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Improve Fertility Now While Fertilizer Prices Are Low
LAMAR, MO.
Fertilizer prices are currently allowing for producers to improve fertility status in neglected pastures according to Jill Scheidt, agronomy specialist with University of Missouri Extension in Barton County.
“Phosphorus and potassium levels should be maintained in fescue pastures to obtain optimum yield, so if fertility is lacking, now is a good time to invest in improving yield,” said Scheidt.
When fertility levels are optimal for fescue and clovers, it reduces competition for weeds because the desired plants can thrive in their most ideal conditions. Weeds thrive in conditions that are not optimal for desired plants. If desired plants are unable to establish and out-compete weeds, weeds will overtake areas in pastures where desired plant stands are thin.
“A soil test should be the first step taken to determine nutrient needs of the pasture, soil tests should be taken every 3-5 years,” said Scheidt.
Once soil tests are obtained, Scheidt says a fertility management plan should be put in place to economically improve fertility status for optimum yields.
“Lower fertility pastures should be targeted first for fertilizer applications as a greater yield response will be seen from adding nutrients,” said Scheidt.
Liming is the second step in the fertilizing process. Lime is not a fertilizer, but a soil conditioner that allows nutrients to become available to the plant for uptake.
“Liming is especially important if legumes are in the field, as clovers need phosphorus available for increased persistence,” said Scheidt.
A pH of 6.0 to 6.5 is desired, especially for clover establishment and maintenance. Lime should be applied at least six months before it is needed; it takes six months for 80 percent of applied lime to be broken down and nine months to completely break down lime.
Phosphorus is responsible for energy conversions and all aspects of plant growth; it is especially important for legume persistence.
“Soil test levels for a high range of phosphorus are 100-150 pounds per acre. At this level, no buildup applications are necessary, only maintenance applications based on crop removal rate are needed,” said Scheidt.
Cool-season grasses, such as fescue remove 9 pounds of phosphorus per ton of hay removed per acre and .05 pounds per acre per cow day. If legumes are present in the field, they need a soil test level of at least 30 pounds/acre of phosphorus to persist in pastures.
“Legumes improve the quality of forage, particularly in endophyte-infected tall fescue pastures. The best solution to offsetting the negative effects of fescue toxicosis is by planting new pastures to novel endophyte fescue varieties mixed with legumes,” said Scheidt.
If 20-30 percent of the plant population, legumes can eliminate spring nitrogen applications reducing fertilizer nitrogen need up to 100 pounds/ acre. If nitrogen is applied at too high a rate, over 100 pounds/ year, in a legume/fescue mixed pasture, the legume population will be reduced.
Potassium is responsible for water uptake, winter hardiness, disease resistance and plant injury repair.
Soil test levels for a high range of potassium depend on the Cation Exchange Capacity (CEC) of the soil, or the ability of the soil to hold positive ions; CEC also defines soil type (sand, sandy loam, silt loam, clay loam, and clay).
Forages, except pure alfalfa stands, have a desired potassium level of 160 lbs. Potassium per acre plus five times the CEC. Row crops desire a level of 220 lbs. Potassium per acre plus five times CEC. For forages, soils with a CEC of 6-11 (sandy loam or silt loam) rank in the high range when potassium levels range from 190-285 pounds per acre.
For forages, soils with a CEC of 12-17 (silt loam or clay loam) rank in the high range when potassium levels range from 220-330 pounds per acre. At this level, no buildup applications are necessary, only maintenance applications based on crop removal rate need to be applied.
Cool season grasses remove 34 pounds per acre per ton of hay produced and .17 pounds per acre per cow day.
“Split applications of nitrogen in the fall and spring help make the growing season more uniform by increasing productivity during less productive times of the season. The optimum application window for fall nitrogen in fescue pastures starts around Aug. 1 and response to fall-applied nitrogen decreases incrementally after Sept. 1,” said Scheidt.
March is the ideal time for a spring nitrogen application to grass, especially hay.
“Pastures may benefit from delaying application until April or even May to push the grazing period farther into the summer. Spring fertilization encourages summer growth during low rainfall periods that occur during the summer,” said Scheidt.
University of Missouri does not test nitrogen levels on normal soil tests because Nitrogen is a mobile nutrient in the soil. The amount of nitrogen present in the soil can change with temperature, rainfall and crop removal. Cool season grass, such as fescue can remove .6 pounds of nitrogen per acre per cow day and 40 pounds of nitrogen per acre per ton of hay removed. ∆
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