Many times I have heard the comments that fertilizer is not all that important if you are” just planting deer food plots” or “clover and alfalfa make their own fertilizer” so you don’t need to add any.
There are volumes of information written on fertilization for different crops. I farmed for many years and have proven to myself the importance of adequate fertilization. I will try to put some of my experiences into a few words to help those of you that are looking for some guidance with this important factor in growing a more productive food plot.
The proper method for accurate fertilization is to get a soil sample analyzed and apply to the recommended rate for the crop you are growing. Your local agricultural fertilizer supplier will help you with the recommendations.
All fertilizers are labeled with three numbers. These three numbers give the percentage by weight of nitrogen (N), phosphate (P205), and potash (K20). Nitrogen is important for leaf and stem growth and provides the rich green color in a plant. Phosphorous (derived by the plant from phosphate) provides for root and flower growth. Potassium (derived by the plant from potash) helps build plant tissue and aids the production of chlorophyll.
The fertilizer I spread last year was sold to me as: DAP 18-46-0, Urea 46-0-0, and potash 0-0-60.
The fertilizer analysis numbers represent in this order – N (nitrogen), P (phosphate), and K (Potash) or N,P and K. So the 18-46-0 equals 18% nitrogen, 46% phosphorus, and 0% potash. If you apply 100lbs/acre of 18-46-0 you have added 18 units (lbs) of N, 46 units (lbs) of P and no K. Urea, 46-0-0, is 46% percent nitrogen, meaning 100 pounds of 46-0-0 equals 46 pound (units) of nitrogen. The other 54 pounds is the carrier needed to produce this type of nitrogen.
If I were to try give a very simple recommendation that could be a somewhat successful for most food plots if you didn’t soil sample, I would suggest to apply the following amount of fertilizer.
70 units of Nitrogen
45 units of phosphate
50 units of potash
Lime can be used to bring soil up to at least 6.5 if you have a low ph soil. The level of acid or alkaline. A ph of 7 is neutral and levels below 7 are acidic and levels above are more alkaline. A ph of 6.5 to 7 are usually good for most crops. Visit with your ag chemical supplier to adjust if needed.
Generally red volcanic soils are low ph soils. Red soils are generally require lime to increase the ph to a level above 6.5. Heavy black soil generally will be more neutral in ph and have a higher K level and generally higher P as well.
What does this all mean?
To add 70 units of N, 45 units of P and 50 units of K you need to apply:
100 lbs/acre 18-46-0
115 lbs/acre 46-0-0
85 lbs/acre 0-0-60
Total 305 lbs/acre
All blended together by your fertilizer supplier will give you a mixture that will need to be applied at 305lbs/acre total. On a 10 acre food plot this is 3050 lbs or about 1 ½ tons total. Your ag chemical supplier may have different analysis on the N,P and K and would then need a different ratio of each to achieve those levels. Application of lime or other ph modifying products would need to be determined by your local supplier. Fertilizer prices can vary significantly from year to year and by volume of purchase.
The above suggestion is a very broad bush approach to fertilization.
If you get the N, P, and K soil sample analysis you could see results like: available N = 50 units, available P = 15 and available K = 100. If you used the above suggested recommendation and applied to soil that tested like this you would end up with a total analysis of 120N, 60P, and 150K. Most would agree this would be a generous recommendation for any deer food plot. Many would likely recommend maybe about 80% of this total analysis. On the other hand if you are planting corn some may want to have 200 units of nitrogen.
If you are inclined to fertilize a bit on the heavy side, you should realize that nitrogen if over applied or the crop does not use it can be lost. In light, sandy soils nitrogen can leach down with rain fall or nitrogen can be lost to denitrification caused by waterlogged soil for extended periods of time at temperatures above 50 degrees in any soil type. Phosphate (phosphorus) is very stable and really will only be removed if the soil actually erodes away by wind or water. Potash can leach but is much less likely to than nitrogen.
My experience about adding nitrogen to clover and alfalfa suggests you will have a higher protein content in crops with more nitrogen. If your supplier does not recommend this I would strongly suggest you add at least 40 units of N, 30 units of P and 40 units of K per acre to one test portion of a plot and leave part of it without adding. Others have told me and I have seen the acres that were fertilized are much harder hit by the deer than the non- supplemented portion.
If you are applying fertilizer at rates similar to this to more an acre or two, I would suggest you talk to you supplier and either have them custom apply or use their spreader if you have a tractor to operate it. Custom application rates can be in the $3 to $5 per acre range. If plots are very small they may have a small mileage charge.
It can also be a big advantage to work with your fertilizer supplier as most can blend seed with the fertilizer and broadcast at the same time. This works well with clover, alfalfa, brasicas, small grains, and others.
MDBA Board Member