Precision Ag 101

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AboutPrecision Ag 101

Welcome to our Precision Ag 101 overview where you can learn and review multiple aspects of precision agriculture. This is also a resource to answer any of your questions and possibly learn how to implement new aspects to your operation.

Precision Agriculture has been a part of the industry for over 20 years in some shape or form from how soil sampling the field is conducted to applying fungicide to corn through variable rate technology. The concept has focused on how to be more efficient on farms and to promote sustainability. Despite its presence in the agriculture industry for many years, grower uptake has been slow due to its constant evolution and limited education of how it can be applied. There are many different options and approaches for growers to implement on the farm which leads to confusion. The best approach is to always keep it simple and hopefully this page will help answer some of your questions around precision ag and how to get started.


1. What is Precision Ag (Agriculture)?

Precision agriculture is a term used to describe a method of farming that utilizes a multitude of technological innovations, such as GPS guidance, precision machinery (planters, sprayers, etc), soil sampling, drone imagery and sensors. This method of farming allows for a more accurate application of inputs as well as allowing to grow crops more efficiently. The goal of precision agriculture is to allow growers to make more timely and informed decisions based on what the crop needs and not a broad application across multiple fields.

2. Why should I use Precision Ag?

As population grows and the amount of farmland decreases, precision agriculture is meant to improve efficiencies and productivity. Following precision ag methods, growers are able to pinpoint plant nutrient needs in season and in between crop rotations, as well as apply it in a precise manner when it is needed. Precision ag has the potential to increase your Return on Investment while increasing or decreasing your inputs in the right areas. In the long term, precision agriculture is helping to nurture and protect farmland so that it remains productive in 20, 50 and 100 years’ (CropLife Canada)

To learn more, visit and the United States Department of Agriculture.

3. What is Field Variability? 

Understanding your field variability will help you determine the success of applying precision agriculture to your operations. Variability has a large impact on yield so it is important to understand your variability inorder to achieve the best yield possible from the various regions of your field.Knowing your variability will also aid in your decision of what methods you will apply - multi-hybrid planting, variable seeding rates, variable rate inputs and even the level of soil sampling that you choose. 

Fields with low variability could have very little variation in terrain, with one or two soil types, similar characteristics. Fields with little variability could also have similar drainage capabilities across the entire acreage.

Fields with high variability could have rolling hills with large variation or with gentle rolling rolls that have a smaller range of variation but still variation. There could be many different soil types ranging from sand to clay that have very different characteristics. The fields could also have multiple different drainage patterns that require different management methods.

To learn about topography in agriculture, visit To learn about topography in agriculture, visit this page.

4. Capturing field variability - Will precision ag work on my fields?

One of the most popular questions out there is “Will Precision Ag work for my farm?” To answer this question we need to look at the backbone of precision agriculture. Some think it is data but the big question is around variability. Do you have enough variability on your farm that precision ag technology and the concept of precision ag will make sense. We can utilize tools such as a variability capture model that can answer how much variability does your farm have and is it enough to make precision ag worthwhile. 

The most important layer to start with to measure your variability is to soil test. There are many different soil sampling systems out there (See Section 5) to utilize to see what is happening in your field. Soil sampling or soil sensing is important to see the total variability across the field. To help decide what level of soil sampling you wish to use, you can use imagery of the field or soil sensing data and overlay with different soil 
sampling levels to see how much variability each soil sampling level actually captures. It can tell you how intensively you need to manage your field and for some, maybe there is very little variability and you can manage with bulk sampling and larger system management. Knowing how much variability is in your field and utilizing the variability capture tool to decide which level of sampling captures the most of your variability helps get you started and answer the important question if precision ag will work before you make big investments.

Additional Resources

5. What is Soil Sampling? 

Soil sampling is important for any farm operation as it allows the grower to maintain and monitor their soil fertility. A healthy soil is paramount to good, sustainable yields. A regularly scheduled soil sampling program guarantees that your fields nutrient management goals are being met and that you are maximizing your crop input investment. A well-balanced soil makes your seed perform as anticipated, your chemical program perform as promised, and your yield levels continue to increase (Veritas, 2018). A soil sampling program will help apply crop nutrients where they are needed following a 4R nutrient stewardship program while maximizing your input investment on every acre.

Provincial regulation states that soil samples need to be taken in preparation for a new nutrient management plan. The maximum interval for soil sampling would be 5 years, unless there is a change in the operation in which a new plan needs to be created (OMAFRA, 2006). If you are not using a nutrient management plan, it is still a good agronomic practice to sample each field every 5 years to ensure you are applying the nutrients that are required. The soil acts as a bank, growers need to make sure there are enough nutrients in the bank to support the crop year over year. 

6. How do I Soil Sample? 

When you are considering soil sampling, you should also consider what you would like to achieve with sampling. Is it for diagnostic purposes  or is it a routine sample to monitor the health of the soil but also for your records and nutrient management plans. Soil sampling is very important when it comes to nutrient recommendations and amendments. It is recommended to measure your nutrient levels before you start applying ensuring that you are applying what you need in the right areas.

Once you have decided to sample you can either use previous sampling points to re-sample the same areas for a check of the nutrient levels. If it is a new field you will need to work with your agronomist to decide which level of sampling you are needing. The variability of your field but also what your end goal for sampling is will determine what resolution you go with (See Section 7).

If you are bulk sampling, you can divide the field into sections no larger than 25 ac for a representative sample. If you are grid, zone or polygon sampling the sampling resolution data layer is applied to the sampling field. This data layer is provided to the soil samplers whether it is from the local lab, agronomist or ag-retail for them to follow and geo-locate the sampling points for future records. For zone or polygon sampling, approximately a dozen individual core samples are collected from that area. To understand more on the difference between soil sampling methods please see Section 7 below. The samples are collected and sent to the lab for analysis. You can choose the different nutrient tests that you would like to receive on your samples. Please refer to your local lab for their sampling test offerings. Once the samples are tested, the results are sent to you and your agronomist. You should receive the nutrient level numbers, as well as a mapbook that shows you spatially the nutrient levels across the field. Recommendations can then be made from these results.

To learn more on how to get started with sampling, check our our webinar Getting Ready for Soil Sampling

For a soil sampling guidebook, please see this guide

Example of a hand soil probe

Example of an automatic soil sampling machine

7. Choosing the right level of soil sampling

When you have decided to soil sample, there are a few different methods to consider. It is important to choose one that will supply you with the most accurate resolution and the most economic rate possible for your business. This case study aims to explain each method available and its differences.

What is bulk soil sampling?

Bulk soil sampling consists of dividing

a field into 1-4 areas, depending on the size of the field, and sampling those areas. The maximum area included in a single sample should be 25 ac (10 ha). The field can be divided into high zones and low zones with all high zone areas being sampled together and similarly for the low areas. The field could also be sampled simply in halves or quarters and depending on its direction, for example, north section, east, south and west. Bulk soil sampling is useful for capturing a snapshot of what the average soil characteristics of the field are. This is useful when first purchasing a new farm, or to better understand the average fertility across the farm measuring the average change over time.

Bulk soil sampling does not separate the soil based on variability, different soil textures or fertility. This method can skew soil texture results and can impact the accuracy of the soil nutrients levels, which leads to the under or over applying of fertilizer.

What is grid soil sampling?

Growers can choose a 1 acre, 2.5 acre, 5 acre, or 10 acre grid. The grid is overlaid onto the field through a computer program and soil cores are taken with each grid using georeferencing. There are on average 10 to 12 cores taken within each grid, the cores are taken in areas that are most representative of the sampling grid. The cores in a grid are mixed and each grid sample is kept separate from the rest.

As shown in the variability example below, it is not until the 2.5 acre grid can you start to see some of the field variability but it is minimal. The 1 acre grid size captures most of the fields variability but is not an economically feasible way to soil sample the field.

Grid sampling on the larger scale can start to capture some variability and produce an overall nutrient level of a field by section but it is hard to narrow down specific nutrient levels by soil characteristic. Grid sampling can average test results across dissimilar soil types, mixing soils that should be kept separate and is also susceptible to mixing uneven fertilizer applications or a variety of other environmental factors. For instance, one grid could have a mix of sand and clay soil. The test results would average the nutrient amounts across that block and lead to a misapplication of fertilizer based on the soil type.

What is polygon soil sampling?

Polygon (zone) are areas drawn on a field based on soil type, topography, yield variability, drainage, fertilizer applications or grower knowledge of the field. The information about the variability across the fields is used to create field management maps. The best zones come from multiple layers of data that when layered on top of each other reveal to us the true variability across the field.

Polygon soil sampling is done to obtain a better understanding of the variability of the field. It also uses the information gathered to determine the specific nutrient levels per polygon area and which ones need adjustments. It is important to ensure that each sampling area is uniform and separate from areas that are obviously different.

Polygon sampling on a larger scale such as 10 acre polygons captures some of the variability and are able to start separating out the high, low and middle ground areas and keeping those samples separate. 

The 5 acre polygon map separates out the field in more detail. It is not until you get down to the 2.5 acre and 1 acre polygons that the true variability of a field is captured. The 1 acre polygon is comparable to a CEC soil map from an optical soil sensor mapping system, which will be discussed in the next section. The 2.5 acre polygon is a more economical sampling method but it also captures the level of variability that is easier for growers to manage, making it the most common approach to sampling at this time.

A regular soil sampling program using polygons can help a grower accurately apply crop nutrients. It also helps maximize input investment on every acre, identifies the fields limiting nutrient, applies 4R nutrient stewardship and make the most of your crop input dollar. Soil Sampling using the polygon approach also allows for deeper analysis to be done on the sampling data.  Because the zones match yield very closely, we are able to analyze the data with new analytics to give growers a deeper look into their fertility programs,

What are soil sampling sensors?

Soil sampling sensors are a newer method of sampling that has grown in recent years. These sensors are used to capture a variety of soil properties. These are used in real-time using GPS (Global Positioning Systems) and can be programmed to capture certain soil properties at one time, such as soil texture, nutrient, and moisture (Adamchuk, Vlacheslav I., et al, 2002). Some programs even capture soil cores throughout the field in different areas along with the scans. These cores are collected to validate and calibrate the sensor maps values.

There are a couple types of sensors being used commercially today, they are electromagnetic (EM-38 sleds or Veris) machines that use electrical conductivity in the soil to measure soil properties. The other popular method is Soil Optix, a sensing system that measures the natural radiation given off to characterize the soil. The variability that an optical sensing unit captures is demonstrated here in a CEC (Cation Exchange Capacity) map. A CEC map helps identify the soil textures of the field.

These sensors are beneficial in capturing the whole fields soil texture variability as well as the moisture and nutrient levels all in one scan. There are multiple other layers that can be applied to the soil sensors, such as topography, drainage and many more that can work together to capture the entire fields soil health. It may not be economical for some growers who are looking for nutrient levels only, in this case, a 2.5 acre polygon sample may be a better option. But for an overall soil health check-up of your field’s characteristics, nutrients, and moisture, it may be the best bang for your buck.

8. What can soil sampling data tell me? (SOIL Insights and Variable Rate Fertilizer)

Soil sampling can tell you a lot about what is happening in the field. It can tell you what the nutrient levels are in various zones/polygons throughout the farm. It can answer questions on yield impact and how much fertilizer do you actually need to put down and where. Depending on the level of sampling being completed you can see what your macronutrients, micronutrients and even water holding capacity, just to name a few. 

SOIL Insights is available to provide the “so what” to soil sampling. SOIL Insights can use your soil test data and your most recent yield to compare what the soil nutrient levels are in each zone or polygon and the resulting yield. It can tell you what nutrient is most limiting in each area, which one is too high, which one is too low but also tell you which one is at optimum level. SOIL Insights can tell you what the optimum nutrient level is to achieve a higher yield or where to limit inputs to improve your return on investment.. It can also help answer which nutrient you need to apply first to see the most benefit to your farms yield and overall soil health. 


Once you have reviewed your soil mapbook and the SOIL Insights you can see what the most limiting nutrients are and you can apply that information to variable rate fertilizer prescriptions. Using the zones or polygons that were created for soil sampling a fertilizer prescription for each nutrient you want to target is created ensuring that the appropriate amount of nutrient is applied in the right areas. There may be even some areas where you do not even need to apply any and that is ok - that could mean you are trying to draw down some of those nutrients to more optimum levels. Variable Rate Fertilizer prescriptions are key for 4R nutrient stewardship on your farm - putting down the right product at the right rate, right place and working with your agronomist to create these prescriptions ensure they are applied at the right time.

For more information on 4R nutrient stewardship, please visit

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