Irrigation Management Zones Research Articles

Future approaches to facilitate large-scale adoption of thermal based images as key input in the production of dynamic irrigation management zones

To use VRI systems, a field is divided into irrigation management zones (IMZs). While IMZs are dynamic in nature, most of IMZs prescription maps are static. High-resolution thermal images (TI) coupled with measured atmospheric conditions have been utilized to map the within-field water status variability and to delineate in-season IMZs. Unfortunately, spaceborne TIs have coarse spatial resolution and aerial platforms require substantial financial investments, which may inhibit their large-scale adoption. Three approaches are proposed to facilitate large-scale adoption of TI-based IMZs: 1) increase of the capacity of aerial TI by enhancing their spatial resolution; 2) sharpening the spatial resolution of satellite TI by fusing satellite multi-spectral images in the visible-near-infrared (VIS-NIR) range; 3) increase the capacity of aerial TI by fusing satellite multi-spectral images in the VIS-NIR range. The scientific and engineering basis of each of the approaches is described together with initial results.

Mapping water status based on aerial thermal imagery: comparison of methodologies for upscaling from a single leaf to commercial fields

Aerial thermal remote sensing can provide a means for collecting spatial plant water status data. Many studies have shown their potential in irrigation management but the adaptation of this technology is not straight forward. In this paper, knowledge accumulated in recent years on thermal imagery analysis methodology for water status mapping is summarized aiming at indicating alternatives to calculate the Crop Water Stress Index (CWSI) for commercial scale water status mapping. Based on literature overview, four forms of wet-baselines to calculate CWSI were selected, namely: artificial wet reference surface, two theoretical calculations and a statistical bio-indicator. These baselines were used to calculate CWSI based on multi-temporal aerial thermal images of cotton fields. CWSI based on a statistical bio-indicator and one of the theoretical wet-baselines provided the best correlations. It is argued though that the statistical one is preferable since it includes the plant characteristics and it is farmer-friendly. Based on bio-indicators, leaf water potential maps of three commercial fields were produced on several dates through the season. Water status spatial patterns were not static and the effect of static factors like sandy soil patches also changed through the season. The maps show the importance of in-season variability mapping for rational irrigation management. To improve current variable-rate irrigation, the concept of in-season irrigation management zones (IMZ) based on thermal-images should be considered and integrated with the delineation of static irrigation IMZ.

Delineation of irrigation management zones in a Quartzipsamment of the Brazilian semiarid region

Abstract The objective of this work was to delineate irrigation management zones using geostatistics and multivariate analysis in different combinations of physical and hydraulic soil properties, as well as to determine the optimal number of management zones in order to avoid overlaping. A field experiment was carried out in a Quartzipsamment, for two years, in an irrigated orchard of table grape, in the Senador Nilo Coelho Irrigation Scheme, in the municipality of Petrolina, in the state of Pernanbuco, Brazil. Soil samples were collected for the determination of soil physico-hydraulic properties. A portable meter was used to measure soil apparent electrical conductivity. Spatial distribution maps were generated using ordinary kriging. Management zones for five different combinations of soil properties were defined using the fuzzy c-means clustering algorithm, and two indexes were applied to determine the optimal number of management zones. Two combinations of soil properties can be used in the management zone planning in order to monitor soil moisture.

Implementing precision irrigation in a humid climate – Recent experiences and on-going challenges

There is growing scientific interest in the potential role that precision irrigation (PI) can make towards improving crop productivity, and increasing water and energy efficiency in irrigated agriculture. Most progress has been made in arid and semi-arid climates for use in high value crop production where irrigation costs coupled with concerns regarding water scarcity have stimulated PI innovation and development. In temperate and humid climates where irrigation is supplemental to rainfall, PI is less developed but nevertheless offers scope to make more effective use of rainfall, help reduce the non-beneficial losses associated with irrigation (deep drainage, nitrate leaching) and provide farmers with evidence to demonstrate environmentally sustainable practices to processors and retailers. This paper reports on recent experiences in developing precision irrigation in UK field-scale agriculture, drawing on evidence from field research and modelling studies. By combining data from these sources, a critical evaluation focusing on selected technical, agronomic and engineering challenges that need to be overcome are described, including issues regarding PI scheduling, and the delineation of irrigation management zones to ensure compatibility with existing methods of overhead irrigation. The findings have relevance to other countries where irrigation is supplemental and where precision agriculture is gaining popularity.

Assessing Application Uniformity of a Variable Rate Irrigation System in a Windy Location

<abstract><title><italic>Abstract. </italic></title> Variable rate irrigation (VRI) systems are commercially available and can easily be retrofitted onto moving sprinkler systems. However, there are few reports on the application performance of such equipment. In this study, application uniformity of two center pivots equipped with a commercial VRI system were tested using fixed-plate sprinklers and a range of irrigation rates (100%, 80%, 70%, 50%, and 30%). Catch cans were arranged in transect, arc-wise, and grid patterns to test the accuracy of application depth, and the uniformity of application in the direction of pivot travel and to investigate changes in uniformity along the pivot lateral between irrigation zones. The mean Heermann and Hein coefficient of uniformity (CU_HH) and the mean lower-quarter distribution uniformity (DU_lq) in the direction of pivot travel and along the pivot lateral were approximately 88% and 80%, respectively. Application uniformity was impacted at the border of adjacent irrigation zones along the pivot lateral when zones were applying different irrigation depths. While wind speed and direction did not appreciably decrease uniformity of application, it did impact absolute catch measurements. The mean evaporation and drift loss for all trials was 9.3%, and ranged from 1% to 19%. Applying variable rate irrigation significantly impacted uniformity of application for a distance 3 m wide between irrigation zones of different irrigation depths in spans 1-3 of the three-span, and a distance 6 to 9 m wide between irrigation zones in spans 5 and 6 of the six-span center pivot. Overall, the uniformity of application in the direction of pivot travel and within each irrigation zone was similar to values reported for other VRI sprinkler systems. The root mean square error between the prescribed and actual applied depth was <3.0 mm for catch collected in all spans along the pivot lateral and in the direction of pivot travel. This indicates that this commercial VRI is well suited for site-specific irrigation management. However, uniformity of application could be affected by the width of the irrigation management zones as well as sprinkler design and environmental factors.

Effect of site-specific irrigation management on grapevine yield and fruit quality attributes

Spatial variation in yield and fruit composition has been observed in many vineyards, leading to low productivity. In this study, site-specific irrigation was applied in a commercial vineyard (Vitis vinifera L. cv. Shiraz) block in the Sunraysia region of Australia to improve production in low-yielding areas of the block and decrease differences in yield and quality between irrigation management zones. Data collected under uniform irrigation management showed that spatial variation in canopy cover, yield and fruit composition across the vineyard block was substantial. Normalised difference vegetation index (NDVI) and canopy temperature data supported delineation of three irrigation management zones and decisions regarding irrigation strategy. Water use efficiency and yield improvements were achieved by implementing site-specific irrigation. Fruit composition results were varied; pH and titratable acidity showed increased similarity between zones, but other parameters maintained differences between zones. These results lend support to the use of NDVI to determine irrigation management zones.

Delineating site‐specific irrigation management zones

ABSTRACTSince spatial heterogeneity of soil physical properties has a significant influence on site‐specific irrigation management, field moisture capacity, saturated moisture content, wilting point and soil dry bulk density were used as the data source to derive irrigation management zones. The spatial heterogeneity and correlations of soil properties were firstly characterized using geostatistics and principal component analysis. Then, irrigation management zones were delineated by running management zone analysis software based on the fuzziness performance index and normalized classification entropy, which were used to determine the least number of subzones. Finally, the zoning of irrigation management was verified by performing a statistical analysis as a statistical control of the above classifications. The study site was divided into two subzones having distinct differences between them, indicating that the delineation of irrigation management zones was reasonable. In additional, a stratified sampling method was also adopted to calculate the optimal sampling size of the soil properties in each subzone. Saturated moisture content has the optimal sampling size of 12 and soil water capacity and wilting point have the least, with only 3. The delineation of irrigation management zones and optimal sampling size could provide data support and science‐based information for site‐specific irrigation management. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Application of improved ant colony clustering method in the delineation of site-specified irrigation management zones.

Application of improved ant colony clustering method in the delineation of site-specified irrigation management zones.

Feasibility study of monitoring the total available water content using non‐invasive electromagnetic induction‐based and electrode‐based soil electrical conductivity measurements

AbstractIrrigation is by far the largest consumer of water in the world. At the same time the need for irrigation may differ between different zones of a particular field due to spatial soil variability. In particular total available water content (TAWC) has effects on irrigation frequency and depth. The objective of our study was to compare the ability of two fast, non‐destructive and sensor‐based apparent soil electrical conductivity (ECa) measurement methods: A contact and electrode‐based sensor (VERIS 3100, both shallow and deep modes); A non‐contact, electromagnetic induction (EMI)‐based sensor (Geonics EM38, both horizontal and vertical orientations) to monitor the within‐field variation of the TAWC. The ECa data, standardized to 25°C (EC25), were collected on a 1 s interval corresponding to 2–3 m data spacing on transects spaced approximately 4–6 m apart. Based on the ECa spatial variability pattern, and to cover the range of ECa values present, 29 calibration points were located using a differential Global Positioning System (DGPS) to develop field‐specific relationships between ECa data and TAWC in the upper 60 cm of soil. However, we found better correlations between TAWC and the VERIS 3100 readings. Calibration equations to estimate TAWC from the shallow mode of VERIS 3100 data exhibited a good fit to the data and had the highest correlation (R2 = 0.77), whereas calibrations to EM38 data (both vertical and horizontal orientation) were low and apparently could not adequately reflect the spatial variability of the TAWC due to the influence of the more highly variable topsoil. We identified six TAWC zones based on fuzzy k‐means unsupervised classification as an optimum number of irrigation management zones within our field (Zone 1: 99–105, Zone 2: 105–116, Zone 3: 116–127, Zone 4: 127–138, Zone 5: 138–149, Zone 6: 149–161 mm per 60 cm). We concluded that under traditional irrigation conditions, Zones 1 and 2 were over‐irrigated whereas Zones 4, 5 and 6 were deficit irrigated. Copyright © 2007 John Wiley &amp; Sons, Ltd.