North
West New York
Dairy, Livestock & Field Crops
Team
Dairy, Livestock & Field Crops
Team
Nate Herendeen, NWNY Team Crops & Soils Educator
Fertilizers and Soil Fertility: A dairy farmer recently called me to help him understand the results listed on a commercial soil test report for fields on his farm. The samples had been submitted to a commercial testing laboratory by his fertilizer vendor representative. The particular sample of concern was from an alfalfa field and the recommendation was for topdressing. The soil test value for Potassium (K) was reported as “medium” by their method of soil extraction and analysis.
Soil testing is a valuable method of taking inventory of soil nutrient resources. But, the results are only as good as the data interpretation used to make recommendations. What would you guess was the recommendation for this field?
Much to my surprise, it was for 500 lbs/acre of potassium. Why would my answer to the farmer be, “This is not a practical recommendation for your farm”? First, there are many years of New York data to show that yield responses are not likely to pay for the additional cost of Potassium beyond 200 lbs/acre even on a “very low” soil test level on sandy soils.
Second, knowing that the soil types (Ontario-Hilton-Lima and Farmington) on this farm fall into Management Group II, the maximum recommendation would be 140 lbs/acre. Group II soils have high Potassium supplying ability. They are derived from glacial till parent materials that are high in illite type clays. In these clay minerals, Potassium is relatively easily released to the surface cation exchange capacity on their surfaces. From there, the Potassium ions make their way into the soil water and across the cell wall into the root hairs. There was no consideration of soil type or the ability of different soils to supply Potassium to crops.
Third, there was a yield goal used of 8 tons/acre, dry hay basis. Yes, 8 tons/acre would be nice to have, especially in 2007! But, is it realistic in New York conditions? Practical yield estimations have been developed for all New York soil types, based on historic trials. They are a part of the Cornell Nutrient Analysis Laboratory recommendation system. There are many years of data to support this data. Other data supports the concept that when weather conditions are ideal and yields exceed the ones used for economic response recommendations, there are plenty of reserve nutrients to support that yield.
Fourth, the soil test recommendation made no allowance for the fact that this was a dairy farm where manure is routinely recycled. It may not be recycled on the alfalfa, but it is part of the total rotation on all dairy farms. This particular soil test did not allow for recycled nutrients from manure, cover crops or crop residues.
Cow Health: What is the other problem with a recommendation of 500 lbs/acre of topdress potassium? The farmer will likely end up with K content in the hay or haylage that is greater than 2 %. Check with the dairy nutritionists regarding the problems of too much K in the ration. Even if it would bring the 8 ton yield goal, it would be too high in K for cows, especially dry cows.
Bottom Line: The farmer should have the decision making authority with regard to fertilizer and other inputs on his crops. Those decisions need to be based on expected economic response. In other words, each increment of input needs to more than pay for itself. It is unlikely that there is a situation in New York where 500 lbs/acre of topdress K will pay for itself. Beyond that, if it produces crop that is too high in K for good nutrition, it is detrimental to cow health.
Vendor services are convenient. Your time is valuable. It may be good to have them take samples on your farm, but encourage them to send the samples to a laboratory that makes objective recommendations. Don’t let someone else make decisions that will decrease your farm profitability and bottom line.
Soil Testing: Fall is a great time to take soil samples and update your field records. The results will help in planning next year’s fertilizer and manure management plans. It can also help with cash flow management this year. Routine use of soil test results saves enough money to pay their cost (including the labor or consultants to take them) many times over. Our work in the Conesus Lake Watershed has shown again that starter phosphorus and nitrogen rates can be reduced on dairy/livestock farms with no loss in yield. Fields that have a long history of manure applications usually have high available phosphorus levels and medium to high available potassium.
Soil test results and crop response based recommendations from the Cornell Nutrient Analysis Laboratory have the greatest amount of back-up research data and experience. Whether you use their laboratory or another, the important step is for you to review the results and make recommendations accordingly. Don’t rely on recommendations that do not take into account manure nutrients, cover crops, nitrogen from sod crops in the rotation, and soil type chemistry.
You can purchase sample input forms and mailing bags at any local office of CCE. Quantity discounts are available. The turn-around time is generally under 10 working days from the date you mail them or send them by a surface carrier.
Call Nate or Mike
if you want to discuss soil testing further.
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