North Dakota State University
NDSU Extension Service
No. 177, August 1999
http://www.ext.nodak.edu/extnews/snouts
Oakes Field Day - August 17
Irrigation Conference in Alberta, Canada
Aerial Photography Using a Radio-Controlled Airplane
Chemigation Management Tips
The Oakes irrigation field day will start at 9 a.m. with coffee and doughnuts. The field tour will start at 9:30 a.m. with comments from new NDSU President Joseph Chapman followed by a field crops tour with presentations on disease control in edible beans, corn hybrids, insect management in corn and potatoes, sprinkler irrigation systems, soybean variety updates and weed control in edible beans. After the noon meal, a spray drift demonstration will be given followed by the afternoon tour of vegetable crops. Presentations will be given on carrots, pumpkins, raspberries, asparagus and weed control in onions and tomatoes.
The Oakes Irrigation Research Site is located 4 miles south of Oakes on ND State Highway 1. For more information call Richard Greenland at (701) 742-2189.
The Canadian National Committee International Commission on Irrigation and Drainage (CANCID) will be hosting an irrigation conference from September 29 to October 1, 1999 at the Lethbridge Lodge Hotel in Lethbridge, Alberta, Canada. Technical sessions will focus on: the future of irrigation development and operations, advances in on-farm and conveyance systems, water quality and irrigation and irrigation water management.
If you would like to receive more information, please contact Brent Paterson, Alberta Irrigation Branch, Bag 3014, Lethbridge, AB, Canada, T1J 4C7 or email len.ring@agric.gov.ab.ca.
Tom Scherer, (701) 231-7239
NDSU Extension Agricultural Engineer
tscherer@ndsuext.nodak.edu
Agriculture is fast becoming an arena filled with new technologies to aid the farmer in crop production. Advances in zonal soil sampling, variable rate chemical application, and yield monitoring are allowing the producer to learn more about the fields he farms. Another tool in the precision farming toolbox is aerial photography. Aerial photos can be very useful for delineating areas in need of drainage, nutrient deficiencies, drought stress, and weed competition.
Obtaining an aerial photo of an area would normally involve contacting a pilot willing to take a camera up in his plane or hiring a professional aerial photography outfit. These avenues can be expensive, and there may be scheduling conflicts if many flights are needed throughout the season.
An alternative is the use of a radio-controlled (R/C) plane. In 1996 we were looking into methods for getting aerial pictures of our research sites near Oakes. Our first try involved using a tethered 10-foot diameter helium balloon with a camera attached to the bottom. We found out very soon that it did not take much wind to make this system unusable.
Further research into the subject led us to try an R/C plane customized to house a small automatic camera. We became aware of a group using such a system (Walker, 1993) and followed their guidelines. In the winter of 1996-1997 we purchased our first Senior Telemaster kit from The Hobby Lobby and began construction. When the kit arrived we were somewhat overwhelmed, having never attempted something like this before. Inside the box were hundreds of pieces of balsa wood, most of which looked nothing like an airplane. Luckily, also included were a set of instructions and a very detailed set of to-scale blueprints. After a couple of months and a few modifications to the design to include a small automatic camera pointing out of the bottom, we had a rather large (8-foot wingspan) R/C plane. The total cost of the finished plane was less than $1000, which includes $200 for the Telemaster airplane kit, $300 for the Super Tiger 61 engine, $325 for the JR 6-channel radio, and $100 for the camera.
Now came the task of learning to fly it. We talked to people at the local hobby store and were told that we should invest in a computer R/C flight simulator. This program allowed us to use the actual radio transmitter that we would be flying the plane with so we got used to the controls. It also showed on the screen the view of the plane from the ground, not the cockpit like other flight simulators often do. Many hours were spent flying (and crashing) the simulated plane before we attempted to fly the real thing. Before we took our plane up by ourselves, we asked some local R/C pilots if they could fly it and make sure everything was set properly. This along with the simulator time paid off since our first solo flights were successful.
After numerous practice flights at the local R/C airfield learning to fly the plane and testing the camera system, it was time to get to work and actually take some pictures of our research sites. The first thing we discovered is that take-off and landing locations were not as ideal as the wide grass airstrip of the R/C airfield. We had to take off from a gravel road, watching out for the power lines overhead. On out initial photo attempt we stood at the edge of the field during the flight and flew the plane over our plots. When we got our pictures back, we discovered that the quality was good but most of the pictures were of an adjacent field. It was very difficult to orient the plane over the correct spot when we were at the side of the field. After that, we walked to the center of the area we wanted to photograph and took a series of pictures as the plane passed directly overhead. Another option would have been to have a second person at the center of the area and use two-way radios to tell the pilot when to take the pictures.
In two years of taking aerial photos with this plane we have discovered a few things. We initially wanted to get photos of entire quarter sections. We found out that that was not possible, at least with our camera. The width of the picture is roughly the same as the height of the plane. This limits the width of the area photographed to about 1500 feet, because if the plane gets much higher than that it is very hard to see. When the plane is at an altitude of 1000-1500 feet, it is very difficult to see its orientation. At that altitude, if the plane is pitched even a couple of degrees left or right, you could get a picture of a different area. We normally shoot a whole roll of film for one site. If we get one or two good pictures of the right area, we consider the flight a success.
We have used aerial photos of our research sites to correlate color (greenness) of the crop at different times throughout the growing season to yield. We have found a high correlation of crop greenness in July and August to yield. In the spring on 1999, we installed a second camera in the plane to shoot color infrared (IR) slide film. The IR film shows near infrared radiation as red on the developed slide. Higher reflectance of near infrared radiation indicates higher chlorophyll levels in plants and is an indication of the health of the plant. Use of IR film may give us a better or earlier indication of plant health and yield potential of the crop.
Although using an R/C plane for aerial photography has a few drawbacks such as the altitude limitation, initial equipment costs, and the time requirement in construction and learning to fly, it does have a number of benefits. Once you have the plane built and learn to fly, the cost to take aerial pictures is the cost of film, film developing, and a little bit of fuel. You can also fly whenever and as often as you want to, depending on the weather, of course. And finally, you have a new hobby that is a lot of fun.
Nathan Derby, (701) 231-7555
Research Specialist II
NDSU Department of Soil Science
derby@badlands.nodak.edu
Chemigation is the injection of any chemical such as nitrogen, phosphorus or a pesticide into irrigation water and applying it to the land using the irrigation system. The proper use of chemigation is recognized as a Best Management Practice (BMP) for irrigated agriculture. However, in order to use chemigation to benefit your crop production, you have to understand the equipment and management requirements and limitations.
Chemigation can be used with sprinkler, drip and surface (gravity) irrigation systems. The most common chemicals applied with chemigation in North Dakota are liquid forms of nitrogen, fungicides, herbicides and insecticides. Liquid nitrogen in the form of UAN 28 is the most common chemical injected into irrigation systems. The label of the pesticide container must indicate that it can be injected into the type of irrigation system you are using or it cannot be used. For example, if you have a center pivot, the label has to specifically say the pesticide can be injected into the irrigation water and applied by the center pivot.
Chemigation in North Dakota is used almost exclusively on center pivot sprinkler irrigation systems. Chemigation is not recommended for use with volume guns (big guns) due to poor application uniformity and wind drift problems. Chemigation can be used with other forms of sprinkler irrigation systems such as wheel rolls, solid set, towline and hand move.
The equipment requirements for protection of the water source when chemigating have been incorporated into the North Dakota Century Code. The law specifically requires the following equipment:
A more detailed explanation of the required equipment was presented in an article in the April issue of this newsletter.
The type of sprinkler package on a center pivot can have a large effect on the degree of benefit the crop derives from the applied chemical. Sprinkler uniformity, wind speed during chemigation, application rate and application amount in conjunction with the characteristics of the applied chemical all contribute to the effectiveness of the applied chemical.
Sprinkler uniformity is critically important because the objective of chemigation is to apply the same volume of chemical to each square foot of the field surface. Sprinkler uniformity can be checked with a "catch can test." A can test involves measuring the amount of water applied at two or more locations under each span of the pivot. This can be done with rain gages or plastic cups, but they all must be of identical construction. After the pivot goes over the cans, the amount in each can and its location in the field should be recorded. The average application amount should be computed and the individual can amounts compared to it. If any deviate from the average by a large amount there is probably a problem with sprinklers at that location on the pivot. While running the can test, you should walk the length of the pivot and check for broken sprinklers and pipeline leaks. If any are found they should be fixed before chemigating.
Chemigating with the endgun on is not recommended for pesticides because of wind drift and usually poor uniformity under the area irrigated by the endgun. Chemigation should not take place when the wind speed is greater than 10 miles per hour (mph), but in North Dakota it is difficult to find days with low wind. A compromise would be to start chemigating in the early evening when wind speeds generally decrease.
The type of sprinkler package and height of the sprinkler head above the ground greatly affect the application rate of a pivot. Application rate is expressed in inches per hour, and the peak application rate of a sprinkler system will determine how much runoff will occur. The application rate of a center pivot is greatest at the last tower and the last tower covers the largest area of the field. The variation of application rate with height of the sprinkler above the ground is shown in Figure 1.
Figure 1. Change in application rate of the sprinklers on a center pivot due to height above the ground. For comparison, the sprinkler head is assumed to be identical in all three cases and applying the same volume of water.
A common question is how much nitrogen should be injected each chemigation event. The most common amounts injected are from10 to 30 pounds per acre (lbs/ac) of N. How much to inject is dependent on the crop, growth stage, the amount applied previously, yield goal and soil type. By the time corn is chest high, it has a deep root system, so applying 30 lbs/ac would be reasonable and this may only be required once in the growing season depending on how much N was applied previously. However, if you have a shallow soil, which restricts full corn root development, you may want to put on two applications of 15 lbs/ac. The root depth of potatoes is only 2 feet so smaller amounts of say 10 to 20 lbs/ac of N applied more frequently are desirable so that N is not lost to leaching events caused by summer storms.
Another question asked is how much water should be put on with the N. Since you want to get the N to the roots, chemigating with N during a regular irrigation event is the most desirable. If circumstances are such that you need to apply the N and are not concerned about the amount of water, than the timer should be set to apply at least a quarter of an inch.
Fungicides are either protectants or systemic. Protectant fungicides applied by chemigation provide protection to the plant by coating the above ground biomass of the plant. Systemic fungicides work by being absorbed by the plant and providing protection from the inside of the plant through the tissues. For both types of fungicides the object is to cover the plant but not put too much water on so that the fungicide is washed off.
Irrigation engineers always worry about maximizing water application efficiency of the sprinkler systems, and interception losses by the crop canopy is always one of the major evaporation losses. Ironically, the so called "interception losses" of water is exactly what you are trying to optimize when chemigating with fungicides. Therefore, low application amounts are applied. Typically the pivot timer is set at 100 percent, which puts on the least amount of water (around 0.1 inches).
To get good coverage of the plant canopy with fungicides, you need to understand your sprinkler package and its application rate. As seen in Figure 1, the application rate can vary depending on sprinkler head height above ground. The peak application rate does not change with the timer setting of the pivot, only the application amount changes. So even if the timer is set to 100 percent and only 0.1 inch of water is applied, the application rate can be so high that much of the fungicide is washed off the plants. A simple analogy would be to imagine standing under a garden hose for 1 minute or standing by an oscillating lawn sprinkler for 1 minute. They both put out the same amount of water but at vastly different application rates.
The object of applying insecticides is the same as fungicides and therefore has similar requirements of the sprinkler system, timer setting and application amount.
Herbicides have two modes. They are applied either before or after weed emergence. If you are applying pre-emergent herbicides you want the water containing the herbicide to penetrate at least 4 inches into the soil. Selecting an application amount from 0.25 to 0.5 inches will accomplish this very well. If you were applying a post-emergent herbicide, then the application amount would be similar to that selected for chemigation with fungicides.
Impact sprinklers have a relatively low application rate because they are mounted on the span pipe of pivot. Sprinkler heads with rotating or oscillating plates at about 8 feet above the ground have low to medium application rates. Sprinkler heads located 4 feet or less above the ground surface will have high application rates. Sprinkler heads with 180-degree spray mounted on the span pipe will have a very high application rate.
If you are contemplating chemigating with pesticides, look at your sprinkler system very carefully to see if it has the application rate to accomplish what you want it to do. If you think the application rate will be too high and won't provide good coverage, then look at some other application method.
Tom Scherer, (701) 231-7239
NDSU Extension Agricultural Engineer
tscherer@ndsuext.nodak.edu
Water Spouts, No. 177, August 1999
NDSU Extension Service, North Dakota State University of Agriculture and Applied Science, and U.S. Department of Agriculture cooperating. Sharon D. Anderson, Director, Fargo, North Dakota. Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. We offer our programs and facilities to all persons regardless of race, color, national origin, religion, sex, disability, age, Vietnam era veterans status, or sexual orientation; and are an equal opportunity employer. This publication will be made available in alternative formats for people with disabilities upon request, 701/231-7881.
North Dakota State University
NDSU Extension Service
