The term site-specific fanning means carefully tailoring soil and crop management to fit the different conditions found in each field. Site-specific farming is sometimes called "prescription farming", "precision farming" or "variable rate technology". It has caused a focus on the use of three technologies - remote sensing, geographic information systems (GIS) and global positioning systems (GPS).

GIS uses computer technology to store cultural and natural resource information that can be recalled in a geographical format or "map". The maps of different information are often referred to as "layers" because they can be overlayed. These "layers" of information can be related to exact field locations. Currently, most researchers are able to analyze only a few layers at a time. In the future, more effort will be made to analyze multi-layers of information.

Systems that collect and transmit remotely sensed data important to farmers have been developed. Farmers can analyze this satellite information themselves or contract for this service with various companies. In North Dakota the process of using satellite imaging with farming has begun in the Red River Valley.

Some people incorrectly use the term "GPS" to imply precision farming. GPS makes use of a series of military satellites to determine a precise geographical location. The value of knowing a precise location includes: 1) accurate geographic identification of soil properties; 2) fertilizer and pesticides can be prescribed to fit measured soil properties (as opposed to estimated from soil maps); and 3) yield data can be monitored from precise locations as one goes across the field.

The real value of site-specific methods for the farmer is to plan more accurate crop protection programs, adjust fertilizer rates from one part of a field to another based upon localized soil tests and know the yield variation within a field. These benefits will enhance the overall cost effectiveness of crop production.

The relevance of site-specific farming to dryland agriculture in the semiarid northern Great Plains needs to be examined. What are the economics and benefits of site-specific management under dryland conditions in the northern Great Plains? The objectives of the project are to determine the feasibility of using site-specific farming technology under dryland conditions in the semiarid northern Great Plains and to develop management strategies for effectively using this technology in crop production systems.

In a cooperative effort, the USDA-ARS at Mandan, NDSU Cooperative Extension Service, Area IV Research Farm Advisory Committee, USDA-NRCS, Concord, Inc., and other interested participants initiated a site-specific farming demonstration and research site during the summer of 1995 on Field I of the Area IV Research Farm. This project covers about 75 acres of land. Yield and disease monitoring began with the 1995 crop. Soil sampling was done after harvest to determine variable fertilizer rates to be applied in the spring of 1996. Continuous cropping and minimum tillage systems will be used in the 1996 production plan.

Figure 2: Nitrate levels of field I-4, I-5, and I-6.

Figure 3: Phosphorus levels of fields I-4, I-5, and I-6.

The work this past summer included obtaining yield data on fields I-4, I-5, and I-6 (Figure 1). The information from I-4 was questionable due to improper operation of the yield monitor. The yield information from I-5, confectionary sunflower and I-6, spring wheat, is included and more accurate. Considerable variation in yield shows up in all fields with the darker area showing higher yields. The spring wheat yielded about 24.5 bushels per acre and the confectionary sunflower yielded about 1190 pounds per acre.

Figures 2 through 4 show the N, P, and K variations across fields I-4, I-5, and I-6. The darker areas show higher levels of various materials. Figure 2 is the nitrogen level after the crop was harvested and varied from less than 15 lb/ac to over 45 lb/ac. The numbers along the left side and along the bottom of the charts are the last 6 digits of the field coordinates in latitude and longitude. The left side of the chart is 46° 45.7500' latitude and less while the bottom of the chart is 100° 55.6000' longitude and lower values.

Figures 3 and 4 show phosphorus and potassium levels on the same fields. Again, lighter shades are lower levels while darker shades show higher amounts of the particular nutrient.

Other work completed this past summer included measuring topographic elevations on fields I-4, I-5, and I-6 (Figure 5). Study is being completed to determine if there is a correlation between field elevation and soil fertility. This could be helpful to produce accurate soil tests without the need for grid soil sampling which could help reduce the number of soil samples that need to be taken. The differences in elevation from the high point to the low point is about 26 1/2 feet. A comparison of first year correlation of topography and 1-2 acre grid estimates with original nitrate-N levels is shown in Table 1.

This project is in an information gathering phase and has been in progress for about 8 months. Very few recommendations can be given at this time. It is felt that at least 2 to 3 more years data is needed to determine if site-specific farming technology can produce an economic benefit to semiarid parts of the northern Great Plains.

Table 1. Comparison of topographic sampling and 1-2 acre grid estimates with original I 10- 150 ft. grids:

Figure 1: Field I-4, I-5, and I-6 yield maps. The I-4 yields may be questionable due to improper operation of the monitor. Consierable variation shows up in all fields.

Figure 4: Potassium levels of fields I-4, I-5, and I-6.

Figure 5: A 3-dimensional topographic map of fields I-4, I-5, and I-6.