Fertilizer management for conservation tillage
Rates of phosphate needed in a band are not different from rates used for banded application in full width tillage. If the soil test for phosphorus is in the very low range, the rate of banded phosphate suggested increases fro 30 to 60 lb./acre as the desired yield increases from 100 to 200+ bu./acre. The suggested rate increases from 20 to 45 lb./acre for the same yield range if the soil test for phosphorus is defined as low. When the phosphorus soil test is in the medium range, suggested rates for the same desired yields increase fro 20 to 35 lb./acre. When the phosphorus test is high, the rate of 10-15 lb. phosphate per acre is suggested for all desired yields.
POTASH USE: The concept for the use of potash is different. The banded application near the seed is still highly recommended. Compared to full width tillage systems, however, rates should change. When soil test values for potassium are less than 160 ppm, a rate of 80 lb. potash per acre is suggested. This should be adequate for two years of production in a corn/soybean rotation. When corn follows corn, the rate of 80 lb. potash per acre should be applied before each corn crop.
ZINC: As with full width tillage systems, base application of zinc on results of a soil test. Application of zinc is most effective if applied in a band at planting.
SOIL TESTING IS STILL IMPORTANT: The previous paragraphs provide a justification for the importance of soil testing in conservation tillage systems. Rates of phosphate, potash, and zinc used in a band vary as the relaative levels of these nutrients in the soil change. There are many questions about the procedure that should be used for the collection of soil samples. Current information suggests that the soil cores should be collected to a depth of 6 to 8 inches at a distance of 6 inches away from the row. This procedure provides the best indicator of nutrients available to the corn crop in conservation tillage systems.
The changes described in the previous paragraphs are important when there is a switch from full width to conservation tillage systems. There will probably be others as more information is collected from various research trials.