Published March 20, 2020 | By Mike Petersen
Feeding the corn plant to produce the most grain as possible takes multiple forms of N.
In my continual search and self education for all of our customers and potential customers which are the rest of you, I read in one of my texts; “2006, Physiology of Crop Production.” by N.K. Fageria, who has been a scientist studying rice and maize production more evidence to support more than one form of Nitrogen during the season . He writes about the energy required to convert NO3 to the more usable form in the maize plant as, ammonium (NH4+). His data states that the amount of energy in ATP/mol is four times higher for the plant to assimilate NO3 than NH4+, that can be a setback in crop production potential. Then in another text of mine, according to Tisdale et al. (1993, Soil Fertility and Fertilizers), the rate of NO3- uptake is usually high and is favored by low-pH conditions. NH4+ uptake proceeds best at neutral pH values and is depressed by increasing acidity. That is pH levels of 5.5-6 and under. Fageria reports that maize and small grains do best in N uptake efficiency when the nitrogen sources are mixed between nitrate and ammonium throughout the season. NH4+ is the N source of choice early in the life of a maize plant.
Now all of this absorption and uptake depends upon the amount of carbon in the soil rhizosphere. If soils are low in available C such as soils in the Sandhills of Kansas, Nebraska, E. Colorado, the efficiency of N uptake and utilization to create grain will depend upon how the grower takes care of the crop aftermath, tills, where possible and available adding a living plants that root down well to supply an addition of carbohydrates, proteins, nucleic acids and lipids in left over tissues. We also know that nitrate is more available to the maize plant in better aerated soils. We also know the factor of nitrate is readily available in soil solution and the plants can access it via the roots as well as the number of soil bacteria that work on nitrate are numerous. But the genetics of upland plants prefer nitrate for a major portion of the plants lifespan so we have thought that we should us nitrate as the source of N to improve yields. Something of a conundrum.
So where do we go with all of this? Early on as I have written before in this blog and many other scientists have written in journals and blogs, NH4+ is preferred in the first 25-30 days after emergence (DAE), then NO3 up until 75-85DAE after that time frame it seems that urea and NH4+ has much value. You as a grower ask what makes all the difference Mike? I buy nitrogen in the form of NO3 and call it good, all what you are saying is fooling around to me. My response – I want to inform you that depending upon your growing which crop of grassy-types or broadleaf crop; certain forms of N are more efficiently absorbed, taken into the root and uploaded in the xylem tissues and moved up towards the sink, the ear or florets or pod. Considering which N source fits the plants physiology is important for you to know how to be as effective as you can be feeding the crop for the optimal yield you can gain. Not everyone can push 600 bu/ac corn, your climatic factors are never perfect or maybe conducive to such. I am concerned tho if we add more and more nitrates as the N source of choice we can cause harm to the soil and water ecosystems, cause groundwater pollution for drinking supplies which in turn cause infant blue baby syndrome and eutrophication of rivers, streams and lakes. To repeat myself then, mixing our N sources can change the plants growth and efficiency, feed it properly and we accentuate yield of biomass and grains.
I will keep digging folks, asking questions of other scientist I rely upon, reading and getting material for you to gain a further understanding that we can grow some amazing crops. This is one thing I have is some time right now with so many venues and events are shut down for me and many others while we work to remain healthy folks. Stay in touch and come back to Precisiontillage.com. As noted on the Home page; you can call me or send an email. Cell number is 1.970.302.1442 or email – firstname.lastname@example.org