Interseeding alfalfa (Medicago sativa L.) into silage corn (Zea mays L.) can improve forage yield, farm profitability, and soil conservation, but unreliable alfalfa establishment hampers on‐farm adoption. This study evaluated seedling survival and growth of 36 alfalfa varieties differing in reported plant traits when interseeded at two Wisconsin sites in 2015 and at single sites in Wisconsin, Michigan, and Pennsylvania in 2016. Subplots of alfalfa varieties were sprayed with prohexadione‐calcium (PHD) at 0 or 0.42 kg acid equivalent (a.e.) ha–1 to assess changes in seedling survival mediated by this growth retardant. After corn harvest in 2015, average stand density of varieties in Wisconsin ranged from 15 to 94 plants m–2 without PHD and from 52 to 199 plants m–2 with PHD. Stand density largely determined subsequent first‐cut alfalfa dry matter yield, which ranged from 1.1 to 6.3 Mg ha–1. After corn harvest in 2016, stand density of varieties averaged across PHD treatments ranged from 113 to 248 plants m–2 in Michigan and Pennsylvania, compared with only 0.5 to 26 plants m–2 in Wisconsin; PHD treatment improved stand density only in Wisconsin but could not ensure adequate establishment under wet conditions that favored vigorous corn growth and foliar disease on alfalfa. Overall, establishment was poorly related to measured or reported alfalfa traits, but ‘55H94’ and hybrids were consistently among the best performing cultivars. Further work is needed to understand seedling survival mechanisms and to develop improved germplasm and production practices to ensure reliable establishment of interseeded alfalfa.

Treatment of toxic endophyte‐infected tall fescue [Lolium arundinaceum (Schreb.) Darbysh] with metsulfuran‐methyl {Methyl 2‐[[[[(4‐methoxyl‐6‐methyl‐1,3,5‐triazin‐2‐yl)‐amino]carbonyl]amino]sulfonyl] benzoate}, as delivered by Chaparral herbicide (Dow AgroSciences, Indianapolis, IN) can mitigate fescue toxicosis and enhance forage nutritive value by suppressing seedhead emergence. A grazing experiment was conducted with steers (2013) and heifers (2014) to evaluate animal and plant responses to grazing management of mixed cool‐season grass pastures treated with Chaparral. Continuous and rotational stocking treatments were assigned to six, 3.0‐ha pastures in a randomized complete block design with three replications in 2013 and two replications in 2014. Each pasture had six tester animals, and stocking rates were varied using put‐and‐take animals. Pastures were grazed from 16 April to 8 July 2013 and 20 May to 12 Aug. 2014. Pasture carrying capacity was 20% greater for rotational than continuous stocking. Calves on rotationally stocked pastures also had 26% greater average daily gain (ADG) and body weight (BW) gain per hectare than those on the continuous treatment. Pre‐grazed herbage had less neutral detergent fiber (NDF) and acid detergent fiber (ADF) than post‐grazed herbage and herbage from continuously stocked pastures in 2013, but they did not differ in 2014. Crude protein (CP) was lower in post‐graze rotational pasture than in continuous or pre‐graze rotational pasture. Fescue roots in rotationally stocked pastures had greater water soluble carbohydrates (WSC) and N concentrations than continuously stocked pastures following the second year of grazing. Results indicated that rotational stocking of Chaparral treated mixed pastures can improve animal performance and pasture productivity.

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