Dale F. Heermann

Development of Reflectance-Based Crop Coefficients for Corn

ABSTRACT Concurrent measurements of reflected canopy radia-tion and the basal crop coefficient (K^b) for corn were conducted throughout a season in order to develop a reflectance-based crop coefficient model. Reflectance was measured in Landsat Thematic Mapper bands TM3 (0.63 - 0.69 um) and TM4 (0.76 - 0.90 um) and used in the calculation of a vegetation index called the normalized difference (ND). A linear transformation of the ND was used as the reflectance-based crop coefficient (Kcr). The transformation equates the ND for dry bare soil and the ND at effective cover, to the basal crop coefficient for dry soil evaporation and at effective cover, respectively. Basal crop coefficient values for com were obtained from daily evapotranspiration measurements of corn and alfalfa, using hydraulic weighing lysimeters. The Richards growth curve function was fitted to both sets of data. The K^b values were determined to be within -2.6% and 4.7% of the K^^ values. The date of effective cover obtained from the K^b data was within four days of the date on which the ND curve reached its maxima according to the Richards function. A comparison of the Kcr with basal crop curves from the literature for several years of data indicated good agreement. Reflectance-based crop coefficients are sensitive to periods of slow and fast growth induced by weather conditions, resulting in a real time coefficient, independent from the traditional time base parameters based on the day of planting and effective cover.

Optimal On-farm Allocation of Irrigation Water

ABSTRACT AN irrigator must make many decisions in determining the date and volume of water to apply to each field. Scheduling programs that rec-ommend the date and volume have been developed and used for assisting management. The new management program optimizes the on-farm alloca-tion of water within the limits of avail-able water and labor as demonstrated on one farm with 40 fields.

Optimal Short Term irrigation schedules

ABSTRACT Amixed-integer optimization model is developed which provides scheduling guidelines for surface irrigation systems over one to two week forecast periods. The primary objective of the model is to minimize labor costs under limitations in available water, while assuming fields are irrigated before crop damaging stress occurs. The model is linked with the USDA-ARS Irrigation Scheduling Program for predicting evapotranspiration and soil moisture depletions. The solution algorithm utilizes a branch and bound technique which involves sequences of linear programming solutions. The utility of the program is demonstrated for an irrigated farm with nine fields over a seven-day forecast period.

Monitoring Temporal Changes Of Irrigated Corn By Aerial Images

Remote sensing provides fast data gathering over large areas. These data sets may be used either to monitor temporal changes crops for detecting abnormalities in the field or to estimate the final crop yield. This would allow practicing timely field management operations to interfere with the abnormalities, which is one of the major elements of precision farming. This paper discusses the potential application of aerial photos to monitor spatial and temporal variability within a field and to estimate the potential yield of corn grown on commercial fields by integrating aerial photo analysis, ground observations and geographical information systems (GIS). False color infrared aerial photography was acquired over two fields at various stages of corn growth. Four vegetation indices [Normalized Difference Vegetation Index (NDVI), Green NDVI (GNDVI), Infrared/Red (IR/R) and Infrared/Green (IR/G)] were calculated and compared with the yield monitor data, SPAD readings and leaf area index. Results indicated that variability in vegetative growth could be monitored by aerial photography as early as the V9 growth stage by employing any of the vegetation indices investigated. The correlation coefficients (r 2 ) were about 0.57 and 0.48, respectively, for estimating SPAD and LAI. Temporal maps of vegetation indices suggested that yield variability could be determined by aerial photos over the growing season. However, at around R5 growth stage the NDVI map resembled yield variability the most. The r 2 between estimated and measured yields was 0.68.

SHANNON-WIENER’S DIVERSITY INDEX FOR LINKING YIELD MONITOR AND REMOTELY SENSED DATA FOR CORN

Yield is the ultimate measure for quantifying the effect of agricultural inputs. Measurement of yield variability is needed for developing and evaluating site-specific crop management strategies. However, there are many sources of error in measuring the actual yield variability. To assess the contribution of harvest practices to yield variability, yield monitor and aerial image data were collected in the 2000 growing season. Aerial images were collected by a DuncanTech MS3100 multispectral digital camera on two dates. The boundary effect on variability of yield monitor data was studied by successive clipping of yield monitor data for determining the effect of the harvester operations at the end of the field on the yield monitor errors. Results indicated that the correlations between grain yield and the normalized difference vegetation index (NDVI) at the V16 growth stage were improved as the field perimeter was clipped to 30.5 m inside of the field boundary; the coefficient of determination (r2) improved from 0.67 to 0.76. The Shannon-Wiener diversity index (SWDI), an index used in ecological studies to determine how diverse a population is, showed that diversity at the perimeter was decreased as additional clipping of data occurred inside the field perimeter. The yield variability was considerably higher in the clipped areas than in other areas due to the speed of the harvester, headland harvest, and time for yield monitor fill-up and emptying. Areas of the highly diverse yield monitor were about twice that of remotely sensed data, as indicated by the SWDI. Results indicated that the outer 6.1 m was responsible for about 34% of the high yield diversity at the perimeter of the field. The headland harvesting effect was included fully in that 34% high yield diversity.

Sensor Placement for Real Time Infiltration Parameter Evaluation

ABSTRACT THE design and operation of surface irrigation systems are significantly influenced by the infiltration rate of the field. Therefore, temporal and spatial variability of infiltration rates must be considered in the management procedures. Surge irrigation requires reliable management procedures to achieve the desirable application efficiency and uniformity coefficient under optimum cycle on and off times. A procedure is proposed to estimate the average application efficiency and uniformity coefficient of a surge irrigation event during the first advance cycle. Data from 28 adjacent furrows in an irrigation event are used to find the best location of two stations for estimation of infiltration parameters. A kinematic wave model is used with an assumed management procedure to find the average application efficiency and uniformity coefficient for the given infiltration parameters and observed surge irrigation event. Comparisons showed that the application efficiencies and uniformity coefficients predicted for station-pairs of 20 to 100 and 40 to 100 m from the inlet are in close agreement with the estimated average values. The station-pair of 20 to 40 m is the poorest choice for prediction of average application efficiency and uniformity coefficient. Increasing the number of sensors decreases the error in predictions; however the relative decrease in the average error is more significant changing from one sensor-pair to two, than from two sensor-pairs to three. Errors in predicting average application efficiency and uniformity coefficient from the poorest station-pair of 20 to 40 m with three pairs of sensors are significantly higher than with a single pair of sensor at 20 to 100 m.

Falling Water Drop Velocities at 1570 m Elevation

ABSTRACT The velocities of freely falling water drops released from various heights in still air were measured using two different techniques at an elevation of 1570 m (5150 ft) above sea level. An electrostatic technique was used to measure the time for an electrically charged water drop to pass through two metal rings of known spacing. A photographic technique, using two electronic flash units, was used to photograph a falling drop against a grid background, at the beginning and ending of a known time interval. The measured results were compared to velocity data measured at sea level and to results from a computer model which predicts freely falling water drop velocities as a function of drop size, air pressure, and air temperature. The high elevation (low air presure and density) environment resulted in measured velocities significantly greater than those measured at sea level. The computer model predicted velocities close to the measured velocities. The computer model was also used to predict velocity differences at various elevations. Finally, the computer model was used with a fmite difference computer program of the ballistics of water drops from sprinklers to show the effect of elevation on the impact velocity and radius of throw of water drops from irrigation sprinklers.

Evapotranspiration Research Priorities for the Next Decade—Irrigation

ABSTRACT IRRIGATION uses ET data for design, management and establishing water rights. The process of irrigation is to apply water to meet the evapotranspiration demands of vegetation. The objective of this paper is to explore areas or topics for research that would enhance the design and operation of irrigation systems. Eight research priorities are identified as topics needing further study to develop the technology for improving the use of ET data in irrigation. Irrigation is one of the major users of our water resources. According to the Irrigation Journals 1985* survey, approximately 24 million ha are irrigated in in the U.S. Irrigation is confined primarily to the western states, but irrigation is expanding quite rapidly in the humid regions of the eastern U.S. as well. In the west, the municipal, industrial and hydropower demands on water supplies are requiring improved irrigation management as the available water for irrigation becomes limited. Even in the east the water available for irrigation can be in short supply, particularly during times of drought. Evapotranspiration is an essential factor in the design of management of irrigation systems. Irrigation is the application of water to meet part of the evapotranspiration demands of vegetation. A significant amount of water is used for the irrigation of lawns, gardens, and ornamentals. However, in this paper the needs for ET research as used in irrigation will emphasize agricultural crop production. The proceedings of the ASAE 1985 National Conference on Advances in Evapotranspiration provide an insight to the emphasis of recent research. Many of the papers in this proceedings were directed towards the uses of ET for irrigation. The primary use of ET information in irrigation is for design, irrigation scheduling and development of water management strategies with and without water constraints. The adjudication of water rights and the transfer or sale of these rights often require past, present and future estimates of ET. The actual ET minus effective precipitation (beneficial use) is the amount of existing water rights that many states allow to be transferred to other uses such as municipal, industrial and other new agricultural development. The objective of this paper is to identify ET research needs for irrigation in the next decade. The following discussion will identify and discuss the uses of ET data for irrigation, but is not intended to be an exhaustive literature review of the subject. This will be followed by a brief discussion on how ET is measured or calculated. The last section proposes potential research needs to obtain adequate ET information for the design and management of irrigation systems..

‘User friendly’ software for an integrated water-energy management system for center pivot irrigation

Abstract Computers are becoming more commonly used by farmers for improving their management. The big need is ‘user friendly’ software for use by farmers. An integrated water-energy management system was developed. It includes ‘user friendly’ software run on a microcomputer which communicates to center pivot irrigation systems via radio. The program provides monitoring, control, irrigation scheduling and electrical load control. The system has been used and accepted by our cooperator for three irrigation seasons. He has been able to improve his management and reduce the amount of overirrigation and the variation between systems of total water applied.

Integrated Water-Energy Management System for Center Pivot Irrigation: Implementation

ABSTRACT AN integrated water-energy management system providing monitoring, pump control, irrigation schedules, and load control for 15 center pivots is described. The logic for establishing priorities for power interruption based on soils, crops, and irrigation systems is presented. An example showing how this system interfaces with the power suppliers existing load control equipment and interruption sequence is given.