Agroecosystem nitrogen (N) loss produces greenhouse gases, induces eutrophication, and is costly for farmers; therefore, conservation agricultural management practices aimed at reducing N loss are increasingly adopted. However, the ecosystem consequences of these practices have not been well-studied. We quantified N loss via leaching, NH3 volatilization, N2O emissions, and N retention in plant and soil pools of corn conservation agroecosystems in Kentucky, USA. Three systems were evaluated: (1) an unfertilized, organic system with cover crops hairy vetch (Vicia villosa), winter wheat (Triticum aestivum), or a mix of the two (bi-culture); (2) an organic system with a hairy vetch cover crop employing three fertilization schemes (0 N, organic N, or a fertilizer N-credit approach); and (3) a conventional system with a winter wheat cover crop and three fertilization schemes (0 N, urea N, or organic N). In the unfertilized organic system, cover crop species affected NO3-N leaching (vetch > bi-culture > wheat) and N2O-N emissions and yield during corn growth (vetch, bi-culture > wheat). Fertilization increased soil inorganic N, gaseous N loss, N leaching, and yield in the organic vetch and conventional wheat systems. Fertilizer scheme affected the magnitude of growing season N2O-N loss in the organic vetch system (organic N > fertilizer N-credit) and the timing of loss (organic N delayed N2O-N loss vs. urea) and NO3-N leaching (urea >> organic N) in the conventional wheat system, but had no effect on yield. Cover crop selection and N fertilization techniques can reduce N leaching and greenhouse gas emissions without sacrificing yield, thereby enhancing N conservation in both organic and conventional conservation agriculture systems.

Milk from 11 domestic shorthair cats (Felis catus; n=7 fed dry low-fat diet, n=4 fed dry high-fat diet) was collected weekly for 6 weeks following parturition, and analysed for total solids (TS), crude protein (CP), fat, lactose and ash. Samples were collected in 1-ml sequential fractions to determine whether within-sampling changes in composition existed Samples of extracted milk fat were also analysed for fatty acid content. Two commercia kitten milk replacers were analysed according to the same procedures utilized for mil samples. In statistical analyses individual cat, diet, stage of lactation, litter size, and teat position influenced concentrations of milk components; parity and sequential sampling had no effect. Averaged cat milk was 27.9% TS, and 8.7% CP, 12.7% fat, 4.2% lactose and 1.3% ash (on a wet basis). Milk protein percentage increased over lactation for both diet groups, but fat percentage increased only for queens fed the high-fat diet. Milk replacers were lower in fat and protein content than milk from queens, and had considerably lower levels of arachidonic acid. Data from this study contribute to the limited information available regarding the composition of domestic cat milk, and give possible reasons for poor growth occasionally observed in kittens fed unsupplemented commercial milk replacers.

Hairy vetch (Vicia villosa Roth) is a promising winter cover crop for northern climates, but germination can be limited by low soil moisture conditions. Farmers may be reluctant to use hairy vetch, concerned that hard seed will emerge as weeds in succeeding crops. This work examines germination, dormancy, and viability of hairy vetch seeds from nine commercial seed sources, and evaluates the effects of mechanical scarification and ambient temperature hydropriming on the degree of hard‐seededness, germination, seed viability and seedling vigor in a range of simulated soil moisture conditions. Hydropriming increased germination by 5% across seed sources and water potentials, but reduced seedling growth by 16%. Mechanical scarification eliminated all hard‐seededness, but increased physiologically dormant seed by ∼5% and nonviable seed by ∼2% and reduced seedling growth by 39%. This work indicates that pretreatments may increase germination and reduce hard‐seededness, but reduce seed viability and seedling vigor in some seed sources.

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A gronomy J our n al • Volume 102 , I s sue 3 • 2 010 895 ABSTRACT Minimizing N pollution from nonpoint agricultural sources is a management challenge in U.S. agriculture and in the Chesapeake Bay watershed. Th is 2-yr fi eld study examined the impact of C/N ratios, through modifi cation of straw residue, on the availability of small grain-hairy vetch (Vicia villosa Roth) derived N in a corn (Zea mays L.) cropping system. Treatments consisted of three levels of straw retention (0, 1, and 2 Mg ha -1 ), with and without a hairy vetch cover crop. Soils were sampled for inorganic N from 0 to 15 cm every 10 d during the growing season, and less frequently at deeper soil depths. Residue decomposition was measured each year using litterbags with residues representative of residue composition in each treatment. Corn productivity was also measured and a partial economic analysis was conducted. On average across sampling dates, soil inorganic N was 7.3% lower in the 1 and 2 Mg ha -1 straw treatments compared to the zero Mg ha -1 straw treatment, although this eff ect was only signifi cant in one of the two study years. Likewise, the 2 Mg ha -1 straw treatment had 16% more N retained in the residues compared to the other two treatments. Results indicate that simple alterations to common management practices, such as the retention of 1 to 2 Mg ha -1 of straw from a small grain crop that precedes a no-till vetch cover crop may reduce the potential for off -site N movement, via leaching, but it may also compromise crop yields and net economic returns.