Corn and soybeans require a steady supply of phosphorus (P) for early seedling vigor, root development, and stalk growth. P is used by plants in the lipid layer of the cell wall, as the backbone to genes (DNA and RNA) and for energy transfer (ATP). While P is an essential element (ranked 8th in the amount needed) it is one of the big 3 nutrients (N-P-K) because it yields more bushels per acre. Recommended corn and soybean soil test are between 20-40 ppm Mehlich. In corn, most rapid P uptake occurs after the V6 stage (six leaf collars). About 80% of absorbed P ends up in the grain. Post-tasseling P availability is critical to maximize yields. In early vegetative planting (Planting to V6), P is essential for root, shoot, and initial ear structure development. Severe P limitations early can permanently reduce yield potential. The most rapid uptake of corn P is V6 (vegetative stage) to R1 (reproductive stage). Demand spikes as biomass multiplies after V6 (4 to 6 weeks after planting)...

Phosphorus (P) runoff has long been blamed for excess harmful algae blooms in Lake Erie. While most experts blame agriculture, humans are also a significant source of P runoff in the form of human sewage. The City of Maumee by Toledo is an example. US EPA recently announced that the City of Maumee has been dumping 150 million gallons of raw sewage into the Maumee River for the last 20 years. The problem occurs because during heavy rains, relatively clean water from downspouts, sump pumps, and other sources of stormwater is mixed with raw sewage, and the sewer system can not handle that much water so it is dumped into the river. Cities are now required to have two piping systems, one for raw sewage and one for relatively clean stormwater. However, the cost is very expensive to replace and update all those sewage systems. It is not only problems in major Cities, it is also rural home systems that need updating. So, everyone needs to do their part to keep water clean. Another new developm...

  Phosphorus (P) is an expensive nutrient but critical for good crop production. Phosphorus is the backbone to the plants genetic code, for ATP (energy transfer/storage) in plants, and for cell division and enlargement. When P is severely limited, plants turn a purple color, which is common on cold wet soils in the spring. However, plants often have a hidden hunger for P which may limit yields. Chad Penn, Research Soil Scientist for USDA from West Lafayette, Indiana at the Ohio No-till conference; shared recent research on corn P nutrition. Available P in soil varies by soil type and weather conditions. Farmers try to optimize P application, but it varies so much, even within a few inches or feet. Even with extensive soil testing and grid soil sampling, P is often either under applied or over applied. The ARS-USDA research is trying to find a way to put on just the right amount of P so that it maximizes yield. Chad discussed the two main sources of soil P. The first fraction is the...

  Phosphorus (P) fertilizer improves crop yields, so farmers add P fertilizer either every year or only once to corn in corn-soybean rotation. Unfortunately, only about 5-15% of applied P fertilizer is used by plants the year it is applied. Since P is so reactive, the remaining 85-95% of applied P fertilizer is quickly tied up or complexed by the soil. When fertilizer costs are high, farmers can use the P that is in their soil bank without sacrificing yield as long as P soil test levels are adequate. Soil P can be lost in two ways. Soluble reactive phosphorus (SRP) or orthophosphate easily leaches while particulate phosphorus (P bound to soil particles) is lost when soils erode. One way of minimizing P losses and utilizing P more efficiently is to understand how soil P is stored. There are four main pools of soil P: SRP, soil microbes, absorbed soil particulate P, and mineral P. The smallest P fraction is the SRP or orthophosphate with 0.5-1#/acre of soil P in solution which is mic...

  Keeping soil nitrogen (N) and phosphorus (P) available and on the land is every farmer’s goal. If a farmer is paying for fertilizer, they want the plant to use it. From an environmental standpoint, N and P that leaches or runs off is bad for water quality. Finding ways to tie up N and P and keeping it on the land is good for everyone. The best way to keep nutrients in the soil is to keep the nutrient available but not soluble. Available nutrients can be used by soil microbes and then transferred to plant roots. Two problems occur with soluble nutrients. First, soluble nutrients flow with water and may either leach or runoff the soil. Second, in dry soils, soluble nutrients are not readily available. Nitrogen in the form of nitrates (NO3 - ) has a negative charge. Soluble reactive phosphorus (SRP) or orthophosphate (PO4 3- ) also has a negative charge as do clay particles. Since negative charges repel each other, these elements tend to be soluble and flow with water. Any organic s...

Tremendous farmer turnout occurred for the new Ohio H20 plan for $30 million being provided to 14 Northwest Ohio counties to improve Lake Erie water quality. Almost everyone agrees that phosphorus (P) in surface water is a major issue. The excess P in surface water is causing Harmful Algal Blooms (HAB) in Lake Erie. Since we are dealing with many algae (singular), the plural is algal not algae (common mistake). One pound of P in water may produce 500 pounds of HAB. The HAB in water need 1/10 the amount of P that our land-based plants need to thrive, so even a little P in surface water causes HAB to thrive. In the 1970’s/1980’s, the problem was total phosphorus which includes dissolved (or soluble) reactive phosphorus (DRP) plus the particulate phosphorus (PP) or P attached to soil particles. Recently, researchers have concentrated mainly on DRP because it flows with the water and is easily HAB absorbed. DRP was rising the fastest while the PP appeared to be stable. Recent information f...

  Phosphorus Problems and Solutions: Part 1  Ohio legislators are considering a number of rules and regulation regarding phosphorus (P) fertilizer and manure. The following article outlines some facts about P runoff. Weather is one of the biggest culprits in P runoff. Over the last several decades, precipitation has changed with more numerous precipitation events occurring with higher amounts, longer duration, and increased intensity. Due to weather, the key facts are that 90% of P runoff comes from 1-2 major runoff events each year and 80% of P runoff comes from 20% of the soil (Dr. Andrew Sharpley). Location and transport are key factors. Fields close to a creek, stream, or river contribute a considerable amount of P in surface runoff. Most soil P is stratified and P is located in the top 2- 3 inches of the topsoil and subject to soil erosion and surface runoff. On measuring P runoff, the P concentration (usually measured in parts per million) times the transport factor (vol...

Culman, Dayton, King, and Labarge, Ohio State University specialists (CORN Newsletter, 2014- 28) say “Current Ohio field research to minimize phosphorus losses at the edge of the field should start with the following recommendations to maximize productivity while minimizing environmental impacts on water quality. Avoid overloading soils. Soil test and follow tri-state fertilizer recommendations. Where soil test levels are above 40 ppm Bray P1 or 58 ppm Mehlich III-ICP, do not apply additional phosphorus in the corn-soybean rotation. These soil test levels require no additional fertilizer, according to the Tri-State Fertilizer recommendations. Fertilizing soils testing above these levels increases risk of P in runoff and tile drainage. Avoid winter application. Eliminate surface application of manure or fertilizer to frozen or snow-covered fields. Frozen ground is ground that is frozen to the degree that tillage is not possible. Surface applied manure or fertilizer is subject to runof...