56 method with meteorological data gathered over a reference surface, usually short grass. However, the density of suitable ET0 stations is often low relative to the microclimatic variability of many arid and semi-arid regions, leading to a potentially inaccurate ET0 for irrigation scheduling. In this study, we investigated multiple ET0 products from six meteorological stations, a satellite ET0 product, and integration (merger) of two stations’ data in Southern California, USA. We evaluated ET0 against lysimetric ET observations from two lysimeter systems (weighing and volumetric) and two crops (wine grapes and Jerusalem artichoke) by calculating crop ET (ETc) using crop coefficients for the lysimetric crops with the different ET0. ETc calculated with ET0 products that incorporated field-specific wind speed had closer agreement with lysimetric ET, with RMSE reduced by 36 and 45% for grape and Jerusalem artichoke, respectively, with on-field anemometer data compared to wind data from the nearest station. The results indicate the potential importance of on-site meteorological sensors for ET0 parameterization; particularly where microclimates are highly variable and/or irrigation water is expensive or scarce.

Valoración de la evapotranspiración real estimada y rendimiento de caña de azúcar en Veracruz, México


 
 
 La caña de azúcar es uno de los principales cultivos en las zonas tropicales y subtropicales, que presentan poca variación climática. Sin embargo, el Panel Intergubernamental de Expertos sobre Cambio Climático (IPCC) afirmó que la agricultura en zonas tropicales tendrán grandes cambios en los próximos 100 años por efecto de este fenómeno. En el estado de Veracruz, México, la precipitación media anual es alrededor de 1 500 mm y una temperatura promedio anual de 23 oC. No obstante, en los últimos 30 años se han registrado alteraciones en el ciclo hidrológico en las áreas cañeras de la zona centro del estado deVeracruz (Distrito de Riego 035 La Antigua), como resultado del fenómeno del cambio climático, impactando significativamente los patrones de precipitación (Pp), evaporación (Ev) y temperatura (T) de la zona. El objetivo del presente estudio fue valorar la evapotranspiración real estimada (ETR) de la caña de azúcar, como resultado del incremento en la tasa de evaporación y temperatura, y cambios en los patrones de precipitación registrados en un periodo de 30 años (1980-2010); así como, la correspondencia entre la ETR con los rendimientos de caña de azúcar observados en dicho periodo en la zona de abasto de los ingenios La Gloria y El Modelo, como consecuencia del cambio climático. La ETR se calculó mediante el uso de los métodos semiempíricos Penman-Monteith FAO, Blaney- Criddle, Hargreaves-Samani y el Tanque Evaporímetro Tipo A. Se encontró que existe una alta correlación entre los métodos Penman-Monteith FAO y Hargreaves-Samani (r2= 0.9307). No se encontró relación alguna entre la ETR y el rendimiento en campo registrado en la zona de abasto de los ingenios referidos. Finalmente, se observe que existe una alta correlación entre la ETR y la temperatura máxima derivada de los métodos de Penman-Monteith FAO (r2= 0.9445) y Hargreaves-Samani (r2= 0.7773).
 
 

Determinación de lisina, triptófano y proteína en germinados de maíz criollo y QPM


 
 
 El objetivo de la presente investigación fue determinar la lisina, triptófano, proteína y rendimiento de forraje verde en maíz QPM y criollo. El trabajo se realizó en el CINVESTAV e Instituto Tecnológico de Roque, Celaya, México, en el año 2014. Se evaluaron dos genotipos de maíz, uno de alto contenido de proteína (QPM) y otro normal. La producción de forraje verde se realizó de acuerdo al método de la FAO (2001). Se realizaron muestreos a los 9, 11, 13, 15, y 17 días después de la siembra y se tomaron como variables la altura de plántula, peso fresco, materia seca, lisina, triptófano, proteína y rendimiento de forraje. El rendimiento de forraje verde alcanzó sus valores más altos a los 17 días, el criollo 25.4 kg m-2 y QPM 27.14 kg m-2. Para el contenido de lisina y triptófano el valor más alto se determinó a los 13 días en ambos genotipos, 0.55 y 1.17% y 1.18 y 0.56%, respectivamente. Asimismo, se concluye que la proteína del maíz QPM fue más alta a los 17 días con un valor de 19.86% y para el maíz criollo a los 15 días con 14.45%.
 
 

Modeling water needs and total irrigation depths of maize crop in the south west of France using high spatial and temporal resolution satellite imagery

Climate change is projected to increase water resources limitation and to impact significantly agricultural production. A big challenge for agriculture will be to reduce the amount of water used to fit the environmental constraints, while maintaining a level of production that ensure food security. In this context, we develop a methodology based on high spatial and temporal resolution remote sensing data combined with a semi-empirical crop model coupling the Simple Algorithm For Yield estimates (SAFY, Duchemin et al., 2008, 2015) with the new formulation (Battude et al., 2016) to a water balance model adapted from the FAO-56 method (Allen et al., 1998). A module was added to automatically simulate irrigation. The model was used to assess the dynamics of actual Evapotranspiration (ETca) and water supplies of maize crop over large areas and during contrasted climatic years in the south west of France. It was first calibrated and evaluated over an experimental field using four years of ETca measurements. The validation was done over 18 maize fields and larger irrigated zones (135ha to 450ha) using total irrigation depths. This work permitted to quantify the ability of different methods to estimate the storage capacity (soil map vs in situ data) and the basal crop coefficient Kcb (standard vs remotely sensed values) and their impact on total irrigation depths. Good estimations were obtained for ETca (R=0.88; RRMSE=20%). The model also reproduced correctly the total irrigation depth over the 18 maize fields (R=0.79; RRMSE=18.8%) and three larger irrigated zones (R=0.8; RRMSE=42%). The underestimation (Bias=−93mm) is due to several reasons such as errors in soil water storage capacity estimates, but also to an overestimation of water needs by water managers or a potential over-irrigation carried out by farmers. Finally, the work demonstrates the high potential of combining a simple agro-meteorological model using only few parameters with satellite imagery for a large-scale monitoring of total irrigation depth.

Developing a User Friendly Decision Tool for Agricultural Land Use Allocation at a Regional Scale

Agricultural land use planning should always be guided by a reliable tool to ensure effective decision making in the allocation of land use and activities. The primary aim of this study is to develop a user friendly system on a spatial basis for agricultural land suitability evaluation of four groups of agriculture commodities, including food crops, horticultural crops, perennial (plantation) crops, grazing, and tambak (fish ponds) to guide land use planning. The procedure used is as follows: (i) conducting soil survey based on generated land mapping units; (ii) developing soil database in GIS; and (iii) designing a user friendly system. The data bases of the study were derived from satellite imagery, digital topographic map, soil characteristics at reconnaissance scale, as well as climate data. Land suitability evaluation in this study uses the FAO method. The study produces a spatial based decision support tool called SUFIG-Wilkom that can give decision makers sets of information interactively for land use allocation purposes.This user friendly system is also amenable to various operations in a vector GIS, so that the system may accommodate possible additional assessment of other land use types.

Temporal Downscaling of Crop Coefficients for Winter Wheat in the North China Plain: A Case Study at the Gucheng Agro-Meteorological Experimental Station

The crop coefficient (Kc) is widely used for operational estimation of actual evapotranspiration (ETa) and crop water requirements. The standard method for obtaining Kc is via a lookup table from FAO-56 (Food and Agriculture Organization of the United Nations Irrigation and Drainage Paper No. 56), which broadly treats Kc as a function of four crop-growing stages. However, the distinctive physiological characteristics of overwintering crops, such as winter wheat (Triticum aestivum L.), which is extensively planted in the North China Plain (NCP), are not addressed in this method. In this study, we propose a stage-wise method that accounts for Kc variations for winter wheat at each critical phenological stage, thereby estimating Kc at finer temporal scales. Compared with the conventional FAO method, the proposed stage-wise method successfully captures the bimodal pattern in Kc time series for winter wheat, which is shown at both ten-day and phenological time scales. In addition, the accuracies of the proposed stage-wise Kc method and the FAO method were evaluated using micro-meteorological measurements of ETa collected at the Gucheng agrometeorological experimental station in the NCP. Using a leave-one-out strategy, the evaluation revealed that the stage-wise method significantly outperformed the FAO method at both daily and critical phenological time scales, with root-mean-square errors in ETa for the stage-wise method and the FAO method being 0.07 mm·day-1 and 0.16 mm·day-1, respectively, at the daily time scale, and 0.01 mm·day-1 and 0.27 mm·day-1 at the critical phenological time scale. Generally, the FAO method underestimates ETa during the initial stage and overestimates ETa during both the development and mid-season stages. It is shown that the proposed stage-wise method is important for the water-stressed NCP where precision irrigation is highly desirable, especially during the critical phenological stages. Results from this study provide insight into accurate estimation of water requirements for winter wheat at phenological time scales.

Comparing evapotranspiration rates estimated from atmospheric flux, soil water balance and FAO56 method in a small orange orchard in Tunisia

Comparing evapotranspiration rates estimated from atmospheric flux, soil water balance and FAO56 method in a small orange orchard in Tunisia

Cotton Irrigation Scheduling Using a Crop Growth Model and FAO-56 Methods: Field and Simulation Studies

Abstract. Crop growth simulation models can address a variety of agricultural problems, but their use to directly assist in-season irrigation management decisions is less common. Confidence in model reliability can be increased if models are shown to provide improved in-season management recommendations, which are explicitly tested in the field. The objective of this study was to compare the CSM-CROPGRO-Cotton model (with recently updated ET routines) to a well-tested FAO-56 irrigation scheduling spreadsheet by (1) using both tools to schedule cotton irrigation during 2014 and 2015 in central Arizona and (2) conducting a post-hoc simulation study to further compare outputs from these tools. Two replications of each irrigation scheduling treatment and a water-stressed treatment were established on a 2.6 ha field. Irrigation schedules were developed on a weekly basis and administered via an overhead lateral-move sprinkler irrigation system. Neutron moisture meters were used weekly to estimate soil moisture status and crop water use, and destructive plant samples were routinely collected to estimate cotton leaf area index (LAI) and canopy weight. Cotton yield was estimated using two mechanical cotton pickers with differing capabilities: (1) a two-row picker that facilitated manual collection of yield samples from 32 m2 areas and (2) a four-row picker equipped with a sensor-based cotton yield monitoring system. In addition to statistical testing of field data via mixed models, the data were used for post-hoc reparameterization and fine-tuning of the irrigation scheduling tools. Post-hoc simulations were conducted to compare measured and simulated evapotranspiration, crop coefficients, root zone soil moisture depletion, cotton growth metrics, and yield for each irrigation treatment. While total seasonal irrigation amounts were similar among the two scheduling tools, the crop model recommended more water during anthesis and less during the early season, which led to higher cotton fiber yield in both seasons (p < 0.05). The tools calculated cumulative evapotranspiration similarly, with root mean squared errors (RMSEs) less than 13%; however, FAO-56 crop coefficient (Kc) plots demonstrated subtle differences in daily evapotranspiration calculations. Root zone soil moisture depletion was better calculated by CSM-CROPGRO-Cotton, perhaps due to its more complex soil profile simulation; however, RMSEs for depletion always exceeded 20% for both tools and reached 149% for the FAO-56 spreadsheet in 2014. CSM-CROPGRO-Cotton simulated cotton LAI, canopy weight, canopy height, and yield with RMSEs less than 21%, while the FAO-56 spreadsheet had no capability for such outputs. Through field verification and thorough post-hoc data analysis, the results demonstrated that the CSM-CROPGRO-Cotton model with updated FAO-56 ET routines could match or exceed the accuracy and capability of an FAO-56 spreadsheet tool for cotton water use calculations and irrigation scheduling. Keywords: Cottonseed, Crop coefficient, Decision support, Depletion, Evapotranspiration, Fiber, Management, Simulation, Soil moisture, Yield.

Assessing irrigation scheduling by FAO method using soil-plant atmosphere water stress indicators on four orange cultivars

Assessing irrigation scheduling by FAO method using soil-plant atmosphere water stress indicators on four orange cultivars

Reference evapotranspiration estimates by means of Hargreaves-samani and Penman-monteith fao methods with missing data in the northwestern Mato Grosso do Sul

Reference evapotranspiration estimates by means of Hargreaves-samani and Penman-monteith fao methods with missing data in the northwestern Mato Grosso do Sul

SUITABILITY OF AGRICULTURAL LAND FOR THE CULTIVATION OF CABBAGE IN THE AREA OF HERZEGOVINA-NERETVA COUNTY

UDK 631.164:635.33(497.6)
 Purpose of this paper was to perform inventory of areas and features of agricultural land in the field of the Herzegovina-Neretva County based on existing data and to assess benefits of agricultural land for cultivation cabbage according to the characteristics of the soil, relief and climate. The evaluation of the land suitability was carried out in line with FAO method (FAO, 1976) according to the agro zone.
 Based on conducted research, it was established that the studied area is very suitable for the production of cabbage. There are 23,249.3 ha (11.68%) suitable land for the production of cabbage and temporarily unsuitable 5,201.2 ha (2.61%) while permanently unsuitable land for intensive production of cabbage are on 170,451.8 ha (85.7%). The main limitations for intensive production of cabbage in the studied area are the slope, the depth of profile and rockiness.
 According to official data on the state of the current production of cabbage in the studied area and data of suitable land and temporarily unsuitable land, the conclusion is that there are basic prerequisites in the form of land resources to expand the production of cabbage in this field.

SUITABILITY OF AGRICULTURAL LAND OF THE HERZEGOVINA- NERETVA COUNTY FOR CULTIVATION OF SOME FRUIT SPECIES

UDK 631.164(497.6 Hercegovina)
 This paper presents the evaluation of benefits of the agricultural land for the cultivation of cherry, sour cherry, plum and apple in the area of Herzegovina-Neretva County (HNC). The evaluation of the land suitability was carried out according to the FAO method (FAO, 1976, Brinckman and Smith, 1973), according to the agro zone (up to 800 m above sea level) and taking into account the features of the soil, climate and topography and the requirements of these fruit cultures. The results of the research are shown with text and graphics (maps of benefits of the agricultural land). Based on the conducted research, the existence of significant and valuable land resources is established for development of fruit cultivation in Herzegovina-Neretva county.
 For the cherry and sour cherry cultivation in the agricultural area of Herzegovina- Neretva county (up to 800 m above sea level) exists 29,682 hectares (28.55%) of suitable land, for the plum and apple cultivation exist 38,345 hectares (36.89%). The convenience of the class structure of the soil for the cherry, sour cherry, plum and apple is the smallest share of the P-1 class benefits. The largest proportion of the land P-3 class benefits for growing cherries, sour cherries, apples and plums with benefits in the soil for growing cherries have less difference between the surfaces of the P-2 and P-3 class suitability. The main limitations are the slope of the terrain, the depth of profile, rockiness and stoniness. Temporarily unsuitable soils had occupied significant area for these fruit species cultivation. Plots of this class can be with adequate, economically justified measures led to a certain class of convenience

Estimation of Crop Coefficients by Remote Sensing based Vegetation Index

Crop coefficient plays a vital role in estimation of crop evapotranspiration for irrigation scheduling in a canal command. Remote sensing-based vegetation indices can help in efficient irrigation water management, as the irrigation systems need near real-time spatial information on types of crop, area under irrigation, crop water requirement, etc.The Surface Energy Balance Algorithm for Land (SEBAL) was used for estimating actual evapotranspiration (AET) based on remotely sensed data. The summer groundnut crop coefficients were estimated using AET and ET0 . The FAO-56 method helped to estimate reference evapotranspiration (ET0 ) and crop evapotranspiration using crop coefficient. The remote sensing based Normalized Difference Vegetation Index (NDVI) for different days of year (DOY) were derived using Landsat imageries for summer crop season in 2014. The relationship between the NDVI and Kc for different DOY was established to estimate the crop coefficients of summer groundnut at field and regional scales for different growth stages for the Ozat-II canal command of Junagadh district of Gujarat State, India. The developed equation might be useful for estimation of crop water requirement and irrigation scheduling of canal command using remote sensing data.

Improving the estimation of evaporation by the FAO-56 dual crop coefficient approach under subsurface drip irrigation

Partitioning of evapotranspiration and estimating of irrigation contribution to evaporation play a crucial role in managing scarce water resources and help in increasing the water productivity of crops, especially of sparsely vegetated plants. In this study, the FAO-56 dual crop coefficient (DCC) approach for estimating evaporation from soil under cropped conditions is adapted for subsurface drip irrigation (SDI). This new approach involves one additional variable, the fraction of the irrigation depth contributing to evaporation (fI,Es), which was defined and integrated into the FAO-56 equations for estimating daily water balance from the evaporation layer (0–15cm). Impacts of soil texture, heterogeneity, irrigation depth, design parameters of the irrigation system on fI,Es, and the fraction of the soil surface wetted by irrigation (fw) (and consequently the exposed and wetted fraction (few)), were evaluated through HYDRUS-2D simulations. The modified procedure was compared with the existing FAO-56 method for estimating components of annual ET for wine grape under SDI.The model simulations showed that the fI,Es fraction in a homogeneous, isotropic light-textured soil was minimal (0.04) when SDI was placed at a depth of 25cm. However, in medium and heavy textured soils fI,Es was 4 times larger than in light-textured soils. The value of fw was slightly higher in fine-textured (0.09) than in medium-textured soils (0.07). In Duplex soils with two contrasting textural layers, fw (0.12–0.16) was higher due to the presence of a heavy-textured soil layer just below the drip line. Similarly, in Triplex soils (3 different textural layers), placing the drip line in the middle layer effectively reduced both fI,Es and fw close to zero. In contrast, fw (0.18–0.30) and fI,Es (0.28–0.42) both increased considerably in heterogeneous soils. Both fractions (fw and fI,Es) increased with an increase in irrigation depths, except for fI,Es in loamy sand. The fractions were slightly lower when a drip line was placed at a depth of 10cm (an evaporation zone) than when it was placed on the soil surface. Applying the same amount of water with different discharge rates had little impact on fI,Es and fw fractions. An increase in the drip line spacing proportionally decreased the wetted fraction on the soil surface. Annual evaporation for SDI irrigated wine grapes at the field study site, estimated using the existing FAO-56 procedure, was overestimated by about 5–6% compared to using the modified procedure. However, this deviation between the two approaches increased (18%) for heavier soil textures. It is concluded that the existing FAO-56 procedure needs to be adjusted when used to estimate evaporation under subsurface drip irrigation. However, the impact of the proposed modification on evaporation needs further evaluation under other crops, soils, and climatic conditions.

Water requirements and crop coefficients of tropical forest seedlings in different shading conditions

ABSTRACT The objective was to determine the crop evapotranspiration (ETc) and crop coefficients (Kc) of tropical forest seedlings over a 135-day cycle, in the climatic conditions of the Cerrado-Amazon transitional region (11º 51’ 08 “S; 55º 30’ 56” W; altitude of 371 m). Five native species (Tabebuia impetiginosa, Tabebuia roseoalba, Handroanthus chrysotrichus, Parkia pendula and Parkia platycephala) and one exotic species (Adenanthera pavonina) were evaluated in seven shading conditions: 35, 50 and 80% black nets (Polyolefin); green Frontinet®, red ChromatiNet® and blue ChromatiNet® of 50% shading; and full sun. Reference evapotranspiration (ETo) was obtained by the Penman-Monteith FAO-56 method and the crop evapotranspiration of the seedlings (ETc) was given by daily weighing. The Kc values were obtained by dividing ETo by ETc. At 135 DAT, destructive analysis was performed to determine the leaf area. In full sun conditions, ETc varied from 3.9 (P. pendula) to 5.0 mm d-1 (T. roseoalba). The increase in the shading percentage promotes reduction in leaf area, ETc and Kc. Colored nets with 50% shading generate similar water demands.

Mathematical modeling of water fluxes in arable chernozems under different land use

The hydrologic regimes of arable chernozems were simulated for two plots located within a watershed. For the last fifty years continuous corn monoculture was practiced in one plot, and permanent bare fallow was practiced in the other plot. Carbonates are detected from a depth of 140–160 cm under corn and from 70–80 cm under bare fallow. The objective of the simulation study was to test the validity of the hypothesis that the shallower depth to carbonates under bare fallow is related to carbonate rise due to changes in the hydrologic regime of bare soil compared to soil under vegetation. Mathematical modeling using the HYDRUS-1D software and the FAO56 method confirmed that the hydrologic regimes of arable chernozems within the two plots are different. The soil water content under bare fallow is generally higher than that under corn. The downward soil water fluxes for the two plots are comparable. The upward soil water fluxes under bare fallow significantly exceed those under corn and affect a thicker soil layer. The changes in the hydrologic regimes of chernozems under bare fallow favor the upward movement of carbonates through both the direct transfer by upward water fluxes and the diffusion of ions.

Comparison of Evapotranspiration Computation by FAO-56 and Hargreaves Methods

AbstractIn an urban environment, vegetated roofs are sustainable systems that provide a variety of valuable benefits, such as the reduction of stormwater volumes and the mitigation of urban heat islands strongly linked to their evaporative processes. The evapotranspiration (ET) is one of the most important processes of the hydrological cycle, but it also represents one of the most difficult hydrological phenomena to quantify because of the complex interaction between the ground surface, vegetation, and atmosphere. However, an accurate computation of ET from vegetated roofs is essential to properly predict the benefits of such systems. The aim of this paper is to evaluate and compare three ET models for the prediction of ET from a green roof: a combination model and two temperature-based models under Mediterranean climate conditions. The study was carried out on an experimental green roof, located at University of Calabria, Italy, by using the onsite data with a time step of 5 min and a monitoring period r...

Modified method of aerodynamic resistance calculation and its application to potential evapotranspiration estimation

Abstract The aim of this study was to present and validate an alternative evapotranspiration calculation procedure that includes specific expression for the aerodynamic resistance. Calculated daily potential evapotranspiration totals were compared to the results of FAO56 procedure application and to the results of measurements taken with a precision weighing lysimeter permanently grown with irrigated, short grass. For the examination period from March 17 through October 31, 2011, it was found that daily potential evapotranspiration estimates obtained by both calculation procedures fitted well to the lysimeter measurements. Potential evapotranspiration daily totals calculated with the use of the proposed aerodynamic resistance calculation procedure gave better results for days with higher evapotranspiration, compared to the FAO56 method. The most important is that the approach based on the proposed alternative aerodynamic resistance could be effectively used even for a wide variety of crops, because it is not limited to any particular crop.