Plant food helps produce more feed

Written by Dr. Jim White on .

What do you see when you look at a forage stand? A source of livestock feed or a commodity to be sold? The more forage you have, the more cattle you can feed. Fertilizer is a principal input cost for a forage crop. There are no substitutes or shortcuts for providing adequate nutrients. Cutting back on fertilizer will likely cost more over the long run because of decreased yields and stand longevity.

When you add up all the pas­ture, grass hay, alfalfa, corn and sorghum-sudan silages, millets and grazing small grains, forages account for the most acreage of any U.S. crop, yet they continue to be neglected when it comes to fertiliza­tion. The majority of grazing lands receive no fertilizer of any kind. The resulting low forage yield and daily rate of gain are widely accepted on land with low perceived value.

It is good to look for ways to reduce fertilizer costs, but it’s all about efficiency of production. Indiscriminate reductions in fertil­izer will likely lead to reductions in yield and an increase in the unit cost of hay. Cutting costs in forage production should be done in a way that has minimal impact on forage yield.

Make the investment in fertilizer more efficient by using soil test re­sults. If you do not soil sample and apply fertilizer and/or lime based on the results of those tests, it is likely that the appropriate amount is not being applied. If nutrients are under-applied, the result is forage yield below its potential. If over-ap­plied, then costs were incurred that won’t produce a positive response. Few other practices in forage pro­duction can improve the profitabili­ty more than soil testing and follow­ing fertility recommendations.

Apply fertilizer to fields where soil test values indicate an economic response and where the soil pH is in the optimum range. If the soil pH is too high or too low, you won’t get a good return on investment. Rather, first focus on adjusting the soil pH in those fields. If the pH drifts much below 6 or much above 7, the availability of some nutrients in the soil will decrease. For exam­ple, a pH difference of 5.6 versus 6.2 can effectively reduce the value of nitrogen fertilizer by as much as 35 percent, phosphorus by as much as 50 percent and potassium by as much as 10 percent.

Lime is a key ingredient to im­proving soil fertility. Since water is required for lime to react with the soil, effects of a lime application will be slower in dry conditions. It often takes six months to a year before a response can be measured, even under perfect circumstances. However, a response may be ob­served within weeks of application when soil pH is extremely low. In areas where needed, it is important to apply lime immediately after the growing season or crop removal to allow it to react and correct soil pH before the next growing season.

Nitrogen is usually the most limiting element in forage produc­tion. This major nutrient is involved in chlorophyll development for photosynthetic activities, yield and forage quality. Nitrogen, however, requires some timing and proper manipulations to get good yields and reduce losses. Splitting N applications will reduce the risk of leaching, volatilization and nitrate toxicity.

Nitrogen-use efficiency can be significantly increased by phospho­rus fertilization. Optimal soil phos­phorus level should be between 30-40 ppm. If the P level is low, it could allow only 40-60 percent of total hay production. In the spring, P is a crucial nutrient in promoting the development of new roots and tillering. Phosphorous can be ap­plied to a hay field any time of year since it is very stable and available to the plant when needed. When fertilizing annual crops, however, P should be applied before planting. Avoid spreading phosphorus fer­tilizer when there is risk of runoff, which is the primary way this nutri­ent is lost from soils.

Potassium allows plants to survive in cold weather and sustain produc­tivity during drought. It is involved in many metabolic processes in the plant. There is a very low environ­mental risk with K applications. The major inefficient use of K is a phenomenon called “luxury con­sumption,” in which forage crops take up more K than required for optimum growth. To avoid this, K should be applied in two or more split applications during the hay season. The environmental risk posed by K is low, but care must be taken to ensure it is used efficiently.

Yes, fertilizer can be expensive, but it’s still a bargain when com­pared to dragging down yield and the cost of renovating perennial forage stands. Proper plant food applications will pay off in extra forage and feed for your livestock