Soil preparation is among the top-ranked action items on growers’ spring “to-do” lists. Growers want to know when is the best time to begin soil preparation, what inputs are needed to achieve bountiful crop yields and whether till or no-till is the best approach to raising bumper crops.
“As a general rule of thumb, many vegetables prefer a soil temperature between 68 and 72 degrees Fahrenheit,” said Alan Henn, an Extension plant pathologist at Mississippi State University. “Tomatoes prefer it a bit cooler, peppers a bit warmer and summer potatoes grow better when temperatures reach 80 degrees.”
Additionally, the soil needs to be loose to allow room for deep-rooted vegetables to reach an optimum depth. Loose soil is equally important for shallow-rooted crops that thrive close to the soil surface. Roots and other debris should be removed from the seed bed to remove competition. Debris makes it difficult for smaller seeds to reach the surface.
Although soil preparation seems to be a straightforward process, in reality it is a multistep process that often spans several years. The purpose is to not only create a seed bed that nurtures a seed or young transplanted seedling, but to also improve overall soil health. Through the addition of organic matter, the overall soil structure improves, which increases its water-holding capacity, provides aeration and adds nutrients.
In what follows, Henn and Melissa Erdman, a district conservationist with the U.S. Department of Agriculture-Agricultural Research Service in Juniata County, Pennsylvania, provide short- and long-term tips for improving soil health and soil preparation practices that increase your chances for bumper crop yields.
Start the soil preparation process with a soil test. Henn emphasized the importance of soil testing to determine the existing pH and nutrient levels in the soil. A soil test also provides information about the level of phosphorus, potassium and nitrogen in the soil, which enables growers to determine if and how much fertilizer is necessary, and if other nutrient management practices, such as cover crops, are having positive effects on the soil.
At a minimum, a soil test should be conducted every three years. However, more frequent tests illustrate how year-round soil management practices are impacting or changing the soil’s nutrient composition.
“Most vegetable crops thrive in a pH between six and seven,” he said.
The closer the pH level is to zero, the more acidic the soil. Conversely, as pH approaches 14, the other end of the scale, it is considered more alkaline. When the soil pH is too high or too low it impacts the availability of nutrients to plants. Soil amendments, typically lime, are recommended to modify the soil pH.
Erdman encourages farmers to also use the USDA’s Soil Health Nutrient Toolbox for an in-depth analysis. The results consider the impact of soil biology on nutrient recommendations. The test accounts for soil microbial activity, with a view that this is nutrient-relevant. The results evaluate the mineralization potential of nitrogen and phosphorus available in the soil and represents nutrients likely to be “plant relevant” from lighter-weight extractants.
In addition to understanding the pH and nutrient levels, Henn emphasized the importance of knowing how fast the soil drains, how quickly it heats up and how it reacts to tilling.
“Soils behave differently. Knowing how your soils react can help you better time soil prep processes for a better outcome,” he said.
To till or not to till
There is much discussion on the benefits of tilling versus no-till practices during the soil preparation process. There is not a one-size-fits-all answer. Weed management and compaction are two of the biggest concerns when discussing till versus no-till.
In some parts of the country, tilling is still an important part of the soil preparation process. Fitting the ground aerates the soil, breaks up hard compaction and disturbs weeds as part of a larger soil preparation plan.
“Most everybody here tills, including a lot of our organic producers,” Henn said. “The combination of the weed pressures and the window of available time to get the hills up for sweet potatoes, watermelons and other crops are so short that till is widely used.”
On the other hand, tilling practices are thought to do more harm than good. Erdman believes that tillage is disruptive to the agroecosystem and soil life and encourages growers not to till and to use other management methods.
“With 90 percent of soil function mediated by the life in the soil, protecting their habitat and limiting disruptive practices is very important. With that being said, I believe that synthetic chemicals can also be disruptive to the agroecosystem and soil life,” she said.
Erdman noted that both inputs need to be used judiciously and with caution.
“First, consider their purpose in your soil health management system and whether or not there is an agronomic solution, such as a deep-rooted cover crop to break up compaction,” she said.
Cover crops, also referred to as green manure, offer additional benefits aside from breaking up rough clods in the field. These crops can suppress weeds, build productive soil, help control pests and diseases and lessen erosion. To maximize the benefits, the cover crops must be managed in a way that ensures they don’t interfere with the main crop.
“Before planting it will need to be chopped or disced and it needs to be done in sufficient time that it decays before the next crop needs nitrogen so that the crops aren’t competing for nutrients,” Henn said.
In the short term, spring soil preparation practices prepare the earth for the coming year’s crop. However, for the long term, growers that invest the time and resources into improving soil health and building organic matter will find that less inputs are needed at the start of the season. At the very least, a focus on soil health means that soil preparation begins much earlier than spring.
Ultimately, soil preparation practices boil down to long-term profitability and sustainability in agriculture. Farmers need to look for ways to reduce their input costs, yet maintain yields if they want to be profitable.
“I’ve heard from many farmers about the continued high-dollar investment to plant an acre of corn and the low return with current commodity prices,” Erdman said. “And yet, there are farmers all over the country who are able to reduce tillage, and fuel use associated with it, fertilizer and herbicide use and maintain yields, by improving soil health.”
Growers that have successfully reduced tillage, fertilizer and herbicide while maintaining yields understand the importance of diversifying crop rotations, planting cover crops and using no-tillage. These farmers have also been willing to try new seed varieties and experiment with earlier harvest schedules.
“In central Pennsylvania, we are working with farmers and suggesting they choose seed varieties with shorter growing seasons,” Erdman said.
Growers are also encouraged to harvest the prior year’s crop off as timely as possible. This leaves a window of time to plant a cover crop before winter weather sets in.
“Adopting a soil health management system that incorporates these core practices will result in soils that infiltrate more water, cycle nutrients more efficiently and are more resilient to extremes in the weather regardless of whether your farm is in Bismarck, North Dakota, or Mifflintown, Pennsylvania,” she said.
Erdman reminds growers that building healthy topsoil is a top-down process.
“You need a diverse crop rotation that includes living covers and no tillage disrupting the soil. Then the biology in the soil will do the rest,” Erdman said. “The ‘underground herd’ of soil life will take all the organic matter you are adding to the soil (whether it be cash crops, cover crops, manure applications) and take it down through the soil profile, building your soil from the top, down.”
Maximizing production and minimizing problems is essential to raising profitable crops. And that begins with soil preparation. A well-prepared seed bed helps with the establishment of a uniform crop stand.
Whether you are an organic farmer with tillage in your system or a conventional no-till farmer with chemical use in the system, working toward improved soil health will help you to minimize the use of those inputs. A wide variety of resources is available to growers who are interested in learning more about soil preparation practices.
A good place to start is the local extension service.
“Those individuals will know best practices and be up on the latest seed varieties without having a sales interest,” Henn said.
The regional USDA Natural Resources Conservation Service office is another solid source of information. Erdman explains that NRCS conservation planners provide farm-specific, field-specific recommendations, using proven conservation practices developed over decades and decades of scientific research and development.
“There is an NRCS field office that covers every county in the nation and we are here to help farmers evaluate their resource concerns and implement real solutions,” she said.
Henn added that national crop-specific or state-wide growers associations are good places to network with other growers with similar challenges on their farms. Independent crop consultants are another option.
“Ask for references before working with a consultant. Some of them are excellent, while others are not as helpful,” Henn said.