The efficacy of enhanced-efficiency (EE) nitrogen (N) fertilizer formulations in reducing N loss and improving the efficiency of urea-based fertilizer products in forage production is unclear. This study compared ammonium nitrate (AN), urea, four EE urea N formulations [A/-(n-butyl) thiophosphoric triamide (NBPT)-treated urea, NBPT and dicyanamide-treated urea, a polymer-coated urea (PGU), and a maleic-itaconic copolymer-treated urea (MICPU)], urea-ammonium nitrate (UAN), and two EE UAN formulations (NBPT-treated UAN, NBPT and dicyanamide-treated UAN) in forage bermudagrass [Cynodon dactylon (L.) Pers.] production. The experimental design was a randomized complete block design with four replications in each of two sites and 2 yr (2008)(2009). Treatment applications were made at the rate of 168 kg N ha ' spring dormancy-break (ca. 30 April) and after the second harvest (ca. 25 July; total of 336 kg N ha ^ season). Response variables included trapped ammonia (NH3) and forage yield, production efficiency, N concentration, N uptake, recovery of applied N, and nitrate concentration. Urea treated with NBPT reduced NH3 volatilization and, in some situations, increased agronomic response relative to urea. Addition of NBPT produced results similar to AN and UAN, and it was never detrimental relative to untreated urea. The MIGPU treatment was ineffectual relative to urea alone. The PGU reduced NH3 volatilization and improved N concentration in the forage but did not improve other agronomic characteristics. Use of UAN solutions produced results that were generally intermediate in response between urea and ammonium nitrate and were not improved by NBPT addition. Adding NBPT can reduce NH3 volatilization and increase the efficiency of urea, but further research is necessary to understand the limits of this additive.

Crazing‐tolerant alfalfa (Medicago sativa L.) cultivars are more persistent than hay‐type cultivars under severe grazing pressure but the influence of defoliation on weed encroachment is not well defined. Our objective was to determine the effect of rest interval between cuttings on encroachment of large crabgrass [Digitaria sanguinatis (L.) Scop.1 or common bermudagrass [Cynodon dactylon (L.) Pers.] into a grazing‐tolerant alfalfa cultivar. We used small‐plot field experiments with four replications of ‘Alfagraze’ alfalfa to evaluate nine treatment combinations of (i) harvesting at 2‐, 4‐, and 6‐wk intervals, and (ii) overseeding with common bermudagrass, large crabgrass, or nothing. Experiments were conducted for 3 yr at Eatonton, CA, on Davidson loam (clayey, kaolinitic, thermic, Humic Paleudult) and at Athens, CA, on Cecil sandy clay loam (clayey, thermic, kaolinitic, %pic Hapudult). Alfalfa yields were similar at both locations when harvested at 4‐ or 6‐wk intervals. Crass invasion was virtually nil with the 4‐ and 6‐wk treatments at Eatonton but at Athens there was some grass encroachment, probably a result of soil compaction,which adversely affected overall alfalfa growth. Cutting at 2‐wk intervals reduced alfalfa yields to 50% of the 4‐ or 6‐wk cut treatments and resulted in heavy bermudagrass encroachment during the third year. Alfalfa cut every 4 or 6 wk persisted well but stands were reduced when cut every 2 wk Results suggest that frequent defoliation will not only reduce alfalfa yield but also favors grass encroachment. Thus, defoliation methods that keep alfalfa canopies at a high level would appear to be desirable in resisting bermudagrass and crabgrass invasion and increasing yield of grazed alfalfa. Research Question Recommended management for alfalfa pasture is rotational stocking to graze off the forage in a few days followed by a 5 to 6 wk rest period. Unfortunately, in actual farm practice, this recommendation is often modified with shorter rest periods or continuous stocking, which may result in grass invasion and alfalfa stand loss. The present study evaluated the effect of rest interval between cutting on encroachment of large crabgrass and common bermudagrass in a sward of a grazing‐tolerant alfalfa cultivar at two locations in north and central Georgia. Literature Summary Alfagraze is much more tolerant of continuous stocking at high grazing pressure than hay‐type alfalfa cultivars. However, under these conditions in the southeastern USA, invasion of the sward by large crabgrass and common bermudagrass is a serious problem. In contrast, under a hay‐cut system, rapid regrowth by alfalfa provides the sward with enough shade to reduce grass establishment competition. Information is lacking in the southeastern USA on the effect of rest interval between cuttings or grazings on encroachment of warm season grass weeds in alfalfa. Study Description Alfalfa yield, persistence, and weed invasion were determined for Alfagraze alfalfa grown alone or overseeded with large crabgrass or bermudagrass an...

The fungal endophyte, Neotyphodium coenophialum (Morgan‐Jones & W. Gams) Glenn, Bacon & Hanlin (syn. Acremonium coenophialum Morgan‐Jones & W. Gams) is generally considered to enhance the competitive ability of tall fescue (Festuca arundinacea Schreb.) with legumes, but substantiating field data are limited. Our objectives were to determine if endophyte infection of tall fescue affects stand density and forage production of (i) red clover (Trifolium pratense L.), ladino clover (T. repens L.), and alfalfa (Medicago sativa L.) harvested at 3‐wk intervals and (ii) alfalfa at low and high seeding rates harvested at 3‐wk and 9‐wk intervals. The first study compared alfalfa, red clover, and ladino clover in association with ‘Jesup’ E+ (endophyte‐infected) and E− (endophyte‐free) tall fescue, harvested at 3‐wk intervals for 3 yr. The second study had alfalfa broadcast planted at 11.2 and 22.4 kg ha−1 with E+ and E− tall fescue planted broadcast at 11.2 and 22.4 kg ha−1 or in rows at 22.4 kg ha−1. This was harvested at 3‐wk intervals for 3 yr, then at 5‐wk intervals for 1 yr. In the first study, clovers and alfalfa cut at 3‐wk intervals for 3 yr had similar (P > 0.05) legume yields when grown with both E+ and E− tall fescue. In the second study harvested at 3‐wk intervals, E+ tall fescue adversely affected (P < 0.05) the associated alfalfa the second year, and by the third year the yield of alfalfa planted at 22.4 kg ha−1 in mixture with E+ tall fescue was only 71% of alfalfa with E− tall fescue (P < 0.05). Similar differences occurred the next year when cut at 5‐wk intervals. Stands of alfalfa or tall fescue after 4 yr were not affected (P > 0.05) by endophyte. The results suggest that endophyte infection of tall fescue increases competition with legumes, but it may be modified by seeding rates or grass sod density.

No abstract

Staggered plantings of pearl millet [Pennisetum glaucum (L.) R. Br.] are recommended to better distribute forage production throughout the growing season, but the effect later planting has on yield potential and distribution are not well understood. The effect of delayed planting on total dry matter (DM) yield and the distribution of the yield produced by pearl millet were compared over three years in a small plot experiment at the University of Georgia's Plant Sciences Farm located near Watkinsville, GA. Five planting date treatments (beginning ca. 27 April of each year and on ca. 30‐day increments thereafter) were compared. Total DM yields were the highest in the late April planting and decreased linearly (by as much as 80 lb/acre) for each day plantings were delayed past late April in 2008 and 2009 and quadratically during the extreme drought conditions of 2007. In contrast to previous reports for irrigated pearl millet plantings, the forage accumulation rate during the season did not result in a skewed distribution of yield in the planting dates of the current study. Staggering plantings beyond late April may not improve yield distribution within the forage system because of the yield decreases associated with later plantings of pearl millet.