Soil Management For Farmland Owners

May 14, 2015
By Colvin
Soil management is one of the top priorities for farmland owners in order to make sure their asset lasts well beyond their life time and many future generations. Farmers use soil tests to understand the proper nutrients required to achieve optimal crop production, but landowners utilize soil tests to maintain the integrity of their investment. Failure of farmland owners to monitor fertility levels can lead to underperforming crop yields and the eventual degradation of the land.
Soil Testing Basics
Soil tests are performed to help farmers analyze and manage nutrient and fertility levels of a property’s soils. Significant technological advances made in agriculture over the past several years have made soil testing an essential part of farming. Farmers use soil tests to create prescription maps which provide precision solutions to fertility issues in fields.
The soil samples are procured using a probe which collects six inches of soil from the property. Agronomists then use the soil samples to test for the level of macro and micronutrients.
Macronutrients include phosphorus and potassium, two nutrients vital for plant growth. Micronutrients tested for include calcium, magnesium, sulfur, and zinc. A typical soil test will measure macronutrients, micronutrients, as well as the organic matter concentration and the pH (acidity or basicity) of the soil.
Test results are displayed on a field map showing areas of high or low nutrient concentration on different areas of the property. These maps allow farmers to better manage specific areas of poor fertility rather than wide broadcast fertilizing across an entire property, allowing for cost savings and limiting the farmer’s environmental impact.
Mandated Soil Tests
Soil fertility management is one of the most important aspects involved in managing farmland. A property’s soil types and past yield history can be used as indicators of production potential, but without maintaining soil fertility, even the best soil types will produce poorly. Proper soil fertility management ensures the land will produce to its optimal potential every year.
Every landowner hopes that their operator is building soil fertility year after year, but this is sometimes not the case. Mandated soil tests are a way for landowners to protect the integrity of their property’s fertility, while also improving their property’s value. In negotiations with operators who are looking to lease a property, or when negotiating the sale of a property with a potential buyer, the presence of up to date soil tests with proper fertility levels will maximize the rental or sale value of a property.
Mandated soil tests are typically written into the lease agreement between the landowner and operator. Often, the largest sticking point during these negotiations revolve around the frequency of the soil tests.
Information from Iowa State University and University of Minnesota schools of Agronomics state, “recommend testing every two to four years.” What is failed to be mentioned is that typically those recommendations are for properties in a crop rotation where corn is planted once every three years.
Properties in the Corn Belt will most likely have corn planted once every two years and many have corn planted annually. Corn uses a significant amount of nutrients, and if the soil nutrients are not replenished, the soil’s fertility can degrade quickly.
We recommend that leases require annual or biennial soil tests from operators. Biennial agreements should stipulate that the operator must sample in the final year of the contract to ensure current fertility of the soils in the event of an operator change.
Grid, Zone, and EC Soil Sampling
Fields can be soil sampled in a variety ways, but the two most common and effective are grid sampling and zone sampling.
Grid sampling is the most common process and, “the most accurate reading of a field’s fertility,” according to the University of Minnesota Extension. When creating a grid sample, a property is broken down into increments ranging from 2.5 to 20.0 acres. A sample is then pulled from the center of each area, documented where on the field it was taken, and sent to an agronomist be tested. After being tested, the results are displayed across a map of the field.
Grid Sample
Zone sampling is done by a similar process, but rather than taking multiple samples across the entire field, soil and topographical maps are used to find areas of like soil and slope, which are then grouped into zones. A sample is then taken from each zone and the test results will be extrapolated across the entire zone.
Areas of similar soil type and slope should have similar nutrient degeneration from crop use and weather runoff. An average 160 acre property will have 4-7 zones depending on the property’s soil and slope diversity.
“While not providing as accurate a reading as a grid sample, a zone sample will still measure fertility and nutrient levels to ensure they aren’t depleted,” noted the University of Minnesota Extension.
Zone Sample
A concern with zone sampling is that soil maps can be inaccurate, causing areas of a property to be placed in an inappropriate zone. To counter soil map inaccuracies, an electro conductivity (EC) test can be performed. An EC test measures the particle makeup of the soil on a property by running electrically charged discs through the property’s soil. The particle make up reading creates a more accurate and detailed soil map that is then used to create the zones of a zone sample.
Conventional Soil Test vs. EC Test
The information from both a grid sample and a zone sample can be entered into a number of farm implements to provide variable rate application of inputs to a field. Variable rate application uses the information determined by the soil test to provide varying amounts of fertilizer or seed to areas of the field based on need. This practice saves farmers money while lessening their environmental impact.
It can take time to get fertility levels to suggested levels, especially if a property has gone unmanaged for a length of time. Focusing on incremental year-to-year improvement is the most realistic way to manage a property’s fertility.
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