|
| Hello Andre,
sorry to be so slow to respond.
I have been scrambling to get ready for the spring semester that starts next week.
here are a few quick thoughts:
1) Your crops are already obtaining some K from non-exchangeable reserves of K
- it is commonly thought that exchangeable K is the reserve of K available to crops but this is definitely an over simplification.
Exchangeable K is the dominant reserve of plant accessible K in many soils BUT only accounts for about half of the K acquired by crops in some soils
2) A soils ability to supply crops with K (or other nutrients) has 2 important dimensions that impact the value of a particular fertilizer program:
nutrient CAPACITY - the amount of nutrient that is potentially available
nutrient INTENSITY - the rate at which the nutrient can be supplied to crops
Current soil testing methods are only moderately effective at quantifying K CAPACITY and INTENSITY (better for some soils than others), resulting in lots of variability in how well soil test K levels predict response to K fertilizer.
I looked at a few research articles related to this topic this morning but need to spend some more time digesting the information :)
3) The easiest way to get a soil's reserves to supply more of the K needed by crops is to use cropping systems with less intense demand for K... i.e., remove less total K, have lower rates of uptake, recycle more K....
4) Many cover crops take up large amounts of K and increase availability to following crops. Radishes typically take up about 50% more K than N. Crops with high uptake but low removal (e.g. corn harvested for grain) may also have this effect but I need to look into this more.
Bottom line is high crop removal year after year (especially forages) tends to overwhelm a soils ability to meet crop demand for K even though depletion of total K in the soil may be small. More thoughts on this when I have a chance.
Joel
WIU Agriculture
Edited by jbgruver 1/13/2017 15:11
| |
|
jbgruver how about we get some locked up mineral K to release
