By Dennis Pennington
Soil is a farm’s greatest resource. It provides the medium for farmers of all commodities to plant and grow their crops. Most farm fields have at least two soil types and usually many more than that. Crop nutrient levels vary not only by soil type but are also impacted by topography, water holding capacity, CEC, organic matter as well as previous crop history and fertilizer management. Learning how to manage the variability in a field will be the key to one of the
Michigan State University Ag Innovation Day sessions titled “Precision Soil Sampling: Every Farm Needs It!”
Figure 1 shows soil type, drainage class and an aerial photograph of a 44-acre field that will be used for the field day. This field has five soil types, land in every drainage class and the aerial image shows how variable the crop was during that growing season.
So how would you manage this kind of field from a soil fertility perspective? It all starts with proper soil sampling. Traditional soil sampling methods would have prescribed pulling random samples in a zig zag pattern across each 20-acre section, composite the samples and submit them to the lab for analysis. However, farmers today are sampling differently, attempting to better quantify the soil test levels and then prescribe fertilizer programs that maximize yield potential while preserving the environment.
Figure 1. Two different methods of soil sampling will be discussed at MSU Agriculture Innovation Day: grid soil sampling and management zone sampling.
Grid soil sampling is usually conducted on 2.5-acre grids. By collecting one sample for every 2.5 acres, farmers are better able to identify the variability in a field. But is 2.5-acre grids small enough? Some farmers will pull samples from 1-acre grids to try to identify problem areas of fields. This is costly upfront, but there may be cases where smaller grids may be a good diagnostic tool.
Management zone sampling is conducted in a different way. Rather than simply splitting a field up into exact 2.5-acre quadrants and pulling one sample from them, the farmer will create zones where soil types, topography, yield potential, organic matter, CEC and previous history shows similar responses to management. Each farm uses their own approach to creating management zones, but the end goal is to collect soil samples in a more informed way than sampling using GPS to put out points every 2.5 acres.
There are benefits and drawbacks to each style of soil sampling. In this session, we will examine a 44-acre field, compare each sampling method and discuss how to use the data to make management decisions. Many farmers already apply nutrients at variable rates across a field. The method you use to sample the soil will have a big impact on how accurate your variable rate spread maps are.
MSU Agriculture Innovation Day is an annual event focusing on in-depth education on critical topics. The event rotates to various locations throughout the state to give farmers access to experts who can help them improve their businesses while maintaining environmentally sound practices on their farms.
MSU Agriculture Innovation Day: Focus on Precision Technology That Pays takes place from 8:30 a.m. to 5 p.m. July 26 at MSU Farms, 3750 N. College Rd., Lansing, MI 48910. The event features how implementing technology that aids in decision-making can improve yields, increase profit margins and reduce environmental impacts on today’s farms. The event has been approved for Restricted Use Pesticide credits (6 credits) and Certified Crop Advisor continuing education units in integrated pest management, crop management, soil and water management and sustainability.