Fertilizer Options for Reducing Production Costs in Alfalfa.

With recent volatility in fertilizer prices, alfalfa producers are searching for ways to reduce their fertilizer input costs. Fertilizer recommendations usually are based on achieving optimum alfalfa production, but do not provide predictions of yield under reduced fertilizer rates. The goal of this study is to compare alfalfa production grown under standard fertilizer recommendations with that from other treatments, including reduced rates and a recommendation program of commercial, foliar and soil applied products designed to lower the amount of fertilization required for achieving high alfalfa yields. A field trial was established in spring 2009 in Ohio to compare the following seven annual fertilizer treatments: no fertilizer control, the Ohio-Indiana-Michigan standard tri-state fertilizer P and K recommendations, tri-state recommendation for P and K plus annual applications of gypsum at 1650 kg/ha, tri-state fertilizer recommendation plus pre-plant incorporated elemental sulfur at 84 kg/ha, annual P and K application based on crop removal rates, half of the annual P and K application based on crop removal rates, and a commercial recommendation including pre-plant applications of P, K, S and annual applications of gypsum at 1650 kg/ha and various soil applied and foliar products containing N, P, K, a suite of micronutrients, and other undisclosed materials.  The treatments were replicated six times in a randomized block design on a soil having the following initial soil test values: pH 6.7, 7.5 mg P/kg, 83 mg K/kg, 1479 mg Ca/kg, 388 mg Mg/kg, 14 g/kg of organic matter, and a cation exchange capacity of 11.2 cmol(+)/kg. Yield differences (P < 0.01) have been observed among treatments in all harvests. The unfertilized control had the lowest total yield (11.3 Mg/ha) across the five harvests taken as of July 2010 while the highest yields have been under the tri-state plus sulfur (18.0 Mg/ha) and tri-state plus gypsum treatments (18.3 Mg/ha). The standard tri-state recommendation has produced 17.3 Mg/ha of alfalfa dry matter to date. Conclusions at this point in the study are pre-mature; however, it is clear that all fertilizer treatments are yielding significantly (P<0.01) more than the no fertilizer control on this site that is deficient in P and K. It is likely differences among treatments in marginal returns (yield revenue vs. fertilizer application costs) will be observed over time.