Within much of the marketing area of Augusta Co-Op, poultry based litters and other animal based manures are very valuable assets for crop producers. But, depending on them exclusively to provide all of the N, K, S and other secondary and minor nutrients to crops is a huge mistake. Why?
There are two major reasons - annual manure application rates and annual crop removal rates.
First, let’s review the nutrient requirements of a corn silage crop. This crops requires 220 lbs of N, 50 lbs of P, and 160 lbs of K. If we apply 6000 lbs of dairy liquid per acre, we would apply only 60 lbs of N, 72 lbs of P, and 50 lbs of K for the crop. Can you see where the fertility holes are?
Once we know where the fertility holes are, we can balance our nutrient needs with the right rates of fertilizer to complement the manure source. Now, what adjustments do we need to make for weather conditions?
With the July and August rains of 2012, row crop yields were 20-40% greater than "normal". With the 2013 crop production year, similar good fortune is with us. Add double cropping to the mix and potash, plus secondary and trace element fertility levels are being reduced significantly.
Solutions - There is only one - Balance crop removal with input replacement.
Nitrogen and sulfur are soluble and must be applied annually. P is very stable and with years of litter or manure applications culminating in Very High soil test levels, additional organic sources of P are unadvisable. Fall applications of potash are very reasonable now and help to spread the workload out. Contact your field representative or store manager and get your field acreage and application rates established. Remember, plan to add extra K because in 2012 and 2013, the crops have been removing more. Certainly, 100 lbs of K per acre would not be excessive and would help keep the soil silo full of "on demand" nutrients for future crop production. While corn silage was used as the example above, don't forget your other crops such as hay, pasture, and small grains. Similar fertility holes exist in these crops too!