Published March 30, 2020 | By Mike Petersen
The index finger is touching the 2nd most important nutrient for many crops we grow. Phosphorus
All over the globe we as Agriculturists are aware of the challenge to provide the nutrient phosphorus to small grains (ie: wheat, rice, oats, barley, rye) larger grain crops being maize and then broadleaf crops (ie: sunflower, soybeans, dry edible beans). The concern stems from the role P plays in photosynthesis for plant growth then the finite supply of rock phosphate around the world which is running low in North America.
Knowing that, how do we use less or somehow obtain access to the material in solution or tied up in polyphosphate forms or in the resident soil organic matter? Adding animal manures is one option. Another is to add bioenhancers or biostimulants that stimulate the resident mycorrhizal fungi and microbiology. It has been determined that more use of fungicides and certain herbicides, that mycorrhizae and some microbial families have been diminished in the soil. To me that is alarming and I have seen such but was not putting the two factors together. Since so much of the biology of our soils is intertwined it all makes sense.
From that said, there can be additions of mycorrhizae spores and specific families of bacteria that work on resident P compounds in the soil. The addition of microbes can be difficult due to these creatures in a water based product for any long period of time may drown since they are predominantly aerobic; do not survive under water very well. There have been efforts with the seed companies to place a coating on the seed which can include Phosphorus specific bacterial spores and to offer an influx of bacterial activity early for the emerging root system. The jury is still out as to the effectiveness of that in the seed bag. But with personal eyes digging the summer of 2018, I was part of a team for Bayer Crop Sciences to examine maize plots in Iowa and NW Missouri as to the effectiveness of said seed coatings, we did see several plots that had definite size, number and root development over hybrids without the microbes.
May I first move this conversation to using certain mineral based P fertilizers? Dry products; mono-ammonium phosphate (MAP, 11-52-0) and Diammonium phosphate (DAP, 18-46-0), Triple superphosphate (0-46-0), MESZ (10-46-0-1Zn), 40Rock (12-40-0-6S-1Zn); have been used and continue to be used for what is touted as ease of handling large quantities, spreading quickly (for the applicator) and lower costs for liquid P products are yes some more cost. Too often to the grower because he/she is adding quantity the cost factor plays a big role in what to use and then the choice of all dry can be fraught with pitfalls and availability to and for the plant. [[I want to insert a question for you all to think on – Are we fertilizing to always to have it easy for us OR are we fertilizing to feed the plant products that will give the desired result?]] We have seen a huge pitfall in the Great Lakes region in the past 5-9 years of enormous algal blooms (eutrophication) in streams, rivers and the Lakes due to growers going ahead and applying in the winter months on frozen ground. Then along comes the shallow winter thaws and rains and off these products run to water courses, my oh my. Now state rulings are being organized to restrict ill-timed applications as well new conservation programs. Let me give a for instance in Ohio; a specific region of the state growers can participate with financial incentives to change their modes of applying P sources in a big 14 county pilot program. This is all happening this spring in Northern and NW Ohio to lessen the soluble P movements of getting P into the lakes. It is called “H2Ohio”. Deep banding, injecting, timing of tillage and that fits perfectly with the practice of Strip Till. Here at Orthman we are responding to be part of the solution.
In the more moist environments east of the Missouri River or the I-29 corridor and east, dry fertilizers will with time become available in soil solution and in moderately acid (pH 5.6 – 6.0) to neutral (pH 6 – 7.3) soils so the ‘fixing’ of Phosphorus is not so ugly. When pH of the soils rise from 7.4 to 9.0 then the calcium and or sodium ions will complex with the P and it is like going into a prison lockdown, phosphorus can take years to become available. It has been observed by this scientist and many others that most polyphosphate products will become tied up and or slowly release into the latter part of the cropping season and not be available at the critical times. Yields can be reduced and that is not good. Saying that folks, using dry products are not a bad choice but one must be aware of the complexities and limitations with timing and product choices with dry. Turn 180 degrees geographically and head west, the growers in Central Nebraska and Kansas out to the Continental Divide where rainfall is less and less, where soils are higher pH, lower cation exchange capacity, lower soil organic matter levels to the subsoil and free calcium carbonate can run as high as 10% — the dry fertilizers are not as widely used. In many geographic areas dry products are not used at all.
So that leads us to change modes of thinking, considering liquid products – there is a big grocery list of liquids available to the grower these days. Orthophosphate and polyphosphate combination products are used to insert the phosphorus right where the roots can gain access quickly. Some of these products are manufacturer specific. Products with more Ortho; breakdown of N-P-K: 9-24-3, 3-18-18, 9-18-9, 10-34-0, 11-37-0, 15-15-15, 15-15-2, 6-24-6, 7-21-7 and the list is longer. These products applied right in the pathway of the roots by deep banding with a Strip-Till implement is ideal.
In the next segment of this topic I started with, I want to cover how the products get engaged then we will turn to the plant needs for Phosphorus, the action of P getting into the soil and available for plant uptake and who in the biological world is assisting the farmer, crop and soils.