Soil Test Levels “The Benefits and Questions”

Do you often wonder; have I applied enough phosphorus or potassium to reach my yield goal for this season? What was last year’s crop removal? How much of my potassium and/or sulfur leached due to rain this year? Has more of my phosphorus mineralized this year and become plant available? These are all concerns that are faced each year. Annual or bi-annual sampling will provide the information needed to create a smart fertility plan for your operation.

Changes in yields will signify changes that have taken place in fertility levels. The common practice in agriculture is to have soil samples taken every three years. While organic nutrients from manure may help keep our analysis on a flattened trajectory there are factors that prevent a consistent manure plan year after year. If yields have consistently increased or decreased by even a few bushels since the last time you sampled, the information leading into next year’s crop is outdated. Increased yields require and use more nutrients.

Weather patterns are never identical and the ability to rely on historical data is disappearing. Prolonged, dry conditions, fewer rain events but larger amounts, a slower start to spring warming and earlier frost conditions in the fall all affect what soil nutrient levels are doing. Cooler conditions in the spring lengthen the time it takes for soil temperatures to rise. Microbes that assist in mineralization of organic matter and help release plant available nutrients do not work effectively under cool temperatures, while drought conditions prevent nutrients from moving into the plant. When heavy rain events come, plants may not take up nutrients quickly enough before they often leach away from the root zone. Because each year presents a different growing environment, you may need to adjust management practices to maintain consistent yields farm – wide. Your farms fertility program is a large investment – and an important one.

A switch from a dry fertilizer planter to a liquid planter may result in a rapid decrease in soil potassium level – especially when potassium is not supplemented in some way pre – plant or post – emergent. No-till operations and tillage practices both present obstacles when placing fertilizer before planting. Aside from the placement of fertilizer during planting, no-till operations rely on broadcast fertilizer applications. Soil surface applications leave nutrients vulnerable to volatilization and reduced levels in the plant root zone. High binding and immobile nutrients like phosphorus are going to quickly attach to nutrient loading sites on a soil particle. Lacking incorporation, this nutrient is going to stay towards the top of the soil profile limiting its effectiveness with plant growth. Farms that utilize tillage practices need to be aware of which implements are being used and when to apply the fertilizer. The goal of primary tillage is to reduce compaction, typically working the soil profile 12 inches or deeper. Fertilizer application beforehand can result in incorporating nutrients below the optimal uptake areas. The best application process is to apply before the final stages of seed bed preparation, so nutrients are worked into the top 4-12 inches.

Understanding what nutrients are doing in the soil profile will help you determine which products to use. Nitrogen is susceptible to weather and is very mobile in the soil. Timing and placement are two crucial factors when considering nitrogen management. Plants take up sulfur in the sulfate form which is very mobile in the soil and prone to leaching. Phosphorus is very immobile once it has been applied and will quickly attach to soil particles. Phosphorus diffusion to the root is only about 1/8 of an inch per year. Placement is critical to ensure our crops are getting the right amount. Potassium is somewhat mobile and certain soil types can lead to leaching issues. Fall testing can help give us a consistent reading of immobile nutrients that could be available for the coming year. While in season testing can help us plan for nutrients like nitrogen and sulfur that have high risk potential for leaching.

If you are using outdated data, you will not know your soil needs from year to year. Regular soil testing done at the optimum time can provide the needed information about nutrient availability, improve fertilizer use efficiency, and increase crop productivity and profitability. Want to stop guessing about what your crop needs are and use a scientific approach to achieve the best results? Give your local CaroVail location a call or visit our website for more information at http://carovail.com/. We can review your current data, help you develop an annual plan, and find ways for your operation to be more productive and profitable.