AGRI-BRIEFS   AGRONOMIC NEWS ITEMS

From Agronomists of the Potash & Phosphate Institute 655 Engineering Drive, Suite 110 Norcross, Georgia 30092-2837 Phone (770) 447-0335

Winter 1998, No. 8

Taking good soil samples is the first step. If magnesium is needed, use a finely ground dolomitic lime. If possible, incorporate the lime deep into the soil where the acidity is located. For surface applications to pastures or untilled fields, consider broadcasting about one ton per acre in the fall and again in the spring until the recommended amount is applied to the field.

Some of the benefits from a good and timely liming program include the following:

· Phosphorus availability to the crop is improved as lime helps to prevent excess iron and aluminum from fixing phosphorus in unavailable forms. As soluble soil manganese levels decline, growth of sensitive crops such as cotton, soybeans and potatoes improves.

· Legumes benefit in two additional ways. First, as soil pH is increased the availability of molybdenum needed for nitrogen fixation is improved. At the same time Rhizobium bacteria, needed for nitrogen fixation, are more plentiful in the soil and effective in supplying nitrogen to the plant.

· Magnesium and calcium are provided from dolomitic limestone. The need for magnesium is well documented on acidic, sandy soils subject to nutrient leaching. Where potassium and other inputs are provided for high yield production, the need for supplemental magnesium should be examined carefully. Potassium and calcium can compete with magnesium for absorption by plant roots. Magnesium shortages can also develop in early spring in rapidly growing forages such as fescue. A shortage of magnesium in the forage in combination with a high level of plant tissue nitrogen can trigger a magnesium shortage in brood cows in late stages of gestation.

· Water and fertilizer use efficiency improve. As lime improves the soil physical and chemical characteristics, plant roots explore the soil more thoroughly in the tillage zone and deeper into the subsoil. This improves root access to water and nutrients from a larger soil reservoir.

Freedom to farm has become a challenge to farm as crop prices and farm profits have taken a nose dive. With a new cropping season comes renewed optimism that 1999 will be better. Two goals, however, should be clearly defined and developed. The first is to strive to lower the unit cost of production of each crop by developing a site-specific lime and nutrient management plan which improves crop use efficiency of each production input. The second is to develop a crop marketing plan with your banker or a marketing specialist that generates a higher return from the increased production. Harvest more profit by lowering the floor with lower unit cost production and raising the ceiling with higher yields of higher value crops.