Improving the efficiency of feed N utilization by dairy cattle is the most effective means to reduce nutrient losses from dairy farms. The objectives of this study were to quantify the impact of different management strategies on the efficiency of feed N utilization for dairy farms in the Chesapeake Bay Drainage Basin. A confidential mail survey was completed in December 1998 by 454 dairy farmers in PA, MD, VA, WV, and DE. Nitrogen intake, urinary and fecal N, and efficiency of feed N utilization was estimated from survey data and milk analysis for each herd. Average efficiency of feed N utilization for milk production by lactating dairy cows (N in milk/N in feed x 100) was 28.4% (SD = 3.9). On average, farmers fed 6.6% more N than recommended by the National Research Council, resulting in a 16% increase in urinary N and a 2.7% increase in fecal N. Use of monthly milk yield and component testing, administration of bovine somatotropin (bST), and extending photoperiod with artificial light each increased efficiency of feed N utilization by 4.2 to 6.9%, while use of a complete feed decreased efficiency by 5.6%. Increased frequency of ration balancing and more frequent forage nutrient testing were associated with higher milk production, but not increased N utilization efficiency. Feeding protein closer to recommendations and increasing production per cow both contributed to improving efficiency of feed N utilization.

The hypothesis of this field study was that providing farmers with information regarding their herd's milk urea nitrogen (MUN) would result in more accurate feed management and a change in MUN toward target values. All dairy herd bulk tanks (n = 1156) in the Maryland and Virginia Milk Producers' Cooperative were tested for MUN each month for six months ending in May 1999. Farmers (n = 454) who returned a survey were provided with the results of their MUN analysis each month along with interpretive information. Survey results indicated that most (89.5%) dairy farmers did not routinely use MUN prior to participating in the project, but most (88%) extension agents and nutritionists in the region recommended it. The average MUN across all farms in the study increased in the spring, but the increase was 0.52 mg/dl lower for farmers receiving MUN results than for those who did not participate in the program. Farmers who indicated they increased dietary crude protein (CP) due to low MUN started with MUN values that were 3 mg/dl below target but ended with target values. Farmers who indicated that they decreased CP due to high MUN began the project with high MUN but decreased it by 1 mg/dl compared to non-participating farmers. At the end of the project, 30% of farmers responding to a follow-up survey indicated they would use MUN analysis in the future. Providing MUN results and interpretive information to farmers was documented to change feeding practices and subsequent MUN results.

A bermudagrass [Cynodon dactylon (L) Pers. × C. transvaalensis Burtt-Davy `Tifgreen'] lawn in the transition zone (about lat. 35°N) was treated in late March for 3 years with a high and a low level each of benefin, bensulide, DCPA, oxadiazon, and siduron. Objectives were to determine if relationships exist between field environment and dates of preemergence herbicide applications for large crabgrass (Digitaria sanguinalis L. Scop.) control, the spring root decline (SRD) phenomenon, and herbicide phytotoxicity to the bermudagrass. Herbicide treatments in late March generally controlled large crabgrass, reduced total weed competition, and appeared to aid bermudagrass spring growth following winter dormancy. Herbicide injury to `Tifgreen' bermudagrass roots during SRD does occur under practical field conditions and was more severe when bermudagrass spring green-up occurred closer to the herbicide treatment date, as in 1982. Bermudagrass stand density was significantly reduced with the high level of siduron in 1980 and 1981, and with both levels of oxadiazon and siduron in 1982. Bensulide and oxadiazon, at both levels, gave 92% to 100% crabgrass control during all three treatment years. The high levels of benefin and DCPA in 1980, both levels of benefin and the high level of DCPA in 1981, and both levels of DCPA and the high level of benefin in 1982 gave crabgrass control in excess of 95%. Chemical names used: N-butyl-N-ethyl-2,6-dinitro-4-(trifluoromethyl)-benzenamine (benefin), O,O-bis(1-methylethyl)-S-[2-[(phenylsulfony l)-amino]ethyl] phosphorodithioate (bensulide), dimethyl 2,3,5,6-tetra-chloro-1,4-benzenedicarboxylate (DCPA), 3-[2,4-dichloro-5-(1-methylethoxy)phenyl]-5-(l,l-dimethylethyl)-l,3,4-oxadiazol-2 -(3H)-one (oxadiazon), N-(2-methylcyclohexyl)-N'-phenylurea (siduron).

No abstract

No abstract