Some farmers bury maize or wheat stover soon after harvesting. They plant the next crop (adding basal fertilizers) before the burried stover has fully decomposed, especially in irrigated inorganic farming. There are various biochemical processes that occur with respect to nitrogen in the soil and the stover. Is there an equation which quantifies the rate of fixation and release of the nitrogen in the soil?
May be you can try net nitrification and n mineralization experiments be performed to get the the idea over this . As well C:N ratio of maize or wheat will be very important in terms of nitrogen being mineralized or immobilised into the soil.
One process worth looking at in tropical systems is asymbiotic nitrogen fixation, see e.g., http://www.tandfonline.com/doi/abs/10.1080/01448765.1982.9754376?journalCode=tbah20#.UX-kaJ-kGYQ
There are more papers by Nick Hill and myself. I can give you refs as you might wish. It is strongly inhibited by N fertilizer, but banding fertilizer allows the N2 fixation to go on between the bands. Trash darkens due to melanic fungi when it begins to fix N2 (Nick's work). Our observation suggests this is widspread in unfertilized systems in the tropics, but there has been little follow-up of our work; certainly it is relevant to organic farming.
Because of high C/N ratio, N may not be released from corn stover but rather immobilized in the soil, thereby resulting in N unavailalbe to crops.
Imagine at the beginning there is an unlimited amount of burried maize stover and x kg of nitrogen in the soil. How will the concentration of soil nitrogen vary with respect to time? How long will it take for the x kg of N to be imobilised? After a period of time the maize stover decomposes and release the nitrogen into the soil. How long will it take for x kg of nitrogen to be released into the soil as a result of the decomposition of the stover.
I think Litter bag experiment will answer such question: We did experiment with wheat and guar residue. It is true C:N ratio have great effect on N released. However, combined application of wheat residue with N fertilizer will improve N mineralization. Incubation experiment will give an idea about potential mineralized N
I don´t think the question might be answerable (if such a word exists) on a general basis. Besides the points mentioned above about stover C/N ratios, several other site-specific data would be needed, and probably local experimentation would be required.
For example, you mention stover burial? How? If you just open the planting lines, as in no-tillage, some of the stover is buried, most stays on top, and there will be little to none stover particle size reduction. On the other hand, if the soil+stover is worked by several ploughing sections, until soil surface is "smooth", there will be a much closer soil particle/stover particle interface, which should fasten decomposition...
And so on....
So I would suggest either local experimentation (even a quite simple one, as just a litter bag decomposition experiment following only litter dry mass) or much more specific literature
Rate of mineralization of wheat straw and maize stover depends on the Si contents present in the dry mass. If Si contents are more, rate of mineralization will be slow. Moreover, this rate can be enhanced by adding urea and molasses solution
Your question is addressed by many simulation models which will calculate the N release from maize or wheat straw residues at a given temperature and precipitation pattern. By giving soil texture and SOM values and adjusting starting values for soil moisture you can let the model mimic the environmental conditions of your particular field. Standard parameters for crop residues are usually available with the models. By using manipulated climate data where temperature and precipitation is set constant you can also reproduce laboratory conditions. Freely available models are e.g. MONICA or SALUS.
At warm and moist conditions, N release should be very quick and last not more than a few weeks before 90% of the N is released. Only at N-limiting conditions, the process may be delayed until other N sources can be used. However, the mentioned models will also consider this and give you (i) a good feeling of how the system responds under alternative conditions and (ii) exactly reproducible rates as you requested it..
- Badges
- Science topic
- Similar topics
- Engineering
- Modeling