Soil Fertility for Grain Crops

— An Article by Jack Lazor —

The principles of soil fertility are the same for grains as any other crop. Balanced, mineralized, high humus soils will produce the most abundant, weed-free harvests. Considering that most of our farms are a work in progress, we can only do our best with the resources we have to achieve this ideal situation. A soil test which gives cation exchange capacity (CEC) and the base saturation of calcium, magnesium, potassium, and hydrogen will indicate if and how much of what type of limestone is needed. Base saturation of calcium should be around 68-72% and magnesium is perfect at 12%. This is the only way one can know to spread high calcium or high magnesium (dolomitic) limestone. A pH of 6.5 to 7.0 is considered ideal for good plant growth.

Cereal grains are part of the grass family and require the same inputs as a productive hayfield. A good clean, friable seedbed is essential for good germination and crop establishment. Spring cereals are best planted on fall plowed ground. Limestone and well finished compost can be applied in either spring or fall. If raw or aged manure is used, fall applications give the nitrates and soluble salts contained in the manure time to mellow out and digest into the soil profile. Excess soluble nitrates and large bulky weeds like lambs quarters and red root pigweed go hand-in-hand. If calcium levels are low, a light application of gypsum (calcium sulfate) or cement kiln dust will elevate Ca levels which in turn will make all the other essential elements more available. (Please note that kiln dust of any kind is not allowed in a certified organic system.)

Enhancing soil biology is an up and coming field. Some farmers have had good luck with microrhyzial stimulants like “Florastim” or “Vitazyme”. These products can be mixed with common molasses and liquid calcium and sprayed right on the soil with generally good results. The sugar in the molasses feeds and wakes up soil microbes. Cereal grains (except for wheat) are very light feeders and usually don’t need much in the way of fertility augmentation. A clover or hay plow down is usually all that is needed to produce a good crop. Row crops like corn, soybeans, and sunflowers have different requirements. Clean tillage and timely early season weed control are essential. Since soybeans are legumes, they only need adequate levels of calcium, magnesium, phosphorous, and potash. A small amount of sul-pomag (200-300 lbs./acre) will usually suffice. Adequate phosphorous levels are necessary for all crops and can be maintained with occasional applications of rock phosphate. Sunflowers are a deep tap rooted plant which scavenges for nutrients. Many northern growers have found that any extra applied nitrogen on sunflowers will produce a large, weak-stalked plant which is much more prone to lodging as it dries down in September and October. Corn does need a lot of nitrogen once the plants really start to grow and canopy the row in early July. A good sod plow down of an existing hay field will allow a crop of corn to thrive without extra nitrogen inputs. Pelletized chicken manure compost applied through the planter’s fertilizer boxes will generally provide enough phosphorous for early root development and some N for later for mid-season growth. If a corn crop is experiencing a nitrogen deficit during mid-summer, a light sidedress application of Chilean nitrate (mined sodium nitrate) will work wonders.

This has been a very limited discussion of soil fertility in grain crops. There is all kinds of information out there from many sources. Publications can be found through the Acres USA bookshelf, Extension, and on line. Your neighbors and fellow farmers are probably the best source of genuine hands-on information.