Quick Tips on Soil Fertility

September 1, 2010 – What are the best placement options for P and K in ridge-till? Banding P and K from 4 to 6 inches deep in the center of the ridge is probably best. This puts P and K below the surface, where actively growing roots can quickly find needed supplies. Such subsurface applications also reduce risks of nutrient losses through runoff and/or erosion. Also, in ridge till systems, P and K nutrient supplies tend to be lowest in the ridge and highest between ridges. Therefore, applications in the ridge place nutrients where soil supplies are most limiting.

September 1, 2010 –
It is Possible to Determine How Effective Your Nutrient Management Program is on a Field?
Yes, one simple and yet useful exercise is to do a basic accounting procedure to see if your nutrient exports contained in harvested crop products sold off farm are equal to the nutrient inputs you add as fertilizers and/or manures. This is most easily done for the major plant nutrients you routinely add as fertilizers, i.e. N, P, K, and S. For example, consider a field where a crop of wheat with a yield of 2700 kg/ha (40 bu/A) was grown. This grain crop contained wheat with an average N, P, K, and S content of 2.3% N, 0.39% P, 0.40% K, and 0.17% S. Using the yield of 2700 kg/ha the amount of N, P, K, and S removed in kg/ha was: 62.1 kg N/ha; 10.5 kg P/ha (24 kg P2O5/ha); 10.8 kg K/ha (13.0 kg K2O/ha), and 4.6 kg S/ha. The fertilizer inputs onto the field were 70 kg N, 25 kg P2O5, 10 kg K2O, and 5 kg S, all on a kg/ha basis. Compared to the export of the nutrients, the fertilizer nutrient inputs appear to be adequate. If in the example only 10 kg P2O5/ha of fertilizer P was added, in the long-term the soil in the field would decline in P supplying ability and crop yields would decline.

September 1, 2010 – Phosphorus fertilizer with wheat seed
Placing P in the seed furrow at wheat planting is a popular and effective placement option. In-furrow P is quickly available to the developing seedling and can promote accelerated early season development that can result in substantial increases in grain and forage yields. Factors that affect maximum safe rates of in-furrow fertilizer include fertilizer source, row spacing, and soil texture. For wheat in 7 in. rows, there is no practical limit to the amount of P applied. However, N+K2O should not exceed 25 lb/A and should be reduced in sandy or very dry soils by about half. The use of urea containing fertilizers for in-furrow application should be avoided.

September 1, 2010 – Potassium Magnesium Sulfate
Potassium magnesium sulfate is a unique geological material that is only found in a few locations in the world. It is a popular fertilizer, especially where several nutrients are needed to provide adequate crop nutrition. It has an advantage of having K, magnesium, and sulfur all contained within a single particle, which helps provide a uniform distribution of nutrients when it is spread in the field. It does not contribute soil acidity or alkalinity, unlike some other common sources of magnesium (such as dolomite which will increase soil pH), or elemental sulfur or ammonium sulfate (which will lower the soil pH).

September 1, 2010 – Soil pH
Soil pH is one of the most important chemical factors affecting nutrient availability. Allowing soils to fall too far below the target pH for a specific crop can induce deficiencies of nutrients like P or result in Al toxicity in some crops like wheat. An optimum soil pH helps plants use nutrients and soil moisture more efficiently. If it has been several years since you limed, now is a good time to test the soil and take corrective action if needed.